Organelle-Targeted Nanotherapeutics for Parkinson’s Disease: From Pathogenesis to Preclinical Strategies and Translational Challenges

Introduction

Parkinson’s disease (PD) is the second most common neurodegenerative disease (NDD). Since the 1980s, the global prevalence of PD has been rising, becoming a significant public health and social burden.^1,2 The pathological hallmark of the disease is the progressive loss of dopaminergic neurons in the substantia nigra (SN) of the midbrain and the abnormal aggregation of αSynuclein (αSyn).^3,4 These pathological processes are intimately linked to dysfunction of intracellular organelles, particularly mitochondria and lysosomes. Recent years, the endoplasmic reticulum (ER), Golgi apparatus, and nuclei have also been found play an important role in PD pathology.⁵ Organelles serve as core structural units maintaining cellular homeostasis and function, and their dysfunction has been identified as a critical component in the pathological progression of PD. For instance, abnormalities in mitochondrial energy metabolism, impaired lysosomal degradation, and activation of the endoplasmic reticulum unfolded protein response not only promote abnormal αSyn aggregation but also exacerbate oxidative stress and neuroinflammation, creating a vicious cycle.^6–9

Current therapeutic strategies for PD primarily consist of pharmacological interventions and surgical treatments. Traditional drugs face limitations such as low blood-brain barrier (BBB) permeability, poor targeting, and systemic side effects, hindering effective intervention at the site of pathology. Long-term use is often associated with fluctuating efficacy and motor complications. While surgical intervention faces challenges such as inconsistent efficacy, the risk of brain tissue damage, and equipment obsolescence.¹⁰ Notably, despite providing partial symptomatic relief, neither treatment can delay or halt disease progression, because they do not address the subcellular pathological mechanisms underlying neuronal loss. In this context, organelle-targeted therapeutic strategies have emerged, aiming to restore neuronal homeostasis by precisely regulating specific subcellular structures, thereby interrupting the pathogenic cascade at its source.¹¹ A major gap in current therapeutic approaches is the inability to precisely target the subcellular sites where pathology originates.

Nanotechnology offers a promising approach to address these limitations for the properties of superior biocompatibility, controllable release properties, and surface functional plasticity.¹² The drug delivery scope of nanoparticles has shifted from broad to specific due to the design of specific targeting ligands. Given that existing therapies fail to address subcellular pathological mechanisms, nanotechnology has been considered as an effective way for achieving precise organelle-level interventions.^13,14 While existed reviews have addressed the general application of nanotherapeutics in PD,¹⁵ this review specifically focuses on how engineered nanoparticles can be directed toward distinct subcellular organelles to restore their function and alleviate dysfunction-related pathology. Rather than providing a broad overview of nanocarriers or neuroprotective agents, we emphasize organelle-targeted strategies that move beyond conventional drug delivery to restore subcellular function. It is important to acknowledge that the evidence discussed here is predominantly derived from preclinical studies. We primarily include PD-specific research; however, when direct evidence in PD is limited, we selectively incorporate findings from other neurodegenerative diseases to provide mechanistic support. Despite the considerable therapeutic potential, several major challenges continue to hinder clinical translation, including heterogeneity in BBB penetration, inefficient endosomal escape, difficulties in accurately validating subcellular targeting, limited manufacturing reproducibility, and uncertainties regarding long-term biosafety.

This review systematically summarizes the role of dysfunctional organelles in pathogenesis of PD, providing effective organelle-targeting pathways and focusing on recent advances in nanotherapeutic strategies. Furthermore, we discuss current challenges and future prospects for clinical translation. This aims to provide theoretical foundations and technical directions for developing next-generation disease-modifying therapies for PD.

The Overview of Nanotechnology Application in PD

The application of nanotechnology in PD treatment has garnered increasing attention, with its core advantage of facilitating targeted delivery, which mitigates the systemic toxicity associated with conventional administration routes. Leveraging surface modification and small size, nanoparticles (NPs) can effectively penetrate the BBB and cell membranes, significantly enhancing drug accumulation at the lesion site via passive or active targeting mechanisms. Additionally, nanomaterials exhibit outstanding drug-loading capacity and controlled-release properties, effectively improving pharmacokinetics of drugs.^16–18 The controlled-release properties of nanocarriers can mitigate motor complications associated with levodopa blood concentration fluctuations, thereby offering considerable potential for clinical application. Diverse nanomaterials enable varied delivery strategies, playing an irreplaceable role particularly in developing novel therapies based on disease-modifying mechanisms. Existing nanocarriers and delivery routes are summarized in Figure 1.

Figure 1 Nanotherapy in CNS disease. Common categories of nanocarriers employed for therapeutic purposes comprise organic, inorganic, and biomimetic nanocarriers. These systems are designed to deliver a diverse range of therapeutic agents, including proteins, nucleic acids, small-molecule drugs, and natural bioactive compounds. To facilitate efficient transport of nanoparticles into the brain, multiple administration routes are utilized, such as oral delivery, intravenous injection, intranasal administration, and localized intracerebral delivery. Following cellular uptake, the nanoparticles undergo lysosomal degradation or structural disassembly, leading to the controlled release of their payloads. These released therapeutics can then target specific intracellular organelles, thereby exerting pharmacological effects and ameliorating pathological conditions. Figure made in BioRender.com.

In PD treatment, delivering dopamine via nanocarriers has proven to be an efficient and viable strategy. Studies indicate that DA-loaded NPs can effectively penetrate the BBB and improve motor function in animal models.¹⁹ Although this targeted approach effectively reduces the accumulation of dopamine in peripheral tissues and minimizes systemic side effects, it provides only symptomatic relief and does not hinder the underlying progression of the disease. Consequently, therapeutic strategies aimed at the pathogenesis of PD have attracted growing attention. Numerous nanosystems targeting oxidative stress, neuroinflammation, αSyn aggregation, impaired autophagy, and neuronal apoptosis are under development.^20–22 Such interventions have been shown to improve the survival of dopaminergic neurons and motor function in preclinical models. Nevertheless, their long-term therapeutic efficacy requires further validation.

The emergence of novel nanomaterials and advancements in auxiliary targeting technologies have significantly enhanced the in vivo targeting efficiency of NPs. Among these, biomimetic delivery systems and stimulus-responsive nanoparticles hold considerable application potential. Modifying NPs with natural membrane components endows them with biomimetic capabilities, enabling more efficient delivery to biologically active sites. Currently, the most mature biomimetic technologies primarily include cell membrane and exosome biomimicry. Cell membranes serve as multifunctional, biocompatible platforms with potential for surface modification and targeted delivery design. They interact with physiological environments to enhance central nervous system drug delivery while mitigating toxic effects. The targeting ability of cell membrane-coated particles is largely derived from the surface proteins of the source cells.²³ Exosomes play a crucial role in intercellular communication. They exhibit high biocompatibility and low immunogenicity, with an inherent ability to traverse the BBB, and selectively interact with specific cells and tissues via surface markers. Exosomes exhibit significant variability due to their different cellular origin. For example, stem cell-derived exosomes are particularly suited for regenerative and neuroprotective applications as they contain unique growth factors, neurotrophic factors, and anti-inflammatory molecules.²⁴ Cell membrane or exosome coated NPs not only retain the benefits of conventional NPs but also enhance biocompatibility, prolong drug circulation time, reduce clearance rates, and improve BBB permeability. These systems are often further modified with targeting motifs to enhance biological specificity. Biomimetic nanotechnology has demonstrated success in multiple PD-related studies, showcasing immense potential as a therapeutic drug delivery vehicle for PD.^20,25

Stimuli-responsive NPs represent another major breakthrough in targeted disease therapy. These NPs are engineered to respond to endogenous biological, chemical, or physical stimuli—such as pH, reactive oxygen species (ROS), temperature, or enzyme activity—enabling spatially and temporally controlled drug release at target sites. This strategy enhances therapeutic efficacy while minimizing off-target effects.^21,26,27 Meanwhile, integrating controllable-release nanomedicine with optogenetics or sono-chemogenetics can effectively achieve drug release under specific conditions, opening new therapeutic avenues for precise spatiotemporal drug release.²⁸

Furthermore, systemic administration of nanomedicines (eg, intravenous injection) requires traversing the BBB to reach target tissues and cells, significantly reducing bioavailability. Nasal-brain delivery bypasses the BBB, transporting NPs to the brain via olfactory and trigeminal nerve pathways. It offers multiple advantages including ease of use, non-invasiveness, avoidance of hepatic first-pass metabolism, reduced systemic toxicity, prolonged residence time at the target site, and minimized unnecessary drug exposure and safety concerns. However, intranasal administration also presents drawbacks such as potential nasal irritation, tissue toxicity, and local adverse reactions.^29–31 Besides, local administration of therapeutics directly into the brain parenchyma can effectively minimize their off-target distribution. However, this method is also associated with challenges such as repeated injections and potential damage to the local brain tissue. To solve this problem, nanoparticles can be integrated with other scaffolds (eg, hydrogels) to form hybrid delivery systems. This approach enables sustained release of therapeutic agents, thereby reducing the frequency of required interventions.³²

In summary, current nanotherapies for PD remain at the cellular or tissue level. However, the continuous evolution of nanomaterials and delivery strategies provides a robust foundation for exploring novel therapeutic paradigms. Given the central role of organelles in maintaining cellular homeostasis and regulatory networks, developing organelle-targeted nanotherapeutic strategies holds immense therapeutic potential, offering new avenues for precise intervention in the pathological progression of PD (Figure 2). To navigate the rapidly expanding field of organelle-targeted nanotherapeutics for PD, a systematic comparative lens is essential. As synthesized in Table 1, we compared approaches head-to-head across organelles in terms of delivery route, cargo class, targeting ligand, PD model relevance, mechanistic evidence, and translational readiness. This framework allows for a clear distinction between early proof-of-concept studies and those with genuine disease-modifying potential across different organelles.

Table 1 Comparative Stratification of Evidence and Translational Maturity for Organelle-Targeted Nanotherapeutics in PD

Figure 2 Organelles-targeted nanotherapy in Parkinson’s Disease. PD is characterized by a central pathological mechanism involving coordinated dysfunction across multiple organelles—including mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus, and nucleus. This interplay of dysfunctional organelles is a key driver of disease pathogenesis. In response, therapeutic strategies are increasingly focusing on agents designed to precisely target these organelles. (Drugs are distinguish by color: red, PD-established evidence in vivo; orange, PD-established evidence in vitro; green, borrowed proof-of concept from other diseases; yellow, prospective conceptual targets). By restoring organellar integrity and function, such targeted interventions may ameliorate intracellular pathology, and their efficacy can be further enhanced through encapsulation within advanced nanocarrier systems. Figure made in BioRender.com.

Targeting Mitochondria

Mitochondria in the Pathophysiology of PD

Mitochondria are the core organelles regulating cellular energy production, apoptosis, and metabolism. The brain—due to the high metabolic activity of neurons—becomes one of most energy-demanding organs. As the most crucial organelle for energy metabolism, mitochondria play an immense role in maintaining normal brain function. It has now been confirmed that mitochondrial dysfunction is closely linked to NDDs.^33–36 Mitochondrial dysfunction manifests in multiple aspects, including mutations and deletions in mitochondrial DNA (mtDNA), disrupted calcium homeostasis, depolarization of the mitochondrial membrane, abnormal fusion and fission processes, impaired mitochondrial biogenesis, and oxidative stress. These alterations subsequently trigger pathological processes such as neurotransmitter metabolism abnormalities, synaptic dysfunction, and impaired neuronal growth and development.^37–41

In PD, neuronal mitochondrial dysfunction is one of the core pathogenic mechanisms. Early evidence emerged from the mitochondrial toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which selectively induces DA neuron death. This mechanism is closely linked to MPTP induced inhibition of mitochondrial complex I, leading to dysfunction in the mitochondrial electron transport chain, reduced adenosine triphosphate (ATP) synthesis, and increased ROS production. Additionally, neurotoxins such as rotenone and 6-OHDA induce PD-like pathology through similar pathways.^42,43

Multiple studies indicate direct associations between PD-related gene mutations and mitochondrial dysfunction. For instance, PINK1 and PARKIN mutations are common causes of autosomal recessive familial PD. The absence of which leads to defective mitochondrial autophagy, causing accumulation of damaged mitochondria and subsequent neuronal injury.⁴⁴ DJ-1, a mitochondrial peroxidase-like enzyme, exhibits mutations that impair mitochondrial antioxidant capacity and heighten cellular sensitivity to oxidative stress. LRRK2 mutations, associated with autosomal dominant PD, are implicated in mitochondrial division, leading to morphological and functional abnormalities that ultimately precipitate PD.^43,45 Although no PD-associated mtDNA mutations have been definitively identified, most studies indicate that mtDNA mutations, deletions, and rearrangements disrupt the mitochondrial respiratory chain, resulting in reduced cytochrome c oxidase (COX) activity and complex I defects. Artificial disruption of mtDNA induces PD onset, demonstrating the critical importance of mtDNA integrity in maintaining healthy mitochondrial function.⁴³

Mitochondrial quality control serves as a vital mechanism for maintaining intracellular mitochondrial homeostasis. This process encompasses monitoring, identifying, repairing, and/or eliminating abnormal or misfolded mitochondrial proteins, as well as dysfunctional mitochondria.⁴⁶ In PD, disrupted mitochondrial quality control manifests primarily as impaired mitochondrial dynamics (fusion and fission), defective mitochondrial autophagy, and abnormal accumulation of mitochondrial αSyn. Mitochondrial fusion proteins (MFN1 and MFN2) and Opa1 (retinitis pigmentosa 1) mediate fusion of the mitochondrial outer and inner membranes, respectively. Opa1 mutations are associated with PD and dementia, and reduced Opa1 expression increases mitochondrial fragmentation and autophagy. Various PD-associated neurotoxic molecules in vitro induce increased mitochondrial fusion-fission imbalance, where disrupted fission leads to synaptic loss and neuronal death. Impairment of the PINK1/PARKIN pathway causes mitochondrial autophagy dysfunction, preventing timely clearance of damaged mitochondria and subsequently triggering cellular energy metabolism disorders and increased oxidative stress. Although studies suggest mitochondrial dysfunction precedes αSyn accumulation, αSyn preferentially binds to mitochondria, inhibiting mitochondrial protein import and depolarizing the mitochondrial membrane. Concurrently, αSyn binds to the electron transport chain, disrupting ATP production, increasing ROS, and impairing mitochondrial respiration, further exacerbating the pathological state. αSyn can also interact with mitochondrial membrane proteins, activating the mitochondrial permeability transition pore to release mitochondrial contents and trigger inflammatory responses. These imbalanced processes collectively drive the pathological progression of PD.^47,48

Ferroptosis, an iron-dependent form of cell death, is closely associated with mitochondrial dysfunction. It has been demonstrated as a prevalent cell death pathway in PD. Mitochondria, as iron-rich organelles, utilize iron ions for iron-sulfur cluster synthesis or store them as mitochondrial ferritin. Disruption of mitochondrial iron homeostasis leads to excessive intracellular iron accumulation, triggering the Fenton reaction. This generates ROS that react with fatty acids to form peroxides, further damaging mitochondrial structure and exacerbating oxidative stress, ultimately causing DA neuron death. In PD models, increased iron influx through the mitochondrial iron channel mitoferrin-2 is observed, and significant iron deposition is present in the SN of PD patients.^49,50

Mitochondria play a crucial role in maintaining intracellular calcium homeostasis. In PD neuronal models with PINK1 defects, reduced NCLX (Na⁺/Ca²⁺ exchanger)-dependent mCa²⁺ efflux leads to mitochondrial calcium overload. This triggers the opening of the mitochondrial permeability transition pore, resulting in mitochondrial swelling and apoptosis. Concurrently, mitochondrial dysfunction increases ROS production, which directly damages intracellular biomolecules including proteins, lipids, and DNA. Reduced glutathione levels in the SN of PD patients weaken antioxidant defenses, and mtDNA damage further degrades mitochondrial quality.^50,51

Given mitochondrial dysfunction’s pivotal role in PD pathogenesis, mitochondrial-associated biomarkers hold potential diagnostic and therapeutic value. For instance, circulating cell-free mitochondrial DNA (cfc-mtDNA) levels may be altered in PD patients, potentially serving as a biomarker for disease diagnosis and progression monitoring.⁵² Additionally, elevated levels of mitochondrial proteins like TOMM40 in cerebrospinal fluid may indicate disease progression.⁴² However, research on these potential biomarkers remains preliminary, requiring further validation of their clinical utility.

Although therapeutic strategies targeting mitochondrial dysfunction face numerous challenges in disease-modifying clinical trials, the ongoing development and maturation of nanotechnology hold promise for targeted mitochondrial therapies in PD.

Mitochondria-Targeting Nano-Delivery Strategies

Mitochondria are semi-autonomous organelles composed of an inner membrane and an outer membrane, forming a natural biological membrane barrier. The outer mitochondrial membrane (OMM) acts as a lipophilic barrier, while the inner mitochondrial membrane (IMM) is rich in phosphatidylserine, exhibiting a higher protein-to-lipid ratio and a strong negative mitochondrial membrane potential (MMP).⁵³ To effectively deliver drugs into mitochondria, these barriers need to be overcome. Current effective approaches include: membrane potential-driven, affinity-driven, and nanotechnology-driven methods.^54,55

First, the mitochondrial-targeted delivery of nanoparticles could be achieved by exploiting the membrane potential difference. The covalent modification of compounds is an important modification method for mitochondrial-targeted carriers, and its chemical synthesis is simple and has a high targeting efficiency. Common lipophilic cations include alkyl-triphenylphosphine cations (TPP⁺), rhodamine, cyanine cations, and cationic peptides, etc. TPP⁺ is currently the most studied cation for targeting mitochondria due to its high chemical stability, ease of modification and strong membrane-penetrating ability and was initially used as a probe to monitor MMP.^53–56 Nowadays, it is widely applied in decorating NPs for targeted delivery to mitochondria. For instance, Yuan et al developed a TPP-PEG-PCL-based carrier that significantly enhances the mitochondrial accumulation of its drug payload.⁵⁷ TPP-modified quercetin NPs (TQCN) delivered intranasally effectively penetrate brain regions and localize to mitochondria to relieve oxidative stress.⁵⁵ Concurrently, novel cationic compounds targeting mitochondria continue to emerge. For instance, Schlichtmann et al developed a TPP derivative, 3-carboxypropyl-triphenylphosphine (CPTP), which enhances its retention on NPs. This approach enables effective mitochondrial targeting to mitigate rotenone-induced mitochondrial damage.⁵⁸

Additionally, mitochondrial-targeting peptides can direct nanomedicines to mitochondria, which comprise either naturally occurring amino acid sequences (MTS) or synthetic peptides. MTS typically reside at the N-terminus of proteins and often contain hydrophobic and positively charged amino acids. MTS facilitates NPs entry into the mitochondrial matrix by interacting with translocase enzymes located in the outer and inner membrane complex.^56,59 For instance, the Szeto-Schiller (SS) peptide combines MTS with an antioxidant motif, selectively accumulating in the IMM due to its affinity for mitochondrial lipids while also exhibiting antioxidant activity.⁵³ Compared to MTS, mitochondrial localization signal peptides (MLSP) enable delivery of nanocarriers to more specialized mitochondrial compartments, facilitating targeted localization for precision medicine.⁶⁰ Mitochondrial penetration peptides (MPP) are artificially designed permeable peptides possessing both cell membrane penetration capability and mitochondrial targeting specificity. MPP may target mitochondria through multiple mechanisms, such as inducing membrane depolarization, mimicking the evolutionary origin of antimicrobial peptides, and selectively binding to phosphatidylserine.^61–63

The preparation of mitochondrial-targeted NP (MTN) is challenging, but they enhance mitochondrial targeting by improving lipid solubility, stability, and membrane permeability, thereby increasing the drug load, protein protection, and precise regulation of mitochondrial release. In summary, the design of MTN requires optimizing the characteristics of the NPs, such as size, charge, lipophilicity, biocompatibility, targeting ligands, and promoting intracellular escape, in order to successfully cross the biological barrier and deliver specific and highly efficient mitochondrial-protecting drugs.⁶⁴

Mitochondria-Targeting Nano-Therapy Strategies

Therapeutic strategies leveraging MTN have demonstrated significant potential in treating PD, with mechanisms including alleviating oxidative stress, promoting antioxidant capacity, and enhancing mitophagy. The mitochondrial-protecting agents, nano-delivery systems, and key therapeutic outcomes reported in recent studies are systematically summarized in Table 2.

Table 2 Examples of Mitochondria-Targeted Nanoparticles for Treatment of Parkinson’s Disease

Antioxidation

Among MTNs, antioxidants are the most prevalent. Numerous neuroprotective agents with efficacy against oxidative stress are hindered from reaching pathological brain regions due to their inherent chemical properties, which limit their ability to cross the BBB and achieve targeted delivery. Thus, nanotechnology play a crucial role in enhancing drug delivery efficacy.⁷⁹ NPs carrying natural antioxidant compounds has been extensively researched. For instance, naringenin (NAR) is a potent antioxidant with anti-apoptotic properties. Human serum albumin (HSA)-coated NAR nanocrystals (HSA-NAR-NCs) has been found maintained MMP and ATP production while regulating ROS levels, counteracting the neurotoxic effects of rotenone.⁶⁵ Besides, the formulation of nanocrystals significantly enhancing solubility, dissolution rate, and stability of the agent, as HSA reduce immune responses and toxicity while prolonging circulation time.⁸⁰ In another research, The RVG29 and RBC membrane-decorated curcumin nanocrystals effectively evaded reticuloendothelial system uptake, prolonged circulation and enhanced BBB penetration, Meanwhile, the nanomedicine restored dopamine level, inhibited αSyn aggregation, and reversed mitochondrial dysfunction in PD mice.²⁰ Despite these preclinical successes, a critical translation gap. For instance, in a randomized controlled clinical trial, curcumin nanogels failed to significantly improve the quality of life and clinical symptoms of PD patients.⁸¹ This indicates that these preclinical trials with positive results still require further replication and validation. This single but important negative result underscores the frequent disconnect between promising preclinical data and clinical efficacy, possibly due to differences in disease chronicity, patient heterogeneity, or the inadequacy of toxin-based animal models to fully recapitulate human PD.

Additionally, emerging physical-assisted technologies offer new avenues for enhancing the efficacy of nanomedicines. Utilizing the photothermal conversion properties of special nanomaterials can enhance the targeting ability of antioxidants to the mitochondria within the brain. Under near infrared (NIR) irradiation, the photothermal effect produced by nanomaterials such as gold, Prussian blue, black phosphorus, etc. can cause local mild heating, temporarily expand the intercellular gaps of endothelial cells or activate the fluidity of the cell membrane, thereby increasing the permeability of the BBB.^82,83 Researchers demonstrated that the zeolitic imidazolate framework 8-coated Prussian blue nanocomposite encapsulating quercetin (ZIF-8@PB-QCT) exhibits excellent NIR responsiveness. Guided by the photothermal effect, it penetrates BBB to reach sites of mitochondrial damage. In the mouse model of PD, ZIF-8@PB-QCT significantly elevated ATP levels, reduced oxidative stress, and reversed both dopaminergic neuronal damage and behavior deficits, without causing harm to normal tissues.⁷⁵ Although photodynamic therapy has effectively enhanced the penetration and targeting properties of NPs, the optimal irradiation parameters, long-term safety and operability require systematic investigation.

Beyond natural or synthetic antioxidants, several reductive agent donors are being actively explored to enhance the release of endogenous antioxidants. For instance, H₂S is an effective endogenous antioxidant. Reduced endogenous H₂S levels may lead to sulfhydryl modification of Parkin protein and decreased enzymatic activity, thereby impairing its ability to recognize toxic proteins and mediating the formation of αSyn aggregates. Zhao et al designed a nanomotor-based H₂S donor PCM (PEG-Cys-MPC). This H₂S donor can cross the BBB and be catalytically formed into H₂S in the mitochondria. Ultimately it eliminated ROS, alleviated neuroinflammation, and reduced αSyn aggregation.⁷⁰ Furthermore, Wang et al encapsulated SNCA siRNA into PCM to reduce αSyn formation, while utilizing H₂S generated during chemotaxis to reduce oxidative damage, achieving a multi-faceted therapeutic approach for PD.⁷¹

Notably, nanotherapeutics targeting mitochondrial energy metabolism have advanced to phase II clinical trials. CNM-Au8^® is a faceted, clean-surfaced gold nanocrystal suspension designed to catalytically enhance energy metabolism in CNS cells, thereby supporting neuroprotection and remyelination. Its novel mechanism involves targeting the NAD⁺/NADH redox couple, which has been validated in multiple independent preclinical models. In a combined cohort of PD and multiple sclerosis (MS) patients, the average cerebral NAD⁺/NADH ratio increased by approximately 10.4% after over 12 weeks of CNM-Au8 treatment compared to baseline. However, likely due to the limited sample size, this improvement did not reach statistical significance when the disease cohorts were analyzed separately. Related long-term extension studies are currently underway.⁸⁴

Nanozymes

Nanozymes are a class of nanomaterials exhibiting catalytic activity analogous to natural enzymes, capable of mimicking the catalytic functions of biological enzymes in complex biological environments.⁸⁵ For instance, when the MoS₂ structure is reduced from bulk to extremely thin monolayer quantum dot (QD) layers, it exhibited unique catalytic activity. Nanoscale MoS₂ serves as an excellent antioxidant, eliminating various free radicals through nanozyme activity. This activity mimics intrinsic major cellular antioxidant enzymes.⁸⁶ Studies indicate that TPP-MoS₂ QDs reducing the pro-inflammatory transformation of microglia by alleviating oxidative stress.⁸⁷

Many metallic nanozymes exhibit dual enzyme-like activities mimicking superoxide dismutase (SOD) and catalase. Octahedral palladium nanoparticles (Pd NPs) scavenge cytotoxic oxygen radicals, maintain MMP, and mitigate damage to lipids, proteins, and DNA under hyperthermia.⁸⁸ The tri-element nanozyme (PtCuSe nanozyme) alleviates neuronal injury by scavenging cellular ROS and reduces behavioral and pathological symptoms in PD animal models.⁷⁴ Furthermore, by binding to mitochondria-targeting peptides, nanozymes can more effectively rescue mitochondrial dysfunction. For instance, TPP-modified Cu_(2-x)Se nanozymes (Cu_(2-x)Se-TPP NPs) effectively scavenge ROS in microglial mitochondria, alleviating mitochondrial oxidative stress.⁸⁹ To more efficiently exert the function of nanozymes, Liu et al integrated Fe-isolated single-atom nanozyme (Fe-ISAzyme) liposome with TPP to the microneedles patch, and adapt in situ delivery. The strategy significantly enhanced deep penetration into brain parenchyma compared to intravenous injection, particularly in key pathological sites like the SN and striatum. Besides, the nanozyme scavenged ROS and alleviated neuroinflammation at the lesion sites, effectively mitigating behavioral deficits and pathological symptoms in PD mice.⁷³ While ligand-conjugated nanozymes like Cu_(2-x)Se-TPP NPs show enhanced mitochondrial targeting, their synthetic complexity and potential for metal-ion leaching raise unresolved long-term safety questions. In contrast, “label-free” nanozymes like the Fe-ISAzyme microneedle patch demonstrate that strategic administration routes can partially compensate for a lack of molecular targeting ligands, achieving deep brain penetration by mechanical means.

Mitochondrial Autophagy

Dysregulation of the Parkin/PINK1 pathway in PD leads to impaired mitochondrial autophagy, preventing the clearance of damaged mitochondria and triggering neuronal dysfunction. Consequently, numerous studies target mitochondrial autophagy to rescue damaged neurons as a therapeutic strategy for PD.

Specifically modified nanocarriers delivering targeted drugs can clear damaged mitochondria by initiating the mitochondrial autophagy program, effectively restoring mitochondrial homeostasis, reducing the neurotoxicity caused by oxidative stress, and rescuing the motor dysfunction in animal models. For instance, Chen, Y. et al employed hyaluronic acid nanoparticles (HA-NPs) of varying molecular weights to protect mitochondria and repair mild, limited damage. For irreversible damage, NPs containing ubiquitin-specific protease 30 (USP30) siRNA were used to promote mitochondrial autophagy. Simultaneously, by incorporating PINK1 antibodies, these NPs selectively targeted irreversibly damaged mitochondria, preventing excessive clearance of healthy mitochondria.⁶⁹ Similarly, Biswal, L. et al employed HSA nanocarrier to deliver melatonin to the brain. This nano-melatonin exhibited enhanced antioxidant and neuroprotective properties associated with promoting mitophagy by upregulating BMI1, thus counteracting rotundone-induced toxicity.⁶⁷ Besides, Xia et al loaded lycopene nanodots into the cavity of recombinant human H-ferritin nanocages and attached TPP to the outer surface. H-ferritin nanocages were transported across the BBB by recognizing transferrin receptor-1, targeting neurons and mitochondria. The anti-ROS components protected mitochondrial function in vivo and in vitro and promoted PINK1/Parkin-mediated mitophagy, thereby facilitating the clearance of pathogenic αSyn and the survival of dopaminergic neurons.⁶⁶ In addition, enhancing mitophagy can also effectively regulate glial cell-associated neuroinflammation. Zhang et al developed a nanomedicine based on stem cell-derived exosomes loaded with hydroxy-terminated phosphorus dendrimers and quercetin (QAE NPs), which exhibited favorable drug release characteristics and ideal cellular compatibility, capable of penetrating the nasal mucosa and accumulating in the brain. QAE NPs possess both anti-inflammatory and antioxidant properties, which induced mitophagy, scavenged ROS, and restored mitochondrial homeostasis, while promoting M2 microglia polarization and reducing neuroinflammation. This nanocomposite improves motor function, coordination, and alleviates depressive-like symptoms in PD mice.⁷⁶

Collectively, these approaches highlight mitophagy modulation as a central and mechanistically coherent strategy for addressing mitochondrial dysfunction in PD; however, their relative efficacy and selectivity remain difficult to compare due to differences in carrier design and experimental models.

Targeting Lysosomes/Endosomes

Lysosomes/Endosomes in the Pathophysiology of PD

Lysosomes are key organelles responsible for degrading biomacromolecules. They eliminate dysfunctional extracellular or intracellular components—including prone-to-aggregate proteins and damaged organelles—via the endocytosis-lysosomal pathway or autophagy-lysosomal pathway (ALP).⁹⁰ Lysosomes play vital roles in maintaining neuronal homeostasis, regulating synaptic signaling, promoting plasma membrane repair, and overseeing protein secretion.^91–93 Currently, autophagy is known to comprise three primary pathways: macroautophagy, chaperone-mediated autophagy (CMA), and microautophagy. Macroautophagy, the most prevalent autophagy form, initiates with the engulfment of cytoplasmic contents into a double-membrane structure called an autophagosome, which ultimately fuses with lysosomes to degrade its contents. CMA does not require double-membrane vesicle formation. Instead, it promotes the unfolding and transport of CMA-targeted proteins to lysosomes through binding to KFERQ-like CMA target motifs, representing a selective form of autophagy. Microautophagy refers to the process where lysosomal or vacuolar membranes directly invaginate, engulf, and degrade cytoplasmic components. The mechanisms underlying microautophagy remain poorly understood.⁹⁴ Given the irreplaceable nature and extensive branching volume of neurons, lysosomal function is crucial for maintaining normal neuronal function. Dysfunction in lysosomes may lead to abnormal protein accumulation and inadequate clearance of neurotoxic proteins, including αSyn, potentially causing dopaminergic neuronal dysfunction and subsequently resulting in PD.⁹³

Numerous PD-associated genes have been implicated in lysosomal protein transport or lysosomal function, including LRRK2, GBA, ATP13A2, and TMEM175. LRRK2 possesses GTPase activity, and its mutations can cause autosomal dominant PD. LRRK2 is a dynamic protein capable of forming distinct complexes and regulating various functions across different subcellular locations, cell types, and conditions, including the autophagy-lysosome-endosome system.⁹¹ LRRK2 induces autophagy via the MAPK/ERK pathway and modulates autophagy through calcium-dependent pathways. LRRK2 mutations impair autophagosome maturation, disrupt LRRK2-v-ATPase interactions, and cause defective lysosomal acidification. Additionally, LRRK2 serves as a CMA substrate. LRRK2 mutations not only evade its own degradation but also inhibit the degradation of other CMA substrates, including αSyn.⁹⁵ GBA encodes the lysosomal enzyme β-glucocerebrosidase (GCase). The estimated prevalence of GBA1 mutations among PD patients ranges from 5% to 25%. Postmortem PD tissues exhibit reduced GCase activity and protein levels. Within lysosomes, diminished GCase activity leads to sphingoglycolipid accumulation, disrupting lysosomal function and autophagy, thereby triggering αSyn accumulation. Furthermore, αSyn aggregates reduce GCase activity, forming a self-perpetuating cycle of lysosomal dysfunction and αSyn accumulation.^95–97 The PD risk gene ATP13A2 encodes a lysosomal P5-type ATPase, considered as a pH regulator, as its mutations or deletions cause polyamine accumulation, elevated pH, and autophagosome/lysosome stacking. ATP13A2 mutations cause familial Parkinson’s syndrome with juvenile-onset.⁹⁸ The endoplasmic reticulum/lysosomal proton channel TMEM175 is another key regulator of lysosomal pH and a risk factor for NDDs like PD and Lewy body dementia. Cells lacking TMEM175 exhibit reduced lysosomal hydrolase activity and pathological αSyn aggregation.⁹⁹

The autophagy pathway plays a crucial role in maintaining appropriate levels of αSyn in neurons. Wild-type αSyn is primarily degraded via autophagy, but mainly through CMA.⁹¹ αSyn carries the sequence 95VKKDQ99, which is specifically recognized by HSP70 and promotes its translocation to the lysosomal surface, where it binds to LAMP2 for subsequent degradation. Alterations in αSyn due to mutations or post-translational modifications affect CMA-mediated turnover. Certain αSyn variants associated with familial PD cases cannot be efficiently degraded via CMA and further block CMA-dependent degradation of other substrates. Cathepsin D in lysosomes has been reported to directly participate in the degradation of both monomeric and aggregated α-syn. Blocking ALP with vancomycin A1 leads to the accumulation of α-syn aggregates in primary cortical neurons and non-neuronal cells.⁹³

The acidic environment of lysosomes is critical for their normal hydrolytic function, with an optimal pH of 4.0–5.0.¹⁰⁰ Lysosomal acidification is primarily maintained by a proton pump called the vacuolar-type H⁺-ATPase (V-ATPase) and multiple ion channels in the lysosomal membrane. Under pathological conditions, lysosomes with elevated pH either fail to fuse with autophagosomes or fuse to form poorly acidified autophagolysosomes, resulting in inefficient or absent degradation of these lysosomes during cellular turnover.^101,102 In PD, impaired lysosomal acidification leads to mitochondrial dysfunction, reduced αSyn clearance, Lewy body pathology, and neurodegeneration. Notably, deficiency of TMEM175, which encodes a K⁺ channel, induces excessive lysosomal acidification rather than deacidification, yet similarly results in reduced cathepsin activity and impaired αSyn aggregation in vitro and in vivo tissues.^99,103

Additionally, increased lysosomal membrane permeability and disrupted lysosomal calcium homeostasis have been implicated in PD.⁹⁹ Various small-molecule compounds applied to PD models have been shown to promote clearance of abnormal protein aggregates in neurons and/or protect neurons from apoptosis by modulating ALP.¹⁰⁴ Nanotechnology plays a crucial role in targeting drug delivery to the lysosomal pathway.

Lysosomes/Endosomes-Targeting Nano-Delivery Strategies

Endocytosis is a crucial pathway for NPs to enter cells, representing a complex process strictly regulated by the plasma membrane. Primary endocytic mechanisms include clathrin-mediated endocytic mechanisms and endocytic pathways that proceed independently of clathrin.¹⁰⁵ The vast majority of NPs enter the cytoplasm through endocytosis mediated by clathrin. The substances will pass through the early endosome - late endosome - lysosome transport pathway and are eventually degraded by hydrolases.¹⁰⁶ These endocytic pathways have been extensively studied and are determined by the physicochemical properties of nanoparticles.¹⁰⁷

Placing drug molecules in the lysosomal pathway may offer advantages, such as enhancing lysosomal acidification, replacing lysosomal enzymes, or promoting autophagy initiation. However, unmodified nanoparticles do not necessarily trigger endocytosis to enter this endocytic-lysosomal pathway. Therefore, researchers promote cellular endocytosis by biologically or chemically modifying nanoparticle surfaces. This includes cell-penetrating peptides, targeting ligands, cationic modifications and biomimetic modifications.^108–111 Binding these natural or synthetic ligands to nanoparticles effectively promotes cell uptake, thereby enhancing the efficiency of drug delivery targeting the lysosomal pathway.^13,106

In recent years, researchers have developed a novel approach to target protein degradation for clearing extracellular or intracellular harmful substances called lysosome-targeting chimeras (LYTACs) or autophagy-targeting chimeras (AUTACs). The chimera recognizes the target protein and links it to a lysosome-targeting receptor (LTR) on the cell membrane surface, initiating receptor-mediated endocytosis. The target protein is then transported to lysosomes for degradation, while the LTR is recycled back to the cell membrane via recycling endosomes.^112,113 Combining LYTACs or AUTACs with nanodelivery significantly enhances the targeting efficiency. For example, Lu et al conjugating target protein and LTR ligands to gold nanoparticles. The large surface area of NPs allows binding of numerous ligands, greatly enhancing the efficiency of capturing pathological proteins and increasing the likelihood of lysosomal degradation.¹¹⁴ This strategy holds significant potential for PD to relieve pathological αSyn aggregation.

Lysosome/Endosome-Targeting Nano-Therapy Strategies

Designing nanostrategies targeting ALP can effectively improve lysosomal defects in PD, including impaired lysosomal acidification and promoting autophagy-mediated degradation of abnormal proteins. Table 3 summarizes recent applications of nanodelivery strategies targeting ALP in PD.

Table 3 Examples of Lysosomes-Targeted Nanoparticles for Treatment of Parkinson’s Disease

Lysosomal Acidification

Extensive research indicates that lysosomal acidification is an effective strategy for restoring lysosomal function.^76,122 Nanodelivery of lysosomal acidification drugs can significantly enhance lysosomal degradation capacity, eliminate pathological proteins, and slow disease progression.

Biocompatible poly(lactic-co-glycolic acid) (PLGA) are the most commonly used acidic nanomaterial. PLGA is completely biodegradable in vivo, ultimately metabolizing into carbon dioxide and water. It leaves no toxic residues and does not cause immune rejection reactions. For example, Arotcarena et al have found that PLGA-aNPs enhanced αSyn degradation by boosting lysosomal activity, thereby improving neurotoxin-induced dopaminergic neurodegeneration in mice.¹¹⁵ This study highlights the potential of acidification-based strategies to restore lysosomal function and promote pathogenic protein clearance, although their long-term effects on lysosomal homeostasis remain to be fully established. Besides, Brouillard, M. et al designed an innovative DNA derivative-based nanocarrier. Nucleolipids carry biocompatible organic acids as prodrugs, which were incorporated into oil-in-water nanomulsion to traverse biomembranes, followed by effective release of the biocompatible acidic components to restore functional pH in lysosomes of neuronal cells. The biosafety has also been validated.¹¹⁸ Compared with polymer-based systems, such prodrug-based designs may offer more controlled and localized pH modulation; however, their stability, release kinetics, and in vivo targeting efficiency require further validation.

Taken together, these approaches suggest that modulating lysosomal acidity is a promising strategy for restoring degradative function in PD. Nevertheless, achieving precise and sustained pH regulation without disrupting physiological lysosomal processes remains a key challenge for future development.

Ameliorate Autophagy

Modulating autophagy effectively clears abnormally accumulated proteins and senescent organelles within cells, improving intracellular protein homeostasis and associated pathological stress. Researchers therefore utilize nanoparticles to deliver natural or synthetic small-molecule drugs that modulate autophagy pathways, restoring impaired autophagy flux in disease states.

Trebose, a small natural autophagy enhancer molecule, is widely applied in NDDs to improve autophagy dysfunction. Cunha. et al designed a trehalose-based nanomedicine. They combined trehalose with an amphiphilic nucleolipid complex, which are incorporated in PLGA NPs or solid lipid NPs. It improved the uptake and internalization into neuronal cells associated with the trehalose-induced autophagy effect, and did not induce any cellular toxicity.⁹⁰ Similarly, Mannose, a disaccharide capable of inducing autophagy, has been demonstrated to reduce αSyn aggregation in vivo. However, free mannose can be rapidly degraded by mannosidase, and its hydrophilic nature hinders cellular membrane penetration. Maruf. et al investigated a mannose-containing nanogel (TR) to promote its cellular uptake. TR inhibits αSyn aggregation formation and synergistically reduces Lewy body-like inclusions in primary hippocampal neurons by promoting aggregate clearance through mannitol-induced autophagy.¹¹⁷ Besides, Liu et al developed a curcumin analogue-based nanoscavenger (NanoCA) using a reprecipitated self-assembly process. This nanomaterial stimulates nuclear translocation of the transcription factor EB (TFEB), a key autophagy regulator, thereby triggering autophagy and calcium-dependent exosome secretion to clear α-syn. NanoCA protects neurons from MPP-induced neurotoxicity. Meanwhile, they designed a rapid-arousaling intranasal delivery system (RA-IDDS) for brain-targeted delivery, which provided potent neuroprotection and promoted clearance of α-syn within the midbrain in MPTP-induced PD mouse models.¹²¹ This strategy highlights the advantage of targeting upstream regulatory nodes such as TFEB to achieve broader activation of the autophagy–lysosome pathway; however, systemic modulation of such central regulators may also raise concerns regarding off-target effects and pathway overactivation.

In addition to natural medicinal compounds, existing drugs have been found to enhance autophagy. For instance, bionic microglial NPs carrying metformin could promote autophagy while reducing oxidative stress and neuroinflammation, which repaired dopaminergic neurons, cleared αSyn aggregates and improved motor function in PD mouse. Enhancing brain targeting of existing drugs like metformin through nanotechnology represents a promising direction for future nanomedicine design. Furthermore, repurposing this category of established drugs can help reduce research and development costs.

Furthermore, autophagy program could be initiated by leveraging the tunable physicochemical properties of nanoparticles and specific stimulus channels on the cell membrane surface. Transient Receptor Potential Vanilloid 1 (TRPV1), as a stimulus-responsive protein on the cell surface, can effectively sense thermal stimuli and regulate the flow of Ca²⁺, thereby activating neurons and precisely regulating neuronal activities. For example, Yuan et al designed photothermal Cu2- (x) Se-based nanoparticles targeting TRPV1 on microglia surfaces (CS-AT NPs). Under NIR-II laser irradiation, these NPs activate surface TRPV1 channels, inducing Ca²⁺ influx and activating ATG5 and Ca²⁺/CaMKK2/AMPK/mTOR signaling pathways to promote αSyn phagocytosis and degradation, significantly improved motor function in treated PD mice.¹²⁰ Similarly, Wu, J. et al described a photothermal wireless DBS nanosystem (ATB NPs) composed of a gold nanocapsule shell conjugated with an anti-TRPV1 antibody. Under pulsed NIR irradiation, ATB NPs initiate autophagy to efficiently eliminate αSyn filaments in neurons. ¹¹⁹ These NIR-driven systems represent a sophisticated convergence of nanotechnology and neuromodulation. However, compared to chemically-driven autophagy enhancers like trehalose nanogels, they are technically more complex, require external hardware for clinical use, and their long-term safety profile within deep brain tissue is unexplored. The choice between a systemic, chemically-defined nanogel that passively enhances autophagy and an implant-free, externally-controlled photothermal system represents a fundamental design trade-off between clinical ease-of-use and spatiotemporal precision that the field has yet to formally evaluate.

Targeting Endoplasmic Reticulum

ER in the Pathophysiology of PD

The endoplasmic reticulum (ER) is a multifunctional organelle primarily responsible for protein folding and post-translational modifications, biosynthesis of carbohydrates and lipids, signal transduction, and calcium homeostasis through storage and dynamic mobilization. It maintains close functional connections with other organelles such as mitochondria and lysosomes via mechanisms like Ca²⁺ signaling, playing a central role in sustaining cellular homeostasis.¹²³ Protein quality control and cellular homeostasis depend on ER involvement. Genetic mutations, aging, oxidative stress, disrupted protein homeostasis, and other stimuli can induce protein misfolding and aggregation, leading to ER stress. To resolve ER stress, eukaryotic cells adapt by reducing protein synthesis rates, upregulating genes encoding chaperones and other proteins that prevent peptide aggregation, and degrading accumulated misfolded proteins—a process termed the “unfolded protein response” (UPR).¹²⁴ The ER possesses three stress sensors: (1) inositol-requiring enzyme 1 (IRE1); (2) polyribose-6-phosphate-6-phosphate-dehydrogenase-2-like ER kinase (PERK); (3) Activated Transcription Factor 6 (ATF6). Each UPR sensor remains inactive or quiescent by binding to the ER chaperone BiP/grp78. They promptly relay information about ER disturbances to the cytoplasm and nucleus, thereby initiating subsequent adaptive responses.¹²⁵ However, prolonged ER stress induces neuronal death, axonal degeneration, neuroinflammation, and synaptic dysfunction, leading to NDDs including Alzheimer’s disease (AD), PD, amyotrophic lateral sclerosis, viral diseases, and other disorders characterized by misfolded protein accumulation and aggregation.¹²⁴

Past studies have confirmed the close association between PD pathology and activated ER stress. Thep-PERK and p-eIF2α, which served as markers of ER stress, have been detected in dopaminergic neurons within the SN of PD patients.¹²⁶ MPTP can induce UPR by disrupting ER Ca²⁺ homeostasis through inhibiting calcium entry.¹²⁷ Ablation of downstream ER stress signaling molecules protects dopaminergic neurons from 6-OHDA induced damage. Furthermore, common PD genetic factors, including Parkin and LRRK2, have also been involved in ER stress processes. For instance, under ER stress conditions, ATF4 binds to the Parkin promoter, leading to increased Parkin expression.¹²⁸ Parkin has been shown to prevent UPR-induced cell death mediated by GPR37.¹²⁹ The knockdown of LRRK2 can promote 6-OHDA or αSyn induced neuron death by eliminating the upregulation of BiP/grp78.¹³⁰ These findings demonstrate the critical role of ER stress in promoting PD pathology. Additionally, extensive studies demonstrate that αSyn aggregates can activate the UPR signaling pathway, while inhibiting ER-Golgi vesicular transport accelerate overexpression of αSyn.^131,132

Recently, the interaction and communication between mitochondria and ER have garnered significant attention.¹³³ Mitochondria-associated ER membrane (MAM) maintains the structural and functional balance of the ER and mitochondria. Many important biological processes, such as calcium exchange, phospholipid exchange, mitochondrial fusion and fission, mitochondrial phagocytosis, oxidative stress and bioenergy production are precisely regulated by MAM. In the MPTP-induced PD mouse model, the morphological changes of MAM were blocked and its biological performance was disordered.¹³⁴ Therapeutic strategies aimed at preserving MAM integrity hold promise for mitigating the pathological progression of PD.

ER-Targeting Nano-Delivery Strategies

Current ER-targeting drug delivery strategies primarily include lipid nanoparticles, small-molecule ligands, and ER-targeting sequence peptides. Identifying ER targets remains challenging due to the organelle’s complex spatial architecture and vast folding surface area. When designing ER-targeting strategies, identifying, constructing, and modifying structural sequences with selective affinity for the ER is crucial. In recent years, numerous compounds and small molecules targeting the UPR through diverse molecular mechanisms have been identified and tested. Attaching these to nanoparticles can promote their efficient accumulation within the ER, thereby enhancing drug delivery efficiency.¹³⁵

Lipid nanoparticles possess inherent advantages for ER targeting due to their lipophilic nature, enabling fusion with the ER’s lipid membrane.¹³⁶ Additionally, nanoparticle shape influences accumulation efficiency within the ER; for instance, rod-shaped nanorods exhibit higher concentration levels compared to spherical nanoparticles.¹³⁷ However, unmodified liposomes exhibit poor specificity for ER targeting and typically require chemical group modifications.

Common small-molecule ligands for ER targeting include sulfonyl ligands, chloride ligands, and zwitterionic ligands, which achieve ER targeting by interacting with ATP-sensitive potassium channels, chloride channels, and positively charged phosphatidylcholine cytidine transferase (CCT) on the ER membrane surface, respectively.¹²³ For example, studies have demonstrated that p-toluenesulfonyl-modified lipid nanoparticles (17AAG-ER-NP) can deliver drugs to disrupt ER function and inhibit tumor growth.¹³⁸ Additionally, literature reports an ER-targeting probe (ER-Naph) bearing a sulfonylurea moiety that specifically detects glutathione (GSH) levels within the ER.¹³⁹

ER-targeting peptides encompass both naturally occurring peptides and synthetic amino acid sequences. KDEL is a C-terminal signal peptide present in ER molecular chaperones, recognized by KDEL receptors on the ER membrane to facilitate chaperone retention within the ER. Additionally, during vesicular transport, KDEL mediates the retrograde transport of soluble proteins that escape from the Golgi apparatus back to the ER.¹⁴⁰ To minimize endogenous biological activity, ER-targeted proteins and peptides are modified through truncation of sub-sequences, introduction of amino acid spacers, and residue substitutions, yielding novel ER localization signals such as the pardaxin (Par) sequence. Liu et al efficiently delivered antigens to the ER of dendritic cells by synthesizing ER-targeted vesicles containing the Par sequence and conjugating them to magnetic mesoporous silica particles, thereby promoting antigen presentation and enhancing immune responses.¹⁴¹ Similarly, Li et al designed a nanoparticle system modified with pardaxin peptides that induces ER stress via photodynamic/photothermal therapy, triggering immunogenic cell death and demonstrating enhanced antitumor efficacy.¹⁴² Furthermore, self-assembling nanoparticles such as enzyme-guided self-assembled (EISA) branched peptides and multifunctional peptide assemblies exert their effects by targeting enzymes or functional proteins on the ER surface.¹⁴³

In recent years, ER-targeting strategies have demonstrated certain advantages and achieved some progress. However, how to effectively target the ER in non-cancerous contexts without compromising its structure or inducing ER stress remains an urgent challenge. This is further complicated by the intricate intracellular microenvironment, given that the ER is a structure extensively interconnected with multiple organelles and signaling pathways.

ER-Targeting Nano-Therapy Strategies

Recent studies indicate that nanoparticle-mediated delivery of small-molecule drugs to ameliorate ER stress in neurons represents a promising neuroprotective strategy. For example, Posadas et al demonstrated that engineered neutral phosphorous dendrimers reduced ER stress and UPR by modulating NMDA receptor-mediated Ca²⁺ influx. This intervention significantly attenuated excitotoxicity in primary cortical neurons, an effect that was also replicated in human brain organoid models.¹⁴⁴ Mitchell et al employed a novel class of nanomaterials—transition metal dichalcogenide (TMD) nanoflowers (NFs)—and demonstrated that MoS₂ and MoSe₂ NFs suppress the α-Syn-induced UPR while promoting autophagic and exocytic clearance of αSyn. In Caenorhabditis elegans models treated with NFs, the burden of αSyn aggregates was significantly reduced, accompanied by a marked extension of lifespan.¹⁴⁵ Similarly, studies have shown that nanocapsules carrying DA and catalase (CAT) effectively reduced neuroinflammation by down-regulating the expression of αSyn and ATF6 and alleviating ER stress.¹⁴⁶ In addition, Chiang, M. C. et al showed, in an Alzheimer’s disease-related model (Aβ-treated human neural stem cells), that glutathione-conjugated gold nanoparticles (GSH-AuNPs) reversed ER stress gene expression and mitochondrial dysfunction. While this finding is not from a PD model, it provides indirect evidence that strategies ameliorating ER stress may be therapeutically relevant for PD and warrant further investigation in α-Syn-based systems.¹⁴⁷

Furthermore, as ER serves as a Ca²⁺ storage site and a hub for multiple signaling pathways, many nanomedicines take advantage of this to regulate cellular physiology. For example, under NIR-II laser irradiation, mPDA-SeMn-IR nanoparticles effectively activate endogenously expressed IP₃ receptors, inducing Ca²⁺ efflux from the ER. The enhanced Ca²⁺ signaling upregulates tyrosine hydroxylase (TH) expression and activity, triggering dopamine release and thereby enhancing dopaminergic function.¹⁴⁸ Interestingly, Li et al engineered a “nanomassage” system based on PEGylated black phosphorus nanosheets (PEG-BPNS) with a lateral size of ~200 nm which can be administrated intranasally. By adhering to the cell membrane, it exerts external mechanical force on cells, promoting interactions among actin, mitochondria, and ER, thereby effectively enhancing cellular function. The nanosheets significantly improved motor performance in MPTP-induced PD mouse models.¹⁴⁹ Notably, these nanodelivered therapeutics not only alleviate ER stress but also mitigate related pathological processes—including mitochondrial oxidative stress, impaired autophagy, and neuroinflammation, offers new insights for advancing nanomedicine in NDDs.

Although the nanomedicines targeting ER are limited, many existing drugs have been proven to have ER protection potential. They exert protective effects by alleviating ER stress or reducing misfolded proteins, such as small-molecule modulators,¹⁵⁰ kinase inhibitors,¹⁵¹ miRNA,¹⁵² anti-prion drugs,¹⁵³ antioxidants,¹⁵⁴ natural compounds,^155–158 and chemical chaperones.¹⁵⁴ These drugs may potentially enhance their efficacy through integration with nanotechnology. Interestingly, moderate ER stress may favor cellular adaptation to exogenous stimuli and improve protein homeostasis. Some reports suggest that activating UPR transcription factors may improve pathological states in PD. In human and cellular studies, UPR-activating agents increased expression of UPR target genes in dopaminergic neurons and reduced neuronal death under MPTP-treated conditions.¹⁵⁹ Therefore, how to effectively regulate the degree of ER modulation remains a question worth exploring.

Targeting Golgi Apparatus

GA in the Pathophysiology of PD

The Golgi apparatus (GA) is a vital organelle in eukaryotic cells. It plays a crucial role in the modification of proteins and lipids, the sorting and transport of cellular membranes, and the synthesis and repair of cell membranes. These functions ensure the proper functioning and localization of intracellular substances, thereby maintaining normal cellular physiological functions.¹⁶⁰ Furthermore, it serves as an intracellular signaling platform and stress sensor, actively participating in regulating cell polarization, stress responses, directed migration, mitosis, metabolism, autophagy, apoptosis, DNA repair, inflammatory responses, and other cellular processes.¹⁶¹

Under normal conditions, the GA may experience transient and mild stress induced by oxidative stress, energy deficiency, or intracellular temperature fluctuations. To maintain cellular homeostasis, the GA primarily adjusts its structure and function by altering its volume, vesicle number, and protein modifications.¹⁶⁰ When protein loads exceed the GA’s transport and modification capacity, ROS levels or glutathione (GSH) levels within the GA lumen rapidly increase or decrease, disrupting redox balance. This phenomenon, characterized by impaired GA function and disrupted redox balance, is termed GA stress.¹⁶² However, when subjected to sustained and irreparable pressure, GA stress may lead to structural fragmentation and abnormal protein accumulation by reducing protein synthesis and modification efficiency, impairing protein quality control, obstructing vesicular transport, and disrupting intracellular calcium homeostasis.¹⁶⁰ As a pivotal signaling hub, GA stress engages multiple signaling pathways and physiological processes, including innate immune signaling, lysosomal autophagy, and cellular metabolism. Dysregulation of these intricate networks can subsequently trigger cell death and contribute to the onset and progression of diseases such as NDDs, autoimmune diseases, and cancer.^163–167

Research indicates that GA fragmentation represents an early pathological event in PD. Literature suggests this fragmentation precedes neuronal cell death, disrupting intracellular protein synthesis and impairing axonal, dendritic, and synaptic transport.¹⁶⁸ Early autopsy analyses of PD samples reveal highly fragmented GA in SN neurons.¹⁶⁹ Some scholars propose that GA stress serves as the initial trigger for αSyn aggregation, Lewy body formation, and microtubule alterations. Changes in transport regulatory proteins and SNARE proteins may represent early disruptions in membrane transport within secretory pathways, leading to GA fragmentation.^5,170 Additionally, multiple PD-associated genetic factors influence GA function. LRRK2 plays a crucial role in intracellular vesicular transport by phosphorylating Rab small GTPases. LRRK2 mutants disrupt GA integrity and vesicle transport. Furthermore, LRRK2 inactivation also leads to GA fragmentation via endocytosis and autophagy.¹⁷¹ Another PD-associated gene is PLA2G6. In fibroblasts from patients carrying this mutation, altered N- and O-linked glycosylation patterns occur, along with impaired ERGIC (ER-GA Intermediate Compartment) and GA function, potentially contributing to neurodegeneration.¹⁷² Animal models of PD demonstrate that αSyn can block membrane transport from the ER to the GA, leading to degeneration and loss of dopaminergic neurons.¹²⁵ Collectively, these findings support GA stress as a critical component in the pathophysiology of PD.

GA-Targeting Nano-Delivery Strategies

To achieve effective targeting of the GA, researchers have identified and engineered a series of ligands and signaling peptides. Ligands accomplish active targeting by binding to receptors or enzymes on GA membranes or within its compartments, while peptide signals enable insertion, fusion, or localization within GA membranes and compartments to facilitate targeted cargo delivery.

Common small-molecule ligands targeting GA include chondroitin sulfate (CS), thioesters, and cysteine.^173–175 CS is a typical sulfated glycosaminoglycan exhibiting excellent biocompatibility, biodegradability, non-immunogenicity, and low toxicity. In cancer, hydrophilic CS can self-assemble with hydrophobic drugs to target GA in liver cancer cells which overexpressing CD44. CS nanomicelles also demonstrate high affinity and effectively target GA in hepatic stellate cells.^176,177 Nanopolymers modified with cell-penetrating peptides and CS have been demonstrated to effectively evade the endosomal degradation pathway while inhibiting ER/GA-mediated exocytosis, thereby enhancing the intracellular retention efficiency of loaded drugs.¹⁷⁸ Research has revealed that peptide thioesters serve as substrates for GA-associated thioesterases. The resulting thiopeptides subsequently form dimers and accumulate within the GA. These peptide thioesters can enter cells via caveolae-mediated endocytosis and specifically accumulate in the GA, regardless of whether they are above or below the critical micelle concentration.¹⁷⁴ Carbon quantum dots and silicon nanoparticles functionalized with L-cysteine residues have also been employed for targeting GA to achieve targeted imaging.¹⁷⁹ These molecules, when conjugated to nanoparticles, demonstrate promising potential for targeted drug delivery to the GA.

On the other hand, identifying signal sequences capable of efficient GA localization provides favorable conditions for GA-targeted nano-delivery. Analysis of certain cytoplasmic domains of glycoproteins present in GA transport network revealed a series of GA-localizing sequences. For example, Alexandra P et al identified a 37-amino acid alternative open reading frame (altORF) within the mRNA of the centromere protein CENP-R. The peptide specifically localizes to the GA surface.¹⁸⁰ Cheng, G. et al discovered a targeting domain within the matrix protein GM130 that localizes to the GA.¹⁸¹ Besides, SXYQRL and RS1-reg peptides promote GA localization by initiating retrograde transport from endosomes to the GA. They have been effectively utilized to selectively deliver therapeutics to target sites within the GA network.^177,182 Concurrently, Li et al designed transformable peptide C₆RVRRF₄KY that can self-assemble into nanoparticles and convert into destructive fibers only under the action of enzymes specifically expressed in the GA of cancer cells, and which incorporate cysteine residues, enhancing GA targeting.¹⁸³ Furthermore, caveolin-mediated endocytosis is linked to cargo transport within the GA. When drugs and their delivery systems utilize vesicular structures, they can bypass lysosomes to reach ER/GA. This allows them to avoid significant loss due to degradation in lysosomes and enables specific targeting of the ER/GA to achieve their therapeutic mechanisms.¹⁶² Since the ER and GA are closely linked cellular structures along the protein synthesis and secretion pathway, transport between them typically lacks specificity. Therefore, when designing ER- or GA-targeted systems, the system should exploit differences between the ER and GA to exert drug efficacy immediately upon reaching the target organelle.

GA-Targeting Nano-Therapy Strategies

Although the role of the GA in regulating cellular homeostasis cannot be overlooked, the exploratory application of improving GA function in PD and even other neurodegenerative diseases remains considerably limited. This scarcity may stem from the unclear mechanisms of the GA in neurological disorders, coupled with the lack of understanding regarding how to leverage the GA for neuroprotective effects. Therefore, we primarily discuss several proof-of-concept studies that are still in the exploratory stage, with the aim of providing a theoretical basis for subsequent targeted nanotherapies. In PD, modulating disease-related genes such as LRRK2, PLA2G6, and VPS35 can indirectly alleviate GA stress. The Rab GTPases family, acting as LRRK2 substrates, plays a role in vesicle transport within the GA. Inhibiting LRRK2 mutations alleviates GA stress by promoting Rab29-mediated recruitment of LRRK2 to the GA, subsequently phosphorylating Rab8A to maintain normal vesicular transport.¹⁸⁴ Similarly, suppressing PLA2G6 mutations reduces GA stress, rescues abnormal glycosylation, and mitigates protein aggregation.¹⁷² Furthermore, VPS35 mutations are associated with hereditary PD and indirectly linked to GA stress. Inhibiting VPS35 mutations promotes cathepsin transport, reduces α-syn accumulation, and ensures post-transport functions of the GA.¹⁸⁵ Additionally, GA-associated proteins such as STX5, Rab1A, and GRASP65 are also considered potential intervention targets.¹⁶⁰ These targets may potentially be precisely targeted through nanotechnology in the future.

However, it must be stressed that the application of GA-targeting NPs in NDDs, and particularly in PD, remains almost entirely unexplored territory. The strategies discussed above, such as CS-based prodrug NPs for cancer or Golgi disruption for immunotherapy, are currently at the proof-of-concept stage in oncology.¹⁸⁶ Their translation to a neuroprotective context in PD is highly speculative and requires a fundamental shift from cytotoxic Golgi disruption to restoring Golgi structural integrity and function. A critical future step is thus to elucidate how to therapeutically promote Golgi recovery in PD models, rather than simply adapting destructive cancer-targeting strategies.

Targeting the Nucleus

Nucleus in the Pathophysiology of PD

The nucleus serves as the primary repository for genetic material DNA. By precisely regulating processes such as DNA replication, transcription, and RNA processing, it directly determines cellular fate and function, acting as the principal organelle governing reproduction, growth, metabolism, and the cell cycle.^187–189 The nucleus maintains its integrity through structures such as the nuclear envelope, nuclear pore complexes (NPCs), and nuclear cytoskeleton.¹⁹⁰ Recent discoveries indicate that nucleophagy selectively removes nuclear components to maintain genomic stability, while abnormalities in nuclear morphology or structure significantly impair cellular activities.¹⁹¹ The nucleus also serves as a hub for inter-organelle communication, coordinating organelle functions and responses to developmental or environmental stimuli through retrograde signaling pathways. NPC-mediated nuclear-cytoplasmic transport is critical for maintaining neuronal function.¹⁹²

Dysfunction of the NPCs is a common feature in NDDs, including ALS, AD, and PD.^193–195 The NPC governs macromolecular exchange between the nucleus and cytoplasm; its disruption leads to abnormal cytoplasmic accumulation and nuclear depletion of RNA-binding proteins like TDP-43 and FUS, as well as transcription factors.¹⁹⁶ In PD, abnormal nuclear localization of multiple transcription factors has been observed. For instance, both total and phosphorylated cyclic AMP response element-binding protein (CREB) and phosphorylated extracellular signal-regulated kinase (ERK) accumulate in the cytoplasm of dopamine neurons exposed to 6-OHDA and in neurons from PD patients.¹⁹⁵ Furthermore, abnormal αSyn blocks NCT-mediated transport of macromolecules in the nucleus by interacting with Ran GTPase.¹⁹⁷

Numerous studies indicate that PD-associated gene mutations disrupt NE architecture, while abnormal processing of the nuclear lamin network destabilizes the nuclear skeleton and accelerates neuronal aging. Triple mutations at the A53T and SNCA loci exacerbate nuclear senescence and compromise NE integrity in stem cell-derived DA neurons. LRRK2 gene mutations accelerate genomic instability by impairing nuclear structural integrity.^197,198

Oxidative stressors increase nuclear translocation of αSyn in DA neurons both in vitro and in vivo.¹⁹⁹ Nuclearly localized αSyn promotes neurotoxicity by altering transcription, histone modifications, and inducing DNA damage.^200,201 It also exacerbates mitochondrial dysfunction and disrupts nuclear-mitochondrial communication through transcriptional regulation of the mitochondrial regulator PGC1-α.²⁰² Currently, multiple epigenetic abnormalities—such as dysregulated histone methylation, promoter methylation of PARK2 and SNCA genes, and DNA methyltransferase (DNMT1) deficiency.²⁰³ Furthermore, specific defects in DNA repair can affect the dopaminergic system and are related to the pathology of human PD.²⁰⁴ The above evidence indicates that nuclear dysfunction plays an important role in the occurrence and development of the disease.

Collectively, disturbances in the nucleus of dopaminergic neurons correlate with PD-associated neurodegeneration. These disturbances involve structural damage to the nuclear envelope and mislocalization of key transcription factors, with oxidative stress, αSyn, and pathogenic mutations potentially exacerbating nuclear injury.

Nucleus-Targeting Nano-Delivery Strategies

The nuclear envelope possesses a double-layered structure that provides highly protective and selective containment for nuclear genetic material. This protective architecture presents a major barrier to nucleolar targeting. After entering cells, nanoparticles must overcome multiple barriers before reaching the nucleus, including capture by endosomes and lysosomes, complex transport pathways within the cytoplasmic sol, and the highly selective nuclear membrane.^205,206 These obstacles significantly limit the therapeutic efficacy of drugs targeting nuclear components. Therefore, designing and preparing nanomaterials capable of entering the nucleus is crucial for enhancing the effectiveness of these therapies.

For nuclear targeting, nanoparticle size is a primary consideration. Studies indicate small particles can enter the nucleus, while larger particles remain confined to the cytoplasm.²⁰⁷ However, excessively small nanoparticles compromise drug loading, necessitating additional targeting modifications. During transport from the cytoplasm to the nucleus, cargo undergoes a precise recognition and transport process where nuclear import proteins play a vital role. Nuclear localization signals (NLS) are recognized by import proteins, allowing NLS-tagged cargo to form complexes with these proteins and enter the nucleus via NPC.²⁰⁸ Consequently, conjugating NLS to various functionalized nanoparticles has proven effective for targeting the nucleus, demonstrating significant value across multiple biomedical fields including drug delivery, gene therapy, and diagnostic imaging.²⁰⁹ The TAT peptide, an 11-amino acid sequence from the HIV-1 transcription activator protein, is one of the most commonly used and versatile NLS peptides for guiding nanoparticles to the nucleus. This peptide has been employed to couple with various types of nanoparticles to achieve intracellular drug delivery.^210–212 Additionally, nuclear localization sequences from other sources—such as those derived from simian virus SV40, bipartite nucleoplasmin, and adenovirus—have been demonstrated to efficiently deliver nanoparticles of varying sizes to the nucleus.¹³ For instance, Li et al designed a nuclear-targeted siRNA delivery system by modifying gold nanoparticles with NLS peptides and siRNA. The NLS peptides translocate the nanoparticle carrier into the nucleus, enabling sustained gene silencing and effectively inhibiting cancer cell proliferation.²¹³ This diversity highlights the potential of NLS-modified nanoparticles as a powerful strategy for enhancing nuclear drug delivery.

Nucleus-Targeting Nano-Therapy Strategies

Nucleic acid-based therapeutics have been extensively studied for their ability to regulate functional protein expression. However, due to their simple structure, they are highly susceptible to peripheral degradation. Consequently, nanotechnology holds significant potential for enhancing the targeting efficiency and therapeutic efficacy of nucleic acids. siRNA can specifically silence disease-related genes through the RNA interference (RNAi) mechanism, offering an effective therapeutic strategy by interfering with αSyn expression. Nano-delivery effectively shield siRNA from serum enzyme degradation, prolonging its half-life in vivo. For example, Feja et al developed a nanoparticle-based intranasal siRNA delivery method. Tyrosine-modified polyethyleneimines (PEIs) or polypropyleneimine dendrimers (PPIs) were complexed with siRNA targeting the SNCA gene (siSNCA) and conjugated with liposomes. In Thy1-aSyn mice, the NPs exhibited extensive distribution throughout the brain, significantly reducing brain aSyn protein and SNCA mRNA levels while demonstrating favorable safety profiles.²¹⁴ Furthermore, certain systems enable co-delivery of siRNA with other therapeutic agents. Katamesh et al developed an intranasal albumin-coated liposome system for co-delivering the MAO-B inhibitor selegiline (SEL) and αSyn-targeted siRNA (C-LipSel-siSNCA2). In PD rats, C-LipSel-siSNCA2 mitigated dopamine degradation and αSyn aggregation, reduced MAO-B levels, and improved motor and non-motor functions.²¹⁵ Although siRNA has shown promising results in animal studies, its clinical advancement has been slow, with no nucleic acid therapeutics yet entering clinical trials for PD treatment.

Plasmid DNA (pDNA) can serve as a vector to introduce target genes into the cell nucleus, enabling replication and expression independent of the host chromosome. It is commonly used for overexpressing endogenous genes or correcting non-functional genes to treat genetic disorders.²¹⁶ In the context of PD, pDNA-based nanodelivery offers a direct approach to restoring deficient pathways; however, its therapeutic potential is closely tied to efficient nuclear delivery and sustained transgene expression, which remain key technical challenges. Recent studies have demonstrated localized GBA1 gene therapy using pDNA-loaded nanoparticles. For example, PEGylated poly(β-amino ester) nanoparticles (PEG-PBAE NPs) were designed to reduce adhesion to the brain extracellular matrix and improve physiological stability. When administered via convection-enhanced delivery, these particles achieved broad distribution within the brain. In a α-Syn preformed fibril (PFF)-induced PD mouse model, they enhanced human GBA1 transgene expression in the SN, reduced α-Syn aggregation, preserved dopaminergic neurons, and alleviated neuroinflammation.²¹⁷ This approach highlights the advantage of combining optimized carrier design with physical delivery strategies to overcome tissue-level barriers, although its clinical applicability may be limited by the invasiveness and complexity of administration. In addition to carrier design, delivery strategies play a critical role in improving therapeutic outcomes. Combining focused ultrasound (FUS) with intranasal administration has been shown to enhance nanoparticle penetration into deep brain regions. Aly et al used this approach to facilitate microglial transfection and increase plasmid nanoparticle delivery to brain parenchyma, resulting in sustained expression of the neurotrophic factor GDNF in PD-affected regions.²¹⁸

Beyond pDNA-based systems, other nucleic acid therapeutics are also being explored. For instance, delivering mRNA encoding immunoregulatory factors via LNPs can activate immune tolerance pathways, thereby achieving indirect neuroprotection in the CNS. Studies indicate that LNPs carrying granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA induce peripheral Treg expansion in PD animal models, reducing reactive microgliosis and thereby protecting dopaminergic neurons in the SN and striatum.²¹⁹

Additionally, gene editing technologies such as CRISPR/Cas9 may offer the potential to fundamentally correct defective genes at the genetic level. However, the underlying genetic mechanisms of PD remain poorly understood, and significant challenges persist regarding precision, off-target effects, and the long-term implications of genetic modification. While precise nanodelivery systems could potentially mitigate some of these issues, rigorous ethical review and extensive preliminary trials remain essential prerequisites for their application.

Overall, nucleic acid–based nanotherapeutics provide a versatile platform for targeting multiple pathogenic mechanisms in PD, including gene deficiency, protein aggregation, and neuroinflammation. However, achieving efficient and cell-specific nuclear delivery, maintaining controlled gene expression, and balancing efficacy with safety remain critical challenges for clinical translation.

Conclusions and Perspective

Parkinson’s disease remains a formidable therapeutic challenge, as current treatments primarily provide symptomatic relief without halting the underlying neurodegenerative process. This review systematically evaluates the potential of organelle-targeted nanotherapeutics—directed toward mitochondria, lysosomes, the endoplasmic reticulum, the Golgi apparatus, and the nucleus—to intervene at the core of PD pathogenesis by restoring subcellular homeostasis. The convergence of nanotechnology and organelle biology represents a promising paradigm for precision medicine in PD. However, a critical and balanced appraisal of the field reveals a markedly uneven landscape of translational maturity, which must be explicitly recognized to more effectively inform and guide future research efforts.

Cumulatively, current preclinical and clinical evidence demonstrates that mitochondria-targeted therapeutic strategies stand out as the most well-established class for PD intervention. Among these, mitochondria-targeted antioxidants and nanozymes have been thoroughly validated and extensively characterized in a wide range of animal disease models, with the lead candidate CNM-Au8 already advancing to Phase II clinical investigation. By comparison, lysosome- and nucleus-targeted therapeutic approaches, while holding considerable therapeutic potential, remain largely limited to preclinical research and face substantial technical challenges and high regulatory barriers to subsequent clinical translation. In sharp contrast, strategies targeting the ER and Golgi apparatus remain far less mature in the PD research field; most available supporting evidence is merely indirect, extrapolated from non-PD models rather than dedicated PD experimental systems. Such marked disparities in research maturity, preclinical validity, and translational progress across subcellular-targeted modalities underscore the urgent need for well-designed, direct head-to-head comparative studies under unified, standardized experimental conditions.

Nanomedicines have introduced a paradigm shift in the biomedical field. However, fundamental barriers that impede or delay their clinical translation remain, including delivery efficiency, safety, reproducibility, storage stability, and scalable manufacturing prior to clinical application.²²⁰ These challenges have been extensively discussed in previous studies, therefore, here we focus specifically on the outstanding issues that remain to be addressed for organelle-targeted nanotherapeutics in PD. First, the disease model gap remains a major limitation. A large proportion of current studies rely on simplified in vitro systems that primarily capture cellular phenotypes, such as oxidative stress or α-synuclein aggregation, without accounting for key physiological barriers, including BBB, systemic circulation, and nanoparticle clearance mechanisms. As a result, these models may overestimate intracellular delivery efficiency and therapeutic efficacy. The widespread use of acute toxin-based models (MPTP, 6-OHDA, rotenone) provides proof-of-concept but does not reflect the chronic and progressive nature of human PD or the interaction between aging, genetic susceptibility, and environmental factors. Validation in non-human primate models with higher construct validity is essential for assessing disease-modifying effects, including α-Syn PFF models and genetic models (eg, LRRK2, GBA1). Second, there is a clear lack of rigorous subcellular targeting validation. Many studies infer organelle specificity based on ligand design (eg, TPP, NLS), but direct in vivo evidence in relevant brain cell types remains limited. Future studies should adopt quantitative and standardized methods, such as transmission electron microscopy with immunogold labeling,²²¹ subcellular fractionation combined with mass spectrometry,²²² and super-resolution imaging in tissue sections,²²³ to allow more reliable and comparable evaluation. Third, a significant gap in long-term safety data persists. While acute toxicity is increasingly reported, chronic exposure studies remain scarce. Key issues include immunogenicity, unintended interference with organelle function, nanoparticle accumulation and clearance, and material-specific risks.²²⁴ Given the need for long-term treatment in PD, systematic evaluation under repeated dosing conditions is critical. Fourth, manufacturing and quality control challenges remain underaddressed.²²⁰ The batch-to-batch reproducibility directly impact biodistribution and efficacy, and parameters such as particle size, surface charge, ligand density, and drug loading require tight control.²²⁵

In summary, organelle-targeted nanotherapeutics represent a promising but still developing strategy for PD treatment. The gap between preclinical findings and clinical application remains substantial. Progress will depend less on expanding the range of nanoplatforms and more on addressing key translational challenges, including model relevance, targeting validation, long-term safety, and manufacturing standardization. Establishing clear and comparable benchmarks will be essential for advancing the most robust candidates toward clinical testing.

Although integration into a precision medicine framework remains a long-term goal, achieving this will first require systematic resolution of the translational challenges outlined above.