Intravesical delivery of rapamycin via folate-modified liposomes dispersed in thermo-reversible hydrogel
Received 20 May 2019
Accepted for publication 12 July 2019
Published 5 August 2019 Volume 2019:14 Pages 6249—6268
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Prof. Dr. Anderson Oliveira Lobo
Ho Yub Yoon,1,* In Ho Chang,2,* Yoon Tae Goo,1 Chang Hyun Kim,1 Tae Hoon Kang,1 Soo-Yeon Kim,3 Sang Jin Lee,3 Seh Hyon Song,4 Young Mi Whang,2 Young Wook Choi1
1College of Pharmacy, Chung-ang University, Seoul, Korea; 2College of Medicine, Chung-ang University, Seoul, Korea; 3Research Institute, National Cancer Center, Goyang, Korea; 4College of Pharmacy, Kyungsung University, Busan, Korea
*These authors contributed equally to this work
Purpose: To develop an intravesical instillation system for the treatment of bladder cancer, rapamycin (Rap) was encapsulated into liposomes and then homogeneously dispersed throughout a poloxamer 407 (P407)-based hydrogel.
Methods: Rap-loaded conventional liposomes (R-CL) and folate-modified liposomes (R-FL) were prepared using a film hydration method and pre-loading technique, and characterized by particle size, drug entrapment efficiency, and drug loading. The cellular uptake behavior in folate receptor-expressing bladder cancer cells was observed by flow cytometry and confocal laser scanning microscopy using a fluorescent probe. In vitro cytotoxic effects were evaluated using MTT assay, colony forming assay, and Western blot. For in vivo intravesical instillation, Rap-loaded liposomes were dispersed in P407-gel, generating R-CL/P407 and R-FL/P407. Gel-forming capacities and drug release were evaluated. Using the MBT2/Luc orthotopic bladder cancer mouse model, in vivo antitumor efficacy was evaluated according to regions of interest (ROI) measurement.
Results: R-CL and R-FL were successfully prepared, at approximately <160 nm, 42% entrapment efficiency, and 57 μg/mg drug loading. FL cellular uptake was enhanced over 2-fold than that of CL; folate receptor-mediated endocytosis was confirmed using a competitive assay with folic acid pretreatment. In vitro cytotoxic effects increased dose-dependently. Rap-loaded liposomes inhibited mTOR signaling and induced autophagy in urothelial carcinoma cells. With gelation time of <30 seconds and gel duration of >12 hrs, both R-CL/P407 and R-FL/P407 preparations transformed into gel immediately after instillation into the mouse bladder. Drug release from the liposomal gel was erosion controlled. In orthotopic bladder cancer mouse model, statistically significant differences in ROI values were found between R-CL/P407 and R-FL/P407 groups at day 11 (P=0.0273) and day 14 (P=0.0088), indicating the highest tumor growth inhibition by R-FL/P407.
Conclusion: Intravesical instillation of R-FL/P407 might represent a good candidate for bladder cancer treatment, owing to its enhanced retention and FR-targeting.
Keywords: bladder cancer, prolonged retention, enhanced uptake, antitumor efficacy, autophagy, mTOR signaling
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