Synthesis and characterization of low-toxicity N-caprinoyl-N-trimethyl chitosan as self-assembled micelles carriers for osthole

Xiao-juan Hu,^1,* Yang Liu,^1,* Xiao-feng Zhou,^2,3 Qiao-ling Zhu,¹ Yong-yan Bei,¹ Ben-gang You,¹ Chun-ge Zhang,¹ Wei-liang Chen,¹ Zhou-li Wang,¹ Ai-jun Zhu,¹ Xue-nong Zhang,¹ Yu-jiang Fan<sup>4

1</sup>Department of Pharmaceutics, College of Pharmaceutical Sciences, Soochow University, Suzhou, People's Republic of China; ²College of Radiological Medicine and Protection, Soochow University, People's Republic of China; ³Changshu Hospital of Traditional Chinese Medicine, Changshu, People's Republic of China; ⁴Department of Clinical Laboratory, Second People's Hospital of Akesu, Akesu, People's Republic of China

^*These authors contributed equally to this work

Abstract: Novel amphiphilic chitosan derivatives (N-caprinoyl-N-trimethyl chitosan [CA-TMC]) were synthesized by grafting the hydrophobic moiety caprinoyl (CA) and hydrophilic moiety trimethyl chitosan to prepare carriers with good compatibility for poorly soluble drugs. Based on self-assembly, CA-TMC can form micelles with sizes ranging from 136 nm to 212 nm. The critical aggregation concentration increased from 0.6 mg · L^-1 to 88 mg · L^-1 with decrease in the degree of CA substitution. Osthole (OST) could be easily encapsulated into the CA-TMC micelles. The highest entrapment efficiency and drug loading of OST-loaded CA-TMC micelles(OST/CA-TMC) were 79.1% and 19.1%, respectively. The antitumor efficacy results show that OST/CA-TMC micelles have significant antitumor activity on Hela and MCF-7 cells, with a 50% of cell growth inhibition (IC50) of 35.8 and 46.7 µg · mL^-1, respectively. Cell apoptosis was the main effect on cell death of Hela and MCF-7 cells after OST administration. The blank micelles did not affect apoptosis or cell death of Hela and MCF-7 cells. The fluorescence imaging results indicated that OST/CA-TMC micelles could be easily uptaken by Hela and MCF-7 cells and could localize in the cell nuclei. These findings suggest that CA-TMC micelles are promising carriers for OST delivery in cancer therapy.

Keywords: N-trimethyl chitosan, micelle solubilization, antitumor activity