Chitosan-based thermosensitive hydrogel containing liposomes for sustained delivery of cytarabine

Sustained release thermosensitive solution containing cytarabine-loaded liposome delivery system offers the possibility of reduced dosing frequency and sustained drug action. Biodegradable and biocompatible chitosan-beta-glycerophosphate (C-GP) thermosensitive solution having the property to gel at body temperature and to maintain its physical integrity for longer period of time was used. The C-GP solution containing cytarabine-loaded liposomes (CGPCLL) was studied, and the results showed that the cytarabine liposomes were capable of high encapsulation efficiency (85.2 +/- 2.58%) with the mean diameter of 220 +/- 6.9 nm of extruded cytarabine-loaded liposome. Furthermore, transmission electron microscopy showed spherical-shaped liposomes after extrusion with smooth surface. In vitro studies of CGPCLL in PBS buffer showed that this system can sustain release of encapsulated drug for more than 60 h compared with drug-loaded liposomal suspension (upto 48 h). Pharmacokinetic studies of CGPCLL resulted in higher t(1/2) (28.86 h) and AUC 2526.88 mug/mL h compared with cytarabine-loaded liposomal suspension (CLLS) and C-GP containing free cytarabine (CGPFC) in rats. CGPCLL was capable of sustaining the cytarabine release for more than 60 h in vivo compared with CLLS and CGPFC which showed maximum amount of drug release within 42 and 10 h, respectively. Thus, these results showed that the CGPCLL gels at body temperature and can sustain the delivery of cytarabine effectively.