In vitro and in vivo studies on ocular vitamin A palmitate cationic liposomal in situ gels.

N-trimethyl chitosan (TMC) with different degree of quaternization (DQ) as the coating materials, vitamin A palmitate (VAP)-loaded cationic liposomes dispersed in thermo-sensitive in situ gels (ISG) with poloxamer 407 (P407) as the base were prepared in this study. VAP-loaded liposomes (VAPL) were prepared using a film dispersion method followed by TMC-coating with DQ of 20%, 40% and 60% (TMC20, TMC40 and TMC60), respectively, then dispersed in P407 solution to obtain TMC-coated VAPL ISG. The in vitro properties of the system including morphology, size, zeta potential, entrapment efficiency, drug release and ocular retention were investigated.