Development of mannosylated liposomes for bioadhesive oral drug delivery via M cells of Peyer's patches

The aim of this study was to develop mannosylated liposomes as bioadhesive carriers for oral drug delivery. Two kinds of acyclovir (ACV)-entrapped mannosylated liposomes, i.e. ManN-ACV-lip and PAM-ACV-lip, were prepared by the use of mannosamine HCl (ManN) and p-aminophenyl-alpha-D-mannopyranoside (PAM), respectively. The mean sizes, drug entrapment efficiency, and loading capacity values of all liposomal formulations were in the ranges of 233-371 nm, 82-95%, and 42-47%, respectively. The mean size of PAM-ACV-lip was significantly smaller than those of conventional ACV liposomes and ManN-ACV-lip due to the more conical packing parameter of mannose-conjugated phospholipid. The mannosylating group grafted into bilayer membrane resulted in a decrease in drug entrapment, owing to competitive binding. The in vitro drug absorptions through everted sacs of mice ileum of both mannosylated ACV liposomes were significantly higher than those of conventional ACV liposomes or suspension.