Development of Stable Polymerized Vinyl Pyrrolidone–Cholesteryl Methacrylate Liposomes as Carriers for Drug Delivery

Abstract

This paper describes the preparation and characterization of stable polymerized liposomes for anticancer drug delivery. Two monomers, vinyl pyrrolidone (VP) and cholesteryl methacrylate (ChMA) were used in the development of polymerized liposomes. Liposomes containing VP and ChMA monomers were prepared by a sonication method and subsequently polymerized using an ammonium persulfate/sodium metabisulphite redox initiators. VP monomeric liposome was prepared for comparison studies. Both monomeric and polymerized liposomes were characterized by FT-IR, FT-NMR, transmission electron microscopy and turbidity measurement. The IR and NMR results clearly established that the VP and ChMA monomers in the liposomes had polymerized. Transmission electron micrograph showed the spherical shape of both monomeric and polymerized liposomes. The average sizes of the VP and VP-ChMA monomeric liposomes are 350 nm and 360 nm respectively and the average sizes of the polymerized VP and VP-ChMA liposomes are 360 nm and 380 nm respectively. The turbidity measurement suggested that the polymerized VP-ChMA liposome is more stable than the polymerized VP liposomes and the monomeric liposomes. An anticancer drug, vincristine sulfate, was chosen for incorporation in both the monomeric and polymerized liposomes. Triton X-100 was used to completely rupture the bilayers to determine the percentage encapsulation of VCR in the monomeric and the polymerized liposomes. In vitro release of the encapsulated VCR from the monomeric and polymerized liposomes were carried out in phosphate buffered saline, pH 7.4, and in 1% v/v human plasma at 37 °C. In both media, the polymerized VP-ChMA liposomes sustained the release of VCR for longer duration than the polymerized VP and monomeric liposomes. These experiments demonstrate that the polymerized VP-ChMA liposomes could be a potential carrier for the delivery of anticancer drugs.