Preparation and assembly of poly(arginine)-coated liposomes to create a free-standing bioscaffold

We created a free-standing membrane as a novel bioscaffold through the assembly of polymer-coated liposomes. Polyarginine (P_Arg) possessing a cell-penetrating activity was used to form the polymer layer onto a negatively charged liposome (lipo-P_Arg). The capsule wall of P_Arg over liposomes made it possible to improve the mechanical property of capsules and to display deoxyribonucleic acid (DNA) over the vesicle surface through the electrostatic attraction (lipo-P_Arg-DNA). The release rates of a fluorescent probe encapsulated in lipo-P_Arg and lipo-P _Arg-DNA were tunable by the number of polymeric layers of the capsule walls. To investigate the cell-membrane permeability of lipo-P _Arg-DNA, polymer-coated liposomes were incubated with human umbilical vein endothelial cells (HUVECs) at 4 °C. It was found that lipo-P _Arg underwent a significant cellular uptake, whereas bare liposomes and liposomes modified with chitosan were incapable of overcoming the plasma membrane barrier. To prepare a free-standing membrane composed of polymer-coated liposomes, a suspension of lipo-P_Arg-DNA was cast over a mesh hole and dried up. SEM observation revealed that a free-standing membrane was obtained through drying-mediated assembly process without rupturing polymer-coated liposomes inside the membrane. On the other hand, it was not possible to obtain a complete membrane from a mixture of lipo-P_Arg and DNA. In summary, lipo-P_Arg-DNA capsules possess versatile functions as a drug carrier, and their assembly enables us to create a free-standing membrane applicable as a bioscaffold.