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.