Liposomes equipped with poly(N-isopropyl acryl amide)-containing coatings as potential drug carriers

Abstract

Polymer coated liposomes are promising drug delivery candidates. Herein, we report on the coating of liposomes with mixed films containing poly(dopamine) (PDA) and different types of poly(N-isopropyl acryl amide) (pNiPAAm). Their potential as drug carriers from solution in the presence of shear stress or in a substrate-mediated manner using macrophages is assessed. Although we found no difference in the cell mean fluorescence (CMF) when applying shear stress when employing fluorescently labeled liposomes, macrophages exposed to liposomes coated with a mixture of PDA and highly-branched pNiPAAm (L^D/HB) exhibited significantly higher CMF after 2.5 h compared to liposomes coated with only PDA (L^D) or with a mixture of PDA and aminated pNiPAAm (L^D/pNH₂). The coated liposomes did not affect the cell viability in the time frame tested, but the application of shear stress reduced the number of surface-adherent macrophages. L^D, L^D/pNH₂ or L^D/pHB could be immobilized to poly(L lysine) pre-coated silica substrates. All substrates were equally suited for macrophages to adhere. The CMF of the adhering macrophages was found to be independent of the coating of the surface-immobilized liposomes when using fluorescently labeled liposomes in the coatings. Taken together, we demonstrate that mixed PDA-based coatings can be used to affect the interaction of liposomes with macrophages with potential in drug delivery.