Many biomedical applications benefit from responsive polymer coatings. The properties of poly(dopamine) (PDA) films can be affected by codepositing dopamine (DA) with the temperature-responsive polymer poly(N-isopropylacrylamide) (pNiPAAm). We characterize the film assembly at 24 and 39 °C using DA and aminated or carboxylated pNiPAAm by a quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray photoelectron spectroscopy, UV-vis, ellipsometry, and atomic force microscopy. It was found that pNiPAAm with both types of end groups are incorporated into the films. We then identified a temperature-dependent adsorption behavior of proteins and liposomes to these PDA and pNiPAAm containing coatings by QCM-D and optical microscopy. Finally, a difference in myoblast cell response was found when these cells were allowed to adhere to these coatings. Taken together, these fundamental findings considerably broaden the potential biomedical applications of PDA films due to the added temperature responsiveness.

Recently, the combination of lipids and block copolymers has become an alternative to liposomes and polymersomes as nano-sized drug carriers. We synthesize novel block copolymers consisting of poly(cholesteryl acrylate) as the hydrophobic core and poly(N-isopropylacrylamide) (PNIPAAm) as the hydrophilic extensions. Their successful phospholipid-assisted assembly into vesicles is demonstrated using the evaporation-hydration method. The preserved thermo-responsive property of the lipid-polymer hybrids is shown by a temperature dependent adsorption behaviour of the vesicles to poly(l lysine) coated surfaces. As expected, the vesicle adsorption is found to be higher at elevated temperatures. The cellular uptake efficiency of hybrids is assessed using macrophages with applied shear stress. The amount of adhering macrophages is affected by the time and level of applied shear stress. Further, it is found that shorter PNIPAAm extensions lead to higher uptake of the assemblies by the macrophages with applied shear stress. No inherent cytotoxicity is observed at the tested conditions. Taken together, this first example of responsive lipid-polymer hybrids, and their positive biological evaluation makes them promising nano-sized drug carrier candidates.

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 PDAbased coatings can be used to affect the interaction of liposomes with macrophages with potential in drug delivery.