Surface-grafted zwitterionic polymers as platforms for functional supported phospholipid membranes

Polymer brushes grafted from surfaces using controlled polymerization techniques, most notably surface-initiated atom-transfer radical polymerization (SI-ATRP), provide robust and reproducible platforms with precise control of surface properties. These platforms are especially useful in biologically oriented applications involving the confinement of membrane proteins onto solid supports, including screening of pharmaceuticals and biosensing. Here we investigate a tunable zwitterion-based polymeric interface that can guide the assembly of neutral lipid membranes with high mechanical stability and reproducibility on various synthetic materials. By controlling the polymer architecture using ATRP, we show that phospholipid membranes can be made to self-assemble on thin layers of charge-balanced poly(sulfobetaine methacrylate) from fusion of DOPC vesicles under physiological conditions. The self-assembly kinetics and functionality of the polymer-supported lipid membranes are investigated using various surface sensitive techniques, including surface plasmon resonance, fluorescence microscopy, and atomic force microscopy. The growth of zwitterionic polymer layers with controlled length and grafting density allows for modulation of the adhesion of the lipid bilayers to surfaces, thus offering unique advantages for the design and synthesis of bioactive surfaces.