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

Abstract

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

New Poly(amino acid methacrylate) Brush Supports the Formation of Well-Defined Lipid Membranes

“… 42 These initiator-functionalized surfaces were subsequently reacted with the relevant brush monomers, as described previously. 43 − 47 All brush layers were characterized by a combination of AFM, XPS, and ellipsometry. For the work described herein, dry brush thicknesses were 5–9 nm.…”

“…No bilayer formation was obtained for swollen brush thicknesses greater than 35 nm, while bilayers formed on ∼16 nm brushes gave lipid diffusion coefficients on the order of 1 μm 2 s –1 . 31 A maleic anhydride-based, pH-responsive brush developed by Renner and coworkers supported bilayer formation if electrostatic repulsion was reduced by lowering the pH to 4. Three brushes of 4, 25, or 60 nm dry thickness were examined, which led to bilayers with diffusion coefficients of 0.26, 0.60, or 1.24 μm 2 s –1 , respectively.…”

A zwitterionic interpenetrating network for improving the blood compatibility of polypropylene membranes applied to leukodepletion

“…Although the membranes were freeze-dried before analysis, remaining water tightly trapped by the zwitterionic units of poly(GMA-co-SBMA) could be detected. It is also worth noting that for membranes immersed in coating baths at a 5 mg/mL and 15 mg/mL copolymer concentration and containing EDA, a clear peak was noticed at 1035 cm −1 corresponding to the characteristic vibration band of the sulfonate head [44]. All in all, this chemical analysis proves the presence of copolymer at the surface of the membranes in some particular conditions of surface modification (copolymer concentration in the coating bath of 15 mg/mL without EDA, and copolymer concentration in the coating bath of 5 and 15 mg/mL with EDA).…”

Zwitterionic Moieties from the Huisgen Reaction: A Case Study with Amphiphilic Dendritic Assemblies

“…Zwitterionics, such as sulfobetaines,28, 29 carboxybetaines,30, 31 and phosphobetaines,32, 33 possess both positive and negative charges on the same monomer unit. These polybetaines are gaining attention as potential alternatives to PEG, due to their overall charge neutrality, high water solubility, and their ability to bind water via electrostatic interactions.…”