Synthesis of surface-anchored stable zwitterionic films for inhibition of biofouling

The article reports a two-step method for the synthesis of antifouling films; wherein we first deposited the copolymer films of poly(4-vinylpyridine-co-ethylene glycol diacrylate) (p-4VP-co-EGDA) onto the surface of different substrates (e.g., delicate substrate such as reverse osmosis (RO) membranes, Si wafers and gold sensors) via an all-dry and substrate-independent technique known as initiated chemical vapor deposition (iCVD). The iCVD technique is based upon free radical polymerization where vapors of initiator and monomers are transported to the surface to be modified to initiate simultaneous polymerization and thin film formation. In a subsequent step, th as-deposited copolymer films were converted to zwitterions by a diffusion limited gas-phase reaction with vapors of 1,3-propane sultone to form polysulfobetaine (pSB) type of zwitterionic surface moieties. Bare and the surface modified substrates were characterized by AFM, FTIR and XPS for their topographical and compositional analysis. The presence of zwitterionic moieties considerably discourages the irreversible attachment/adhesion of proteins and bacterial cells as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) and SEM analysis respectively. The results of bacterial adhesion studies showed 99.6% lower attachment of Pseudomonas aeruginosa cells onto the surface of modified RO membranes as compared to bare membranes. The authors wish to mention that a new pyridine-based pSB type of antifouling zwitterionic films has been added to the library of iCVD films. We believe that the demonstrated attempt of membrane surface modification strategy holds promise for potentially controlling the biofouling of other polymeric membranes such as ultrafiltration, nanofiltration and RO membranes. Furthermore, salient features such as solvent less nature, the easy tunablity of film and the capability of retention of functional group make iCVD a unique method to modify the surface of virtually any substrate including, metals, polymeric membranes, Si and gold sensors etc. Thus, it is expected that the developed coating technique could possibly lead to prepare a wide spectrum of environmentally benign antifouling films for other applications such as biomedical devices, medical implants and ship hulls where inhibition of microbial adhesion and subsequent biofilm growth is a severe challenge.