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Direct synthesis of quaternized polymer brushes and their application for guiding neuronal growth.

We show that the poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) (PMETA) brush modified surfaces are excellent substrates for the directed growth of rat hippocampal neurons, which could prove useful for the coating of neural devices. Direct synthesis of quaternized poly(dimethylaminoethyl methacrylate) brushes was achieved by surface-initiated atom transfer radical polymerization (SI-ATRP) of META in protic media at room temperature. PMETA brushes were photolithographically patterned on silicon substrates in combination with patterned regions backfilled with short polyethylene glycol (PEG) SAMs. The resulting hybrid patterned surfaces consisting of both "cytophilic" and "cytophobic" materials were successfully employed to guide a neuronal outgrowth. These surfaces should thus provide an excellent platform for studies of neuronal function, use in neuronal implants, cell-based biosensors, and other applications.