Nonbiofouling polymer brush with latent aldehyde functionality as a template for protein micropatterning

A novel, nonfouling polymer brush, poly-N-[(2,3-dihydroxypropyl)acrylamide] (PDHPA), containing latent aldehyde groups, was synthesized by surface initiated atom transfer radical polymerization (SI-ATRP). The synthetic parameters were adjusted to produce brushes with varying graft densities and molecular weights. High-density PDHPA brushes successfully prevented the nonspecific protein adsorption from single protein solutions as well as from human platelet poor plasma. Patterns of nonfouling PDHPA and reactive PDHPA-aldehyde domains on the brush surface were created by a combination of photo and wet chemical lithography from a single homogeneous PDHPA brush. Successful micropatterning of single proteins and multiple proteins were achieved using this novel substrate. The high-density brush prevented the diffusion of large proteins into the brush, while a monolayer of covalently coupled proteins was formed on the PDHPA-aldehyde domains. Atomic force microscopy (AFM) force measurements using a biotin coupled AFM tip showed that covalently coupled streptavidin retained its activity, while PDHPA domains showed little nonspecific adsorption of streptavidin. The current study avoids tedious and complicated synthetic processes employed in conventional approaches by providing a novel approach to protein micropatterning from a single, multifunctional polymer brush.