Facile modification of protein-imprinted polydopamine coatings over nanoparticles with enhanced binding selectivity

Mussel-inspired dopamine (DA) self-polymerization over a variety of substrates has become a simple but versatile approach for synthesis of surface protein-imprinted materials. However, relatively high nonspecific binding to the imprinted polydopamine (PDA) coatings has long been an open problem because of their multifunctionalities. We herein propose a facile strategy for reduction of the nonspecific adsorption by covering the imprinted PDA coatings with slightly crosslinked nonlinear poly(ethylene glycol) (PEG) layers via aqueous precipitation polymerization before template removal. Vinyl groups are introduced onto the PDA coatings via Cu2+ mediated metal coordination for facilitating surface polymerization. The Cu2+ and embedded template are removed after polymerization. For proof of hypothesis, the protein imprinted PDA coatings were formed with SiO2 nanoparticles as representative nano-supports and lysozyme as a model protein template. Protein binding tests show that the grafted PEG layers with an optimized feed crosslinking degree can significantly enhance both recognition selectivity and specific binding capacity to the imprinted nanoparticles, typically with the imprinting factor increasing from 2.6 to 6.4. Also, the PEG layers can remarkably improve the stability of the PDA coatings in the acidic template removal solution. The presented strategy represents the first example for PEGylation of protein-imprinted PDA coatings, and may be extended for surface imprinting of other bio/organic molecules over other substrate materials.