Nature-inspired creation of protein-polysaccharide conjugate and its subsequent assembly onto a patterned surface

A protein's functional properties can be adjusted by conjugating it to other polymers. We used a nature-inspired route to create a protein-polysaccharide conjugate and examined the properties of this conjugate. Specifically, the enzyme tyrosinase was used to oxidize accessible tyrosine residues of the model protein green fluorescent protein (GFP). Oxidation yields quinone residues that are "activated" for the covalent conjugation of GFP to nucleophilic groups of the aminopolysaccharide chitosan. Conjugation to chitosan conferred distinct properties to GFP. The GFP-chitosan conjugate was observed to have pH-responsive, "smart" properties, and GFP could be conjugated onto a gel matrix. Additionally, the GFP-chitosan conjugate can be selectively deposited onto a micropatterned surface in response to an applied voltage. This nature-inspired method provides a simple and safe method to conjugate proteins to chitosan, and these conjugates can be readily assembled onto patterned surfaces.