Nonfouling polyampholyte polymer brushes with protein conjugation capacity

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The elimination of nonspecific protein adsorption is a very important challenge in many biomaterial applications. This work reports on the multi-functional properties of a mixed-charge or polyampholyte copolymer composed of positively charged [2-(acryloyloxy) ethyl] trimethyl ammonium chloride (TMA) and negatively charged 2-carboxy ethyl acrylate (CAA) monomers. TMA:CAA copolymers have previously been shown to have nonfouling properties, but the optimal conditions for nonfouling have not been determined. To accomplish this, the thickness of the polymer brush coating was varied by manipulating the surface-initiated atom transfer radical polymerization conditions. The nonspecific adsorption of fibrinogen and lysozyme was determined using a surface plasmon resonance biosensor as a function of the copolymer brush thickness. At the optimal thickness for nonfouling, nonspecific adsorption from 10% and 100% fetal bovine serum (FBS) was also determined. The results indicate that at the optimal copolymer brush thickness, TMA:CAA polyampholyte materials have ultralow fouling characteristics even upon exposure to 100% FBS (<5 ng/cm2 of nonspecific protein adsorption). The multi-functional properties of the TMA:CAA copolymers were demonstrated by conjugating fibrinogen to the copolymer brush over a range of brush thicknesses. The conjugation experiments clearly demonstrate that TMA:CAA copolymers have the capacity for protein conjugation even at the optimal thickness for nonfouling.