Dopamine-assisted deposition and zwitteration of hyaluronic acid for the nanoscale fabrication of low-fouling surfaces.

In this study, we proposed a bioinspired approach for the deposition and zwitteration of hyaluronic acid (HA) with a reduced glutathione (GSH) to form a composite layer that functions as a low fouling coating. A polyanion of the HA-dopamine conjugate (HADA) possessing catechol groups was synthesized by carbodiimide chemistry between HA and dopamine. Then, the dopamine conjugated biofunctional polymers (HADA) were grafted onto Au substrates via the transformation of catechol into a quinone group under mild oxidative conditions followed by a reaction with GSH to avoid undesired adhesion and also to shield the exposed Au substrate. Analysis of XPS spectra and wettability indicated that HADA and GSH were successfully grafted onto Au substrates. Surface plasmon resonance analysis showed that both HADA and further GSH modified surfaces exhibited reduced nonspecific adsorption. The attachment of GSH to HADA modified surfaces (HADA-G) resulted in better antifouling performance, with a low or ultralow protein adsorption of 0-7.51 ng cm when exposed to single protein solutions, and a reduction in nonspecific adsorption from cow's milk to 10% compared to that of bare gold. The enhanced antifouling performance of HADA-G modified surfaces was likely due to the zwitterionic structure in GSH, which can induce stronger surface hydration through electrostatic interactions as well as the hydrogen bonding induced by HADA. Our results provide a facile and universal approach to surface modification and demonstrate the benefits of using a composite layer for the design of low fouling surfaces.