Effect of Substituents in Mussel‐inspired Surface Primers on their Oxidation and Priming Efficiency

Abstract

Marine mussels contain an abundant catechol moiety, 3,4‐dihydroxyphenylalanine (DOPA), in their interfacial foot proteins. DOPA contributes to both surface adhesion and bridging between the surface and overhead proteins (surface priming) by taking advantage of the unique redox properties of catechol. Inspired by the mussel surface priming mechanism, herein we synthesized a series of DOPA‐mimetic analogs – a bifunctional group molecule, consisting of a catechol group and an acrylic group at the opposite ends. The surface primers with differently substituted (−COOH, −CH3) alkyl chains in the middle spacer were synthesized. Time‐dependent oxidation and redox potentials of the surface primers were studied in an oxidizing environment to gain a better understanding of the mussel‘s redox chemistry. The thickness and degree of priming of the surface primers on silicon‐based substrates were analyzed by ellipsometry and UV/Vis absorption spectroscopy. The post‐reactivity of the acrylic groups of the primed layer was first visualized through a reaction with an acrylic group‐reactive dye.

Effect of N-Methylation on Dopamine Surface Chemistry

“…Compared with the UV–vis DA spectra, a dramatic increase in the peak intensity in the range from 300 to 400 nm was observed from the MDA, implying excessive catechol oxidation . Moreover, the absorption peak at 476 nm corresponding to a cyclization product, dopamine chrome, was observed in the initial 4 h MDA incubation under alkaline conditions . In contrast, the DMDA displayed totally different UV–vis spectra.…”

“…8 Moreover, the absorption peak at 476 nm corresponding to a cyclization product, dopamine chrome, was observed in the initial 4 h MDA incubation under alkaline conditions. 19 In contrast, the DMDA displayed totally different UV−vis spectra. Only a slight increase in peak intensity at 310 nm, with a concurrent decrease in peak intensity at 280 nm, was observable.…”

“…Modification of the R 3 position, the primary amine, has been extensively used for synthesizing DA derivatives . Various functional molecules were conjugated at this site through amide-bond-forming reactions. − However, the conjugation to the R 3 position prevents indole formation, which is another key intermediate for surface coating; thus, the coating efficiency is not as high that compared to DA. , The indole formation inhibition may be due to the decrease in nitrogen nucleophilicity. The nitrogen in amides is less nucleophilic than that in free amines because of the nitrogen lone pair resonance stabilization by the carbonyl group.…”