Reversible Self-Assembling of Comb-Like Functionalized Dextran Surfactant Polymers as an SPR-Sensing Surfaces

Abstract

Novel surface plasmon resonance (SPR) sensing surfaces were developed from the perspective of reversible self-assembling of the mixed dextran surfactant polymers onto SPR gold chips. Two comb-like dextran surfactant polymers, which are different in their dextran molecular weight (MW) distribution and the presence of amine functional groups, and their characterization were synthesized. These structurally well-defined surfactant polymers include a bimodal amine dextran surfactant polymer and a monomodal dextran surfactant polymer. The bimodal one consists of poly (vinyl amine) (PVAm) backbone with amine functionalized high MW dextran, non-functionalized low MW dextran and hydrophobic hexyl pendant groups. Allyl high MW dextran aldonic acid and low MW dextran aldonic acid chains with various ratios were sequentially attached to PVAm. The unreacted amine groups on the backbone were further grafted with hexanoic acid and the allyl groups on the high MW dextran were finally converted to amine. The monomodal surfactant polymer, PVAm with non-functionalized low MW dextran and hexyl branches, was synthesized and characterized using similar procedures, except with the absence of allyl high MW dextran aldonic acid and the amine functionalization. The molecular compositions of the surfactant polymers were determined by FTIR and 1H-NMR. Surface active properties at the air-water interface were determined using tensiometer. Reduction in water contact angles was observed on the surfactant treated surfaces. Reversible self-assembling of the synthesized surfactant polymers on SPR gold chip surface was monitored using SPR analysis. Reproducibility of the mixed surfactant assembling process was preliminarily confirmed by a consistent increase in reflectivity change, while no detectable changes in the reflectivity under a 1-h buffer flow indicated stability of the absorbed surfactant layer. Moreover, a simple, quick flow of a basis regeneration solution completely removed the adsorbed surfactant from the surface. Our preliminary investigation also exhibited that the regenerated SPR gold chip was effectively reusable.