Non-Fouling Multi-Azide Polyoxazoline Brush-co-Polymers for Sensing Applications

Abstract

One of the key parameters of an artificial biosensor is a high signal-to-noise ratio. This is achieved by limiting non-specific interactions while simultaneously maximizing the targeted specific interaction. Here, it is combined non-fouling characteristics of poly(2-methyl-2-oxazoline) (PMOXA) coatings with an abundance of azide groups to create a multi-azide containing poly(2-methyl-2-oxazoline-co-2-(3-azidopropyl)-2-oxazoline) (PMCA) that can participate in bioorthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) for functionalization. This functional polymer is made surface-active using the PAcrAm™ technology to obtain well-defined spontaneously adsorbed monolayers on gold surfaces. The resistance to non-specific interactions is tested against full human serum (HS), analyzed via variable angle spectroscopic ellipsometry (VASE), and compared to equivalent coatings based on PMOXA and azido-poly(ethylene glycol) (PEG-N₃). The specific interactions are investigated via VASE and quartz crystal microbalance with dissipation (QCM-D) by immobilization of dibenzocyclooctyne-PEG4-biotin conjugate (DBCO-biotin) and streptavidin. The new PMCA-based coating shows superior resistance to non-specific protein adhesion than equivalent coatings based on commercially available PEG-N₃ and significantly increases capacity for SPAAC. A proof of principle assay (biotin-streptavidin/biotin-BSA/anti-BSA) shows improved binding for the new PMCA polymer compared with single azide PEG.