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.