Photo-crosslinkable O2-riched PEGylated Terpolymer for Long-term Enhanced Glucose Sensing

Biofouling, co-substrate inefficiency and enzymatic stability are major concerns for long-lived implantable devices. To provide extra co-substrate supply while allowing for minimizing protein absorption and photopatterning, a novel poly(ethylene glycol) (PEG)-based random copolymer is synthesized and utilized for redox enzyme-based devices. Higher concentration polymer solution (10 mg�mL-1) can easily crosslink into hydrogel using traditional UV (300 nm) photolithography via 2+2 cycloaddition of cinnamoyloxyethyl (CEMA) moieties. This hydrogel affords improved stability and activity for the immobilized GOx enzyme, while reducing non-specific protein fouling by an order of magnitude. Increasing the amount of GOx loading was found to improve sensitivity (up to 330 nA�mM-1�mm-2 at 10mg�mL-1GOx-loading) while decreasing linearity (km of 23 and 11 mM for 1 and 10 mg�mL-1 GOx-loading, respectively). Continuous in vitro sensor with GOx covalently immobilized in such hydrogel testing in phosphate buffer saline (PBS) shows enhanced stability with only 10% in gradual loss of sensitivity over 30 days due to covalently enzyme immobilization via glycidyl methacrylate (GMA) functionality epoxy-amine coupling. At low concentration (1 mg�mL-1), this amphiphilic polymer with proper hydrophilic and hydrophobic ratio can self-assemble into single chain polymeric nanoparticles (SCPNs). The hydrophobic cores of resulted SCPN supplied extra co-substrate (oxygen) to enzymes and the dynamic assemblies can be stabilized by core-crosslinking with proper UV exposure time. Cationchelated PEG side chains exhibited slight positive charge, which resulted in self-arrested enzyme assembly in one-to-one manner with constant association coefficient (Ka=6.5 M- 1) followed by covalently enzyme immobilization between SCPN and GOx (SCPN-GOx). Wire sensors dip-coated with such SCPN-GOx concentrated solution showed almost the same sensitivity as 10 mg�mL-1 GOx-loading in hydrogel condition with siginificantly enhanced linearity ((km of 50 mM). Such high linearity maintained almost constant over 80 days test and the sensitivity of the sensors only lost less than 15%. These results indicate the potential importance of this type of amphiphilic random copolymer and related hydrogels as host matrices in various enzyme based device platforms.