Antifouling Zwitterionic Coating via Electrochemically Mediated Atom Transfer Radical Polymerization on Enzyme-Based Glucose Sensors for Long-Time Stability in 37 °C Serum

In this study, a versatile fabrication method for coating enzyme-based biosensors with ultrathin antifouling zwitterionic polymer films to meet the challenge of the long-time stability of sensors in vivo was developed. Electrochemically mediated atom transfer radical polymerization (eATRP) was applied to polymerize zwitterionic sulfobetaine methacrylate monomers on the rough enzyme-absorbed electrode surfaces; meanwhile, a refined overall bromination was developed to improve the coverage of polymers on the biosensor surfaces and to maintain the enzyme activity simultaneously for the first time. X-ray photoelectron spectroscopy and atomic force microscopy were used to characterize the properties of the polymer layers. The antifouling performance and long-time stability in 37 °C undiluted bovine serum in vitro were evaluated. The results showed that the polymer brush coatings diminished over 99% nonspecific protein adsorption and that the sensitivity of the evaluated sensor was maintained at 94% after 15 days. The overall sensitivity deviation of 7% was nearly 50% lower than that of the polyurethane-coated ones and also much smaller than the current commercially available glucose biosensors. The results suggested that this highly controllable electrodeposition procedure could be a promising method to develop implantable biosensors with long-time stability.