Abbreviations: (AP) acetaminophen, (BSA) bovine serum albumin, (FAD) flavin adenine dinucleotide, (GO x ) glucose oxidase, (PBS) phosphatebuffered saline, (PPh) polyphenol, (PU) polyurethane, (PVA) polyvinyl alcohol Keywords: bienzymatic, biosensor lag time, drug delivery coatings, foreign body response, implantable glucose sensors, outer membranes, selectivity Development of electrochemical sensors for continuous glucose monitoring is currently hindered by a variety of problems associated with low selectivity, low sensitivity, narrow linearities, delayed response times, hysteresis, biofouling, and tissue inflammation. We present an optimized sensor architecture based on layer stratification, which provides solutions that help address the aforementioned issues. Method:The working electrode of the electrochemical glucose sensors is sequentially coated with five layers containing: (1) electropolymerized polyphenol (PPh), (2) glutaraldehyde-immobilized glucose oxidase (GO x ) enzyme, (3) dip-coated polyurethane (PU), (4) glutaraldehyde-immobilized catalase enzyme, and (5) a physically cross linked polyvinyl alcohol (PVA) hydrogel membrane. The response of these sensors to glucose and electroactive interference agents (i.e., acetaminophen) was investigated following application of the various layers. Sensor hysteresis (i.e., the difference in current for a particular glucose concentration during ascending and descending cycles after 200 s) was also investigated. Results:The inner PPh membrane improved sensor selectivity via elimination of electrochemical interferences, while the third PU layer afforded high linearity by decreasing the glucose-to-O 2 ratio. The fourth catalase layer improved sensor response time and eliminated hysteresis through active withdrawal of GO x -generated H 2 O 2 from the inner sensory compartments. The outer PVA hydrogel provided mechanical support and a continuous pathway for diffusion of various participating species while acting as a host matrix for drug-eluting microspheres. Conclusions:Optimal sensor performance has been achieved through a five-layer stratification, where each coating layer works complementarily with the others. The versatility of the sensor design together with the ease of fabrication renders it a powerful tool for continuous glucose monitoring.

Enhanced sensor performance in terms of sensitivity and large signal-to-noise ratio has been attained via electrochemical rebuilding of the WE. This approach also bypasses the need for conventional and nanostructured mediators currently employed to enhance sensor performance.

Nanopatterning as a surface area enhancement method has the potential to increase signal and sensitivity of biosensors. Platinum-based bulk metallic glass (Pt-BMG) is a biocompatible material with electrical properties conducive for biosensor electrode applications, which can be processed in air at comparably low temperatures to produce nonrandom topography at the nanoscale. Work presented here employs nanopatterned Pt-BMG electrodes functionalized with glucose oxidase enzyme to explore the impact of nonrandom and highly reproducible nanoscale surface area enhancement on glucose biosensor performance. Electrochemical measurements including cyclic voltammetry (CV) and amperometric voltammetry (AV) were completed to compare the performance of 200 nm Pt-BMG electrodes vs Flat Pt-BMG control electrodes. Glucose dosing response was studied in a range of 2 mM to 10 mM. Effective current density dynamic range for the 200 nm Pt-BMG was 10-12 times greater than that of the Flat BMG control. Nanopatterned electrode sensitivity was measured to be 3.28 μA/cm/mM, which was also an order of magnitude greater than the flat electrode. These results suggest that nonrandom nanotopography is a scalable and customizable engineering tool which can be integrated with Pt-BMGs to produce biocompatible biosensors with enhanced signal and sensitivity.