Quantitative Comparison of Enzyme Immobilization Strategies for Glucose Biosensing in Real‐Time Using Fast‐Scan Cyclic Voltammetry Coupled with Carbon‐Fiber Microelectrodes

Abstract

Electrochemical monitoring of non-electroactive species requires a biosensor that is stable and selective, with sensitivity to physiological concentrations of targeted analytes. We have combined glucose oxidase-modified carbon-fiber microelectrodes with fast-scan cyclic voltammetry for real-time measurements of glucose fluctuations in brain tissue. Work presented herein quantitatively compares three approaches to enzyme immobilization on the microelectrode surface-physical adsorption, hydrogel entrapment, and entrapment in electrospun nanofibers. The data suggest that each of these methods can be used to create functional microbiosensors. Immobilization of glucose oxidase by physical adsorption generates a biosensor with poor sensitivity to glucose and unstable performance. Entrapment of glucose oxidase in poly(vinyl alcohol) nanofibers generates microbiosensors that are effective for glucose measurements over a large linear range, and that may be particularly useful when targeting glucose concentrations in excess of 3 mm, such as in blood. Hydrogel entrapment is the most effective in terms of sensitivity and stability. These microbiosensors can be used for simultaneous monitoring of glucose and dopamine in real time. The findings outlined herein should be applicable to other oxidase enzymes, and thus they are broadly important for the development of new tools for real-time measurements of fluctuating molecules that are not inherently electroactive.

Exploration of Chitinous Scaffold-Based Interfaces for Glucose Sensing Assemblies

“…The long-term stability of such µ-electrodes was possibly due to strong chemical bonding between BQ-CS and GOx through free amines of lysine residues on the enzyme to the CS-matrix. Smith et al, 2018; demonstrated and confirmed that GOx immobilization by entrapment in a CS-hydrogel is another effective method for µ-electrode fabrication, which can be used for the measurements of brain glucose. Researchers combined GOx-modified carbon-fiber µ-electrodes with fast-scan voltammetry (CV) for real-time measurements of glucose in brain tissues [95].…”

“…Smith et al, 2018; demonstrated and confirmed that GOx immobilization by entrapment in a CS-hydrogel is another effective method for µ-electrode fabrication, which can be used for the measurements of brain glucose. Researchers combined GOx-modified carbon-fiber µ-electrodes with fast-scan voltammetry (CV) for real-time measurements of glucose in brain tissues [95]. The detection range of the sensor was from 0.2 to 50 mM glucose in vitro using the flow-injection apparatus.…”

Electroresponsive Hydrogels for Therapeutic Applications in the Brain

“…Functions in the brain are regulated by neurotransmission events at the subsecond scale, which is why neuroscientists rely on electrochemical methods to detect instantaneous changes in neurotransmitters in vivo. [200] Biosensors utilize these electrochemical methods to monitor non-electroactive molecules [201] with precise, rapid, and continuous measurements of metabolites in situ. [202] While alternative methods such as nuclear magnetic resonance and microdialysis have limitations in spatial and temporal resolutions, the electrodes of electrochemical sensors can be placed directly in target tissues for real time monitoring and convert the analytes at the electrode site within seconds for fast response times.…”

“…[205,206] Subjecting the electrode to a potential drives a redox reaction process, with the resulting current being proportional to the concentration of the target analyte electrolyzed. [201] In 1962, Clark and Lyons were the first group to develop a glucose oxidase enzyme based electrode for detecting glucose and hydrogen peroxide (H 2 O 2 ). [207] Fast scan cyclic voltammetry (FSCV) is another detection method which can distinguish between the target analyte and interfering molecules.…”

Recent Applications of Point-of-Care Devices for Glucose Detection on the Basis of Stimuli-Responsive Volume Phase Transition of Hydrogel

“…c Illustration of the preparation of IPNs hydrogel (reprinted with permission from Ref. [19]) a more consistent active surface, thus improve the catalytic efficiency and avoid loss [24]. For higher activity, on the one hand, increase the available covalent bonding sites by introducing some monomers rich in -NH 2 and -COOH via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) by forming amide bonds between the amine groups and carboxyl groups [25][26][27][28][29] or glutaraldehyde via covalent attachment to amino-actived polymers [30][31][32][33][34]; on the other hand, increase the specific surface area using microcapsules as Fig.…”