Enzyme-Modified Carbon-Fiber Microelectrode for the Quantification of Dynamic Fluctuations of Nonelectroactive Analytes Using Fast-Scan Cyclic Voltammetry

Abstract

Neurotransmission occurs on a millisecond timescale, but conventional methods for monitoring non-electroactive neurochemicals are limited by slow sampling rates. Despite a significant global market, a sensor capable of measuring the dynamics of rapidly fluctuating, non-electroactive molecules at a single recording site with high sensitivity, electrochemical selectivity, and a subsecond response time is still lacking. To address this need, we have enabled the real-time detection of dynamic glucose fluctuations in live brain tissue using background-subtracted, fast-scan cyclic voltammetry. The novel microbiosensor consists of a simple carbon fiber surface modified with an electrodeposited chitosan hydrogel encapsulating glucose oxidase. The selectivity afforded by voltammetry enables quantitative and qualitative measurements of enzymatically-generated H2O2 without the need for additional strategies to eliminate interferents. The microbiosensors possess a sensitivity and limit of detection for glucose of 19.4 ± 0.2 nA mM−1 and 13.9 ± 0.7 μM, respectively. They are stable, even under deviations from physiological normoxic conditions, and show minimal interference from endogenous electroactive substances. Using this approach, we have quantitatively and selectively monitored pharmacologically, evoked glucose fluctuations with unprecedented chemical and spatial resolution. Furthermore, this novel biosensing strategy is widely applicable to the immobilization of any H2O2 producing enzyme, enabling rapid monitoring of many non-electroactive enzyme substrates.

Simultaneous Voltammetric Measurements of Glucose and Dopamine Demonstrate the Coupling of Glucose Availability with Increased Metabolic Demand in the Rat Striatum

“…GOx EMEs were prepared as previously described 41 . Briefly, electrodes were conditioned by the application of a voltammetric waveform of −0.4 V to +1.4 V for ~15 min at 60 Hz, and then ~5 min at 10 Hz.…”

Electrochemical Analysis of Neurotransmitters

“…Because the overoxidation process occurs near the anodic switching potential with this extended waveform, the oxidation peak for H 2 O 2 appears at +1.2 V on the reverse scan. To detect glucose with this waveform, carbon-fiber microelectrodes were coated by electrodeposition of glucose-oxidase in chitosan, a nontoxic polysaccharide (44). This sensor has a 13-μM limit of detection for glucose; stable performance over a 4-h period; and the ability to discriminate against interferents such as dopamine, ascorbic acid, and pH.…”

PtAu alloy nanoflowers on 3D porous ionic liquid functionalized graphene-wrapped activated carbon fiber as a flexible microelectrode for near-cell detection of cancer

“…Nevertheless, it remains a challenge to construct a 3D graphene architecture on a single microscale CF owing to its finite size, smooth surface and insufficient surface active sites. 21,22 More importantly, the chemical or electrochemical reaction kinetics for assembling 3D graphene materials from their graphene oxide (GO) nanosheets precursor requires high driving forces, which cannot be easily obtained under conventional reaction conditions.…”