Electrochemical sensor for enzymatic lactate detection based on laser-scribed graphitic carbon modified with platinum, chitosan and lactate oxidase.

We developed a flexible laser scribed graphitic carbon based lactate biosensor fabricated using a low cost 450 nm laser. We demonstrated a facile fabrication method involving electrodeposition of platinum followed by two casting steps for modification with chitosan and lactate oxidase. The biosensor demonstrated chronoamperometric lactate detection within a linear range from 0.2 mM to 3 mM, (R2 > 0.99), with a limit of detection of 0.11 mM and a sensitivity of 35.8 µA/mM/cm2. The biosensor was successful in performing up to 10 consecutive measurements (one after the other) indicating good working stability (RSD <5%). Concerning storage stability, there was no decrease in signal response after 30 days of storage at 4 °C. Additionally, we demonstrate enzymatic lactate detection whilst the flexible polyimide substrates were fixed at a curvature (K) of 0.14 mm-1. No noticeable change in signal response was observed in comparison to calibrations obtained at a curvature of 0 mm-1, signifying potential opportunities for sensor attachment or integration with oral-care products such as mouth swabs. Both laser scribed graphitic carbon and Ag/AgCl modified-laser scribed graphitic carbon were successful as reference electrodes for chronoamperometric lactate measurements. Furthermore, using a three-electrode configuration on polyimide, lactate detection in both artificial saliva and sterile human serum samples was achieved for two spiked concentrations (0.5 mM and 1 mM).

On-Chip Glucose Detection Based on Glucose Oxidase Immobilized on a Platinum-Modified, Gold Microband Electrode.

We report the microfabrication and characterization of gold microband electrodes on silicon using standard microfabrication methods, i.e., lithography and etching techniques. A two-step electrodeposition process was carried out using the on-chip platinum reference and gold counter electrodes, thus incorporating glucose oxidase onto a platinum-modified, gold microband electrode with an o-phenylenediamine and ß-cyclodextrin mixture. The as-fabricated electrodes were studied using optical microscopy, scanning electron microscopy, and atomic force microscopy. The two-step electrodeposition process was conducted in low sample volumes (50 µL) of both solutions required for biosensor construction. Cyclic voltammetry and electrochemical impedance spectroscopy were utilised for electrochemical characterization at each stage of the deposition process. The enzymatic-based microband biosensor demonstrated a linear response to glucose from 2.5-15 mM, using both linear sweep voltammetry and chronoamperometric measurements in buffer-based solutions. The biosensor performance was examined in 30 µL volumes of fetal bovine serum. Whilst a reduction in the sensor sensitivity was evident within 100% serum samples (compared to buffer media), the sensor demonstrated linear glucose detection with increasing glucose concentrations (5-17 mM).