Electrochemical Flow Injection Analysis Biosensors Using Biomolecules-immobilized Carbon Felt

Abstract

Amperometric flow injection analysis (FIA) biosensors were developed by using various biomolecules-modified carbon felt (CF) as a working electrode unit of flow-through electrochemical cell-based FIA detector. The CF is a micro-electrode ensemble of micro-carbon fiber (ca. 7 μm diameter) that possesses a three-dimensional random structure. The CF has high conductivity and a large effective surface area, which allows large measurable current density and high electrolytic efficiency. In addition, a high porosity of CF (> 90 %) permits a low diffusion barrier of solution-flow. Four enzymes (tyrosinase, peroxidase, glucose oxidase, uricase), heme proteins (myoglobin, hemoglobin) and hemin were immobilized on the CF surface by chemical modification and physical adsorption. The developed FIA biosensors are divided into the following categories: 1) Tyrosinase (polyphenol oxidase)-modified CF for highly sensitive amperometric flow determination of phenol and catechol compounds, based on signal amplification due to the enzymatic/electrochemical redox recycling; 2) Peroxidase-modified CF for the amperometric flow determination of H2O2 based on direct electron transfer (DET)-based bioelectrocatalysis; 3) Oxidases (glucose oxidase and uricase)-modified CF-based enzyme reactors coupled with peroxidase-CF for amperometric flow determination of glucose and uric acid; 4) Hemin-modified CF for amperometric flow determination of dissolved oxygen (DO), based on an electrocatalytic activity of hemin for the reduction of DO; 5) Heme-proteins-modified CFs for the amperometric flow determination of respiratory toxins (N–3 and CN–), based on reversible inhibition of toxins on bioelectrocatalytic activity of heme-proteins for the reduction of DO. These FIA biosensors do not need any indication reagents, sample-pretreatment and column separation, because biomolecules immobilized on the CF surface possesses highly selective bio-specificity and specific bio-affinities, which allows simple and consecutive analysis of many samples. Therefore, in future, these FIA biosensors can be expected to be applied to on-line automated analysis systems coupled with advanced IoT and AI technology.