Cheap and Sustainable Biosensor Fabrication by Enzyme Immobilization in Commercial Polyacrylic Acid/Carbon Nanotube Films

Novel glucose biosensors were constructed by loading glucose oxidase (GOx) into the nanopores of homogenous carbon nanotube (CNT) films on the surface of Pt disk electrodes and trapping the enzyme by subsequent deposition of polyacrylic acid (PAA), forming PAA/GOx-CNT-modified Pt disks. In amperometric biosensing with anodic hydrogen peroxide (H₂O₂) detection at a potential of +600 mV, increasing electrolyte glucose concentrations produced instantaneous steps in the H₂O₂ oxidation current. Glucose biosensor amperometry was feasible down to 10 μM, with a sensitivity of about 34 μA mM^-1 cm^-2 and linear current response up to 5 mM. The biosensors reliably determined glucose concentrations in human serum and a beverage. Successful trials with PAA/GOx-CNT-modified screen-printed Pt electrode disks demonstrated the potential of this means of enzyme fixation in biosensor mass fabrication, which offers a unique combination of cheap availability of the two matrix constituents and sensor layer formation through simple drop-and-dry steps. PAA/GOx-CNT/Pt biosensors are green and user-friendly bioanalytical tools that do not need large budgets, special skills, or laboratory amenities for their production. Any user, from industrial, university, or school laboratories, even if inexperienced in biosensor construction, can prepare functional biosensors with GOx, as in these proof-of-principle studies, or with other redox enzymes, for clinical, environmental, pharmaceutical, or food sample analysis.