Single-use nonenzymatic glucose biosensor based on CuO nanoparticles ink printed on thin film gold electrode by micro-plotter technology

The conventional glucose sensors use enzymes such as glucose oxidase or other enzymes to react with glucose yielding hydrogen peroxide, which can then be electrochemically oxidized at an appropriate condition. Insufficient reproducibility of enzyme sensors, enzyme activity loss, and instability of the immobilization of the enzymes are the main disadvantages limiting the application of enzyme-based glucose sensors. This is particularly of significance in continuous glucose concentration monitoring.

Therefore, there is a need to have non-enzymatic glucose sensors that are reproducible, stable and sensitive. Above all, their production should be cost-effective. Copper oxide, a semiconductor material with a narrow band gap, is applied in photovoltaic devices, gas sensing, heterogeneous catalyst, and in glucose sensing. Its low cost of production and high catalytic activity are the main indicators that copper oxide could be used for the fabrication of non-enzymatic glucose biosensors.

Researchers led by Professor Chung-Chiun Liu from Case Western Reserve University and in collaboration with Alireza Molazemhosseini, Luca Magagnin, and Pasquale Vena at Politecnico di Milano fabricated a non-enzymatic glucose sensor based on copper oxide nanoparticles printed on gold electrode. They made on a polyethylene terephthalate sheet a three-electrode configuration biosensor composed of a thin gold film working and counter electrodes as well as a thick-film printed silver-silver chloride reference electrode. They also formulated and printed on the working electrode an aqueous-based copper oxide nanoparticle ink using the micro-plotter technology. Their research work is published in Journal of Electroanalytical Chemistry.

The fabricated copper oxide nanoparticles with varying concentrations were mixed with water-ethylene glycol. The authors then performed micro-plotter printing applying a glass micropipette onto thin film gold working electrode of the biosensor. They picked a 2.0V dispensing voltage for printing. The cleaned micropipette was then filled with the copper oxide ink by capillary action then moved towards the surface of the gold-film electrode until the fluid meniscus was in contact with the surface. The researchers then printed a square area on the gold electrode of the biosensor. The printed specimens were the heat-treated.

The authors performed cyclic voltammetry as well as chronoamperometry measurements. Electrochemical tests were done in sodium hydroxide solution. The authors then performed cyclic voltammetry measurements for bare copper oxide printed and gold electrodes in the presence and absence of glucose. In addition, they carried out cyclic voltammetry measurements for varying concentrations of glucose.

Microfabrication methods such as sputtering vapor deposition, thick film printing and laser ablation were implemented to generate the biosensor. Copper oxide nanoparticles, averagely 7nm, were successfully fabricated by a one-step precipitation method. This resulted in the formation of an aqueous-based nanoparticle ink.

The high resolution as well as dimensional accuracy of the adopted micro-plotter printing method yielded a better development of Nano-catalyst biosensors as opposed to typical ink-jet printing. Field Emission Scanning Electron Microscopy characterizations of the copper oxide printed attributes indicated a Nano porous morphology as well as high printing resolution. Cyclic voltammetry as well as chronoamperometry measurements indicated a superior electro catalytic performance of the printed biosensor with very high sensitivity, sufficient stability, and high interference rejection against urine acid, dopamine, lactose and ascorbic acid. In addition, rejection analyses were done in undiluted human serum in a bid to confirm the operation of the sensor for real samples.

The proposed biosensors exhibited linear response towards glucose in the 0.1-6.5mM range. 0.5µM was identified as the lower detection limit of the sensors. These results indicate that a high performance robust glucose biosensor is not only fit for biomedical single-use in-vitro applications, but also for industrial long-term applications.