A Parametric Design Study of an Electrochemical Sensor

Abstract

T he development of highly sensitive biosensors for the detection of biomolecules, such as the biomarker interleukin-8 for the early detection of oral cancer, requires optimization of sensor design. To augment the performance of an electrochemical sensor, this study used a microscale, aptamer-based electrochemical sensor for detecting botulinum neurotoxin aptamer hybridization. We first used topedown lithographic processing to define the pattern of the electrodes and then used bottomeup manufacturing to modify the surface molecular properties for reducing nonspecific binding. We systemically examined the effects of the design parameters of an aptamerbased electrochemical sensor. Specifically, five key design parameters were examined: the area of the working electrode (WE), the area of the counter electrode (CE), the separation distance between the WE and CE, the overlap length between the WE and CE, and the aptamer concentration. Through an analysis of the signal and noise generated across variations of the different parameters, the significance of each parameter in sensor performance was determined. In particular, we found that the area of the WE was the only key parameter that influenced the performance of the sensor. The output signal level increased with the area of the WE and the signal-to-noise ratio was about constant in the tested range (i.e., from 0.02 to 4 mm 2 ). ( JALA 2010;15:179-88) INTRODUCTIONElectrochemical biosensors synergize the biological recognition element of a biosensor with an electrochemical transducer and have been used to detect a variety of biological targets, such as uropathogenic bacteria, the hepatitis B virus, and the cholera toxin produced by Vibrio cholerae. 1e4 Amenable to miniaturization, the development of microfabricated electrochemical biosensors has resulted in high sensitivity, portability, improved performance and spatial resolution, low power consumption, and the opportunity for integration with other technologies, such as microfluidics. 5,6 Such advantages enable MicroElectrical-Mechanical Systems (MEMS)-based electrochemical biosensors to identify pathogens present in a variety of mediums and bodily fluids, such as blood, saliva, and air more quickly than previous, laboratory-based detection methods. 7e10 Previous work has been done using an electrochemical biosensor in which a sensing paradigm was tested and developed. 7,11e13 For example, Gau et al. 14 developed a MEMS-based electrochemical biosensor for the amperometric detection of Escherichia coli. The electrochemical detection system resulted from the synergy of microfabricated electrodes, self-assembled monolayers via thiol chemistry, DNA hybridization, and enzyme-mediated signal amplification. 14 Gau's 14 electrochemical biosensor used three microfabricated gold electrodes: a working electrode (WE), a counter electrode (CE), and a reference electrode (RE). Using an identical electrode design, Wei et al. 11 and Wei and Ho 15 detected salivary interleukin-8 (IL-8) mRNA using a hairpin probe and botulinum ...

Environmental Monitoring Systems: A Review

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