Development of micropillar array electrodes for highly sensitive detection of biomarkers

Micropillar array electrodes (mu AEs) have been widely applied in electrochemical detection owing to their advantages of increased mass transport, lower detection limit, and potential to be miniaturized. This paper reports the fabrication, simulation, surface modification, and characterization of PDMS-based mu AEs coated with gold films. The mu AEs consist of 9 x 10 micropillars with a height of either 100 mu m, 300 mu m, or 500 mu m in a 0.09 cm(2) region. Numerical simulation was employed to study the influence of geometrical parameters on the current density. The mu AEs were fabricated by soft lithography and characterized using both SEM and cyclic voltammetry. Experiments revealed that high pillars enabled enhanced voltammetric current density regardless of the scan rates. The platinum-palladium/multi-walled carbon nanotubes (Pt-Pd/MWCNTs) were coated on the mu AEs to improve their electrochemical detection capability. The mu AEs demonstrated 1.5 times larger sensitivity compared with the planar electrode when hydrogen peroxide was detected. Furthermore, mu AE500 with Pt-Pd/MWCNTs was employed to detect sarcosine, a potential biomarker for prostate cancer. The linear range and limit of detection for sarcosine were from 5 to 60 mu M and 1.28 mu M, respectively. This detection range covers the concentration of sarcosine in human tissues (0-60 mu M). These results suggest that the mu AEs have better detection performance in comparison to planar electrodes due to their large surface area and pillar height. This paper provides essential guidelines for the application of mu AEs in high sensitivity electrochemical detection of low abundance analytes.