Multi-layer SU-8 based micro dispensing system for microarray immunoassay

Abstract

This paper reports a micro dispensing system and its usage for printing protein microarray on nylon membrane for clinical immunoassay. The system is based on pneumatic actuation, multi-layer SU-8 dispensing chip, and the printing buffer contains dimethyl sulfoxide (DMSO), borate, and phosphate buffered saline (PBS). The optimal volume proportion of DMSO, borate, and PBS in the printing buffer is 9:1:1 for delivering and dispensing human IgG, while avoiding protein dehydration and absorption via SU-8 based micro-channels in the micro dispensing chip. Immuno-reaction experiments revealed that the signal intensity of protein spots on nylon membrane would increase by increasing IgG or borate concentration in the printing buffer. The coefficient of variation (CV) of intensities within all arrayed membrane for different storage times reached 4.8%, and the CV of average intensities within all 25 spots in one membrane for each optimized printing buffer was as low as 4.1%. Extensive experiments with different proteins showed ascertained carry-over and cross-talk free by our micro dispensing system.