Integration of thin film amorphous silicon photodetector with lab-on-chip for monitoring protein fluorescence in solution and in live microbial cells

Green fluorescent protein (GFP) and other fluorescent protein variants are widely used as powerful tools to tag and monitor complex biological processes at the cellular, tissue, and organism level. A micrometer-scale GFP detection system is demonstrated in which a p-i-n thin-film amorphous silicon light sensitive layer microfabricated on a glass substrate is integrated with an amorphous silicon carbon alloy absorption filter and an ultra-thin PDMS sheet to detect intracellular expression of GFP. GFP fluorescence was detected in aqueous solution in the nM range, and inside living cells (Escherichia coli) expressing GFP in the 106 cell/mL range. The temporal evolution of the integrated fluorescence from promoter-induced GFP production was monitored in E. coli in solution over 12 h using the detection system. This microfabricated thin-film detection system can potentially be developed into an array-based sensing of GFP allowing for high-throughput and multiplexed analysis of biological and biomedical samples.