Biomarker analysis on a power-free microfluidic chip driven by degassed poly(dimethylsiloxane).

Point-of-care testing (POCT) of biomarkers, such as proteins and nucleic acids, is a hot topic in modern medical engineering toward the early diagnosis of various diseases including cancer. Although microfluidic chips show great promise as a new platform for POCT, external pumps and valves for driving those chips have hindered the realization of POCT on the chips. To eliminate the need for pumps and valves, a power-free microfluidic pumping method utilizing degassed poly(dimethylsiloxane) (PDMS) was invented in 2004. In this article, the working principle of the degas-driven power-free microfluidic chip is first described, and then applications of those chips to biomarker analysis are reviewed. The biomarker analysis on the chip was typically achieved with a small sample volume of ∼1 μL and a short analysis time of ∼20 min. For protein analysis, the sandwich immunoassay format was adopted. The limit of detection (LOD) was improved by three orders of magnitude by using laminar flow-assisted dendritic amplification (LFDA), which was a newly devised amplification method specialized for microfluidic chips. For analysis of nucleic acids such as DNA and microRNA, the sandwich hybridization format was adopted, and the LFDA was also effective to reduce the LOD. With the LFDA, typical LOD values for proteins and nucleic acids were both around 1 pM.