著者

Kazuo HOSOKAWA

出版者

The Japan Society for Analytical Chemistry

雑誌

Analytical Sciences (ISSN:09106340)

巻号頁・発行日

vol.37, no.3, pp.399-406, 2021-03-10 (Released:2021-03-10)

参考文献数

35

被引用文献数

9

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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.

著者

Young-Jin KIM Kazuo HOSOKAWA Mizuo MAEDA

出版者

The Japan Society for Analytical Chemistry

雑誌

Analytical Sciences (ISSN:09106340)

巻号頁・発行日

vol.35, no.11, pp.1227-1236, 2019-11-10 (Released:2019-11-10)

参考文献数

40

被引用文献数

11

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We present a microRNA (miRNA) detection method that achieves enhanced sensitivity by means of a power-free microfluidic chip without the requirement of an external power source. The miRNA detection is completed by sandwich hybridization between probe DNAs and target miRNA with small sample volume (0.5 μL) within 20 min. Fluorescence signals after hybridization were amplified by laminar flow-assisted dendritic amplification (LFDA) using fluorescein isothiocyanate (FITC)-labeled streptavidin (F-SA) and biotinylated anti-streptavidin (B-anti-SA) as amplification reagents. To enhance the sensitivity of on-chip miRNA detection, the hybridization buffer solution was newly optimized with three main components—sodium dodecyl sulfate (SDS), formamide and dextran sulfate—that are known to strongly influence hybridization. An on-chip miRNA detection test in the newly optimized hybridization buffer (0.2% SDS, 5% formamide and 1% dextran sulfate) revealed dramatic increases in both the LFDA signal in the sample channel and the signal-to-background ratio (S/B ratio). Moreover, the LFDA signals in a blank reference channel remained low due to the suppression of non-specific bindings and hybridizations. By changing the hybridization buffer, we obtained an improved limit of detection (LOD) that was 0.045 pM (miRNA-196a) and 0.45 pM (miRNA-331), which are around 30- and 10-fold better than that of when control hybridization buffer was used. The improved performance of our miRNA detection system with short running time and high sensitivity could contribute to future research, including point-of-care diagnostic systems.