A blocking-free microfluidic fluorescence heterogeneous immunoassay for point-of-care diagnostics
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In this article, a rapid, sensitive, and disposable microfluidic immunosensor is presented for point-of-care (POC) testing and clinical diagnosis. For the first time, the blocking process is eliminated from a microfluidic heterogeneous immunoassay by using protein A functionalized polydimethylsiloxane microchannels. The nonspecific binding of the assay is maintained around the chip background level by using a pair of antibodies with different affinity to protein A under optimized experimental conditions. C-reactive protein (CRP), a biomarker for inflammation and cardiovascular disease risk assessment, is selected as a model analyte to demonstrate the sensitivity of this blocking-free microfluidic heterogeneous immunoassay. A four parameter logistic function is used to model and assess the data. The limit of detection obtained is 0.54 μg/mL, which is lower than the cut-off value for clinical diagnosis. The overall assay is completed in 5 min. The protein A modified PDMS chips wet-stored at 4°C can maintain biofunctionality up to 14 months. The developed blocking-free microfluidic heterogeneous immunoassay will immediately provide benefits to most immunosensing microdevices targeted for POC diagnostics by shortening analysis time, simplifying fluid transportation, reducing sample consumption, and lowering waste generation.
KeywordsMicrofluidic immunoassay Blocking-free Fluorescence detection C-reactive protein Point-of-care diagnostics Poly(dimethylsiloxane)
This work was supported by the National Science Foundation (NSF-OISE-0530203) and the NSF EPSCoR Fellowship (to P. Li). We thank Paul W. Johnson at the RI Genomics and Sequencing Center for his technical assistance with the fluorescence imaging, and Kurt Broderick at the Microsystems Technology Laboratories of Massachusetts Institute of Technology for his technical assistance with the microfluidic chip fabrication.
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