Photothermal Bar-chart Microfluidic Chips for Detector-free Quantitative Bioanalysis

Conventional biomolecular quantitation methods such as ELISA often have limited applications in low-resource settings due to their dependence on expensive and bulky analytical instruments and signal detectors such as microplate readers. Although the nanoparticle-mediated photothermal effect has attracted increasing attention for photothermal cancer therapy, it has not been systematically studied for quantitative biochemical analysis. We for the first time exploited the photothermal effect for quantitative biomolecular detection in multiple immunoassay systems as well as genetic assays. Herein, we introduced nanomaterial-mediated photothermal effects to bar-chart Chips, and for the first time developed a new type of bar-chart Chip, photothermal bar-chart microfluidic chip (PT-Chip), for visual quantitative detection of biochemicals without any bulky and costly detectors. Immunosensing signals were converted to visual readout signals via photothermal effects, the on-chip bar-chart movements, enabling quantitative biomarker detection on a low-cost polymer hybrid PT-Chip with on-chip scale rulers. Multiple different human serum samples containing prostate-specific antigen (PSA) as a model analyte were detected simultaneously using the PT-Chip, with the limit of detection of 2.1 ng/mL, meeting clinical diagnostic requirements. Although no conventional signal detectors were used, it achieved comparable detection sensitivity to absorbance measurements with a microplate reader. The PT-Chip was further validated by testing human whole blood without the color interference problem, demonstrating good analytical performance of our method even in complex matrices. This new PT-Chip driven by nanomaterial-mediated photothermal effects opens a new horizon of microfluidic platforms for instrument-free diagnostics at the point of care. Financial support from NIH, NSF, CPRIT, DOT, UT STARS Award, UTEP, Philadelphia Foundation, and MCA foundation is gratefully acknowledged.