Integrated optofluidic nanopore sensor technologies have enabled label-free quantification of molecular biomarkers by digital detection of target biomolecules with the electrical translocation signal created during passage through a nanoscale opening. The approach utilizes planar waveguide-based optical trapping combined with a customized microfluidic channel geometry for million-fold target concentration enhancement underneath a nanopore. The optofluidic device design is optimized for better optical trapping performance utilizing both gradient and scattering optical forces. Combined with a target-specific bioassay, this simple, direct, and highly sensitive detection method enables amplification-free and calibration-free biomarker quantification. Using this platform, we show viral load day progression of Zika and SARS-CoV-2 infections from different biofluids in primate models across the clinically relevant concentrations range (five orders) down to 10 aM –comparable to and sometimes improving upon qRT-PCR results. We also report the use of this integrated sensor for extracellular vesicle cargo monitoring from cerebral organoids grown in conditioned media.
Integrated nanopore sensors enable label-free electrical detection of single molecular biomarkers using modulations in ionic current across a nanoscale opening in a solid-state membrane. Optical trapping can dramatically increase the rate of molecular detection and, thus, significantly speed up the sensing process. This is accomplished by optical delivery of microbeads that carry molecular targets that are specifically bound to their surface. Once trapped at the nanopore location, targets are released from the carrier bead and drawn through the pore by the large electric field that is present right at the pore location. We review the principle and implementation of this approach on an optofluidic chip. We report over 1000x improvement in sensing time and the application of these devices to detection of different molecular biomarkers and for infectious disease diagnosis of clinical samples.
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