An Optofluidic System for Monitoring Fluorescently Activated Protein Biomarkers

The ability to monitor protein biomarkers at clinically relevant concentrations is a powerful approach that provides insights into health status. The synergistic combination of microfluidics and photonics (optofluidic) has emerged as a new means to achieve this capability for detection and manipulation of biological samples. Here in this work, we demonstrate an optofluidic device which integrates the detection and the particle-focusing components to facilitate on-chip measurement of protein levels. With this design, we use a laser-induced fluorescence technique for the direct measurement of protein levels on magnetic bead complexes tagged with fluorescein isothiocyanate (FITC) fluorophore. The developed system was employed for the detection of human immunoglobulin G (IgG) as a model protein within a range of 0–20 μg/mL, showing an ability to resolve the fluorescence signal from different IgG concentrations down to 5.4 nM (0.81 μg/mL). The selectivity in detecting specific IgG target was tested by comparing the fluorescence signal levels from other interfering proteins such as bovine serum albumin (BSA) and human IgM. Although our system was designed for detecting IgG protein, this optofluidic device can be a powerful platform for the rapid detection of a diverse range of biomarkers, including viral pathogens retaining adequate signal sensitivity and selectivity.