A miniaturized optoelectronic biosensor for real-time point-of-care total protein analysis.

A miniaturized optoelectronic sensor is demonstrated that measures total protein concentration in serum and urine with sensitivity and accuracy comparable to gold-standard methods. The sensor is comprised of a vertical cavity surface emitting laser (VCSEL), photodetector and other custom optical components and electronics that can be hybrid packaged into a portable, handheld form factor. In conjunction, a custom fluorescence assay has been developed based on the protein-induced fluorescence enhancement (PIFE) phenomenon, enabling real-time sensor response to changes in protein concentration. Methods are described for the following:•Standard curves: Used to determine the sensitivity, dynamic range, and linearity of the VCSEL biosensor/PIFE assay system in buffer as well as in human blood and urine samples.•Comparison of VCSEL biosensor performance with a benchtop fluorimetric microplate reader.•Accuracy of the VCSEL biosensor/PIFE assay system: Evaluated by comparing sensor measurements with gold-standard clinical laboratory measurements of total protein in serum and urine samples from patients with diabetes.

Real-time point-of-care total protein measurement with a miniaturized optoelectronic biosensor and fast fluorescence-based assay.

Measurement of total protein in urine is key to monitoring kidney health in diabetes. However, most total protein assays are performed using large, expensive laboratory chemistry analyzers that are not amenable to point-of-care analysis or home monitoring and cannot provide real-time readouts. We developed a miniaturized optoelectronic biosensor using a vertical cavity surface-emitting laser (VCSEL), coupled with a fast protein assay based on protein-induced fluorescence enhancement (PIFE), that can dynamically measure protein concentrations in protein-spiked buffer, serum, and urine in seconds with excellent sensitivity (urine LOD = 0.023 g/L, LOQ = 0.075 g/L) and over a broad range of physiologically relevant concentrations. Comparison with gold standard clinical assays and standard fluorimetry tools showed that the sensor can accurately and reliably quantitate total protein in clinical urine samples from patients with diabetes. Our VCSEL biosensor is amenable to integration with miniaturized electronics, which could afford a portable, low-cost, easy-to-use device for sensitive, accurate, and real-time total protein measurements from small biofluid volumes.