Smartphone-based portable photoelectrochemical biosensing system for point-of-care detection of urine creatinine and albumin

Creatinine and albumin are crucial biomarkers for health monitoring and their ratio in urine is an effective approach for albuminuria assessment. Herein, to address the challenges of point-of-care and efficient analysis of the biomarkers simultaneously, we developed a fully integrated handheld smartphone-based photoelectrochemical biosensing system. A miniaturized printed circuit board included a potentiostat for photocurrent measurements and single-wavelength light-emitting diodes (LEDs) for photo-excitation, which was controlled with a Bluetooth-enabled smartphone. Graphitic carbon nitride (g-C3N4)/chitosan nanocomposites were modified on a transparent indium tin oxide (ITO) electrode as photoactive materials. Creatinine was detected through chelate formation with copper ion probes, while albumin was recognized specifically by an antigen–antibody reaction based on immunoassay. The biosensing system demonstrated good linearity and high sensitivity, with detection ranges of 100 μg mL−1 to 1500 μg mL−1 for creatinine, and 9.9 μg mL−1 to 500 μg mL−1 for albumin. Spiked artificial urine samples with different concentrations were tested to confirm the practical validity of the biosensing system, where an acceptable recovery rate ranged from 98.7% to 105.3%. This portable photoelectrochemical biosensing platform provides a convenient and cost-effective method for biofluid analysis, which has an extensive prospect in point-of-care testing (POCT) for mobile health.