Development of a smartphone integrated 3D-printed point of care platform for sensitive detection of bilirubin

Strategic design and development of nanomaterials-based detection platforms specific to critical biomarkers like bilirubin holds immense promise for revolutionizing early disease detection. Bilirubin (BR) plays a pivotal role as a biomarker for liver function, making accurate and timely detection of BR crucial for diagnosing and monitoring of liver diseases. In this work, we synthesized blue light emitting graphene quantum dots (GQDs) via a single step pyrolysis method, which exhibited excellent photostability and biocompatibility. Under optimal conditions, the fluorescence of GQDs was significantly quenched with the successive addition of BR achieving an ultra-low detection limit (38.96 nM) over a concentration range of 0.18 μM-14.29 μM with high selectivity, and rapid response towards free BR. The sensing mechanism was identified as the inner filter effect after extensive investigations. Thereafter, the sensor system was directly applied to human serum and urine samples and was further compared with the conventional Jendrassik and Grof method, yielding satisfactory recoveries. To demonstrate the sensor system's potential for real world applications, we designed and fabricated a prototype point-of-care device (POC) through 3D printing, incorporating paper microfluidic devices and fluorescence image analysis-based android application through smartphone. The compact 3D-printed POC device achieved a detection limit of 114.66 nM for BR detection, proving to be a promising platform for affordable, efficient and rapid BR detection.