Smartphone-Based High-Throughput Fluorimetric Assay for Histidine Quantification in Human Urine Using 96-Well Plates

A high-throughput fluorimetric assay for histidine was developed, using a 96-well plates platform. The analyte reacts selectively with o-phthalaldehyde under mild alkaline conditions to form a stable derivative. Instrumental-free detection was carried out using a smartphone after illumination under UV light (365 nm). The method was proved to be linear up to 100 & mu;M histidine, with an LLOQ (lower limit of quantification) of 10 & mu;M. The assay was only prone to interference from glutathione and histamine that exist in the urine samples at levels that are orders of magnitude lower compared to histidine. Human urine samples were analyzed following minimum treatment and were found to contain histidine in the range of 280 to 1540 & mu;M. The results were in good agreement with an HPLC corroborative method.

Automated summary

A high-throughput fluorimetric assay for histidine was developed using a 96-well plates platform. The method detects histidine in human urine samples using a smartphone after illumination under UV light without the need for instruments. The results were in good agreement with an HPLC corroborative method, and the assay showed minimal interference from other substances in urine.