Portable electrophoresis titration chip model for sensing of uric acid in urine and blood by moving reaction boundary

Assays of uric acid (UA) in human urine and blood are of great significance to clinic diagnoses of many diseases, such as gout, renal failure, and hyperuricemia. Portable and visual quantification method, however, has been rarely developed for POCT detection of UA in urine and blood samples. In this work, we developed the electrophoresis titration (ET) model, the relevant sensing method and the portable chip device for portable and visual detection of UA in both urine and blood based on moving reaction boundary (MRB). In the model, uricase catalyzes UA in the anode well to allantoin, producing hydrogen peroxide, which oxidizes leucocrystal violet dye without charge to crystal violet (CV+) with one positive charge. Under an electric field, a MRB was created between the violet CV+ moving from the anode well into the channel and the alkaline sodium acetate in channel, resulting in an ET sensing. The model indicated that the distance of MRB under given conditions was as a function of UA content, implying an extraordinary simple sensing for UA. Based on the MRB-ET model, a series of experiments were conducted. The results evidently validated the model and method of ET-MRB. The experiments not only demonstrated the high facility and portability of MRB-ET model, but also showed the visuality, selectivity and rapidity. In addition, the experiments revealed the fair sensitivity (< 0.1 mM), linearity (0.1-4.0 mM, r(2) = 0.9948), recovery (85%-106%) and stability (RSD 3.8-7.1%). Finally, the developed method was successfully used for the determination of UA both in urine and blood. All these results manifested the simple, portable and visual sensing of UA in human body fluid samples, and implied the potential of MRB-ET method to real POCT assay of UA in urine and blood samples.