Simplified Salivary Uric acid Sensing System using a Filter paper for Saliva Collection

Here, we report an electrochemical biosensor aimed at daily self-check of salivary uric acid (UA). For this purpose, a paper-based sampling device and an amperometric biosensor with a reaction chamber designed for inserting the sampling device were employed. Our sampling device was made of a flexible material based on filter paper and it is possible to collect certain amount of saliva with sufficient reproducibility by gently putting it on the salivary gland for about 5 seconds. The biosensor measures UA contained in the sampling device by inserting it into the reaction chamber, filled with phosphate buffer saline (PBS). The output current of the biosensor was proportional to the concentration of UA, which contained in the solution collected by the sampling device, from 10 μM – 400 μM. As a real sample test, the biosensor was used for the measurement of UA levels of a healthy male volunteer. The output current increased immediately when the sampling device containing saliva was inserted to the reaction chamber. Concentration of salivary UA was estimated to 150 μM, which value was compatible to the reported UA levels in saliva.