Highly permselective uric acid detection using kidney cell membrane-functionalized enzymatic biosensors

Abnormal blood uric acid (UA) levels can lead to its crystallization in the joints, consequently resulting in gout. Accurate detection of UA in the blood is imperative for the early diagnosis of gout. However, electrochemical UA biosensors are vulnerable to antioxidants in the blood, limiting accurate UA detection. To address this issue, we focused on the function of uric acid transporter 1 (URAT1), which is selectively permeable to UA. URAT1 is abundant in the kidney cell membrane (KCM). To apply URAT1 to a sensor, we developed a KCM-coated UA biosensor (called the KCM sensor) that could selectively detect UA through URAT1. The KCM coating in the fabricated KCM sensor was verified via scanning electron microscopy, atomic force microscopy, and confocal microscopy. The KCM sensor enabled the detection of UA in the range of 0-1000 μM, with a limit of detection of 8.5 μM, suggesting that it allows the diagnosis of the early stages of gout. On the other hand, the UA permeability of the KCM sensor was significantly reduced in the presence of a URAT1 inhibitor, implying that URAT1 is a key factor for UA detection. The selectivity of the KCM sensor was demonstrated by measuring the amount for UA in the presence of various antioxidants. Finally, the KCM sensor was capable of measuring UA in human serum and was reproducible with 0.5-1.6% deviation. The UA permeability and selectivity of the KCM sensor were maintained even after 3 weeks of storage.