Biomimetic Polythiophene: g-C₃N₄ Nanotube Composites with Induced Creatinine and Uric Acid Specificity for Portable CKD and Gout Detection

Despite significant advancements in disease diagnostics, the development of portable, highly selective, and low-cost electrochemical sensors for real-time, noninvasive detection of chronic kidney disease (CKD) and gout biomarkers remains a challenge. In this work, we demonstrate an inexpensive CKD and gout diagnostic platform with the incorporation of biomimetic polymer matrix nanocomposites based on creatinine (CRE) and uric acid (UA) imprinted conducting polythiophene (MIP) and graphitic carbon nitride nanotubes (NTs). These nanocomposites are termed CRE-MIPNT or UA-MIPNT, depending on the template. Disposable electrochemical devices are fabricated by anchoring CRE-MIPNT or UA-MIPNT nanocomposites on screen-printed Au microelectrodes. The surface micrographs exhibit the integration of NTs in the polymer matrix, resulting in highly leptokurtic surfaces. Consequently, the charge transfer resistance at the electrode-electrolyte interface is significantly reduced, as characterized by electrochemical impedance spectroscopy. An increase in the electroactive surface area and charge transfer kinetics is also observed for the CRE-MIPNT/Au-SPE and UA-MIPNT/Au-SPE sensors. In comparison to nonimprinted sensors, their performance is investigated in terms of their voltammetric response toward various biomarker concentrations in standard redox solutions. The sensitivity in the CV measurements is 0.59 μA cm^-2 nM^-1 for CRE-MIPNT/Au-SPE and 0.78 μA cm^-2 μM^-1 for UA-MIPNT/Au-SPE sensors, with detection limits of 390 pM and 162 nM for CRE and UA, respectively. The sensors demonstrate high selectivity toward the target analytes while showing minimal interference from other metabolites. Moreover, recovery rates for spiked saliva samples ranged between 97 and 102%, which indicates the reliability of the sensor for real-world applications.