Discerning biomimetic nanozyme electrodes based on g-C3N4 nanosheets and molecularly imprinted polythiophene nanofibers for detecting creatinine in microliter droplets of human saliva

The growing risk of death associated with kidney dysfunction underlines the requirement for a cost-effective and precise point-of-care (POC) diagnostic tool to identify chronic kidney disease (CKD) at an early stage. This work reports the development of a non-invasive POC diagnostic based on cost-efficient, disposable electrodes and in situ-designed biomimetic nanozymes. The nanozymes are composed of graphitic carbon nitride nanosheets (gCN) and creatinine-imprinted polythiophene nanofibers (miPTh). Microscopic analyses reveal porous nanofibrous surface morphology of biomimetic miPTh/gCN nanozymes. Bulk imprinting and the inclusion of conductive gCN nanosheets drastically reduced the charge transfer resistance and improved the electron exchange kinetics at the nanozyme-electrolyte interface. The electrochemical oxidation of creatinine is studied via cyclic voltammetry (CV), and differential pulse voltammetry (DPV), which exhibit excellent creatinine recognition ability of biomimetic miPTh/gCN nanozyme sensors compared to pristine polymeric or non-imprinted nanozymes. The sensor reveals linear response toward 200–1000 nmol L−1 creatinine, high sensitivity (4.27 μA cm−2 nmol−1 L), sub-nanomolar detection limit (340 pmol L−1), and excellent selectivity over common salivary analytes. To corroborate its real-world utility, the miPTh/gCN nanozyme sensor shows an impressive 94.8% recovery of spiked creatinine concentrations in microliter droplets of human saliva samples. This disposable sensor reveals great potential in the realm of reliable and efficient non-invasive POC diagnostics for healthcare delivery.