Enzyme-free detection of creatinine as a kidney dysfunction biomarker using TiO₂ flow-through membranes

TiO₂ nanotube flow-through membranes (TNTsM) were fabricated via anodization of Ti foil and explored as a biosensing platform for creatinine detection. The electrodes were prepared in different configurations including TNT membrane with top surface up (TNTsMTU/TNPs/FTO), TNT membrane with bottom surface up (TNTsMBU/TNPs/FTO), TNT membrane with top surface up containing nanograss (TNTsMNG/TNPs/FTO), and TNTs/NPs/FTO and TiO₂ nanoparticles (TNPs) film on fluorine doped tin oxide (TNPs/FTO). Electrochemical studies depict the higher electrochemical activity (sensitivity ∼19.88 μA μM^-1 cm^-2) of TNTsMTU/TNPs/FTO towards creatinine compared to other configurations. This exceptional performance of the TNTsMTU/TNPs/FTO electrode results from the flow-through nature of TNTsM and the removal of the bottom oxide barrier layer through etching in H₂O₂. The underlying layer of TiO₂ NPs also contributes to the higher current response of the TNTsMTU/TNPs/FTO. The relevance of the biosensor structural design is demonstrated by the increased amperometric response of TNTsMTU/TNPs/FTO and greater redox peak current in cyclic voltammograms. Furthermore, the higher selectivity, stability, and reproducibility of the electrode can be due to the suitable redox potential, chemical stability, and controlled fabrication process of TNT membranes.