Electrochemically-functionalized CNT/ABTS nanozyme enabling sensitive and selective voltammetric detection of microalbuminuria

Developing a cost-effective and reliable sensing platform for the routine screening of microalbuminuria and early diagnosis of chronic kidney disease is of great importance. Herein, we report on the high specificity and electrocatalytic activity of CNT/ABTS_(CV) nanozyme, derived from the electrochemical functionalization of the carbon nanotube/2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) nanocomposite CNT/ABTS), towards electrochemical oxidation of human serum albumin (HSA) in urine. The potential cycling of CNT/ABTS electrode resulted in the surface functionalization with imine and carbonyl functional groups, which enhances electrode's affinity towards the electroactive tyrosine and tryptophan amino acids and thus facilitates the adsorption and subsequent electrochemical oxidation of HSA. The developed CNT/ABTS_(CV) nanozyme modified electrode showed promising sensing characteristics for the point-of-care diagnosis of microalbuminuria without any sample pretreatment and inclusion of additional label or redox probes during measurement, including a practical sensing range up to 1.50 μM, a low detection limit of 60 nM, good reusability (>5 cycles), good long-term stability (>28 days), and high accuracy (error <15%) for the detection of HSA in urine. This work opens a new avenue for the detection and quantification of proteins in physiological conditions.