A comparative study of non-enzymatic glucose detection in artificial human urine and human urine specimens by using mesoporous bimetallic cobalt-iron supported N-doped graphene biosensor based on differential pulse voltammetry

Development of non-invasive glucose measurement allows future advancement of smart sensing platform for diagnostic technology. Especially for endocrine disorders, advanced kidney diseases, and diabetes, monitoring excessive glucose level in urine can provide invaluable information for clinical prognosis and preventive healthcare. Herein, we present a comparative electrochemical study of cobalt/iron (CoFe) catalyst on nitrogen-doped graphene (NG) for non-enzymatic glucose detection, carried out in physiological pH urine including (i) modified artificial urine medium (mAUM), (ii) commercial standard urine (Surine), and (iii) human urine specimens. With no requirement of strong alkaline addition, catalytic properties of CoFe-NG were assessed by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) on a glassy carbon rotating disk electrode. Upon successive glucose additions from 0 to 3 mM, DPV results revealed two anodic peaks at +0.18 V and +0.42 V versus Ag/AgCl, corresponding to Co3+ and Co4+ as a result of glucose binding in urine. By evaluating at +0.18 V, the sensitivities of CoFe-NG were estimated to be 16.77 (R-2 = 0.987), 45.36 (R-2 = 0.988), and 20.26 (R-2 = 0.991) mu A mM(-1) cm(-2) with the limit of detection of 0.25, 0.07, and 0.19 mM in mAUM, Surine, and human urine specimen with low serum creatinine, respectively. Furthermore, the effects of CoFe on graphene (G) and carbon Vulcan XC-72 (C) were also studied in comparison of NG on the bimetal. Interestingly, CoFe-C showed a good electrochemical trend in glucose detection in urine. However, negligible catalytic activity was presented in CoFe-G. Thus, electrochemical responses of CoFe-C were also further studied in the comparison of CoFe-NG in each type of urine. Overall, CoFe-NG outperformed CoFe-C in all types of urine and exhibited an excellent anti-interference property toward uric acid, thereby suggesting great potential for the next generation of glucose sensing platform in urine.