A nanoporous palladium(II) bridged coordination polymer acting as a peroxidase mimic in a method for visual detection of glucose in tear and saliva.

A nanoporous coordination polymer (NPCP) was prepared from palladium(II) chloride and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole and is shown to act as a peroxidase mimetic. It can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 which is formed on enzymatic oxidation of glucose by glucose oxidase. Based on these findings, a sensitive glucose test was worked out at 652 nm where the intensity if the greenish-blue product is related to the actual concentration of glucose. Figures of merit include (a) rather low Km value (30 μM) which evidences the strong binding affinity of the NPCP toward glucose, (b) a high v(max) (8.5 M·s-1), (c) a 47 nM detection limit, (d) a lifetime of a month, (e) a wide working pH range (2-10), and (f) a 25-80 °C temperature range. The assay was applied to non-invasive determination of glucose assay in tear, saliva where the detection limits are found to be 61 and 91 nM, respectively. Graphical abstract DSchematic of the mechanism of the peroxidase like catalytic activity of AHMT-Pd NPCP that was applied in a selective colorimetric method for glucose detection based on TMB oxidation in the presence of enzymatically generated H2O2.