Hetero Metal-Organic Hybrids as Highly Active Peroxidase Mimics for Biosensing Application

We have described a facile methodology for producing a series of novel homo and hetero metal organic hybrids (OGH) using Fe, Cu and trithiocyanuric acid (TTCA), and have demonstrated that the presence of both metals together considerably enhances the peroxidase activity of the hybrids, relative to either metal on its own. Characterization by XRD, FTIR, Raman spectroscopy and XPS indicated that the hetero materials consisted of predominantly Fe2+ and Cu+ and that bonding to Cu was largely through the N and S of the TTCA, while bonding to Fe was largely through Fe-S bonds. The Fe : Cu content of the hetero materials was varied systematically in the approximate ratios 1 : 1, 1 : 2 and 2 : 1, as confirmed by elemental analysis. Peroxidase activity was examined using 3,3 ',5,5 '-tetramethylbenzidine (TMB), dopamine (DA) and luminol as co-substrates. The 1 : 1 Fe : Cu catalyst was found to have the highest activity. Kinetic analysis indicated that TMB and dopamine oxidation proceeded by a sequential Bi-Bi mechanism. This mechanism utilized dissolved O-2 and generated (OH)-O-. radicals, as indicated by experiments with N-2 purging and a hydroxyl trapping reagent. Based on K-M values, substrate affinities were in the order TMB>H2O2>dopamine. Chemiluminescence in the presence of luminol and glucose oxidase-generated H2O2 was used to calibrate glucose in the range 2-10 mM. The hetero metal hybrid catalyst was stable for two months when stored at room temperature.