Magnetite as a platform material in the detection of glucose, ethanol and cholesterol

In the present study, amperometric biosensor platforms based on polydopamine-coated magnetite nanoparticles were fabricated for the detection of biomolecules, such as glucose, cholesterol and ethanol. Briefly, magnetite nanoparticles were electrochemically obtained and subsequently coated with polydopamine to prevent aggregation and degradation. The modified nanoparticles were evaluated for their ability to detect hydrogen peroxide as a global reaction; the detection of glucose, cholesterol and ethanol are all based on detecting hydrogen peroxide. Although polydopamine is a non-conducting polymer, its detection limit and sensitivity values were similar to those observed for sensors with uncovered magnetite nanoparticles as a platform, indicating the viability of using these polydopamine-modified magnetic nanoparticles as a platform via further immobilization of the enzymes onto their surfaces. Subsequently, the enzymes used to detect biomolecules (Glucose oxidase, Alcohol oxidase and Cholesterol oxidase) were covalently attached to the polydopamine coating following EDC/NHS chemistry for the conjugation of amine and carboxyl acid groups. The detection capacity of the biosensors for the three biomolecules was investigated using amperometric measurements. In all cases, the detection limit and sensitivity values were comparable or even better than previously reported. In addition, these biosensors showed high selectivity for the studied biomolecules, excluding interference from other analytes, such as ascorbic acid, uric acid and NaCl. Moreover, the determination of biomolecules in actual samples was performed, and the results in all cases were consistent with the values reported using the fabricant.