Enzyme-Free Colorimetric Detection of Glucose Using a Composite Entrapping Gold and Magnetic Nanoparticles Within an Agarose Gel Matrix

In this study, we developed a highly stable nonenzymatic biosensor for the colorimetric detection of glucose using a composite that entraps gold and iron oxide magnetic nanoparticles (AuNPs and MNPs, respectively) in an agarose gel matrix. The glucose sensing mechanism relies on the generation of H₂O₂ through the glucose oxidase-mimicking activity of AuNPs in the presence of glucose, which consequently activates the subsequent peroxidase-like catalytic property of MNPs to convert a chromogenic substrate into a colored end product. Using this method, the targeted glucose can be successfully detected over a wide linear range, from 5 to 500 mM, and with a lower detection limit of 1 mM, which is compatible with the diagnosis of high levels of glucose (hyperglycemia) in human blood. Moreover, excellent stability and reusability were yielded. The biosensor also exhibited an acceptable selectivity toward detecting target glucose molecules, even in the presence of interfering biomolecules commonly found in human blood, and a high degree of precision when testing real human blood samples. Therefore, this enzyme-free method could provide a convenient tool toward the stable analysis of glucose, and represent a new analytical paradigm, capable of replacing conventional, but unstable, natural enzyme-based methods.