Glucose oxidase stabilized fluorescent gold nanoparticles as an ideal sensor matrix for dual mode sensing of glucose

In this work, a simple, facile and green route for the preparation of glucose oxidase (GOx) stabilized, size controlled gold nanoparticles (Au NPs) is demonstrated. Interestingly upon changing pH, these Au NPs are disintegrated leading to the formation of GOx stabilized fluorescent gold nanoparticles (FL Au NPs) that emit an intense yellowish green colour on excitation at 365 nm using UV light. Structural and morphological changes are analyzed by using spectroscopy (FTIR and UV-vis), microscopy (TEM) and electrochemical studies. Further colourimetric and electrochemical measurements show the feasibility of employing such materials as an ideal sensor matrix for the determination of glucose using a dual mode sensing strategy. Essentially both Au NPs and FL Au NPs detect glucose at a low concentration with high sensitivity, good stability and reproducibility suggesting promising applications in the field of biosensors. Here, the enzyme GOx plays a bifunctional role as a stabilizer as well as a reducing agent during the preparation of these nanostructured materials. Particularly GOx retains its enzymatic activity and redox activity even after the stabilization of both Au NPs and FL Au NPs. Among the two, GOx-FL Au NPs displays a better catalytic behaviour for detection of glucose and exhibits higher sensitivity, lower detection limits and impressive turn-over frequency numbers for enzymatic catalysis when compared to GOx-Au NPs and other materials reported for the enzymatic detection of glucose. Finally the analytical feasibility of employing such materials as biosensors for the detection of glucose in real samples is evaluated using human blood serum samples and the results are promising indicating the potential utility of these nanomaterials.