Fluorometric methods for determination of H2O2, glucose and cholesterol by using MnO2 nanosheets modified with 5-carboxyfluorescein

A fluorescent probe for H2O2 is described. It is composed of MnO2 nanosheets and 5-carboxyfluorescein and was characterized by fluorescence, transmission electron microscopy, ultraviolet-visible absorption spectra, energy dispersive X-ray and Fourier transform infrared spectroscopy. The probe, with fluorescence excitation/emission maxima at 490/518nm, responds to H2O2 in the 1 to 200M concentration range and has a 0.33M detection limit. The probe was used in enzymatic assays for glucose and cholesterol by using the respective oxidases which produce H2O2. Responses are linear in the concentration range from 0.5 to 200M in case of glucose, and from 1 to 300M in case of cholesterol. The method was applied to quantify glucose and cholesterol in (spiked) serum samples.