A multilevel fluorometric biosensor based on boric acid embedded in carbon dots to detect intracellular and serum glucose

Diabetes mellitus is one of the most common chronic diseases, and blood glucose monitoring benefits for diagnosis and management of diabetic mellitus. In this paper, a multimodal photoluminescence (PL) bio-platform, R-CDs/B2O3, with solid-state fluorescence, was developed by dispersing Rhodamine B carbon dots (R-CDs) in the matrix of boric acid (BA) as a simple, cheap agent for the visual assay of intracellular and serum glucose concentration, which was based on BA can specially bound with 1, 2-diol of glucose. The good linear relationship between the PL spectra of the R-CDs/B2O3 and glucose concentration indicated that R-CDs/B2O3 could dynamically monitor glucose concentration in vitro. Furthermore, the fluorescent color variations of R-CDs/B2O3 gel were monitored by the UV lamp and the green channel intensities of the colored images were processed by using the RGB option of a smartphone, manifesting that R-CDs/B2O3 could be used as a portable test gel for serum glucose. Significantly, it is convenient for self-monitoring of blood glucose for diabetic patients. The method was also successfully used for the assay of glucose in blood serum. Hence, the proposed fluorescence sensor opens the door for further research and development of more reliable non-enzymatic assays for continuous glucose monitoring systems.