Optical Nanosensors for Real-time Feedback on Insulin Secretion by β-Cells

Quantification of insulin is essential for diabetes research in general, and for the study of pancreatic {beta}-cell function in particular. Herein, fluorescent single-walled carbon nanotubes (SWCNT) are used for the recognition and real-time quantification of insulin. Two approaches for rendering the SWCNT sensors for insulin are compared, using surface functionalization with either a natural insulin aptamer with known affinity to insulin, or a synthetic PEGylated-lipid (C16-PEG(2000Da)-Ceramide), both of which show a modulation of the emitted fluorescence in response to insulin. Although the PEGylated-lipid has no prior affinity to insulin, the response of C16-PEG(2000Da)-Ceramide-SWCNTs to insulin is more stable and reproducible compared to the insulin aptamer-SWCNTs. The C16-PEG(2000Da)-Ceramide-SWCNTs optical response is excitation-wavelength dependent, where resonant excitation leads to a larger fluorescence decrease in response to insulin. The SWCNT sensors successfully detect insulin secreted by {beta}-cells within the complex environment of the conditioned media. The insulin is quantified by comparing the SWCNTs fluorescence response to a standard calibration curve, and the results are found to be in agreement with an enzyme-linked immunosorbent assay (ELISA). This novel analytical tool for real time quantification of insulin secreted by {beta}-cells provides new opportunities for rapid assessment of {beta}-cell function, with the ability to push forward many aspects of diabetes research.