Real-Time, Label-Free Detection of Local Exocytosis Outside Pancreatic β Cells Using Laser Tweezers Raman Spectroscopy.

The examination of insulin (Ins) exocytosis at the single-cell level by conventional methods, such as electrophysiological approaches, total internal reflection imaging, and two-photon imaging technology, often requires an invasive microelectrode puncture or label. In this study, high concentrations of glucose and potassium chloride were used to stimulate β cell Ins exocytosis, while low concentrations of glucose and calcium channel blockers served as the blank and negative control, respectively. Laser tweezers Raman spectroscopy (LTRS) was used to capture the possible Raman scattering signal from a local zone outside of the cell edge. The results show that the frequencies of the strong signals from the local zones outside the cellular edge in the stimulated groups are greater than those of the control. The Raman spectra from the cellular edge, Ins and cell membrane were compared. Thus, local Ins exocytosis activity outside pancreatic β cells might be observed indirectly using LTRS, a non-invasive optical method.