Figure 5: Specific photoswitching of beta cell function in the violet-blue spectrum.

(a) JB253-treated cells loaded with the red-shifted Ca²⁺ indicator X-Rhod1 (λ excitation=561 nm) similarly respond to 405 nm with Ca²⁺ rises (representative traces from n=3 recordings). (b) As in a, but imposition of oscillations (representative traces from n=3 recordings). (c) JB253-treated beta cells display large increases in cytosolic Ca²⁺ following exposure to 440 nm (representative trace from n=6 recordings). (d) As in c, but following illumination with 491 nm (Tb, tolbutamide; positive control) (representative trace from n=5 recordings). (e) A single islet can be photoswitched using a targeting laser while leaving its neighbour quiescent (~200 μm center–center) (representative traces from n=3 recordings). A global laser pulse evokes activity in both islets (grey, raw; red, smoothed). (f) Incubation of islets with JB253 does not alter cell viability as assessed by calcein-AM and propidium iodide incorporation (NS, not significant versus DMSO alone, Student’s t-test) (n=28 islets from four animals). Values represent mean±s.e.m.