Fig. 3

Focused diode laser stimuli rapidly increase temperature at the bottom of a cell culture dish. A–C Photothermal study using temperature-sensitive L-DNA beacons suspended in Tyrode's solution with GFP transfected HEK cells for size comparison. A laser pulse of 135 mW for 200 ms induces a fluorescence signal with a Gaussian spatial distribution (C). Dotted red lines indicate 1/e of maximum used to determine spot diameter (60 µm). D–F Ratiometric microfluorimetry of calcium transients in HEK cells transfected with TRPV1 and loaded with FURA-2. The calcium response profile of responding cells reflects the spatial heating pattern (F), dotted red lines indicate 1/e diameter. This diameter (about 100 µm) was used for definition of ROIs within laser radiated area