Functional expression of FRET-based glucose nanosensor FLII12GLU-700μΔ6 in a cultured astrocyte.
a, CFP and YFP emission images show the expression of the FLII12GLU-700μΔ6 fluorescent nanosensor in an astrocyte. The upper panels show an astrocyte in the medium containing 10 mm
d-glucose; the lower panels show the same cell after superfusion with 0 mm
d-glucose. Scale bar, 10 μm. b, integration of the ratio over the entire cell was used to quantify the change in the ratio. Superfusion of cells initially bathed in high glucose solution (10 mm) with the solution containing 0 mm glucose (gray lines) induced an increase in the CFP fluorescence intensity (left panel) and a decrease in the YFP intensity (middle panel), thus decreasing the YFP/CFP ratio (right panel) and indicating a decrease in the cytosolic glucose levels. Subsequent superfusion with 10 mm
d-glucose induced an increase in the FRET ratio, indicating an increase of intracellular d-glucose caused by glucose entry into the cell. fluo, fluorescence; a.u., arbitrary units.