Fig. 2. (a) Schematic of the monosaccharide expression process. Following nanopipette injection of an artificial monosaccharide ManNAz, SiaNAz was expressed on the surface of a selected cell, and then tagged by alkyne-AF488 (green). Microscopic images showing SiaNAz level under (b) various expression times (from up to down: 5, 6, 15 h); (c) various injection times (from up to down: 2, 3, 5, 8 min); (d) various injection voltages (from up to down: 200, 400, 600, 800 mV) & (e) control. Column from left to right (b–e): Bright field, green fluorescence, 2D color-coded green channel intensity. Scale bar, 20 μm. (f) Average green channel intensity of MCF-7 cells corresponding to different conditions in (b), (c) and (d) ((i): (b), (ii): (c), (iii): (d)). *Optimized condition (b–e). (g) Optimized conditions for the nanopipette labeling experiments.