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Figure 2: Schematic illustration for metal-free amino-yne click bioconjugation between chitosan and PEG with fluorescent activated alkynes. (a) Functionalization of natural polymers via the amino-yne click reaction. (b) Photographs of chitosan, Chit-TPA, and Chit-TPE in the presence of UV irradiation or not. (c) Synthetic rout of PEGylation of triphenylamine (TPA) via the amino-yne click reaction. (d) Hydrodynamic diameter distribution and TEM image (inset) determined for the aqueous dispersion of PEG-TPA. (e) Fluorescent emission spectrum of PEG-TPA aqueous dispersion ( = 405 nm, insert photographs: the water dispersion under white light and UV irradiation). (f) CLSM images of EMT-6 cells upon incubating with the aqueous dispersion of PEG-TPA at 5 μM for 4 h and cell nucleus were costained with Red dot1.