Biotin-PEG5-azide

Li, Hang, et al. Journal of Photochemistry and Photobiology B: Biology 217 (2021): 112172.

One cyanine dye, named G0, is an excellent near-infrared fluorophore with high photostability and resistance to photobleaching. Furthermore, the two alkynyl groups in G0 can be easily modified with targeting ligands via a copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. Two novel NIR probes, G1 and G2, were developed by conjugating biotin-PEG5-azide to G0. A PEG linker was introduced into the probe structure to reduce its aggregation tendency. First, the octanol-water partition coefficient, absorption intensity and fluorescence intensity of G0, G1 and G2 were compared. The imaging effect of the probe in BR-positive tumor cells and tumor-bearing mice was then studied. Both in vitro and in vivo results indicate that G1 and G2 have a reduced tendency to aggregate in aqueous solutions and can specifically recognize tumors.
Compound G0 (38.0 mg, 0.0648 mmol, 1 eq) and biotin-PEG5-azide
(24.1 mg, 0.0454 mmol, 0.7 eq) were added to CuSO4·5H2O (5.7 mg, 0.0227 mmol, 0.35 eq). Then L-ascorbic acid sodium salt (9.0 mg, 0.0454 mmol, 0.7 equiv) and tris(3-hydroxypropyltriazolylmethyl)amine (THPTA, 9.85 mg, 0.0227 mmol, 0.35 equiv) were added. All compounds were dissolved in N,N-dimethylformamide (DMF) and H2O (DMF:H2O=5:1). The solution was stirred at 25°C for 1.5 h. Afterwards, the solvent was evaporated to dryness. The solid was purified by column chromatography (2-20% MeOH in DCM). After evaporation, G1 was obtained as a dark green solid in 62% yield (45.0 mg, 0.0402 mmol)