Synthesis and cellular properties of Near-IR BODIPY-PEG and carbohydrate conjugates

A series of red and near-IR fluorescent BODIPY conjugates, containing either one or two indolylstyryl groups at the 3- and/or 5-positions and a low molecular weight PEG or carbohydrate group, were synthesized using a Cu(I)-catalyzed azide-alkyne Huisgen cycloaddition ('click' reaction). All BODIPY conjugates show emission and fluorescence quantum yields in the ranges of 642-732 nm and 0.24-0.56, respectively, and Stokes' shifts of ca. 30 nm. In vitro cellular investigations using human carcinoma HEp2 cells showed that all BODIPYs are non-toxic, both in the absence and presence of light (1 J/cm2), up to 100 μM concentrations. The PEG and galactose conjugates were more efficient at cell internalization than the unconjugated BODIPYs. The mono-indolylstyryl-BODIPYs showed higher cellular uptake (about five-fold) compared with the di-indolylstyryl-BODIPYs, and higher fluorescence quantum yields.

Graphical abstractDownload full-size imageA series of novel BODIPY conjugates, containing either one or two indolylstyryl moieties and a PEG or carbohydrate group were synthesized and investigated. The conjugates show near-IR emissions (642-732 nm), quantum yields in the range 0.24-0.56, no cytotoxicity and high cellular permeability in human carcinoma HEp2 cells.