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Graphical abstract:

A simple and low-cost chemical modification process was employed for the synthesis of fluorescently labeled galactoxyloglucan (FITC-GXG). Reactive carbamoyl groups of fluorescent dye were covalently attached to activated hydroxyl groups of GXG through thiocarbamoyl linkage. Fourier transform infrared spectrometry, UV–visible absorbance spectrophotometry, thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) confirmed the successful introduction of the fluorescent groups. Compared with a mixture of uncoupled FITC and GXG, covalently linked FITC-GXG displayed a more obvious fluorescence intensity and higher photostability. Furthermore, FITC-GXG was biocompatible with cells and could be easily internalized. Mechanisms of internalization of FITC-GXG were studied using pharmacological inhibitors for clathrin-mediated and caveolae-mediated endocytosis in lung adenocarcinoma cell lines. In vitro and in vivo bio-distribution of these fluorescently labeled polysaccharides revealed the higher rate of accumulation in tumor tissues due to the tumor homing property of GXG.