Tracing transport of chitosan nanoparticles and molecules in Caco-2 cells by fluorescent labeling

The aim of this study was to explore the transport properties of chitosan nanoparticles and molecules in Caco-2 cells. Fluorescein isothiocyanate-labeled chitosan (f-CS) was synthesized and prepared into nanoparticles (f-CNP). The f-CNP exhibit a mean size of 58.04 nm and a mean charge with +41.63 mV. Cytotoxicities of the f-CNP and the f-CS against Caco-2 cells were disregarded in the transport study. The transport was observed under fluorescence microscope. The f-CNP could be transported into Caco-2 cells across the cell membrane, and showed concentration-dependent and saturable intracellular fluorescence signal at 37 °C. Meanwhile, the energy-dependence of the trans-membrane transport of f-CNP was not observed at 4 °C. The f-CS was mainly accumulated in the cell peripheral and showed a concentration-dependent intercellular fluorescence signal. Thus, formulation of chitosan into nanoparticles significantly improved its trans-membrane transport in Caco-2 cells.