Cellular uptake mechanism of molecular umbrella.

Molecular umbrella provided a promising avenue for the design of the intracellular delivery of hydrophilic therapeutic agents. However, the limited understanding of its cellular uptake would be a roadblock to its effective application. Herein, we investigate the ability and mechanism of cellular entry of a fluorescently labeled diwalled molecular umbrella, which was synthesized from cholic acid, spermine, and 5-carboxyfluorescein, into Hela cells, with the extent of uptake analyzed by confocal fluorescence microscopy and flow cytometry. It is found that the as-synthesized diwalled molecular umbrella can greatly facilitate cellular uptake of hydrophilic agent, 5-carboxyfluorescein. In vitro experiments with diffuse marker, endocytic marker, and inhibitors suggested that several distinct uptake pathways (e.g., passive diffuse, clathrin-mediated endocytosis, and caveolae/lipid-raft-dependent endocytosis) are involved in the internalization of diwalled molecular umbrella. These results, together with its low toxicity and good biocompatibility, thus demonstrate the suitability of molecular umbrella for application as vectors in drug delivery systems.