Cellular Uptake Mechanism of Paclitaxel Nanocrystals Determined by Confocal Imaging and Kinetic Measurement.

Nanocrystal formulation has become a viable solution for delivering poorly soluble drugs including chemotherapeutic agents. The purpose of this study was to examine cellular uptake of paclitaxel nanocrystals by confocal imaging and concentration measurement. It was found that drug nanocrystals could be internalized by KB cells at much higher concentrations than a conventional, solubilized formulation. The imaging and quantitative results suggest that nanocrystals could be directly taken up by cells as solid particles, likely via endocytosis. Moreover, it was found that polymer treatment to drug nanocrystals, such as surface coating and lattice entrapment, significantly influenced the cellular uptake. While drug molecules are in the most stable physical state, nanocrystals of a poorly soluble drug are capable of achieving concentrated intracellular presence enabling needed therapeutic effects.