In vitro cytotoxic activity of cationic paclitaxel nanoparticles on MDR-3T3 cells.

Cationic paclitaxel nanoparticles were developed and the possible delivery mechanism was explored by cellular uptake studies. In vitro cytotoxicity of paclitaxel-loaded nanoparticles was evaluated with NIH-3T3 cells and multidrug resistant MDR-3T3 cells (with active P-glycoprotein). The IC(50)s of paclitaxel nanoparticles, liposomal paclitaxel, and Taxol (R) on NIH-3T3 cells were 0.7 mu g/mL, 3.0 mu g/mL, and 3.6 mu g/mL, respectively, and on MDR-3T3 cells changed to 1.4 mu g/mL, 4.4 mu g/mL, and 7.3 mu g/mL respectively. After addition of verapamil (nonspecific P-glycoprotein inhibition), the IC(50)s on MDR-3T3 cells changed to 0.3 mu g/mL, 0.7 mu g/mL, and 1.5 mu g/mL, respectively. The cellular uptake study of NBD-DOPE labeled nanoparticles by MDR-3T3 cells showed more cellular associated fluorescence than neutral liposomes (EPC/cholesterol). The cellular uptake was not affected by verapamil. Fluorescent nanoparticle-encapsulated 10-nonyl bromide acridine orange also demonstrated an enhanced uptake compared to neutral liposomes. The cellular uptake was increased after verapamil's addition. The cellular uptake of formulations with increased positive charges and the competition of free cationic lipid GL89 demonstrated that the positive charge of the particles enhanced the cellular uptake. In conclusion, although the cationic paclitaxel nanoparticle is susceptible to P-glycoprotein efflux, it is still a promising delivery system for paclitaxel, because of enhanced uptake, which resulted in significantly increased cytotoxicity.