Delineating intracellular pharmacokinetics of paclitaxel delivered by PLGA nanoparticles.

Although many studies have shown that drug delivery and efficacy can be improved by nano-sized drug carriers, we understand little regarding their pharmacokinetics (PK). PK calculations for drugs delivered by carriers are more complex than those for drug-only solutions. The overall PK depends on many factors, including drug-release rate and the PK of both the drug itself and the carrier. We built a mathematical model to describe the intracellular PK of paclitaxel delivered by nanoparticles. Paclitaxel was incorporated into poly (lactic-co-glycolic acid) nanoparticles, which were chemically labeled with a fluorescence probe for quantification. PK profiles of drug alone, nanoparticles alone, and drug delivered by nanoparticles were studied in human breast cancer MCF7 cells. Simulated results from the model were similar to observed data, indicating that the model was properly developed. The model clearly and quantitatively represented the effects of relative factors, such as drug dose, drug-release kinetics, and nanoparticle PK, on the PK of paclitaxel delivered by nanoparticles. We also used this model to estimate the intracellular drug-release rate, which was found to be slightly slower than the in vitro release rate in this study. This mathematical model could be used to provide guidelines to design, evaluate, and optimize nano-sized drug carriers.