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Cellular uptake and concentrations of tamoxifen upon administration in poly(ε-caprolactone) nanoparticles

Purpose: In an attempt to increase the local concentration of tamoxifen in estrogen receptor positive breast cancer cells, we have prepared and characterized poly (ε-caprolactone) (PCL) nanoparticle formulation. Methods: PCL (mol wt 14,800 daltons) nanoparticles were prepared by the solvent displacement method in acetonewater system in the presence of Pluronic F-68. PCL nanoparticles, labeled with rhodamine 123, were incubated with MCF-7 estrogen receptor positive breast cancer cells to determine uptake, intracellular distribution, and localization as a function of time. Intracellular drug concentrations over a specified period of time using different initial doses were examined using tritiated [3H]-tamoxifen. Results: A significant fraction of the administered rhodamine 123-loaded PCL nanoparticles was found in the perinuclear region of the MCF-7 cells, where estrogen receptors are also localized, after 1 hour of incubation. Measurements of the intracellular concentrations revealed that most of the administered nanoparticle dose was internalized within the first 30 minutes of incubation, and the uptake followed saturable transport kinetics. Conclusion: Results of this study show that PCL nanoparticles were rapidly internalized in MCF-7 cells and intracellular tamoxifen concentrations followed a saturable process. This approach may provide better therapeutic benefit by delivering the drug locally, near the tumor cells, for a longer period of time.