Internalization and retention of nanodiamonds by MCF-7 cells in vitro: a potential drug delivery platform.

Abstract

Abstract Abstract #2134 Background: Selective uptake and prolonged retention of drugs will facilitate pharmacotherapy to the breast. This may be accomplished by complexing of drugs to carbon-based nanodiamond (ND) particles, 2-8nm size. ND particles are attractive for this purpose because they are inert and non-toxic.We tested the uptake and retention of ND particles by the estrogen receptor positive breast cancer cell line MCF-7.
 Methods: Polylysine coated ND were labeled with fluorescein isothiocyanate (FITC-ND), and examined by UV-visible spectra and found to be stable. MCF-7 cells were cultured on Lab-Tek II chamber slides using DMEM with 10% FCS, insulin, sodium pyruvate, L-glutamine, and Pen/Strep. To assess the efficiency of ND internalization, we added 10ug/ml ND-FITC in complete media to the chamber slides and incubated for 30 min, 1 hr, 3 hr, 4 hr, 17 hr, and 24 hr. FITC-ND was withdrawn from the medium after an initial exposure of 17 hr by washing of cells, and retention of fluorescence was measured at intervals, up to 3 days after withdrawal. To assess the ability of MCF-7 cells to take up NDs under low metabolic conditions MCF-7 cells were incubated in serum-free medium. As a control soluble FITC alone was incubated at 10 ug/ml with MCF-7 cells. Cells were imaged on the laser confocal microscope and FITC detection at 488nm was analyzed by three dimensional Z stack imaging.
 Results: Fluorescence was initially associated with the membrane surface, and later was visualized in the cytoplasm and in the perinuclear zone. Cellular uptake of FITC and ND-FITC occurred at 30 minutes and reached a maximum at 17 hr of incubation. After washing of cells, the retention studies showed little decrease in the intensity of the ND-FITC signal within the cells up to 96 hours. The FITC molecule was readily released from the cells by passive diffusion within 24 hours while NDs appeared to be compartmentalized in cytoplasmic vesicles.
 
 Conclusions: Internalization of ND particles within the cell cytoplasm occurs within a relatively short time, and the ND particles are retained for at least 96 hours following removal from the culture medium. This prolonged retention is likely to be an advantage when considering novel routes of drug delivery to the breast, such as transdermal or intraductal approaches.
 Funded by Avon. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2134.