Doxorubicin-Nanocarriers Enhance Doxorubicin Uptake and Clathrin-Mediated Endocytosis in Drug-Resistant Ovarian Cancer Cells

We tested Fe3O4 TiO2 metal oxide core-shell nanocomposites as carriers for doxorubicin and investigated the distribution of "doxorubicin-nanocarriers" and free doxorubicin in doxorubicin-sensitive and -resistant ovarian cancer cell lines. We hypothesized that doxorubicin-nanocarriers (DOX-NCs) would increase doxorubicin uptake in a drug-resistant cell line. Our expectation was that doxorubicin would bind to the TiO2 surface either by a labile monodentate link or through adsorption and subsequent disassociation from the nanocomposite carriers upon acidification in cell endosomes. Released doxorubicin could then traverse the intracellular milieu to enter the cell nucleus, overcoming the p-glycoprotein mediated doxorubicin resistance. Using a combination of confocal fluorescent microscopy, flow cytometry, and X-ray fluorescence microscopy we were able to evaluate the uptake and distribution of doxorubicin-nanocarriers in cells. Moreover, we found that nanocomposite treatment modulates the simultaneous uptake and distribution of fluorescent transferrin in ovarian cancer cell lines. This increased transferrin uptake still occurred by clathrin-mediated endocytosis; it appears that the nanocomposites and DOX-NCs alike may interfere with trans-Golgi apparatus function.