Analysis of doxorubicin distribution in MCF-7 cells treated with drug-loaded nanoparticles by combination of two fluorescence-based techniques, confocal spectral imaging and capillary electrophoresis.

The intracellular distribution of the antiancer drug doxorubicin (DOX) was followed qualitatively by fluorescence confocal spectral imaging (FCSI) and quantitatively by capillary electrophoresis (CE). FCSI permits the localization of the major fluorescent species in cell compartments, with spectral shifts indicating the polarity of the respective environment. However, distinction between drug and metabolites by FCSI is difficult due to their similar fluorochromes, and direct quantification of their fluorescence is complicated by quantum yield variation between different subcellular environments. On the other hand, capillary electrophoresis with fluorescence detection (CE-LIF) is a quantitative method capable of separating doxorubicin and its metabolites. In this paper, we propose a method for determining drug and metabolite concentration in enriched nuclear and cytosolic fractions of cancer cells by CE-LIF, and we compare these data with those of FCSI. Significant differences in the subcellular distribution of DOX are observed between the drug administered as a molecular solution or as a suspension of drug-loaded iron oxide nanoparticles coated with polyethylene glycol. Comparative analysis of the CE-LIF vs FCSI data may lead to a tentative calibration of this latter method in terms of DOX fluorescence quantum yields in the nucleus and more or less polar regions of the cytosol.

SERS spectroscopic approach to study doxorubicin complexes with Fe(2+) ions and drug release from SPION-based nanocarriers.

The aim of this work is to present a surface-enhanced Raman scattering (SERS) spectroscopic approach to study complexes of a frequently used antineoplastic agent, doxorubicin (DOX), with ferrous ions, at sub-micromolar concentrations in aqueous solution. The SERS bands of DOX were assigned according to critical analysis of literature. Prior to the complexation study, the spectral changes related to the drug orientation on the silver surface and to its protonation state were highlighted. The SERS spectra of DOX-Fe(2+) complexes showed several features distinguishing them from the free drug, protonated or not on the phenolic part of its chromophore. The lowest detectable content of the DOX-iron complex in the presence of free DOX was estimated to be 5-10%. This property is particularly interesting from the analytical point of view, since it allows for study of drug-iron interactions upon the drug loading on and release from magnetic drug carriers based on superparamagnetic iron oxide nanoparticles (SPIONs), stabilized with citrate ions or coated with polyethylene glycol (PEG) polymer. Our SERS data indicate that the drug loaded on magnetic nanocarriers as DOX-iron chelate was mainly released in the free DOX form. These results demonstrate the strength of the SERS approach for the study of DOX-iron interactions in relation to delivery issues and drug action mechanisms.