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WITHDRAWN: 5-Fluorouracil-loaded iron/ethylcellulose (core/shell) nanoparticles for active targeting of cancer

Even though 5-fluorouracil has been demonstrated to display antitumor activity against a wide variety of cancers, it is needed to be administered at high doses to elicit the required therapeutic activity, simultaneously leading to severe side effects. We hypothesized that the efficient delivery of 5-fluorouracil to tumors using a magnetic colloid could reduce the dose required to bring out sufficient therapeutic response. Thus, we have formulated a 5-fluorouracil-loaded magnetic nanomedicine consisting of a magnetic core (iron) and a biocompatible polymeric shell (ethylcellulose), suitable for parenteral administration. These core/shell nanoparticles were synthesized by an emulsion solvent evaporation process. Two drug loading methods were analyzed: the first one based on 5-fluorouracil surface adsorption onto the preformed nanoparticles, and the second method being drug addition prior to the emulsion solvent evaporation process leading to drug entrapment into the polymeric network. 5-Fluorouracil entrapment into the polymeric matrix yielded a higher drug loading and a slower drug release profile as compared with drug adsorption. Finally, as a proof of concept, Prussian blue staining has demonstrated the considerable accumulation of these magnetically guided composite nanoparticles in the tumors, suggesting the potential of this stimuli-sensitive drug carrier for the efficient treatment of cancer by active targeting.