Loading of 5-Fluorouracil to Poly(ethyl-2-cyanoacrylate) Nanoparticles with a Magnetic Core

In this article we describe a detailed investigation of the capabilities of poly(ethyl-2-cyanoacrylate, PE-2-CA) and magnetite/PE-2-CA core/shell nanoparticles to load the antitumour drug 5-fluorouracil (5-FU). The nuclear magnetic resonance and secondary ion mass spectrometry analysis of the polymeric particles allowed us to conclude about their composition and molecular weight distribution. The hysteresis cycles of both magnetite and magnetite/polymer particles demonstrated that the polymer shell reduces the magnetic responsiveness of the particles but keeps unchanged their soft ferrimagnetic character. The effect of synthesis residues on the absorbance of supernatants was considered in the loading measurement methodology, because of their potentially perturbing influence on the determination of 5-FU concentration in solution. We found first of all that most of the drug incorporation took place as absorption or entrapment in the polymeric network, with little contribution of surface adsorption, in turn only detectable by means of electrophoretic mobility measurements. Another remarkable finding is that neither ethyl-2-cyanoacrylate nor dextran-70 concentrations had significant effects on the drug absorption per unit mass of polymer. On the contrary, the acidity of the medium needs to be controlled to avoid formation of macroaggregates, because of a too fast polymerization, and to reach a significant absorption of 5-FU. The optimum conditions found were used to perform evaluations of 5-FU loading to polymeric and composite particles, and it was demonstrated that under such conditions the drug loading attainable with our magnetic carriers is comparable to that found for different polymer particles in this and other works.