Biodistribution of free and encapsulated 99m Tc-fluconazole in an infection model induced by Candida albicans.

Background: Candida spp is an etiologic agent of fungal infections in hospitals and resistance to treatment with antifungals has been extensively reported. Thus, it is very important to develop formulations that increase effectiveness with low toxicity. In this sense, nanocarriers have been investigated, once they modify drug biodistribution profile. Thus, this study aimed to evaluate the biodistribution of free and encapsulated ^99m Tc-fluconazole into nanocapsules (NCs) in an experimental immunosuppressed murine model of Candida albicans infection.
Methods: Fluconazole was radiolabeled with technetium-99 metastable ( ^99m Tc) and encapsulated into conventional ( ^99m Tc-Fluconazole-PLA-POLOX) and surface-modified ( ^99m Tc-Fluconazole-PLA-PEG) NCs by the interfacial deposition of the preformed biodegradable polymer [poly (D,L-lactic acid) (PLA) and PLA-PEG (polyethyleneglycol)] followed by solvent evaporation. The size distribution and zeta potential of the NCs preparations were determined in a Zetasizer by photon correlation spectroscopy and laser Doppler anemometry, respectively. Free and encapsulated ^99m Tc-fluconazole were administered intravenously in immunosuppressed mice bearing a local infection induced by Candida Albicans inoculation in the right thigh muscle. At pre-established time intervals, tissues and organs of interest were removed and radioactivity was measured in an automatic gamma radiation counter.
Results: The NCs diameter was between 200 and 400 nm with negative zeta potential values. Free ^99m Tc-fluconazole was more rapidly eliminated by the renal system compared to the encapsulated drug in NCs, which remained longer in blood circulation. The uptake of conventional NCs by mononuclear phagocyte system organs was higher than the one demonstrated by the surface-modified NCs. Both NCs remained longer in the infectious focus when compared to free ^99m Tc-fluconazole, but the results did not show a significant difference between NC formulations.
Conclusion: These data indicate that these NCs might represent a therapeutic alternative for the treatment of candidiasis, once they remain more time in the infectious focus, allowing high retention of ^99m Tc-fluconazole at this site.
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