Brucellosis is a worldwide zoonosis caused by different species of the genus Brucella. The intracellular localisation of this pathogen, particularly in macrophages, renders treatment difficult since most antibiotics known to be efficient in vitro do not actively pass through cellular membranes. As alternative to current treatment, polymeric drug delivery systems containing gentamicin have been developed. These particulate carriers target the drug into the mononuclear-phagocytic system, where the pathogen resides that will allow intracellular accumulation of the antibiotic after particle degradation. Besides, particle uptake may induce macrophage activation, increasing the production of reactive oxygen intermediates, involved in host defense against the intracellular pathogen. The aim of the present work was to study the suitability of polymeric nanoparticles for gentamicin entrapment in view to treat brucellosis. Different poly(lactide-co-glycolide) PLGA polymers were used to formulate the nanoparticles containing gentamicin by a water-oil-water solvent evaporation method. Furthermore, in vitro macrophage activation upon nanoparticles phagocytosis and in vivo distribution of the nanocarriers in the target organs for Brucella (liver and spleen) were also studied. The nanoparticle sizes were below 350 nm, the gentamicin encapsulation efficiency depended on the polymer type used for their preparation and the in vitro release of the antibiotic exhibited a continuos pattern (PLGA 502H). PLGA 502H nanoparticles were the most suitable due to the highest entrapment and the most sustained release. The nanoparticles were successfully phagocyted by a J774 murine monocytes cell line and biodistribution studies in mice after intravenous administration of the delivery systems revealed that the particles reached the target organs of Brucella (liver and spleen). All together, these results indicate that the nanocarriers described in this work may be suitable as gentamicin delivery system to control brucellosis.

Altogether, these results suggest that 502H and 75:25H microspheres are suitable carriers for gentamicin targeting inside human macrophages and thus for brucellosis treatment.

All these data favour the use of chromatography-mass spectrometry as a versatile technique not only suitable for gentamicin quantification loaded in drug delivery systems, but also sensitive and specific enough for in vivo and intracellular studies.

The results indicate that PLGA 50:50-microencapsulated gentamicin sulphate may be suitable for efficient drug targeting and delivery to reduce intracellular Brucella infections.

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