Assessing the performance of copaiba oil and allantoin nanoparticles on multidrug-resistant Candida parapsilosis

This study investigated the chemical and morphological structure of solid lipid nanoparticles made from copaiba oil. Moreover, the influence of allantoin in the formulations was investigated, as was the mechanism of action of the nanoparticles against multidrug-resistant Candida parapsilosis. Formulations were prepared via high-pressure homogenisation. Photon correlation spectroscopy and laser diffraction showed nanoparticles with diameters below 150 nm, narrow size distribution and negative zeta potential values. The nanoparticles' antifungal activity was assessed using a sorbitol protection assay. The ergosterol content and the influence of sorbitol on the minimum inhibitory concentrations were determined. The nanoparticles displayed nonspecific action on fungal cells. The antifungal effect is related to a complex synergism of natural substances with deeper action on cell replication. Thermogravimetric analysis showed that the individual behaviour of each component was modified in the formulation. Transmission electron microscopy showed differences in morphology caused by the presence of allantoin. The smaller particles can penetrate deeply into fungal cells. These findings indicated that even without antifungal effects when used in isolation, the incorporation of allantoin modified the size distribution, zeta potential and morphological structure of copaiba oil nanoparticles, resulting in particles with greater antifungal effects against multidrug-resistant yeasts. (C) 2017 Elsevier B.V. All rights reserved.