Produção de nanocápsulas poliméricas de óleo de copaíba: aspectos físico-químicos e atividade antimicrobiana

Abstract

Skin infections are a common condition in humanity and can evolve into resistance if not treated correctly. The metabolites present in copaiba essential (CEO) and fixed (CFO) oils are an alternative, since they have already been shown to inhibit microorganisms. However, their therapeutic use, especially if associated with delivery nanosystems, enhances their action, favoring passage through the defense mechanisms of microorganisms. Therefore, this study aimed to evaluate the physicochemical and antimicrobial aspects of polymeric nanocapsules (PNCs) carrying copaiba fixed and essential oils. To this end, the oils were characterized by gas chromatography coupled to mass spectrometry, and their antioxidant action was evaluated by DPPH and ABTS radical reduction methods. The PNCs were developed, varying the polymers polycaprolactone 10 kDa (PCL-10) and 80 kDa (PCL-80) (25─200 mg), the oils (CEO, CFO, 15─200 mg) and the surfactants Span®60, Lipoid®s100, Tween®20, Tween®80 and Kolliphor®ELP (20─100 mg). The PNCs were characterized by mean size, polydispersity index (PdI), Zeta potential, infrared spectroscopy (FTIR), optical microscopy and scanning electron microscopy (SEM), drug loading and encapsulation efficiency (EE%). Complexation with collagen and stability at 4 and 25 °C for 90 days of the final CEO (NcOEsC) and CFO (NcOFiC) nanocapsules were analyzed. Furthermore, the antimicrobial and antibiofilm activities of the oils, NcOEsC and NcOFiC were evaluated against Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 13150) and Candida albicans (ATCC 76645). CEO had β-caryophyllene (44.30%) as its major compound, while CFO had a chromatographic profile indicative of the presence of diterpenes. CEO showed antioxidant activity in DPPH, with an EC50 of 45.76 mg/mL; CFO reduced 9.44% regardless of the concentration used. CEO showed no activity in the ABTS test. PCL-10 and PCL-80 had saturation at 150 and 40 mg in the nanosystems, respectively, with higher amounts negatively influencing mean size and PdI. The stable oil limit concentration was 100 mg, with higher concentrations negatively interfering with mean size and PdI and leading to oil externalization, as observed by optical microscopy and infrared transmittances. The studied PNCs showed complex behavior in surfactant variation, which led to different results depending on the concentrations and types of surfactants used. The size, PdI and Zeta potential of NcOEsC were 216.03±1.63 nm, 0.22±0.01 and -29.65±0.68 mV, while NcOFiC were 243.37±2.89 nm, 0.14±0.05 and -24.26±0.44 mV. These nanocapsules had FTIR spectra similar to PCL-80 and Kolliphor®ELP and spherical shapes in SEM. NcOEsC showed a drug loading of 20.02±0.25 mg/ml and an EE% of 99.99%, and it was not possible to perform these tests with NcOFiC. They had low interaction with incubations from 1 to 40 mg collagen/ml and low interaction with incubation of 5 mg collagen/ml over 24 hours. PNCs were stable at the observed temperatures of 4 and 25°C, except for NcOFiC which destabilized within 60 days at 25°C. CEO showed a Minimum Inhibitory Concentration (MIC) of 1024 μg/ml against the studied microorganisms, but no antibiofilm activity. CFO showed no biological activity. NcOEsC showed no activity against C. albicans, but had an MIC against P. aeruginosa, E. coli and S. aureus of 0.5, 128 and 128 μg/ml and a biofilm inhibitory activity at 64, 128 and 128 μg/ml, respectively. NcOFiC had an MIC against P. aeruginosa, E. coli, S. aureus and C. albicans of 0.5, 16, 32 and 16 μg/ml and a biofilm inhibitory activity at 16, 16, 32 and 16 μg/ml, respectively. In conclusion, PNCs helped improve the performance of copaiba oils against skin pathogens.