Nanopartículas poliméricas preenchidas com óleo essencial de Piper nigrum: caracterização química e morfológica

Abstract

The bioactive compounds found in the essential oil (EO) of Piper nigrum present biological activities, such as anti-inflammatory, antioxidant, antibacterial, antifungal and inseticide activities [1]. However, the compounds are limited by the volatility and rapid degradation of the EO. To avoid this and prolong the efficacy of the active compounds, the EO of Piper nigrum was encapsulated in biodegradable nanoparticles, which had as wall material gelatin and poly-ε-caprolactan (PCL). Thus, the objective of this research is to characterize the biodegradable polymeric nanoparticles, synthesized as nanocarriers of Piper nigrum EO. Firstly, the EO was extracted by hydrodistillation and a study was made of its extraction kinetics and its physical properties. The GC/MS analysis of OE in natura revealed a composition mostly consisting of E-caryophyllene (34.87%), sabinene (14.96), silvestrene (14.17) and α-pinene (5.28%). The DLS, SEM and AFM techniques were used to perform a morphological characterization of nanoparticles. By DLS the charged and empty nanoparticles had an average size of 316 nm and 285 nm respectively. By AFM the charged and empty nanoparticles had an average size of 208 nm and 196 nm. The UV-Vis spectroscopy was used to determine the encapsulation efficiency measured at an absolute concentration of 500 μg.mLˉ¹ (95.8%) and for the controlled release of EO at different pH. Through Zeta Potential analysis, an excellent stability of the nanoparticles was found. Using the FTIR, Raman and AFM-IR spectra, a chemical analysis was performed. The AFM-IR proved to be an effective technique for nanocapsule characterization, being able to verify the encapsulation of the EO and to identify an approximate value of the thickness of the wall material of the nanoparticles (<25nm). The Peak-Force Tapping measurements provided an analysis of the surface area of nanoparticles by adhesion images. Therefore, these data provide a broad understanding of the characteristics of OE-containing nanoparticles, showing that nanoparticle formulation represents an effective alternative in the use of Piper nigrum OE.