Increasing interest in nanoparticles of technological application has been improving their fabrication processes. The encapsulation of essential oils as bioactive compounds has proved to be an excellent alternative to the use of less environment friendly compounds. However, the difficulty of identifying their constitution and interaction with carrier agents have aroused scientific interest and a problem to overcome. Bilayer-based nanoparticles were developed using gelatin and poly-ε-caprolactone (PCL) aiming the encapsulation of Piper nigrum essential oil. based on atomic force microscopy images and dynamic light scattering analysis, the size of the unloaded and loaded nanoparticles was found around (194 ± 40) and (296 ± 54) nm, respectively. The spatial patterns revealed that the surface of nanoparticles presented different surface roughness, similar shapes and height distribution asymmetry, lower dominant spatial frequencies, and different spatial complexity. Traditional infrared spectroscopy allowed the identification of the nanoparticle outermost layer formed by the gelatin carrier, but microscopy-based infrared spectroscopy revealed a band at 1742 cm−1 related to the carbonyl stretching mode of PCL, as well as a band at 1557 cm−1 due to the amide II group from gelatin. The combination of microscopy and spectroscopy techniques proved to be an efficient alternative to quickly identify differences in chemical composition by evaluating different functional groups in bilayer PLC/gelatin nanoparticles of technological application.

RESUMO Óleos essenciais derivados de plantas têm chamado a atenção devido a uma série de propriedades físico-químicas e atividades biológicas. Entretanto, eles possuem diversas limitações, pois são voláteis e instáveis na presença de umidade, altas temperaturas, ar e luz e, assim, técnicas de encapsulamento surgem como alternativa para proteção das propriedades funcionais desses óleos fornecendo, ainda, uma liberação lenta e controlada. Devido a lenta degradação biológica dos materiais que compõem a parede da cápsula e a duração prolongada da ação de liberação do óleo, micro e nanocápsulas são de grande interesse científico e tecnológico. Neste trabalho, nanopartículas à base de bicamada foram desenvolvidas usando gelatina e poli-ε-caprolactona visando proteger o óleo essencial de Piper nigrum por meio de encapsulamento e analisadas por microscopia de força atômica. Nanopartículas com e sem óleo essencial de pimenta preta foram preparadas e gotejadas em lâminas de vidro para formar filmes que foram investigados por imagens com resoluções de 256 x 256 pixels com áreas de 5 x 5 mm2. O óleo foi obtido por meio de sementes de pimenta que foram trituradas e submetidas à hidrodestilação usando um aparelho do tipo Clevenger. Gelatina e poli-?-caprolactano foram usados como material de parede, cuja eficiência de encapsulamento foi de 98,50 %. Foram obtidas nanopartículas com diâmetros variando de 193,52 ± 40,14 até 295,54 ± 53,50 nm (sem e com óleo, respectivamente). Além disto, foram comparadas também as alturas, densidades e o desvio médio quadrático das rugosidades das amostras indicando uma tendência de aumento nestes parâmetros em função da incorporação de óleo essencial na síntese, exceto na densidade devido ao crescimento das outras dimensões.

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Gelatin/PCL bilayered particles loaded with Piper nigrum essential oil was synthesized aiming to access their morphological and surface dynamic patterns. Atomic force microscopy (AFM) was applied to investigate the 3D morphology and multifractal aspects of the particles surface. The AFM maps revealed spherical surfaces and well dispersed particles, besides a rougher surface on the loaded system. Minkowski functionals showed that shape of the rough peaks was similar in the unloaded and loaded systems; however, the presence of deep valleys on the loaded particles revealed their rougher pattern. Multifractal analysis revealed that unloaded and loaded particles presented multifractal behavior with different surface dynamics. The loaded surface presented a greater width of the multifractal spectrum and smaller difference of fractal dimensions, confirming their more vertically growing. These results can be useful in the development of novel polymeric‐based particles loaded with essential oil. Their unique surface dynamics can provide enhanced physical properties and performance in emerging biotechnological applications.

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