(+)-Limonene 1,2-Epoxide-Loaded SLNs: Evaluation of Drug Release, Antioxidant Activity, and Cytotoxicity in an HaCaT Cell Line

In this work, we developed a solid lipid nanoparticle (SLN) formulation with (+)-limonene 1,2-epoxide and glycerol monostearate (Lim-SLNs), stabilized with Poloxamer® 188 in aqueous dispersion to modify the release profile of the loaded monoterpene derivative. We also evaluated the role of SLNs in lipid peroxidation and cytotoxicity in a spontaneously transformed aneuploid immortal keratinocyte cell line from adult human skin (the HaCaT cell line). For the cell viability assay, the colorimetric 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used. Lim-SLNs with a loading capacity and encapsulation efficiency of 0.39% and 63%, respectively, were produced by high pressure homogenization. A mean particle size of 194 ± 3.4 nm and polydispersity index of 0.244 were recorded for the loaded Lim-SLNs, as compared to 203 ± 1.5 nm (PI 0.213) for the non-loaded (blank) SLNs. The loading of the monoterpene derivative into glycerol monostearate SLNs fitted into the zero-order kinetics, and ameliorated both lipid peroxidation and cytotoxicity in a keratinocyte cell line. A promising formulation for antioxidant and anti-tumoral activities is here proposed. The authors wish to acknowledge the financial support from CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico, from CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), and from FAPITEC/SE (Fundação de Apoio à Pesquisa e Inovação Tecnológica do Estado de Sergipe). E. B. Souto acknowledges the sponsorship of the projects M-ERA-NET-0004/2015-PAIRED and UIDB/04469/2020 (strategic fund), received support from the Portuguese Science and Technology Foundation, Ministry of Science and Education (FCT/MEC) through national funds, and was co-financed by FEDER, under the Partnership Agreement PT2020. A.M. Silva acknowledges FCT/MEC for the project PEst-/UID/AGR/04033/2019 (CITAB).