Desenvolvimento de Nanogéis à Base de Bioativos Naturais como Abordagem Inovadora para o Controle e Tratamento de Doenças Tropicais Negligenciadas e Avaliação Toxicológica em Modelo Zebrafish (Danio rerio)

Abstract

Neglected Tropical Diseases (NTDs), such as American cutaneous leishmaniasis (ACL), remain a public health challenge due to the toxicity of available treatments. Arboviruses, also classified as NTDs, are transmitted by Aedes aegypti, whose control using conventional insecticides leads to significant environmental impacts due to their high toxicity. In this context, there is growing interest in safer alternatives, such as formulations based on natural bioactive compounds. In this study, semisolid nanogels containing essential oil of Duguetia stelechantha (EOs) were developed, using the copolymers F127, 974P, and water as the sole solvent, aiming at an eco-friendly approach. The EO from D. stelechantha was extracted by hydrodistillation and characterized by GC-MS, identifying sabinene (41.44%), terpinen-4-ol (17.61%), and p-cymene (3.70%) as major constituents, confirmed by ¹H and ¹³C NMR. Different concentrations of EOs were tested in the formulations, with the most stable being that with 1% oil (nGF2002Ds), which was subsequently combined with increasing concentrations of curcumin (CUR), with 0.02% CUR (nGF2002DsC) being the most suitable. Fourier-transform infrared (FTIR) spectroscopy revealed vibrational changes in the O—H, C—H, and C=O bonds of the nanogel polymeric matrix, indicating interactions with the bioactives (EOs and EOs/Curcumin). Dynamic light scattering (DLS) analysis showed that the presence of these compounds promoted greater colloidal stability, evidenced by the reduction in hydrodynamic diameter (Dh) and the increase in the diffusion coefficient (Dif). Rheological analysis confirmed the increase in viscosity, elasticity, and structural organization of the matrix containing the bioactives. Additionally, differential scanning calorimetry (DSC) indicated thermal stability of the nGF2002Ds nanogel, while morphological analyses using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed homogeneous morphology and increased surface rigidity after oil incorporation. Due to the successful encapsulation of the bioactives, the nGF2002Ds nanogel exhibited strong larvicidal activity against Aedes aegypti larvae, with an LC₅₀ of 97.7 µg/mL and LC₉₀ of 177.7 µg/mL within 24 hours. In the toxicological evaluation using zebrafish (Danio rerio), the nGF2002Ds nanogel demonstrated dose-dependent toxicity, with an increase in teratogenic alterations as the oil concentration increased. In an in vitro assay against Leishmania amazonensis, the nanogel achieved 100% mortality within 24 hours, surpassing the activity of pure EOs (96.5%). These results highlight the potential of nanogels as a sustainable nanotechnological approach to overcome the limitations of natural bioactives in the control and treatment of NTDs.