Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) have emerged as promising systems for delivering active ingredients. They are derived from physiological, biodegradable, and biocompatible lipids, offering benefits such as sustained release promotion and increased drug stability. These systems are apt for the efficient transport of therapeutic drugs to target tissues while also providing advantages such as facilitating large-scale industrial production, bioavailability, and protection against degradation. The preparation of these nanoparticles involves utilizing diverse types of lipids, surfactants, and solvents. Common lipid varieties encompass triglycerides, steroids, and fatty acids, selected based on the active ingredient for stabilization within the lipid matrix. Preparation methods can be categorized into high-energy and low-energy approaches. This study investigated the differences between the main methodologies used, comparing SLN and NLC systems, and scrutinizing their respective advantages, disadvantages, and applications.

Background/Objectives: Actinobacteria are one of the largest bacterial phyla. These microbes produce bioactive compounds, such as antifungals, antibiotics, immunological modulators, and anti-tumor agents. Studies on actinobacteria isolated from the Brazilian Savannah biome (Cerrado) are scarce and mostly address metagenomics or the search for hydrolytic enzyme-producing microbes. Solanum lycocarpum (lobeira) is a tree widely employed in regional gastronomy and pharmacopeia in Central Brazil. Methods: In this work, 60 actinobacteria isolates were purified from the rhizosphere of S. lycocarpum. Eight Streptomyces spp. isolates were selected for in vitro antifungal activity against Cryptococcus neoformans H99, the C. neoformans 89-610 fluconazole-tolerant strain, C. gattii NIH198, Candida albicans, C. glabrata, and C. parapsilosis. The ability of the aqueous extracts of the isolates to induce the in vitro secretion of tumor necrosis factor (TNF-α), nitric oxide (NO), interleukin-6 (IL-6), and IL-10 by murine macrophages was also evaluated. Results: All extracts showed antifungal activity against at least two yeast species. Streptomyces spp. LAP11, LDB2, and LDB17 inhibited C. neoformans growth by 40–93%. Most extracts (except LAP2) also inhibited C. gattii. None inhibited C. albicans, but all inhibited C. glabrata (40–90%). Streptomyces sp. LAP8 extract increased nitric oxide production by approximately 347-fold in murine macrophages, while LDB11 extract suppressed LPS-induced TNF-α production by 70% and simultaneously increased IL-10 secretion, suggesting immunosuppressive potential. Conclusions: The results revealed that Cerrado actinobacteria-derived aqueous extracts are potential sources of antifungal and immunomodulatory biocompounds.