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| Author(s): |
Luiz Gustavo Ribeiro
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2025-02-27 |
| Examining board members: |
Ana Olívia de Souza;
Francine Côa;
Leonardo Fernandes Fraceto;
José Roberto Kfoury Junior;
Juliana Delatim Simonato Rocha
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| Advisor: | Ana Olívia de Souza |
| Abstract | |
Silver nanoparticles (AgNPs) have been extensively studied due to their antimicrobial properties and potential applications in fields such as medicine, agriculture, and the pharmaceutical industry. In this study, biosynthesized AgNPs were evaluated using different fungal species from the phylum Ascomycota, including Aspergillus tubingensis, Aspergillus spp., Cladosporium pini-ponderosae, Fusarium proliferatum, Epicoccum nigrum, Exserohilum rostratum, and Bionectria ochroleuca, isolated from Brazilian biomes, specifically mangroves and the Caatinga. The AgNPs were characterized by ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS), zeta potential (ZP), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The AgNPs exhibited sizes ranging from 21.8 to 120.6 nm, negative ZP, and a protein coating. The antifungal activity was tested against pathogenic yeasts primarily found in hospital environments (Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, Candida tropicalis, and Candida guilliermondii) and phytopathogens (Fusarium oxysporum, Fusarium phaseoli, Fusarium sacchari, Fusarium subglutinans, Fusarium verticillioides e Curvularia lunata). The minimum inhibitory concentrations (MICs) ranged from 1.25 to 250 µM, demonstrating broad antifungal potential. The effect of AgNPs synthesized using A. tubingensis (AgNP-AT) was evaluated in the shrimp Palaemon pandaliformis and Nile tilapia (Oreochromis niloticus). In shrimp, exposure to 10 µM of AgNP-AT reduced oxygen consumption by 60% and ammonia excretion by 87%, with reversible morphological changes in the gills and hepatopancreas. The median lethal concentrations (LC50) for shrimp were 17.4 µM at 24 hours and 0.5 µM at 96 hours. For tilapia, the LC50 was 8.8 µM at 96 hours, indicating lower sensitivity to AgNP-AT compared to silver nitrate (AgNO3), which had an LC50 of 0.028 µM. The high LC50 value of AgNP-AT suggests that the release of Ag+ ions occurs more slowly than in the free form (AgNO3) due to the presence of the external protein layer, which not only provides stability but also reduces the toxicity of this nanomaterial. In tilapia, exposure to 30, 35, and 40 µM of AgNP-AT resulted in increased oxygen consumption and reduced swimming activity, without changes in ammonia excretion. Morphologically, there was a decrease in the length and an increase in the width of the gill lamellae, indicating physiological stress. AgNO3 showed significantly higher toxicity, with acute and severe effects on both tested aquatic organisms. The results demonstrate the potential of AgNP-AT as a broad-spectrum antifungal agent and highlight the importance of evaluating the environmental impact of this nanomaterial, especially on sensitive aquatic organisms known as indicators of environmental conditions. This study represents a contribution to the development of safe applications of these nanoparticles in biotechnology. (AU) | |
| FAPESP's process: | 20/03883-4 - Study of biological silver nanoparticles effect on Zebrafish, Nile Tilapia and Lambari |
| Grantee: | Luiz Gustavo Ribeiro |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |