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Avaliação do uso de nano carreadores de ramnolipídeos associados ao fotossensibilizador azul de Taylor na terapia fotodinâmica antimicrobiana contra Staphylococcus aureus: estudo in vitro

Fri, 26 Dec 2025 00:00:00 GMT

Título: Avaliação do uso de nano carreadores de ramnolipídeos associados ao fotossensibilizador azul de Taylor na terapia fotodinâmica antimicrobiana contra Staphylococcus aureus: estudo in vitro Autor(es): Jesus, Romário Santiago de Primeiro Orientador: Pinheiro, Antonio Luiz Barbosa Abstract: The increase in bacterial resistance to antibiotics has driven the search for alternative therapies, such as Antimicrobial Photodynamic Therapy (PDT). With the advancement of science, nanotechnology techniques are increasingly present, promoting the enhancement of existing techniques. This study evaluated, in vitro, the efficacy of PDT coupled with carrier nanotechnology against Staphylococcus aureus (ATCC 25923) in planktonic cultures, using the photosensitizer 1,9-dimethylmethylene blue (DMMB, λ ≈ 656 nm) and rhamnolipid nanocarriers (RL-NPs) produced by Pseudomonas aeruginosa. Seven experimental groups were established: Control (no treatment); LED (irradiation only, 20 J/cm²); DMMB (300 ng/mL); RL-NPs (300 ng/mL); RL-NPs/DMMB (300 ng/mL); PDT (DMMB + LED); and PDT+RL-NPs/DMMB (nanocarrier + LED). Photodynamic activation was performed with a prototype red LED (λ = 630 nm, power of 45.2 mW/cm²). Statistical analysis (one-way ANOVA with Tukey's post-hoc test) demonstrated that PDT promoted a significant reduction of ~2 logs (99.1%, p<0.0001) in bacterial viability. Notably, the group containing PDT+RL-NPs/DMMB nanotechnology showed a marked reduction of ~3 logs (99.9%, p<0.0001), significantly exceeding the standard PDT. The results indicate that the encapsulation of DMMB in rhamnolipid nanostructures enhances the antimicrobial efficacy of PDT. The characterizations performed on the nanocarrier elucidated in more detail the nature of the particles formed, including size, surface charge, and shape, which contributed to the enhanced effect, thus representing a promising strategy for the development of innovative clinical protocols against bacterial infections. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Tese

Prospecção e caracterização funcional de genes associados a estresse abiótico em mamona (Ricinus communis L.)

Fri, 12 Dec 2025 00:00:00 GMT

Título: Prospecção e caracterização funcional de genes associados a estresse abiótico em mamona (Ricinus communis L.) Autor(es): Oliveira Júnior, Jair Lucas Primeiro Orientador: Castro, Renato Delmondez de Abstract: Castor (Ricinus communis L.) is an oilseed species of great economic and industrial importance, widely recognized for the high commercial value of the oil extracted from its seeds, which is used in the production of medicines, cosmetics, and biofuels. In Brazil, the crop holds significant socioeconomic relevance, being traditionally cultivated by smallholder farmers in the semi-arid region of the Northeast, where rudimentary agricultural systems and adverse environmental conditions prevail. In these regions, plants are frequently exposed to abiotic stresses such as drought, salinity, and high temperatures. To survive these challenges and maintain cellular homeostasis, castor bean exhibits complex defense mechanisms involving antioxidant enzymes, such as superoxide dismutase (SOD), and regulatory and protective proteins, such as heat shock transcription factors (HSFs) and heat shock proteins (HSPs). The objective of this thesis was to elucidate the molecular and biochemical mechanisms associated with castor bean adaptation to abiotic stress conditions, through the functional characterization of the RcFeSOD8 gene and the genomic analysis of the HSF, HSP70, and HSP100 gene families. In Chapter 1 (published article), the RcFeSOD8 gene was characterized, and its physiological, biochemical, and metabolic roles were investigated through overexpression in Arabidopsis thaliana. RcFeSOD8 was strongly induced under heat stress in R. communis during seed germination and seedling growth. Arabidopsis lines overexpressing RcFeSOD8 exhibited improved germination under drought, salinity, and heat conditions, accompanied by increased antioxidant enzyme activity, higher chlorophyll content, and enhanced thermotolerance. Metabolomic analysis revealed differential accumulation of key amino acids (threonine, valine, isoleucine, sarcosine, and glycine) and sucrose in transgenic lines under stress, suggesting that RcFeSOD8 participates in the modulation of carbon and nitrogen metabolism, contributing to redox homeostasis and protecting amino acid biosynthetic pathways from oxidative damage. In Chapter 2 (submitted article), 18 RcHSF genes were identified, distributed across seven chromosomes of R. communis. These genes were classified into three major classes and ten subclasses, containing cis-regulatory elements associated with abiotic stress responses (ABRE, MeJARE, GARE, and SARE). The results showed that RcHSFs respond to both high and low temperatures during seed germination and early seedling development, as demonstrated by microarray analysis at the stages of imbibition, radicle protrusion (germination per se), and post-germination (young seedlings), as well as by qPCR validation of selected genes. In particular, RcHSF08 (Class A) showed strong induction under heat stress during the early seedling stage, whereas RcHSF10 (Class C) was upregulated during the initial developmental stages under both control and stress conditions compared with dry seeds. In Chapter 3 (article 9 in preparation), 14 members of the RcHSP70 gene family and five RcHSP100 genes were identified and characterized in R. communis. Based on sequence divergence, members of these families from five plant species were systematically grouped according to their predicted subcellular localization. Genomic analyses revealed that these genes harbor regulatory elements related to growth, development, hormonal signaling, and abiotic stress tolerance. Expression profiling indicated differential expression patterns of HSP70 and HSP100 genes across tissues and under various stress conditions (drought, salinity, and heat), confirming their participation in the castor bean stress response and adaptation mechanisms. Altogether, the results of this thesis contribute to advancing the understanding of the molecular and physiological mechanisms underlying abiotic stress tolerance in R. communis and highlight the potential of genes such as RcFeSOD8 and members of the RcHSF, RcHSP70, and RcHSP100 families as promising candidates for genetic improvement programs aimed at enhancing castor bean vigor and resilience under adverse environmental conditions—ultimately supporting greater productivity, particularly for smallholder farmers in the Brazilian semi-arid region. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Tese

Controle microbiano por fotoinativação em cepas bacterianas resistentes isoladas em trechos do rio Camarajipe

Thu, 26 Sep 2024 00:00:00 GMT

Título: Controle microbiano por fotoinativação em cepas bacterianas resistentes isoladas em trechos do rio Camarajipe Autor(es): Davi, Léda Gonçalves Primeiro Orientador: Santos, Gustavo Miranda Pires Abstract: Introduction: Camarajipe River belongs to one of the most polluted watersheds in Salvador, having been degraded due to the lack of sanitation and the illegal discharge of contaminated effluents. These metropolitan rivers are often populated by multidrug-resistant microorganisms. Microbial resistance is a growing concern for public health, especially in densely populated urban areas where antibiotic contamination can promote the emergence of multidrug-resistant strains. This dissertation explores photoinactivation, an alternative technique for microbial control that uses light and a photosensitizing molecule as a possible solution to combat these strains without promoting additional resistance. Objective: The main objective of the study was to investigate the effectiveness of photoinactivation against resistant bacterial strains isolated from the Camarajipe River. Additionally, the study explored the potential synergy between photoinactivation and the use of high-frequency equipment to amplify antimicrobial effects. Methods: This study involved the collection of water samples from different points along the Camarajipe River to isolate multidrug-resistant Pseudomonas spp. strains. After identifying the strains, photoinactivation experiments were conducted using Methylene Blue as a photosensitizer and a red LED light device. High-frequency current experiments were also conducted to evaluate its bactericidal capacity, both in isolation and in combination with photoinactivation. Results: Photoinactivation proved to be effective against multidrug-resistant strains, with significant inhibition observed in bacterial cultures when an appropriate concentration of Methylene Blue was used. The application of high-frequency currents also demonstrated bactericidal efficacy but only when applied before the addition of the photosensitizer, when the therapy was conducted in liquid media, showing significant effect alone when done in solid media. The combination of the two techniques showed promising results, suggesting that the use of high-frequency currents can enhance the effects of photoinactivation. This study highlights the relevance of alternative methods, such as photoinactivation combined with high frequency, in combating infections caused by resistant strains, offering a potential pathway to reduce the dependence on antibiotics in the treatment of bacterial infections. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação

Do perfil químico à inovação cosmética: potencial antioxidante e antimicrobiano do óleo essencial de Cymbopogon densiflorus

Mon, 27 Oct 2025 00:00:00 GMT

Título: Do perfil químico à inovação cosmética: potencial antioxidante e antimicrobiano do óleo essencial de Cymbopogon densiflorus Autor(es): Sabino, Atílio Araújo Primeiro Orientador: Vale, Ademir Evangelista do Abstract: This study aimed to characterize the chemical profile, evaluate the antioxidant and antimicrobial potential of Cymbopogon densiflorus essential oil, and develop and analyze a topical cosmetic formulation incorporating the oil. The plant material was collected in the North-Central region of Bahia, and the essential oil was obtained by hydrodistillation in a Clevenger apparatus. Chemical characterization was performed by gas chromatography-mass spectrometry (GC-MS), complemented by molecular network analysis using the GNPS platform. The antioxidant evaluation was conducted by the DPPH• radical method, while the antimicrobial activity was determined by the disk diffusion and broth microdilution methods, against the strains Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922. The GC-MS analysis revealed eleven major constituents, representing 40.7% of the total composition, with a predominance of oxygenated monoterpenes, highlighting Trans-isopulegol (18.9%), Cis-p-mentha-1(7),8-dien-2-ol (16.9%), Trans-p-mentha-1(7),8-dien-2-ol (15.0%) and D-limonene (14.0%). The essential oil showed dose-dependent antioxidant activity, reaching 10.4% inhibition of the DPPH• radical at a concentration of 80 mg/mL. In antimicrobial tests, significant activity was observed against S. aureus, with mean inhibition zones of 14.3 ± 0.5 mm, and a moderate effect against E. coli, with a zone of 9.8 ± 0.6 mm, in addition to a Minimum Inhibitory Concentration (MIC) of 400 µg/mL for the pure oil. The nonionic cream cosmetic formulation containing 10% essential oil demonstrated good physical and organoleptic stability over 30 days, maintaining a stable pH and the absence of phase separation. The product also demonstrated antimicrobial activity against S. aureus and E. coli, suggesting potential application as an active agent in natural dermocosmetic formulations. The results obtained confirm the biotechnological potential of Cymbopogon densiflorus essential oil, indicating it as a promising source of bioactive compounds with antioxidant and antimicrobial properties, suitable for application in the cosmetic, pharmaceutical and herbal medicine industries. Editora / Evento / Instituição: UNIVERSIDADE FEDERAL DA BAHIA Tipo: Dissertação