Navegando por Palavras-chave "Silver Nanoparticles"
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- ItemSomente MetadadadosFuncionalização De Nanopartículas Metálicas Com Diferentes Combinações De Peptídeos Para Aplicações Como Agentes Antimicrobianos E Antitumorais(Universidade Federal de São Paulo (UNIFESP), 2017-11-27) Formaggio, Daniela Maria Ducatti [UNIFESP]; Tada, Dayane Batista [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Metal nanoparticles (NPs) have showing promising applications in the biomedical field. These NPs have unique physicochemical properties, as well as great chemical versatility on their surface, which allows new modifications and incorporations of different molecules. In addition, they have the advantage of accumulating preferentially in tumor tissues due to the enhanced permeability and retention effect, known as EPR. The incorporation of therapeutic peptides to the surface of metallic NPs could be a promising strategy to improve their applications as therapeutic molecules. Peptides are highly selective molecules. However, they are also vulnerable to some in vivo pharmacologic barriers limiting their effective action, including low bioavailability or deactivation by enzymes. In this work, three types of metal NPs were prepared: gold NPs (AuNPs), silver NPs (AgNPs) and bimetallic NPs composed by gold and platinum (AuPtNPs). NPs were characterized by ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD). Aiming at biomedical applications, NPs were firstly evaluated regarding their toxicity by cell viability assays using human fibroblast cells (HS68 cell line) and embryonic toxicity test in zebrafish (Danio rerio). The assays showed better biocompatibility of AuNPs compared to AgNPs and AuPtNPs. Thus, AuNPs were studied as carriers of antitumor and antimicrobial peptides as an alternative approach of overcoming the pharmacokinetic limitations inherent in these molecules. Two peptides derived from complementary monoclonal antibodies (CDRs) with amino acid sequences YISCYNGATSYNQKFK (C7H2) and RASQSVSSYLA (HuAL1) were previously identified by collaborators of this project demonstrating excellent toxicity against tumor cells, antimetastatic activity as well as a potent antimicrobial activity. The peptides were individually conjugated to the AuNPs surface, forming the AuNPsC7H2 and AuNPsHuAL1 NPs. The peptides were also linked together forming the AuNPsC7H2HuAL1. The in vitro results suggested an improved antitumor activity for AuNPsHuAL1 and AuNPsC7H2HuAL1 against metastatic melanoma tumor cell line (B16F10-Nex2) compared to the peptides in solution. In vivo, the peptide combination of HuAL1 and C7H2 was even more efficient when linked to AuNPs. The antimicrobial activity of the three NPs separately as well as the peptide functionalized AuNPs were also evaluated employing microdilution test against strains of Candida Albicans, Pseudomonas aeruginosa and Staphylococcus aureus. The results confirm an intrinsic antimicrobial action of the three metal NPs and an optimal antibiotic action for AuNPsHuAL1.
- ItemSomente MetadadadosPhytofabricated metallic nanoparticles and their clinical applications(Dove Medical Press Ltd, 2016) Baranwal, Anupriya; Mahato, Kuldeep; Srivastava, Ananya; Maurya, Pawan Kumar [UNIFESP]; Chandra, PranjalMetallic nanoparticles (MNPs) have seen myriad applications in various fields of science and technology. Green chemistry based NP synthesis offers several advantages over conventional approaches. In addition to being inexpensive, the biological approach is a facile, rapid, and environmentally benign method to synthesize NPs. Characterization of NPs is generally based on their dimension, surface area, and dispersity and the most common techniques used for the purpose are UV-Vis, DLS, AFM, SEM, FTIR, XRD, TEM, Raman spectroscopy, etc. These techniques are considered very useful as they provide valuable information which helps these materials to be used for diverse biological and environmental applications. Until now, numerous plant sources have been utilized to generate copious MNPs, such as silver, gold, copper, titanium, platinum, palladium, zinc, and iron NP. Among these MNPs, the noble ones have attracted significant researchers' attention because they are non-corrosive and resistant to oxidation in moist air. They have been useful in providing remedies with less or no adverse effects for several acute diseases like cancer, malaria, HIV, and hepatitis. Herein, we present a systematic review, focusing on phytofabricated MNPs and their wide range of applications, such as sensors, diagnostics and therapeutics, antimicrobial agents, anti-inflammatory agents, cancer treatment, etc.
- ItemSomente MetadadadosPreparação e avaliação de membranas de celulose com propriedades condutoras e microbicidas(Universidade Federal de São Paulo (UNIFESP), 2020-06-02) Oliveira, Roselaine Da Silva [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São PauloThere is a growing interest in developing methods that allow the immobilization of different types of materials (polymers and nanomaterials) in biopolymers. Among them, cellulose (CEL) is of the most indicated because it is natural, abundant, and non-toxic. In this thesis, new methods of immobilizing a conductive polymer and silver nanoparticles on cellulose membranes were developed. In order to overcome the insolubility and difficult processing of cellulose, in these procedures the biopolymer was dissolved in an ionic liquid called 1-butyl-3-methylimidazolium chloride (BMImCl). To simplify the comprehension of this thesis, it was divided into three chapters. In the first chapter (CHAPTER 1), the preparation of electrically conductive cellulose membranes, containing silver nanoparticles and polyaniline (PANI), which is a conductive polymer, will be shown. These membranes (CEL / PANI / Ag) showed high electrical conductivity and catalytic activity toward the reduction of p-nitrophenol. In the second chapter (CHAPTER 2), the preparation of several aqueous and non-aqueous dispersions (1-butanol) of silver nanoparticles (AgNP) with high metal concentration will be presented. A simple and fast method was developed, under mild reaction conditions. The dispersions presented excellent microbicidal activities. In the third chapter (CHAPTER 3) a new method of immobilizing the dispersions of AgNP produced in chapter 2 on cellulose membranes will be presented. These membranes will have their microbiological activity evaluated. An illustration of the chapters of thesis is in Figure 1.
- ItemSomente MetadadadosProcessamento e Caracterização de Scaffolds de β-Fosfato Tricálcico pelo Método de Gelcasting com Incorporação de Nanopartículas para Atividade Antimicrobiana(Universidade Federal de São Paulo (UNIFESP), 2020-02-14) Barbosa, Lucas [UNIFESP]; Triches, Eliandra De Sousa [UNIFESP]; Universidade Federal de São PauloTissue engineering and regenerative medicine are highly relevant to the science of biomaterials, promoting advances in the treatment and recovery of patients with problems caused by diseases, injuries and fractures. Recent studies in tissue engineering have sought to develop multifunctional scaffolds that in addition to having regenerative capacity, have antimicrobial properties through the incorporation of antimicrobial agents, providing a better recovery to the patient and avoiding new surgical procedures for treatment or removal of the implant, since inflammations and infections are often caused by microorganisms. For the production of ceramic scaffolds for bone tissue regeneration, tricalcium β-phosphate (β-TCP) stands out due to its chemical stability and more suitable resorption speed for bone implants. Among the antimicrobial agents that have been studied are metallic nanoparticles, such as silver, and chemical compounds, such as methylene blue. Thus, this work aimed to obtain β-TCP scaffolds by the gelcasting method applied to foams with the incorporation of methylene blue and silver nanoparticles in order to confer antimicrobial properties. For this, the obtained β-TCP scaffolds were immersed in the silver nanoparticles solution and stirring by ultrasonic. Methylene blue was incorporated by dripping the solution into the scaffolds. The synthesized ceramic powder presented the crystalline phase of interest, β-TCP, average particle size after grinding 1.56 μm and density 2.99 g/cm³. Regarding antimicrobial agents, silver nanoparticles had an average hydrodynamic diameter of 39 ± 2 nm, with maximum absorption in the UV-visible spectrum at 429 nm and the methylene blue solution had a concentration of 1.044 mM, with maximum absorption in the UV-visible spectrum at 654 nm. In turn, the β-TCP scaffolds had porosity of 81 ± 2 % and mechanical compressive strength of 1.3 ± 0.5 MPa with spherical and interconnected pores. The test to evaluate the antimicrobial activity, in relation to S. aureus bacteria, of the scaffolds incorporated with antimicrobial agents revealed that the studied samples had little inhibitory action. It is understood that it is not enough to just incorporate an agent with a high antimicrobial capacity into the scaffold, but to understand how this agent will be incorporated into the scaffold and whether this incorporation will leave it in contact with the microorganism during the antimicrobial activity test. Therefore, it was possible to obtain β-TCP scaffolds, incorporate them with antimicrobial agents and although they have little inhibitory action, it was possible to observe the relevance of the research and guide the studies for future work.
- ItemSomente MetadadadosStructural and Conductivity Relationship of Binary and Ternary Composites of Polypyrrole, Montmorillonite and Silver(Amer Scientific Publishers, 2017) Franca, Debora; Rebessi, Ana Claudia; Lacerda Rubinger, Carla Patricia; Ribeiro, Geraldo Mathias; Camilo, Fernanda Ferraz [UNIFESP]; Faez, RoselenaThis work focuses on the synthesis of binary composites of polypyrrole and silver and of ternary composites of polypyrrole, silver and organomontmorillonite performed in the presence of mixtures of two surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), in aqueous media. Polypyrrole-silver composites were obtained easily by the direct oxidation of pyrrole by silver nitrate using surfactant mixture. These samples exhibited polypyrrole doped with dodecylsulfate and nitrate and silver contents varied between 60 and 90 wt.%. The electrical conductivity is highly dependent on SDS/CTAB presence and proportions. NO3- acts as the main dopant in the absence of surfactants and the resistivity reaches the highest for PPy-OMt composites compared to silver-content ones. Besides the dopant effect, the surfactants mixtures have noticeable influence on silver particle size and morphology. In ternary composites the silver nanoparticles were spherically (around 100-200 nm) and well dispersed in the polymeric matrix. Activation energy, density of states and hopping characteristic length were calculated and it was found to be influenced by intercalating doped polypyrrole into the layers of montmorillonite in the presence of the Ag and surfactant. One-dimensional Mott's variable range hopping process was observed and interpreted in terms of straightening and linearization of the polymer chains.
- ItemSomente MetadadadosUsing femtosecond lasers to modify sizes of gold nanoparticles(Spie-int soc optical engineering, 2016) Cordeiro, Thiago da Silva; de Matos, Ricardo Almeida [UNIFESP]; de Oliveira Silva, Flavia Rodrigues; Vieira, Nilson Dias, Jr.; Courrol, Lilia Coronato [UNIFESP]; Samad, Ricardo ElgulMetallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the potential defined by the nanoparticle size and geometry. There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp irradiation. This technique is characterized as a "green" synthesis because the natural polymers are inoffensive to the environment. We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth centered at 800 nm. The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.