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- ItemAcesso aberto (Open Access)Avaliação do efeito da massa molar na quaternização da quitosana e nas propriedades dos filmes de quitosana quaternizada(Universidade Federal de São Paulo, 2023-07-31) Faria, Danielle Bitencourt [UNIFESP]; Moraes, Mariana Agostini de [UNIFESP]; Silva, Classius Ferreira da [UNIFESP]; http://lattes.cnpq.br/4514485329529047; http://lattes.cnpq.br/0644374691728856; https://lattes.cnpq.br/4567597606259744A quitosana é um polissacarídeo biocompatível, biodegradável e biofuncional. Entretanto, a maioria das quitosanas comerciais e desenvolvidas em laboratórios de pesquisa são solúveis apenas em pHs ácidos, o que motivou o desenvolvimento de modificações químicas, tais como a quaternização, que tornam a quitosana solúvel em todas as faixas de pH e expandem seu campo de aplicação. O processo de quaternização mais comum é o de N-alquilação, a partir do qual obtém-se o composto Cloreto de N-(2-hidroxi)-propril-3-trimetilamônio quitosana (HTCC), que é amplamente utilizado em aplicações biológicas e farmacêuticas. Sabe-se que as propriedades da quitosana são influenciadas diretamente pela massa molar e grau de desacetilação. No entanto, a literatura carece de estudos que analisem a influência da massa molar da quitosana no processo de quaternização e nas propriedades dos filmes obtidos a partir da quitosana quaternizada, sendo este o objetivo do presente estudo. Os resultados obtidos indicaram que o aumento da massa molar da quitosana resulta no aumento do grau de quaternização, possivelmente devido à maior disponibilidade para reação dos grupos amino presentes na molécula de quitosana. Além disso, os filmes de quitosana quaternizada foram preparados por casting e analisados quanto às suas propriedades físico-químicas e biológicas. Os filmes de quitosana quaternizada apresentaram comportamento elastomérico, com deformação na ruptura variando de 73 a 102%, valor 74% maior, em média, do que os filmes de quitosana. Além disso, os filmes de quitosana quaternizada apresentaram excelente atividade antimicrobiana, com halos de inibição de S. aureus e E. coli variando de 30 a 36 mm. Desta forma, é possível concluir que a massa molar é um fator preponderante que deve ser considerado na análise de reações de quaternização da quitosana e que os filmes de quitosana quaternizada são uma excelente opção para aplicações que exijam grande elasticidade e controle do crescimento microbiano, abrangendo desde a área de embalagens e recobrimentos até a área médico-farmacêutica.
- ItemAcesso aberto (Open Access)Estudo da caracterização de sílica do tipo SBA-15,funcionalizada: novo materiais para remediação de sistemas aquosos contaminados com metais potencialmente tóxicos, utilizando Pb2+ como poluente modelo(Universidade Federal de São Paulo, 2014-10-03) Silva, Fernanda Alves da [UNIFESP]; Mercuri, Lucildes Pita [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Heavy metals are among the most harmful aquatic contaminants. Therefore, there is a growing interest in obtaining materials adsorbents to capture these contaminants from effluent In this work the synthesis of mesoporous silica SBA-15 and its functionalization with aminopropyltrimethoxysilane (APTMS) , chitosan (QTS) and ethylenediaminetetraacetic acid (EDTA) were carried out in order to compare the functionalization of silicatic support with different organic agents and apply the new materials as adsorbents to uptake heavy metals from water. The functionalization of SBA-15 with APTMS was based on the post-synthesis grafting method, in toluene, and the EDTA and QTS incorporation were made by impregnation method, using dichloromethane and 2 % aqueous acetic acid as solvent, respectively. APTMS, EDTA, QTS, SBA-15 and new obtained materials (SBA-15/APTMS, SBA-15/QTS, SBA-15/EDTA, SBA-15/APTMS/QTS and SBA-15/APTMS/EDTA) were characterized by analytical and physical chemistry techniques: Thermogravimetry / Derivative Thermogravimetry (TG / DTG), Differential Scanning Calorimetry (DSC), Elemental Analysis (EA), Adsorption/Desorption of Nitrogen, Fourier Transformed Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Regarding functionalized samples, the functionalization of SBA-15 with APTMS there was effective and about 30% of agent was incorporated to silica, as all results showed. The incorporation of chitosan was effective in SBA-15 supported functionalized with APTMS and also to the pure support, presenting an increase of the thermal stability of the polymer impregnated to silica. Regarding the incorporation of EDTA, there was no experimental evidence that indicates incorporation of the agent to the substrate. Furthermore, it was found that stirring times had little influence on incorporation of the actives. The preliminary tests of sorption of Pb2+ in aqueous media showed SBA-15/APTMS and SBA-15/APTMS/QTS samples presented the best results, with sorption of 100.0% and 39.5% of the lead present in the solution, respectively. On the other hand, the sample of pure commercial quitosan retained 99.1% of Pb2+ ions in the solution after 30 minutes of contact.
- 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 MetadadadosPreparation and characterization of maleic anhydride grafted poly (hydroxybutirate-co-hydroxyvalerate) - phbv-g-ma(Univ fed sao carlos, dept engenharia materials, 2016) do Amaral Montanheiro, Thais Larissa [UNIFESP]; Passador, Fabio Roberto [UNIFESP]; de Oliveira, Mauricio Pinheiro [UNIFESP]; Duran, Nelson; Lemes, Ana Paula [UNIFESP]A compatibilizer agent was successfully produced by grafting maleic anhydride (MA) to poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) chains on a reactive processing by mechanical mixing, using a mixture of PHBV, MA and dicumyl peroxide (DCP) as initiator. The resulting PHBV grafted MA. (PHBV-g-MA) was characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC), and its properties were compared to neat PHBV. FTIR showed an absorption band at 699 cm(-1) for PHBV-g-MA, related to CH group of grafted anhydride ring. The initial thermal degradation temperature of the compatibilizer agent was reduced when compared to neat PHBV. DSC analysis showed that after grafting MA onto PHBV the crystallization temperature was about 20 degrees C higher than neat PHBV, and the degree of crystallinity was increased. GPC analysis showed that MA when grafted onto PHBV led to a reduction of molecular weight and polydispersity.
- ItemSomente MetadadadosPressure-driven opening of carbon nanotubes(Royal soc chemistry, 2016) Chaban, Vitaly V. [UNIFESP]; Prezhdo, Oleg V.The closing and opening of carbon nanotubes (CNTs) is essential for their applications in nanoscale chemistry and biology. We report reactive molecular dynamics simulations of CNT opening triggered by internal pressure of encapsulated gas molecules. Confined argon generates 4000 bars of pressure inside capped CNT and lowers the opening temperature by 200 K. Chemical interactions greatly enhance the efficiency of CNT opening: fluorine-filled CNTs open by fluorination of carbon bonds at temperature and pressure that are 700 K and 1000 bar lower than for argon-filled CNTs. Moreover, pressure induced CNT opening by confined gases leaves the CNT cylinders intact and removes only the fullerene caps, while the empty CNT decomposes completely. In practice, the increase in pressure can be achieved by near-infrared light, which penetrates through water and biological tissues and is absorbed by CNTs, resulting in rapid local heating. Spanning over a thousand of bars and Kelvin, the reactive and non-reactive scenarios of CNT opening represent extreme cases and allow for a broad experimental control over properties of the CNT interior and release conditions of the confined species. The detailed insights into the thermodynamic conditions and chemical mechanisms of the pressure-induced CNT opening provide practical guidelines for the development of novel nanoreactors, catalysts, photo-catalysts, imaging labels and drug delivery vehicles.