This study examines the antimicrobial activity of silver nanoparticles incorporated into nanostructured membranes made of cellulose acetate (CA) and blends of chitosan/poly-(ethylene oxide, CTS/PEO) and prepared by electrospinning. The formation of chemically synthesized Ag nanoparticles (AgNPs) was monitored by UV-visible spectroscopy (UV-Vis) and characterized by transmission electron microscopy (TEM). The size distribution of the AgNPs was measured by dynamic light scattering (DLS), with an average size of approximately 20 nm. The presence of AgNPs on the surface of electrospun nanofibers was observed by field emission electron microscopy (FEG) and confirmed by TEM. The antimicrobial activity of AgNPs incorporated into nanostructured membranes made of CA and CTS/PEO electrospun nanofibers was evaluated in the presence of both Gram-positive bacteria, such as Staphylococcus aureus ATCC 29213 and Propionibacterium acnes ATCC 6919, and Gram-negative bacteria, such as Escherichia coli ATCC 25992 and Pseudomonas aeruginosa ATCC 17933. Microbiological results showed that the presence of AgNPs in CA and CTS/PEO nanostructured membranes has significant antimicrobial activity for the Gram-positive bacteria Escherichia coli and Propionibacterium acnes.
Uniterms:Electrospinning. Silver nanoparticles/antibacterial activity. Cellulose acetate. Chitosan.Neste trabalho avaliou-se a atividade antimicrobiana das nanopartículas de prata (AgNPs) incorporadas em membranas de acetato celulose (AC) e blendas de quitosana/poli-óxido de etileno (CTS/PEO) preparadas pelo método de eletrofiação. A formação das AgNPs previamente sintetizadas foi monitorada por UV-Vis e caracterizada por microscopia eletrônica de transmissão (MET). A distribuição de tamanho das AgNPs foi mensurada por espalhamento de luz dinâmico, com tamanho médio em torno de 20 nm. A presença das NPs na superfície das nanofibras eletrofiadas foi observada por microscopia eletrônica com emissão de campo (FEG) e confirmada por MET. A atividade antimicrobiana das membranas nanoestruturadas de AC e CTS/PEO foi avaliada pelo uso de bactérias Gram-positivas, tais como Staphylococcus aureus ATCC 29213 e Propionibacterium acnes ATCC 6919, e Gram-negativas, como Escherichia coli ATCC 25992 e Pseudomonas aeruginosa ATCC 17933. Os resultados microbiológicos mostraram a presença das AgNPs nas membranas de AC e CTS/PEO com significativa atividade antimicrobiana para Escherichia coli e Propionibacterium acnes, respectivamente.Unitermos: Eletrofiação. Nanopartículas de prata/atividade antimicrobiana. Acetato de celulose. Quitosana.
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INTRODUCTIONThe use of metal nanoparticles in various medical and biotechnological applications is one of the most investigated areas in materials science. These applications require appropriate chemical functionalization of the nanoparticles with organic molecules or their incorporation into polymer matrices (Dallas, Sharma, Zboril, 2011). Among the numerous types of nanoparticles that have been used to decorate polymers, silver nanoparticles (AgNPs) ...
The extracts of three different medicinal plants –Calendula officinalis L., Maytenus ilicifolia Martius ex Reissek and Cymbopogon citratus (DC) Stapf – obtained with 70% and 95% v/v ethanol had their antimicrobial activity tested against five pathogenic microorganisms. A quantitative analysis of total phenols, flavonoids and mineral species was performed on the extracts using UV‐vis spectroscopy and atomic absorption spectroscopy. Klebsiella pneumoniae showed the greatest sensibility to the extracts tested. The mineral content of the medicinal herbs varied according to the type of plant (Cu = not detected to 10.90; Zn = 0.85 to 10.04; Na = 24.94 to 153.62; Al = 90.04 to 420.39; Mg = 9.62 to 1,129.15; Ca = 7.15 to 167.27 and K = 913.85 to 9,578.94 µg/g); however, the concentration of heavy elements (Pb, Cd and Cr) was null in the extracts. The concentrations of flavonoids ranged from 13.55 to 41.54 mg/g and 92.35 to 518.28 mg/g for phenolic acids.
PRACTICAL APPLICATIONS
The use of plants with pharmacological activities has increased significantly because of their functional properties in the diet for the promotion of human health and antimicrobial effects. Moreover, medicinal herbs play an important role in public health, especially in developing countries. In Brazil, the use of plant extracts in the treatment of certain diseases is very common. This habit can be explained, at least in part, by the belief that herbs with therapeutic effects do not have toxic effects on the organism. In this paper, ethanolic extracts of three medicinal plants, widely cultivated and used by the population of Brazil and worldwide, had their levels of metals ions and total phenolic compounds determined. Antimicrobial activity of the extracts was evaluated against foodborne pathogens or food spoilage organisms or clinically isolates microorganisms.
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