Efetividade de membrana polimérica obtida por eletrofiação e funcionalizada com tungstato de prata (α-Ag2WO4)

Abstract

Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus) and methicillin-resistant Staphylococcus aureus (MRSA) are often associated with the increase of multidrug-resistant strains and has been generating global problems. This present research aimed to study the antimicrobial activity of a polymeric membrane obtained by electrospinning and functionalized with silver tungstate ( -Ag2WO4). The membranes were obtained by the horizontal electrospinning method in five proportions of 1:1, 0.75/1, 0.50/1, 0.25/1 and 0.1:1 of -Ag2WO4 to polycaprolactone (PCL) (wt/wt). The alpha phase of silver tungstates was obtained by the hydrothermal method at 120 ºC and 140 ºC, which was confirmed by X-ray diffraction (XRD) with XRD peaks characteristics of -Ag2WO4 in the 2θ = 30.3º, 31.6º, 33º and 45.2º, which correspond to the crystallographic planes of (002), (231), (400) and (402). The vibrational active modes of PCL and -Ag2WO4 were confirmed by the Fourier transform infrared spectroscopy (FTIR), where active modes associated to the O-W-O bonds were identified in the range of 807 and 865 cm-1 in the pure (standard) and membranes materials. The membranes were characterized by scanning electron microscopy (SEM), which is identified the randomly distributed and less diameter of fibers for membrane in the proportion of 1:1. As also, for samples prepared in the proportion of 0.25/1 and 0.1:1 a high homogeneous fiber diameter and absence of beads is reached. The presence of silver (Ag), tungsten (W) and oxygen (O) elements by energy dispersive spectroscopy (EDS) confirm the presence of -Ag2WO4 in the fibers. Thermogravimetric curves (TGA) revealed that there were no changes in the thermal stability of membranes in comparison of pure PCL (standard). The antimicrobial activities result of membranes against Pseudomonas strains with an average halo ranging from 22 ± 0.55 cm to 13 ± 0.57 cm and diffusely adherent E. coli (DAEC) with an average halo of 16 ± 0.55 cm. The fibers are shown the microbicidal and microbiostatic action against enterotoxigenic E. coli (ETEC ST) and enteroinvasive E. coli (EIEC), with a reduction to zero in the log CFU/ mL in proportions of 1:1 to 0.25/1 in intervals of 0 to 48 hours. Also, against three strains of P. aeruginosa, with reduction to zero in log CFU/ mL in proportions ranging from 1:1 to 0.75/1. The best antibiofilm activities were with DAEC, EHEC, and EIEC E. colis, non-diarrheal E. coli and P. aeruginosa ATCC 15442 in all proportions. Cellular changes were evaluated with the membrane contact in a 1:1 ratio, which exerted a similar effect on strains of E. coli, P. aeruginosa, S. aureus and MRSA, and presented damage such as ruptures in the plasma membrane, internal structure decomposing, cell wall disintegration and large vacuoles. Therefore, silver tungstate coupled to PCL as membrane by electrospinning method appears as an alternative material for the treatment and prevention of microbial infections.