Preparação e caracterização de membranas de poli(fluoreto de vinilideno) eletrofiadas com nanopartículas de prata

Abstract

In this study, investigations were carried out to explore the potential of electrospun poly(vinylidene fluoride) (PVDF) membranes with silver nanoparticles with the purpose of adding antimicrobial activity. Five membranes were prepared from silver-doped PVDF. This polymer is well-known in the industry due to its mechanical properties (tensile, flexural, torsional, and compressive) and electrical and thermal properties (pyroelectricity and piezoelectricity). Additionally, PVDF demonstrates resistance to chemicals, contributing to the durability of the produced membranes. The main objective was to optimize standardized PVDF membranes by establishing a constant polymer mass quantity in order to meet the minimum requirements for electrospinning, and subsequently incorporating silver (Ag) in the following quantities (12, 24, 60, 120, and 240) mg. To understand the structure and properties of the produced membranes, analytical techniques such as X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to estimate and understand the degree of crystallinity of the polymer. As PVDF is a semi-crystalline material, crystallinity can vary between 33% to 60% according to this study. To analyze the phenomena influencing the electrospinning technique, the morphology of the membranes was investigated using scanning electron microscopy (SEM) on pure and incorporated samples. It also allowed for the evaluation of the diameters of the microfibers formed after the electrospinning process, ranging from 1.40 μm to 5.20 μm. Depending on the experimental conditions of the electrospinning parameters such as solution, working, and ambient conditions, these values can strongly influence the characteristics related to surface, diameter, and length of these fibers. Another applied technique was Fourier-transform infrared spectroscopy (FTIR) used to identify the functional groups present and distinguish the composition of pure and incorporated polymeric materials, and to verify if there are significant changes in the analysis profile when the polymer is electrospun. Furthermore, the contact angle was measured through wettability to observe the confirmation of the typical hydrophobic properties of PVDF. Finally, biological assays were conducted with different bacteria in wells and Brain Heart Infusion (BHI) and Agar culture media to certify if there is inhibition or reduction in bacterial propagation. The results showed a reduction in contamination and the formation of inhibitory halos for the bacteria: Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli, in which the membrane incorporated with the highest silver concentration showed the best antimicrobial activity compared to the other doped membranes.