Desenvolvimento e modificação a plasma de materiais a base de poli(ácido lático)/α-Ag2WO4 com potencial ação antimicrobiana

Abstract

Recently, the world has been facing several microbial infections that have caused great losses and fatalities. In this scenario, the development of new materials that can be used to fight these potentially pathogenic microorganisms has been growing. Nanocomposite materials formed from the combination of a polymer matrix and an inorganic filler on a nanometric scale have been widely developed aiming biomedical applications such as devices that presents an antimicrobial activity. Poly(lactic acid) (PLA) is one of the polyesters that has shown the greatest market growth in recent years due to its good properties such as processability, biodegradability and biocompatibility. However, despite these advantages, PLA has some drawbacks related to its bulk and surface that limits its applicability. In this sense, efforts have been made to increase the applicability of PLA, minimizing the effect of its limitations, such as the incorporation of particles and plasma treatment, which can promote both chemical and morphological surface modification. Additionally, plasma etching treatment can expose the incorporated particles, enhancing the antimicrobial effect. In this work, α-Ag2WO4 nanoparticles were synthesized and incorporated at different concentrations in PLA matrix. Nanocomposite films were later exposed to oxygen plasma treatment. The influence of the incorporation of different concentrations of α-Ag2WO4 on the thermal properties of the polymer were investigated. The calculated degree of crystallinity indicated that the particle has no potential to act as a nucleating agent under the conditions of the analysis (quiescent crystallization). However, under non-quiescent conditions, the presence of the nanoparticles affected the induction time for the onset of crystallization at the shear rates used. Rheology analysis showed that there was an increase in complex viscosity values for all samples containing α-Ag2WO4 when compared to the pure polymer, indicating good dispersion and charge distribution. The chemical changes caused by the plasma treatment were analyzed by means of contact angle, Fourier transform infrared transmittance spectroscopy (FTIR-ATR) and X-ray excited photoelectron spectroscopy (XPS). The results indicated an increase in the hydrophilicity of the polymer surface and changes in the concentration of preexisting functional groups on the surface when compared to PLA without treatment. Morphological changes on the films surface caused by exposure to plasma were analyzed by atomic force microscopy (AFM) and SEM. Finally, the antimicrobial activity (against bacteria and fungus) of the nanocomposite was confirmed. Furthermore, it was found that the plasma treatment can enhance the antimicrobial effect by exposing the particles on the surface.