Obtenção e caracterização de embalagens antimicrobianas contendo nanopartículas de prata obtidas por síntese verde empregando extrato aquoso de macela (Achyrocline satureioides)

Abstract

Nanostructured materials have stood out in the market today and have different applicability. Among them are silver nanoparticles (AgNPs) that stand out in the food industry, in dental materials and packaging as they have excellent antimicrobial activity, good conductivity and have a high catalytic effect. As a result, green synthesis is currently being used as a sustainable alternative to replace chemical reagents and their environmental impact on the environment and health. Thus, the objective of this work was to synthesize and characterize AgNPs using the green synthesis process, using an aqueous macela extract, and to prepare cassava starch films by the casting technique with the suspension of AgNPs, as well as to analyze the characteristics of the polymeric materials obtained. Therefore, the AgNPs were obtained using 25mL of aqueous solution containing 7.5% of the plant extract (macela), 2% or 5% (v/v) of a 1% (m/v) capping agent solution (PVA or PVP or sodium citrate) (with and without pH adjustment to 8.5), then 250mL of silver nitrate solution (0.02 mmol) was dropped into the extract solution. Suspensions containing AgNPs were characterized by UV-vis, DLS, Zeta Potential, TGA, DSC and antimicrobial activity by the diffuse disk technique. Then 3 experiments were selected from the analysis of the results of nanoparticles size, suspension stability, and antimicrobial activity, then the suspension of these AgNPs was used to obtain cassava starch films. The casting method was used, where cassava starch was dispersed in the suspension of AgNPs, then the system was heated under stirring to the starch gelatinization temperature, kept for 10 minutes, then citric acid was added and after cooling the system to 60º Glycerol was added, the gel obtained was poured into silicone molds and dried in a study with air circulation at 50°C for 24 hours. The films were characterized by DSC, tensile test, thickness, moisture, weight, solubility, and antimicrobial activity by the diffuse disc technique. Through the analysis of UV-Vis, DSC and TGA it was observed that the macela played a role of reducing agent. With the DLS analysis we observed the particle size and through the Zeta Potential the stability of the suspension that were influenced by the change in pH, type and concentration of the capping agent used, and it was also possible to verify that the AgNPs suspensions obtained presented good antimicrobial ability. The casting technique to obtain starch films containing AgNPs proved to be simple and adequate, and after analyzing the results of the characterization of the films, it was verified that the films obtained presented satisfactory antimicrobial activity, and that the AgNPs with capping agents acted in such a way as to leaving the films more flexible, but less resistant, suggesting that AgNPs with capping acted as a plasticizer. Thus, it can be concluded that green synthesis is a promising process for obtaining AgNPs, and that these can be used to obtain antimicrobial polymeric films intended, for example, for packaging.