Desenvolvimento de membranas antimicrobianas a partir da extração e purificação da celulose da casca da batata

Abstract

Agroindustrial waste stands out as an abundant and low cost material that can be transformed into value-added products in the medical sector. Researching materials that are even cheaper and more sustainable has become an important task, since wound treatment is a public health problem. Thus, this study aims to develop an innovative “green” technology by isolating cellulose from potato peels to prepare antimicrobial membranes through the use of silver nanoparticle (Np-Ag) biosynthesis, using the geranium leaves extract (Pelargonium zonale). The process for extracting and purifying the potato peel cellulose, with consequent film formation, was done using sodium hydroxide (NaOH) and hydrogen peroxide (H2O2), using factorial design 22 in the alkaline pulping stage. Results showed that both concentration and temperature influenced in the yield; however, only temperature was significant enough to form films (membrane). Among the tests a film was obtained. The highest yield occurred under the conditions of 0.5 mol/L NaOH, at 80°C for 2.5h, followed by bleaching with H2O2 15% w/w. FTIR analysis of this material exhibited characteristic bands of cellulose, while bands related to hemicellulose and lignin were not observed. XRD spectra confirmed that the extracted cellulose had a crystalline pattern similar to type I and II cellulose and the crystallinity index was 73.42%. The membrane thermal behavior revealed that about 80% of the cellulose chain was degraded at temperatures of 340°C and 442°C, with activation energy of 163.82 kJ/mol. Swelling studies showed that membrane has a high swelling content (between 200% and 300%) at temperatures of 10, 25 and 40°C and the diffusion process did not follow the Fick model. In addition, a phase transition temperature of about 40°C was found. Characterization analyzes (UV-visible and FTIR spectra) of the geranium extract exhibited functional chemical groups that are capable of reducing and stabilizing silver ions (Ag+) to Np-Ag. This reduction in an aqueous medium with geranium extract was confirmed by the presence of absorption bands typical of the surface plasmon resonance region (RPS) for Np-Ag at 370 and 470 nm. XRD analyses of the cellulose fiber/silver nanoparticle (FC/Np-Ag) biocomposites showed that the crystalline profile of the cellulose matrix was not modified, although crystallinity has decreased to the samples that were swollen in Ag+ solution. The mean size of the Np-Ag varied between 20-12 nm. Microbiological assays revealed that the antimicrobial activity of Np-Ag was effective for both Escherichia coli bacteria and Staphylococcus aureus, with inhibition halos in the range of 12-17 mm. Releasing studies showed that the Np-Ag were only released at 370 nm. Release profiles for the temperatures of 23, 30 and 37 ° C exhibited satisfactory exponential adjustments, following a bimodal model. The equilibrium was faster reached at 23°C, releasing 0.0095 mg/mL of Np-Ag. Thus, it could be inferred that temperature decreasing resulted in greater release. It was also observed that the Np-Ag release followed a zero-order kinetic profile for the three temperatures studied. The release activation energy (EL) between 30°C and 37°C was 67.50 kJ/mol. In the same temperature range, thermodynamic parameters for enthalpy, entropy and free energy of Gibbs of the activated complex revealed an endothermic process, tending to decrease the system disorder and naturally not spontaneous. Therefore, using a lowcost agroindustrial residue, this study contributed to the synthesis and characterization of the FC/Np-Ag biocomposite, which due to its physic-chemical and antimicrobial characteristics, has great potential in wound treatment.