Biossíntese de nanopartículas de prata utilizando cinnamomum zeylanicum em matriz de hidrogel para aplicação biomédica

Abstract

The aim of the present thesis was to study the biosynthesis of silver nanoparticles reduction (AgNPs) in situ in the presence of polyvinyl alcohol (PVA), using aqueous extract of Cinnamomum zeylanicum (cinnamon) as reducing and stabilizer agent and citric acid, as crosslinking agent in order to obtain and characterize the PVAEXT-AgNPs hydrogel membrane, for application in the treatment of cutaneous wounds. In situ biosynthesis of AgNPs in the presence of PVA was confirmed by UV-vis spectroscopy from the RPS band observed at 423 nm. The kinetic study of the in situ biosynthesis of AgNPs at 23 °C showed that this follows a first order kinetics, with k=0.0021 min-1. The thermogravimetric study showed higher thermal stability of PVAEXT-AgNPs membranes compared to pure PVA. The MEV-EDS mapping of the PVAEXT-AgNPs membrane revealed the presence of AgNPs aggregates distributed along the membrane surface. The middle value diameter of nanoparticles of PVAEXT-AgNPs membranes was 0.04, 0.06 e 0.1, was 12 nm, 11 nm e 9 nm, respectively. The study of PVAEXT-AgNPs membrane swelling in distilled water at 23 °C revealed a degree of swelling at equilibrium of 130%. The swelling values adjusted to the beginning of the process, at temperature of 23 °C, by the equation of Fick, difusional n ≤ 0.5 constant presented, and proportionality constant k = 0.509. The kinetic study of PVAEXT-AgNPs membrane swelling process in distilled water, in the first few minutes, at 23 °C was adjusted to a first-order kinetics, using the model of Lagergren. The linear adjustment provided the value k = 0.117 min-1. For the study of AgNPs release was built an analytical calibration curve, linear regression R2 = 0.95. The kinetic and thermodynamic study of AgNPs release was carried out in distilled water a 37 °C e 40 °C. The kinetic study of AgNPs release at both temperatures was adjusted to a first order kinetics. The rate constant was k= 0.00209 min-1 at 37 °C and k= 0.0742 min- 1 at 40 °C. The activation energy was determined from the Arrhenius equation of 959.87 kJ/mol. The thermodynamic study was performed from the Eyring equation and presented the non-linear release system, with values of G0≠=91.93 kJ/mol at 37 ºC and G0≠=83.55 kJ/mol at 40 ºC. The release system is endothermic with enthalpy of 957.28 kJ/mol. The entropy change reveals a slight increase in the disorder, with S0≠= 2.76 kJ/mol*K at 37 °C and S0≠=2.76 kJ/mol*K at 40 °C. The study of antimicrobial activity showed that the PVAEXT-AgNPs membrane is effective for both bacteria Staphylococcus aureus and Escherichia coli. The antimicrobial action was effective from the concentration of 0.02 mol/L AgNO3. The PVAEXT-NPsAg membrane cytotoxicity assay against chinese hamster ovary cell lines (CHO-K1, ATCC CCL 61, American Type Culture Collection) showed that cell viability remained > 90% for all concentrations of extracts studied, being the PVAEXT-AgNPs membrane considered non-cytotoxic.