Atividade antimicrobiana da combinação de nanopartículas de prata, quitosana e antibióticos avaliada por ensaios de concentração inibitória mínima e espectroscopia SERS

Abstract

Investigation of the synergistic effect present in the association involving chitosan (QT), silver nanoparticles (AgNPs) and antibiotics (ATBs) was performed by in vitro analysis of their antibacterial action against Gram negative (Escherichia coli) and Gram positive (Staphylococcus aureus) bacterial strains. The chemical interactions of the adsorbates on the surface of the AgNPs were studied by the technique of surface-enhanced Raman scattering (SERS) spectroscopy. Comparative analyzes involving each component isolated from colloid and the mixture of QT-stabilized AgNPs and ATBs: azithromycin (AZ), levofloxacin (LE) and tetracycline (TE) were performed by minimum inhibitory concentration (MIC) and checkerboard test. The tests showed synergistic and additive antibacterial effect. The pH impact of the solutions in the culture medium was evaluated, as well as the best conditions for QT solubilization, and the biological tests were performed in such a way that the pH effect did not interfere with the antimicrobial activity. The synergism observed in the combination of QT and AgNP was remarkable, also significantly improving the results of the association of AgNP-QT and ATBs, which led to a reduction of 37% to 99% in the MIC of ATBs. The SERS and Raman spectra of the ATBs LV, TC, AZ, cefepime (CE), chloramphenicol (CL), ampicillin (AM), sulfamethoxazole (SF), benzylpenicillin procaine (BP) and penicillin G (PG) were also obtained. As well as complementary evaluations of the dynamic light scattering (DLS) and zeta potential to assess the size and stability of the suspensions of AgNPs and QT.