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Previous issue date: 2017-08-07 === A investigação do efeito sinérgico presente na associação envolvendo quitosana (QT), nanopartículas de prata (AgNPs) e antibióticos (ATBs) foi realizada por análise in vitro de sua ação antibacteriana contra estirpes bacterianas Gram negativas (Escherichia coli) e Gram positivas (Staphylococcus aureus). As interações químicas dos adsorbatos na superfície das AgNPs foram estudadas através da técnica de espectroscopia por espalhamento Raman intensificada por superfície (surface-enhanced Raman scattering - SERS). As análises comparativas, envolvendo cada componente isolado do coloide e a mistura de AgNPs estabilizadas com QT e os ATBs: azitromicina (AZ), levofloxacina (LE) e tetraciclina (TE), foram realizadas por teste de Concentração Inibitória Mínima (CIM) e teste de checkerboard. Os ensaios mostraram efeitos antibacterianos sinérgicos e aditivos. O impacto do pH das soluções no meio de cultura foi avaliado, bem como as melhores condições para solubilização da QT, sendo os testes biológicos realizados de forma que o efeito do pH não interferisse na atividade antimicrobiana. O sinergismo observado na combinação de QT e AgNP foi notável, melhorando significativamente também os resultados da associação de AgNP-QT e ATBs, o que levou a uma redução de 37% para 99% na CIM dos ATBs. Também foram obtidos os espectros SERS e Raman dos ATB LV, TC, AZ, cefepime (CE), cloranfenicol (CL), ampicilina (AM), sulfametoxazol (SF), benzilpenicilina procaína (BP), penicilina G (PG). Assim como avaliações complementares do espalhamento da luz dinâmica (DLS) e potencial zeta para avaliação do tamanho e estabilidade das suspensões de AgNPs e QT. === 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.
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