Adesão e formação de biofilmes bacterianos em superfícies de processamento de alimentos funcionalizadas com nanopartículas de prata
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2015-07-03
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Universidade Federal de Viçosa
Resumo
A nanotecnologia representa um grande avanço na ciência em diversos campos com desenvolvimento de novos materiais com diferentes funcionalidades e potenciais de aplicação. Desta forma, destacam-se as nanopartículas de prata (Ag NPs) como agentes antimicrobianos promissores para inibição de adesão bacteriana em superfícies de processamento de alimentos. A contaminação de superfícies de processamento de alimentos, principalmente com patógenos, é de grande preocupação, por se tratar de um problema de saúde pública. Neste contexto, este trabalho objetivou estudar o efeito antimicrobiano das superfícies de aço inoxidável e de polietileno (PE) funcionalizadas com Ag NPs sobre a adesão de diferentes espécies bacterianas, bem como avaliar possíveis alterações nas características físico-químicas dessas superfícies que possam influenciar no processo de formação de biofilmes de micro-organismos. Observou-se que de acordo com o critério quantitativo, ou seja, com base nos resultados da variação da energia TOT livre da interação hidrofóbica ( Gsas ), tanto as superfícies de aço inoxidável analisadas quanto as superfícies poliméricas foram TOT consideradas hidrofóbicas por apresentarem o valor Gsas negativo; além TOT disso, houve diferença (p < 0,05) entre os valores de Gsas encontrados para ambas as superfícies funcionalizadas quando comparadas às superfícies controles. No estudo das superfícies bacterianas em termos TOT de Gsas , verificou-se que são hidrofílicas. A partir da variação da energia livre de adesão (ΔGadesão), verificou-se que para todas as superfícies analisadas a ΔG adesão foi termodinamicamente favorável (ΔGadesão < 0) sendo que, para todas as superfícies funcionalizadas com Ag NPs, obteve-se diferença (p < 0,05) no valor de ΔGadesão em relação à superfície controle. Em adição, a superfície de PE funcionalizado com Ag NPs tornou a superfície de processamento termodinamicamente mais favorável à adesão para as três bactérias avaliadas em comparação com o controle. Em relação à adesão das células vegetativas de E. coli, S. aureus e P. fluorescens, observou-se que não houve diferença (p < 0,05) entre as superfícies controle e funcionalizadas, embora o resultado da termodinâmica de adesão ter sugerido diferença. No estudo da adesão de P. fluorescens em cilindro de aço inoxidável revestido com Ag NPs, simularam-se as forças de cisalhamento e a turbulência provocadas pelo bombeamento do fluido, encontrando-se 4,47 log UFC.cm-2 no cilindro controle e 4,17 log UFC.cm-2 no cilindro funcionalizado, não havendo diferença entres eles (p < 0,05). A concentração mínima inibitória (CMI) da dispersão de Ag NPs determinada foi de 12,50 mg.L -1 para as três bactérias avaliadas: S. aureus, E. coli e P. fluorescens. Para as em cilindro de aço inoxidável revestido com Ag NPs em pó a CMI foi de 6,25 mg.L-1 para todos micro-organismos. Utilizando a técnica de espectroscopia de absorção atômica, verificou-se que não houve lixiviação de Ag NPs da superfície de aço funcionalizada para os dois simulantes testados (água e leite desnatado reconstituído), reforçando a hipótese de uma forte interação na matriz do aço entre as Ag NPs e o silano, formando uma ligação ordenada e complexa que interferiu na efetividade do antimicrobiano. As topografias das superfícies também foram observadas por meio da microscopia de força atômica (MFA), sendo a rugosidade média da superfície de aço controle de 325 ± 21,9 nm, a de aço funcionalizada de 343 ± 20,6 nm, a de PE controle 370 ± 55,9 nm e a de PE funcionalizado de 425 ± 24,7 nm. Os resultados mostraram que as Ag NPs não foram eficientes para inibição de adesão bacteriana nas superfícies consideradas, necessitando, portanto, de mais estudos físico-químicos para compreensão do aprisionamento da prata nas superfícies de processamento.
The nanotechnology represents a huge advance through science in several areas with development in new materials and possible uses. Thus, we can stress the silver nanoparticles (Ag NPs) as promising antimicrobial agents to inhibition of bacteria access in food processes areas. The surface’s contamination of food processes areas, mainly by pathogens, is worry’s target because it is a public health problem. In this sense, this search aimed to study the antimicrobial effect from surfaces made of stainless steel and coated by polyethylene with Ag NPs affected by different bacterial species besides possible changes in the physical- chemical characteristics in these surfaces that could influence the micro- organisms access process. We could observe that according to the quantity criterion, so, based on the energy variety of free hydrophobic TOT interaction results ( Gsas ) both, the stainless steel surfaces analyzed and the polymer surfaces were considered hydrophobic because they present TOT the negative value for ( Gsas ) besides there was a huge difference (p < TOT 0,05) between the values of ( Gsas ) found for both surfaces used when compared to the control surfaces. In the study of bacterial surfaces in TOT Gsas we checked they are hydrophilic. From the variation of free energy of access ΔGadesão, we checked that for all the analyzed surfaces to ΔGadesão was favorable thermodynamicly (ΔGadesão < 0) being for all used surfaces with Ag NPs, we obtained a huge difference (p < 0,05) in the value of ΔGadesão related to the control surface. In addition, the surface of polymer used with Ag NPs became the process surface thermodynamically more favorable to access for three bacteria evaluated. About the access from vegetative cells from E. coli, S. aureus e P. fluorescens, we observed that didn’t have important difference (p < 0,05) between the control surfaces and used, although the results from the thermodynamic access suggested difference. In the study of access from P. fluorescens in stainless steel cylinder functionalized and control, we simulate the forces of deformation and the disturb promoted by pumping fluid, there wasn’t relevant difference between them (p < 0,05). The minimum inhibition concentration (CMI) from the dispersion Ag NPs determined was of 12, 50 mgL -1 for the three bacteria evaluated: S. aureus, E. coli e P. fluorescens. In order to the poder of Ag NPs the CMI was from 6,25 mg.L-1 for all micro-organisms. Using the spectroscopy technique of atomic absorption, we concluded that there wasn’t silver diffusion from the used steel surface to two tested simulants (water and skim reconstituted milk), reinforcing the hypothesis from a strong interaction in the steel matrix between Ag NPs and the silane, making na ordenated and complex connection that interfered in the effectiveness of the antimicrobial. The surface topographies also were observed by the atomic force microscopy (MFA), resulting the media roughness of steel surface control was 325 ± 21,9 nm, the steel one used was de 343 ± 20,6 nm, the control polymer 370 ± 55,9 nm and the used polymer from 425 ± 24,7 nm. The results showed that in this study, the nanoparticles of silver wasn’t efficient to inhibition of bacterial access in the considered surfaces, requiring therefore, from more physical-chemical studies to comprehension of imprisonment of silver in the surface of the processing.
The nanotechnology represents a huge advance through science in several areas with development in new materials and possible uses. Thus, we can stress the silver nanoparticles (Ag NPs) as promising antimicrobial agents to inhibition of bacteria access in food processes areas. The surface’s contamination of food processes areas, mainly by pathogens, is worry’s target because it is a public health problem. In this sense, this search aimed to study the antimicrobial effect from surfaces made of stainless steel and coated by polyethylene with Ag NPs affected by different bacterial species besides possible changes in the physical- chemical characteristics in these surfaces that could influence the micro- organisms access process. We could observe that according to the quantity criterion, so, based on the energy variety of free hydrophobic TOT interaction results ( Gsas ) both, the stainless steel surfaces analyzed and the polymer surfaces were considered hydrophobic because they present TOT the negative value for ( Gsas ) besides there was a huge difference (p < TOT 0,05) between the values of ( Gsas ) found for both surfaces used when compared to the control surfaces. In the study of bacterial surfaces in TOT Gsas we checked they are hydrophilic. From the variation of free energy of access ΔGadesão, we checked that for all the analyzed surfaces to ΔGadesão was favorable thermodynamicly (ΔGadesão < 0) being for all used surfaces with Ag NPs, we obtained a huge difference (p < 0,05) in the value of ΔGadesão related to the control surface. In addition, the surface of polymer used with Ag NPs became the process surface thermodynamically more favorable to access for three bacteria evaluated. About the access from vegetative cells from E. coli, S. aureus e P. fluorescens, we observed that didn’t have important difference (p < 0,05) between the control surfaces and used, although the results from the thermodynamic access suggested difference. In the study of access from P. fluorescens in stainless steel cylinder functionalized and control, we simulate the forces of deformation and the disturb promoted by pumping fluid, there wasn’t relevant difference between them (p < 0,05). The minimum inhibition concentration (CMI) from the dispersion Ag NPs determined was of 12, 50 mgL -1 for the three bacteria evaluated: S. aureus, E. coli e P. fluorescens. In order to the poder of Ag NPs the CMI was from 6,25 mg.L-1 for all micro-organisms. Using the spectroscopy technique of atomic absorption, we concluded that there wasn’t silver diffusion from the used steel surface to two tested simulants (water and skim reconstituted milk), reinforcing the hypothesis from a strong interaction in the steel matrix between Ag NPs and the silane, making na ordenated and complex connection that interfered in the effectiveness of the antimicrobial. The surface topographies also were observed by the atomic force microscopy (MFA), resulting the media roughness of steel surface control was 325 ± 21,9 nm, the steel one used was de 343 ± 20,6 nm, the control polymer 370 ± 55,9 nm and the used polymer from 425 ± 24,7 nm. The results showed that in this study, the nanoparticles of silver wasn’t efficient to inhibition of bacterial access in the considered surfaces, requiring therefore, from more physical-chemical studies to comprehension of imprisonment of silver in the surface of the processing.
Descrição
Palavras-chave
Biofilmes bacterianos - Adesão em aço inoxidável, Polietileno, Nanopartículas de prata
Citação
FIALHO JÚNIOR, José Felício Queiroz. Adesão e formação de biofilmes bacterianos em superfícies de processamento de alimentos funcionalizadas com nanopartículas de prata. 2015. 49 f. Dissertação (Mestrado em Ciência e Tecnologia de Alimentos) - Universidade Federal de Viçosa, Viçosa. 2015.