Journal of Food Protection, Vol. 75, No. 4, 2012, Pages 701–705 doi:10.4315/0362-028X.JFP-11-276
Copyright G, International Association for Food Protection
Antimicrobial Effects of Silver Nanoparticles against Bacterial Cells Adhered to Stainless Steel Surfaces
´ ´ ´ EMILIANE A. ARAUJO,1 NELIO J. ANDRADE,1* LUIS HENRIQUE M. DA SILVA,2 PATRICIA C. BERNARDES,1 ´ ´ ˜ ´ ´ ´ ALVARO V. N. DEC. TEIXEIRA,3 JOAO PAULO N. DE SA,1 JOSE FELICIO Q. FIALHO, JR.,1 AND PATRICIA E. FERNANDES1
Technology Department, 2Chemistry Department, and 3Physics Department, Federal University of Vicosa, 36570-000, Vicosa, Minas Gerais, Brazil ¸ ¸ MS 11-276: Received 5 June 2011/Accepted 20 November 2011
Given the increasing number of antibiotic-resistant bacteria and the need tosynthesize new antimicrobials, silver has attracted interest in the scientific community because of its recognized antimicrobial activity. This study aimed to evaluate the antimicrobial effects of silver nanoparticles (NP) obtained by a new method and tested at concentrations of 6 mg/ml and 60 mg/ml against the species Staphylococcus aureus, Listeria innocua, Salmonella Choleraesuis, Pseudomonasaeruginosa, Escherichia coli, and Bacillus cereus. The ability of these nanoparticles to remove or kill vegetative cells adhered to stainless steel surfaces was also evaluated. We observed that the NP obtained with the new method, concentrated silver nanoparticles (CNP), and silver nanoparticles with added sodium chloride (NPNaCl) had high antimicrobial activities (P , 0.05). We also verified that themost effective condition for the removal of P. aeruginosa cells on stainless steel coupons (10 by 10 mm) was immersion of the surfaces in CNP. The CNP treatment produced a 5-log reduction of the microbial population after 30 to 60 min of immersion. The CNP treatment also performed better than water and sodium carbonate, a compound commonly applied in clean-in-place procedures in the food industry,in removing adherent B. cereus cells from stainless steel cylinders. Therefore, these results suggest that NP synthesized by a new procedure may be used as antimicrobials in the food industry, for example, for the sanitization of utensils that come into contact with foods.
The antibacterial properties of silver are well known, and it has been demonstrated that silver is nontoxic to human cellsat low concentrations (14). In the past, silver was used in water containers and was also used to prevent the deterioration of foods and liquids. Silver ions were used to treat burns and as chemotherapeutic agents against pathogens such as Staphylococcus aureus and Streptococcus pneumoniae. The use of silver as an antimicrobial agent decreased after 1940, following the discovery of penicillin andits use in medicine. However, with the indiscriminate use of antibiotics, the selection of resistant microbial species, and the need to develop new antimicrobials, silver has again attracted attention from the scientific community (2, 18). Nanoscale materials have recently emerged as new antimicrobials. The term ‘‘nano’’ is used to indicate a dimension of 1029 m. These nanoparticles are clustersof atoms with sizes ranging from 1 to 100 nm (15). The novel medical use of nanoparticles as antimicrobial agents includes infection reduction and the prevention of bacterial colonization on the surfaces of prostheses, catheters, dental materials, and food processing surfaces, such as stainless steel (8, 11). Nanoparticles can also be used for microbial control in textiles and water treatment (7).The control of particle size is
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an important factor in the synthesis of nanoparticles; smaller particles exhibit greater antimicrobial effects (17). The mechanisms of action of silver ions and silver nanoparticles (NP) on microorganisms are varied and are not well established. Some...
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