Preparation of silver nanoparticles/polymethylmethacrylate/cellulose acetate film and its inhibitory effect on Cronobacter sakazakii in infant formula milk.

Cronobacter sakazakii is a harmful foodborne pathogen, and its contaminated food will pose a huge threat to human health. Prevention of C. sakazakii contamination of food is valuable for food safety as well as for human health. In this study, silver nanoparticles (AgNP) were successfully immobilized on the surface of cellulose acetate (CA) and polymethylmethacrylate (PMMA) composite to obtain AgNP/PMMA/CA film. Through the inhibition zone and growth curve experiments, we found that AgNP/PMMA/CA films has excellent antibacterial activity on C. sakazakii. The AgNP/PMMA/CA film can prolong the lag phase of the growth curve of C. sakazakii from 2 to 8 h. The antibacterial films were found to reduce the survival of C. sakazakii in Luria-Bertani and infant formula by combining it with a mild heat treatment (45°C, 50°C, and 55°C). The AgNP/PMMA/CA film combined with 55°C water bath can completely inactivate C. sakazakii in infant formula within 120 min. Finally, the potential mechanism by which AgNP/PMMA/CA films reduce the heat tolerance of C. sakazakii was investigated by quantitative real-time PCR. The results showed that AgNP/PMMA/CA films could reduce the expression of environmental tolerance-related genes in C. sakazakii. The current research shows that AgNP/PMMA/CA film has strong antibacterial activity, and the antibacterial film combined with mild heat treatment can accelerate the inactivation of C. sakazakii and effectively reduce the harm of foodborne pathogens. The AgNP/PMMA/CA film can be used as a potential packaging material or antibacterial surface coating.

Silver nanoparticles reduce the tolerance of Cronobacter sakazakii to environmental stress by inhibiting expression of related genes.

Cronobacter sakazakii is a food-borne pathogen that is resistant to a variety of environmental stress conditions. It can survive in harsh environments. We studied the effects of silver nanoparticles (AgNP) on the environmental tolerance and biofilm formation of C. sakazakii. First, we determined the minimum inhibitory concentration (MIC) of AgNP to C. sakazakii and determined the growth curve of C. sakazakii treated with different concentrations of AgNP by using the plate counting method. After determining the sub-inhibition concentrations (SIC) of AgNP on C. sakazakii, we studied the effects of AgNP on the resistance of C. sakazakii to heat, desiccation, osmotic pressure, and acid. The antibiofilm activity of AgNP was also studied. Finally, real-time quantitative PCR was used to analyze the transcription levels of 16 genes related to the environmental tolerance of C. sakazakii. The SIC of AgNP significantly reduced the survival rate of C. sakazakii under various environmental stress conditions. The results showed that AgNP at 0.625 and 1.25 µg/mL significantly inhibited the formation of C. sakazakii biofilms. The expression levels of most genes were significantly downregulated in C. sakazakii cells treated with 0.625 and 1.25 µg/mL AgNP. Therefore, AgNP may reduce the environmental tolerance of C. sakazakii by inhibiting the expression of genes related to stress tolerance. Moreover, AgNP inhibited the production of ATP in C. sakazakii cells and the formation of C. sakazakii biofilms. Our research provides a theoretical basis for the application of AgNP in food packaging, bactericidal coatings, and other fields.

A novel approach to wound healing: Green synthetic nano-zinc oxide embedded with sodium alginate and polyvinyl alcohol hydrogels for dressings.

Wound healing constitutes a formidable challenge within the healthcare system, attributable to infection risks and protracted recovery periods. The pressing need for innovative wound healing methods has spurred the urgency to develop novel approaches. This study sought to advance wound healing by introducing a novel approach employing a composite sponge dressing. The composite sponge dressing, derived from LFL-ZnO (synthesized through the green methodology utilizing Lactobacillus plantarum ZDY2013 fermentation liquid), polyvinyl alcohol (PVA), and sodium alginate (SA) via a freeze-thaw cycle and freeze-drying molding process, demonstrated notable properties. The findings elucidate the commendable swelling, moisturizing, and mechanical attributes of the SA/LFL-ZnO/PVA composite sponge dressing, characterized by a porous structure. Remarkably, the dressing incorporating LFL-ZnO exhibited substantial inhibition against both methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus (S. aureus). Hemolysis and cytotoxicity tests corroborated the excellent biocompatibility of the sponge dressing. In vivo evaluation of the therapeutic efficacy of the 1 mg/mL LFL-ZnO composite dressing on scald wounds and S. aureus-infected wounds revealed its capacity to accelerate wound healing and exert pronounced antibacterial effects. Consequently, the composite sponge dressings synthesized in this study hold significant potential for application in wound treatment.