Study On Characterization Of Cu～(2+)-loaded Layer Silicate Nanoparticles And Its Mechanism Of Applied Effect In Broilers

One of the bad results from overuse of antibiotics in animal and the pollution of the environment has been the rapid evolution of pathogenic bacteria that are resistant to multiple drugs. These bacteria have been harmful to the public heath and living environment, and even threaten the lives of mankind. To decrease antibiotic use and overcome antibiotic resistance, it is very important and urgent to prepare and develop safe antibacterial agents that can replace antibiotics as feed additive.In the present work, silicate and CUSO4 were used as main materials to prepare Cu2+-loaded layer silicate nanoparticles (CSN) by nano-technology. The characteristic of CSN and its mechanism of positive effect on broiler performance were comparatively studied by using a series of investigations such as the structure and characteristic of CSN, antimicrobial effect and anti-adhesion in vitro, cell culture, and feed trial. The results showed that CSN, with a particle size of about 70 nm, had very larger specific surface area and pore volume than that of Cu2+-loaded layer silicate powder (CSP). This implies that treatment with nano-technology significantly increases the capacity of silicate in physical adsorption. Most of the loaded Cu2+ entered into the interlayer position of silicate in hydrated or composite cation by ion exchange with original metal ions, and a small fraction penetrated into Si-0 tetrahedral and Al-0 octahedral micro-pore by chemical adsorption. As compared to the LSN, the external surface area, pore volume and pore diameter of CSN were relatively high, while total surface area, micro-pore surface area and micro-pore volume were low implying that treatment with Cu2+ could change the surface characteristic of silicate nanoparticles. Absolute values of total charge, layer charge, edge charge and Zeta potential of CSN were lower than that of LSN suggesting that the loaded Cu2+ reduced the negative charge of silicate. This can enhance electrostatic interaction between CSN and bacteria.Silicate nanoparticles, treated with or without Cu2+ ion, had a great ability to adsorb methylene blue (MB). However, the adsorptive capacity of CSN was slightly low as compared to the LSN. Temperature, pH value and ionic strength in medium have more or less effects on interaction between MB and the tested nano-material. The action of either LSN or CSN on MB was not fitted in with Freundlish equations. But both Langmuir and BET equations could be used to describe the adsorptive processoccurring between MB and nanoparticles. Also, the adsorption processes were spontaneous in thermodynamics.The results obtained from antimicrobial trial in vitro indicated that CSN, as compared to CSP, had very great activity against Escherichia coli, Salmonella typhimuriwn and Staphylococcus aureus, while LSN revealed no antibacterial effect. The antibacterial mechanism of CSN might be due to large adsorption of silicate nanoparticles and bactericidal activity of Cu2+ ion, moreover, CSN could rupture bacterial wall, and then the contents in cell leaked and bacterium died.Chicken intestinal glycoproteins isolated from different intestinal regions were used as a model for intestinal mucus to investigate the effect of CSN on the adhesion of bacteria. The results showed that CSN revealed a strong ability to inhibit adhesion of pathogenic strains to intestinal mucus. The active percentages of CSN against adhesion of E. coli 078, E. coli ATCC 25922, S. pullorum and S. typhimurium to intestinal mucus were about 63.37%~ 78.67%, while against Bifidobacterium bifidum, and Lactobacillus acidophilus were about 22.60%~40.65%. In addition, there was a decreasing tendency for the inhibitions of CSN to the adhesions of B. bifidum, L. acidophilus, S. pullorum and S. typhimurium to mucus with the change of intestine from proximal to distal part.1-d-old Arbor Acres broiler chicks were used to investigate the effect of CSN on the growth performance and its mechanism. The chicks were fed on the corn-soybean meal diet supplemented with l~2g/kg CSN for 42 d. The resu...