Synthesis and Study of Silver Nanoparticles.
Synthesis of silver nanoparticles.
Biofilms are three-dimensional structures that contains billions of genetically identical bacteria submerged in a self-produced extracellular matrix, which protect bacteria from antibiotics and the human immunological defenses. More than 85 % of chronic and/or recurrent human infections are linked to bacterial biofilms. In addition, spore-forming pathogenic bacteria represent an additional community threat because of their intrinsic refractory behavior against antibiotics, phagocytes and their easy utilization in bioterrorist attacks. Therefore, every day the available microbicide arsenal against biofilms and spores becomes scarcer. Accordingly, nano-material biotechnology emerges as a promising alternative for reducing the detrimental effects of microbial-related diseases. Here we describe the development of novel nanostructured coating systems with improved photocatalytic and antibacterial activities. These systems comprise, in one case, layers of SiO2 followed by layers of mesoporous or dense TiO2-anatase, and doping with silver nanoparticles (Ag NPs). In the other case, we developed Copper NPs and its oxides by a chemical method based on a bottom up approach and its stabilization using aminosilanes as surface modifiers. The activity of CuNPs and AgNPs (MNPs) was measured against spores and vegetative (planktonic and sessile) forms of the relevant human pathogens Enterohemorrhagic Escherichia coli (etiological agent of Hemolytic Uremic Syndrome), Listeria monocytogenes (etiological agent of septic abortion), Bacillus anthracis (etiological agent of Anthrax), Clostridium perfringens (etiological agent of food-associated diarrhea and Gas Gangrene), cystic-fibrosis related Pseudomona aeruginosa and methicillin-resistant Staphylococcus aureus ( etiological agent of sepsis and myocardiopathies). The planktonic and sessile growth (measured as the final cellular yield at 600 nm and crystal violet staining, respectively) of each pathogen, as well as the sporocide effect on C. perfringens and B. anthracis spores, was very significant at submillimolar concentrations of MNPs (95 % of vegetative growth inhibition and sporocide effect, p
Keywords Nanoparticle, Synthesis, Silver nanoparticle, Mechanism.
The administration of nanoparticles to tumors followed by alternating magnetic field application was shown to efficiently destroy tumors both preclinically and clinically, especially glioma. However, antitumor efficacy remains suboptimal and requires further improvements. We therefore developed a new type of nanoparticles synthesized by magnetotactic bacteria called magnetosomes. Due to their chain arrangement that leads to uniform distribution, ferrimagnetic properties that enhance their heating power and to a controlled release of endotoxins that attract polynuclearneutrophiles, we show that chains of magnetosomes achieve full destruction of intracranial U87-Luc glioma tumors under AMF application in 40% of treated mice using a rather low quantity of magnetosomes administered of 13 µg of magnetosomes per mm3 of tumor. By contrast, under the same treatment conditions, signs of antitumor activity are not observed with chemically synthesized nanoparticles currently used in the magnetic hyperthermia treatment of tumors. It also appears that full glioma destruction is achieved when magnetosomes occupy only 10% of the whole tumor volume, which suggests the involvement of an indirect mechanism of tumor destruction, which is desired for the treatment of infiltrating tumors, such as glioma, for which whole tumor coverage by nanoparticles can hardly be achieved.