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
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N2 - Transparent thin films of layered inorganic-organic nanocomposites were prepared by the sol-gel reactions of alkyldimethylmethoxysilane, alkylmethyldimethoxysilane, and alkyltrimethoxysilane in the presence of tetramethoxysilane followed by spin-coating. The macroscopic homogeneity and the nanostructural ordering of the films were strongly affected by the degree of polycondensation in the precursor solutions. The formation of siloxane networks containing organosiloxane units was confirmed by 29Si MAS NMR, suggesting that the structure of the inorganic-organic interface can be designed at a molecular level by the functionalities in the alkylmethoxysilanes used. On the other hand, the 29Si NMR spectra of the precursor solutions showed that the monomeric species almost disappeared and that co-condensed oligomers were formed at the initial stages of the reactions. In the cases of mono- and dimethoxysilanes, the ability to form ordered structures depends largely on the co-condensation with tetramethoxysilane in the precursor solutions.
Synthesis of α-alkyl ω-trimethoxysilane polyoxazolines …
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However, no reaction, decomposition, or hydrolytic C-Si bond cleavage to produce silanol 9 was observed in all cases, even in the presence of molecular sieves.
Silanes comprising branched alkyl chains Abstract
Block copolymers containing dimethyl siloxane and carboxylic acid sequences were synthesized by group transfer polymerization (GTP) of various methacrylates and acrylates using silyl ketene acetal terminated poly(dimethylsiloxane) (PDMS) as initiator, followed by hydrolysis of the ester sequences to the free acid. The block copolymers were obtained with controlled molecular weight and narrow molecular weight distribution. The -butyl methacrylate (tBMA) and trimethyl silyl methacrylate (TMSMA) polymerized more slowly than corresponding acrylates. -Butyl and trimethyl silyl ester groups in the poly(meth)acrylate block could be quantitatively hydrolyzed. Most copolymers were contaminated by unincorporated homo-PDMS, which was efficiently removed by hexane or supercritical CO2 extraction. The solubility and thermal properties (DSC, TGA) were investigated for the hydrolyzed amphiphilic polymers.
organosilicon compounds are widely used in organic synthesis
AB - A novel class of telechelic α-alkyl ω-trimethoxysilane poly(N-propionylethylene imine)s (TMS-PPEIs) has been synthesized by living cationic ring-opening polymerization of 2-oxazolines. A new route for the termination reaction of the living polyoxazoline is dcscribed. These block copolymers have been tested as coatings for glass fibres. The polymers were applied by means of a solvent dip test. It is supposed that the affinity of the polyoxazoline block for glass surfaces promotes the reaction of the silane with the silanol groups of the glass substrate. Because of the presence of the apolar α-block, the surface tension of the glass surface will be lowered, as was shown by contact angle measurements. The presence of the polymer on the glass surface was also demonstrated by XPS measurements. The interfacial properties of coated glass plates and polymer matrices were determined by performing lap-shear tests.