Siderophore-based detection of Fe(iii) and microbial pathogens

Siderophores are low-molecular-weight iron chelators that are produced and exported by bacteria, fungi and plants during periods of nutrient deprivation. The structures, biosynthetic logic, and coordination chemistry of these molecules have fascinated chemists for decades. Studies of such fundamental phenomena guide the use of siderophores and siderophore conjugates in a variety of medicinal applications that include iron-chelation therapies and drug delivery. Sensing applications constitute another important facet of siderophore-based technologies. The high affinities of siderophores for both ferric ions and siderophore receptors, proteins expressed on the cell surface that are required for ferric siderophore import, indicate that these small molecules may be employed for the selective capture of metal ions, proteins, and live bacteria. This minireview summaries progress in methods that utilize native bacterial and fungal siderophore scaffolds for the detection of Fe(III) or microbial pathogens.Massachusetts Institute of Technology. Dept. of Chemistr

Synthesis of sponge mesoporous silicas from lecithin/dodecylamine mixed-micelles in ethanol/water media: A route towards efficient biocatalysts

Mixed-micelles of long-chain phosphatidylcholine and surfactants are of considerable scientific and biomedical interest. Lecithins are natural phospholipids from egg or soybean. Lecithin/dodecylamine mixed-micelles in an alcoholic/aqueous media allow to template the formation of sponge mesoporous silica (SMS) materials through a self-assembly process between mixed-micelles and tetraethoxysilane (TEOS). SMS synthesis adds a porosity control to the classical sol–gel synthesis used for enzymes encapsulation. We are reporting here the key parameters of SMS synthesis procedure (amount of amine, TEOS, ethanol, water, lecithin nature, salt addition, etc.), as well as a fine description of SMS structure by TEM. SMS features an isotropic 3-dimensional (3-D) pore structure similarly to SBA-16, but with a lower degree of mesoscopic structural order. Its porosity results from cavities and connecting channels, whose length is controlled by the synthesis conditions. Cavity diameters can reach 4.7 nm in accordance to the lecithin maximum alkyl chain length. Surface areas range from 300 to 800 m2/g, and pore volumes from 0.30 to 0.85 mL/g. The use of lactose as an enzyme stabilizing agent does not change the pore structure of SMS. A very fragile enzyme, alcohol dehydrogenase, has been successfully encapsulated by this way, providing the first example of successful entrapment of this enzyme in an inorganic matrix. SMS encapsulation procedure is biomolecules friendly and opens a bright perspective for biomolecules processing for biocatalysis, biosensors or biofuel cell applications

Laccase immobilized on mesoporous silica supports as an efficient system for wastewater bioremediation

The feasibility of using laccase from Trametes versicolor for degradation of aromatic hydrocar-bons has been investigated. In the experiments, benzo[a]pyrene (BaP) was used. Laccase was immobilized onto mesoporous micelle-templated silica such as Santa Barbara Amorphous (SBA-15) and hexagonal mesoporous silica (HMS) as well as corresponding amino-functionalized supports. The best results were obtained for SBA-15 mesoporous silica however the HMS support could be as well considered for this type of application. The reusability of laccase immobilized into both silica supports was tested for five reaction cycles and the conversion reached about 70% of the initial value

Ni-exchanged AlSBA-15 mesoporous materials as outstanding catalysts for ethylene oligomerization

Ni-exchanged mesoporous materials with SBA-15 topology were prepared by post-synthesis alumination of SBA-15 silica with sodium aluminate at room temperature, followed by ion exchange with nickel. Exploration of various parameters resulted in a simple preparation method for catalysts with perfect pore system and aluminium tetrahedrally coordinated in the silica framework for Si/Al > 6. These properties were proved by using appropriate characterisation techniques, including powder X-ray diffraction, N2 sorption, TEM, and 27Al MAS NMR. Ni-AlSBA-15 exhibited outstanding catalytic properties in the oligomerization reaction of ethylene performed at 150 ∘C and 3.5 MPa. Activity up to 175 g of oligomers per gram of catalyst per hour was the highest reported to date with Ni-based solid catalysts