Catalytic Macroporous Biohydrogels Made of Ferritin-Encapsulated Gold Nanoparticles

Reported is a modular approach for the incorporation and stabilization of gold nanoparticles inside a three-dimensional macroporous hydrogel made of ferritin. The strategy, which involves the dynamic templating of surfactant H-1 domains, demineralization, and remineralization helps to overcome aggregation and degradation issues usually associated with bare-metal-based nanocatalysts. The catalytic activity of the so-synthesized bionanocomposite hydrogel was demonstrated in both nitroaldol (Henry) and nitroreduction model reactions in aqueous solution at room temperature. An interesting synergistic effect between basic residues of the protein and the gold nanoparticles was found in the nitroaldol reaction when carried out in water in the presence of a phase-transfer catalyst. Furthermore, the reduction of 4-nitrophenol and 4-nitroaniline catalyzed by the nanocomposite scaffold in the presence of NaBH4 proceeded significantly faster than that using other known Au- and Ag-based catalysts under similar conditions

Omniphilic Polymeric Sponges by Ice Templating

Sponges that absorb a large quantity of solvent relative to their weight, independent of the solvent polarity, represent useful universal absorbents for laboratory and industrial spills. We report the preparation of macroporous polymer sponges by ice templating of polyethylenimine aqueous solutions and their cross-linking in the frozen state. The as-prepared monolith is hydrophilic and absorbs over 30-fold its weight in water. Modification of this sponge using valeroyl chloride renders it omniphilic; viz., a modified sponge absorbs over 10-fold its dry weight of either water or hexane. Modification using palmitoyl chloride that has a longer chain length results in the preparation of a hydrophobic sponge with a water contact angle around 130°, which retains its oleophilicity underwater. The solvent absorbed in these sponges can be simply squeezed out, and the sponges are stable to several hundred cycles of compression. The large pore sizes of these sponges allow rapid absorption of even high viscosity solvents such as pump oil. Finally, we demonstrate that these sponges are also able to separate apolar oils that are emulsified in water using surfactants. These high porosity sponges with controllable solvophilicity represent inexpensive, high performance universal absorbents for general solvent spills

Synthesis and characterization of poly-L-lysine-grafted silica nanoparticles synthesized via NCA polymerization and click chemistry

Polypeptide polymer-grafted silica nanoparticles are of considerable interest because the ordered secondary structure of the polypeptide grafts imparts novel functional properties onto the nanoparticle composite. The synthesis of poly-L-lysine-grafted silica nanoparticles would be of particular interest because the high density of cationic charges on the surface could lead to many applications such as gene delivery and antimicrobial agents. In this work, we have developed a “grafting-to” approach using a combination of NCA polymerization and “click chemistry” to synthesize poly-L-lysine-grafted silica nanoparticles with a high graft density of 1 chain/nm2. The covalent attachment of poly-L-lysine to silica nanoparticles (PLL−silica) was confirmed using a variety of techniques such as 13C CP MAS NMR, TGA and IR. This methodology was then extended to graft poly-L-lysine-b-poly-L-leucine copolymer (PLL-b-PLLeu−silica) and poly-L-benzylglutamate (PLBG−silica) onto silica nanoparticles. All of these polypeptide-grafted nanoparticles show interesting aggregation properties in solution. The efficacy of PLL−silica and PLL-b-PLLeu−silica as antimicrobial agents was tested on both gram-negative E. coli and gram-positive Bacillus subtilis

Iron Complex Catalyzed Selective C–H Bond Oxidation with Broad Substrate Scope

The use of a peroxidase-mimicking Fe complex has been reported on the basis of the biuret-modified TAML macrocyclic ligand framework (Fe–bTAML) as a catalyst to perform selective oxidation of unactivated 3° C–H bonds and activated 2° C–H bonds with low catalyst loading (1 mol %) and high product yield (excellent mass balance) under near-neutral conditions and broad substrate scope (18 substrates which includes arenes, heteroaromatics, and polar functional groups). Aliphatic C–H oxidation of 3° and 2° sites of complex substrates was achieved with predictable selectivity using steric, electronic, and stereoelectronic rules that govern site selectivity, which included oxidation of (+)-artemisinin to (+)-10β-hydroxyartemisinin. Mechanistic studies indicate Fe^V(O) to be the active oxidant during these reactions

Functionalization of SBA-15 mesoporous materials using "thiol-ene click" Michael addition reaction

Methacrylate-labeled SBA-15 has been successfully synthesized from calcined SBA-15 and commercially available 3-trichlorosilyl propylmethacrylate. This material undergoes efficient thiol-ene "click reaction" with a variety of both thiol and disulfide-containing substrates in aqueous and organic media. The products were thoroughly characterized by a variety of analytical techniques including multinuclear (<SUP>13</SUP>C, <SUP>29</SUP>Si) solid-state NMR, TG-DTA, and nitrogen adsorption desorption studies. Disulfide-containing substrates in which the TCEP-mediated reduction of the disulfide bond and its subsequent addition to the methacrylate group anchored in SBA-15 in one-pot were used to synthesize a silica-protein hybrid material composed of biotin-labeled SBA-15 and streptavidin. Electrochemically active material was synthesized from the reaction of ferrocene-containing thiol and the methacrylate-labeled SBA-15. The ease of synthesis for the methacrylate-labeled SBA-15 material together with its ability to undergo efficient chemoselective thiol-ene reaction would make it a very attractive platform for the development of covalently anchored enzymes and sensors