Bioinspired enzymatic synthesis of silica nanocrystals provided by recombinant silicatein from the marine sponge Latrunculia oparinae.

The process of silica formation in marine sponges is thought to be mediated by a family of catalytically active structure-directing enzymes called silicateins. It has been demonstrated in biomimicking syntheses that silicateins facilitated the formation of amorphous SiO2. Here, we present evidence that the silicatein LoSiLA1 from the marine sponge Latrunculia oparinae catalyzes the in vitro synthesis of hexa-tetrahedral SiO2 crystals of 200­300 nm. This was possible in the presence of the silica precursor tetrakis-(2-hydroxyethyl)-orthosilicate that is completely soluble in water and biocompatible, experiences hydrolysis­condensation at neutral pH and ambient conditions.

Synthesis of poly(methyl methacrylate)-block-poly(L-histidine) and its use as a hybrid silver nanoparticle conjugate.

Poly[(methyl methacrylate)-block-poly(L-histidine)] (PMMA-b-PHIS) was synthesized by combining atom transfer radical polymerization and living ring-opening polymerization of alpha-amino acid-N-carboxyanhydride. The resulting hybrid block copolymer forms reverse micelles in the mixture solution of water and N,N-dimethylformamide (DMF) and self-assembles into PHIS/PMMA core/shell spheres with controllable size in the range of 80 to 250 nm depending on the micellization temperature. The self-assembly of PMMA-b-PHIS was carried out in H2O/DMF (3/7) mixture in the presence of AgNO3. Reduction of the resulting Ag ions encapsulated inside of the reverse micelles yielded an attractive Ag nanoparticle core/polymer shell conjugate system.

Polymerized assemblies of cationic gemini surfactants in aqueous solution.

A variety of polymerized assemblies of cationic gemini surfactants has been demonstrated as a function of the electrolyte concentration in aqueous solution. The gemini surfactant consists of two cationic monomeric surfactants linked with an ethylene spacer at the level of the quaternary ammonium groups. Polymerizable methacryloxy groups are covalently attached to the terminal of the hydrocarbon chains. In the lower electrolyte concentration region, radical polymerization results in the formation of spherical aggregates [Langmuir 22 (2006) 8293]. However, in the higher electrolyte concentration region, elongated tubular hollow assemblies are observed with transmission electron microscopy, as a result of polymerization of vesicular hollow assemblies spontaneously formed in the aqueous solution. These experimental results suggest that it is possible to prepare different shapes of polymerized assemblies by changing the electrolyte concentration.