Cellular complexity captured in durable silica biocomposites.

Tissue-derived cultured cells exhibit a remarkable range of morphological features in vitro, depending on phenotypic expression and environmental interactions. Translation of these cellular architectures into inorganic materials would provide routes to generate hierarchical nanomaterials with stabilized structures and functions. Here, we describe the fabrication of cell/silica composites (CSCs) and their conversion to silica replicas using mammalian cells as scaffolds to direct complex structure formation. Under mildly acidic solution conditions, silica deposition is restricted to the molecularly crowded cellular template. Inter- and intracellular heterogeneity from the nano- to macroscale is captured and dimensionally preserved in CSCs following drying and subjection to extreme temperatures allowing, for instance, size and shape preserving pyrolysis of cellular architectures to form conductive carbon replicas. The structural and behavioral malleability of the starting material (cultured cells) provides opportunities to develop robust and economical biocomposites with programmed structures and functions.

Tin(II) amide/alkoxide coordination compounds for production of Sn-based nanowires for lithium ion battery anode materials.

A series of tin(II) amide alkoxides ([(OR)Sn(NMe(2))](n)) and tin(II) alkoxides ([Sn(OR)(2)](n)) were investigated as precursors for the production of tin oxide (SnO(x)) nanowires. The precursors were synthesized from the metathesis of tin dimethylamide ([Sn(NMe(2))(2)](2)) and a series of aryl alcohols {H-OAr = H-OC(6)H(4)(R)-2: R = CH(3) (H-oMP), CH(CH(3))(2) (H-oPP), C(CH(3))(3) (H-oBP)] or [H-OC(6)H(3)(R)(2)-2,6: R = CH(3) (H-DMP), CH(CH(3))(2) (H-DIP), C(CH(3))(3) (H-DBP)]}. The 1:1 products were all identified as the dinuclear species [(OAr)Sn(µ-NMe(2))](2) where OAr = oMP (1), oPP (2), oBP (3), DMP (4), DIP (5), DBP (6). The 1:2 products were identified as either a polymer ([Sn(µ-OAr)(2)](∞) (where OAr = oMP (7), oPP (8)), dinuclear [(OAr)Sn(µ-OAr)](2) (where OAr = oBP (9), DMP (10) or DIP/HNMe(2) (11)), or mononuclear [Sn(DBP)(2)] (12) complexes. These novel families of compounds (heteroleptic 1-6, and homoleptic 7-12) were evaluated for the production of SnO(x) nanowires using solution precipitation (SPPT; oleylamine/octadecene solvent system) or electrospinning (ES; THF solvent) processing conditions. The SPPT route that employed the heteroleptic precursors yielded mixed phases of Sn(o):romarchite [1 (100:0); 2 (80:20); 3 (68:32); 4 (86:14); 5 (66:35); 6 (88:12)], with a variety of spherical sized particles [1 (350-900 nm); 2 (150-1200 nm); 3 (250-950 nm); 4 (20-180 nm); 5 (80-400 nm); 6 (40-200 nm)]. For the homoleptic precursors, similar phased [7 (80:20); 8 (23:77); 9 (15:85); 10 (34:66); 11 (77:23); 12 (77:23)] spherical nanodots were isolated [7 (50-300 nm); 8: (irregular); 10 (200-800 nm); 11 (50-150 nm); 12 (50-450 nm)], except for 9 which formed polycrystalline rods [Sn(o):romarchite (15:85)] with aspect ratios >100. From ES routes, the heteroleptic species were found to form 'tadpole-shaped' materials whereas the homoleptic species formed electrosprayed nanodots. The one exception noted was for 7, where, without use of a polymer matrix, nanowires of Sn(o), decorated with micron sized 'balls' were observed. Due to the small amount of material generated, PXRD patterns were inconclusive to the identity of the generated material; however, cyclic voltammetry on select samples was used to tentatively identify the final Sn(o) (from 7) with the other sample identified as SnO(x) (from 1).

Delivery of small interfering RNA by peptide-targeted mesoporous silica nanoparticle-supported lipid bilayers.

The therapeutic potential of small interfering RNAs (siRNAs) is severely limited by the availability of delivery platforms that protect siRNA from degradation, deliver it to the target cell with high specificity and efficiency, and promote its endosomal escape and cytosolic dispersion. Here we report that mesoporous silica nanoparticle-supported lipid bilayers (or "protocells") exhibit multiple properties that overcome many of the limitations of existing delivery platforms. Protocells have a 10- to 100-fold greater capacity for siRNA than corresponding lipid nanoparticles and are markedly more stable when incubated under physiological conditions. Protocells loaded with a cocktail of siRNAs bind to cells in a manner dependent on the presence of an appropriate targeting peptide and, through an endocytic pathway followed by endosomal disruption, promote delivery of the silencing nucleotides to the cytoplasm. The expression of each of the genes targeted by the siRNAs was shown to be repressed at the protein level, resulting in a potent induction of growth arrest and apoptosis. Incubation of control cells that lack expression of the antigen recognized by the targeting peptide with siRNA-loaded protocells induced neither repression of protein expression nor apoptosis, indicating the precise specificity of cytotoxic activity. In terms of loading capacity, targeting capabilities, and potency of action, protocells provide unique attributes as a delivery platform for therapeutic oligonucleotides.