Novel magnetite-silica nanocomposite (Fe3O4-SBA-15) particles for DNA binding and gene delivery aided by a magnet array.

Novel magnetite-silica nanocomposite particles were prepared using SBA-15 nanoporous silica as template. Magnetite nanoparticles were impregnated into the nanopore array of the silica template through thermal decomposition of iron(III) acetylacetonate, Fe(AcAc)3 at 200 degrees C. These composite particles were characterized using TEM, XRD and SQUID magnetometry. The TEM images showed that the size of composite particles was around 500 nm and the particles retained the nanoporous array of SBA-15. The formation of magnetite nanoparticles was confirmed by the powder XRD study. These composite particles also exhibited ferrimagnetic properties. By coating with short chain polyethyleneimine (PEI), these particles are capable of binding DNA molecules for gene delivery and transfection. With an external magnetic field, the transfection efficiency was shown to have an increase of around 15%. The results indicated that these composite nanoparticles may be further developed as a new tool for nanomagnetic gene transfection.

Preparation and characterization of polyethylenimine-coated Fe3O4-MCM-48 nanocomposite particles as a novel agent for magnet-assisted transfection.

A new type of magnetic nanoparticle was synthesized using mesoporous silica MCM-48 as a template. Magnetite (Fe(3)O(4)) nanocrystals were incorporated onto the MCM-48 silica structure by thermal decomposition of iron(III) acetylacetonate. The particle size of these Fe(3)O(4)-MCM-48 composite particles is around 300 nm with an iron oxide content of ca. 20% w/w. Measurements from SQUID magnetometry suggest that these nanoparticles possess superparamagnetic properties similar to those of Fe(3)O(4) nanoparticles. By coating positively charged polyethylenimine on to the surface, DNA can be bound onto the Fe(3)O(4)-MCM-48 nanoparticles. Transfection studies showed that these PEI-Fe(3)O(4)-MCM-48 particles were highly effective as a transfection reagent, and a 400% increase of transfection efficiency compared with the commercial products was recorded.

Polymorphism and variable structural dimensionality in the iron(III) phosphate oxalate system: a new polymorph of 3D [Fe2(HPO4)2(C2O4)(H2O)2] x 2 H2O and the layered material [Fe2(HPO4)2(C2O4)(H2O)2].

Two new iron (III) phosphate oxalates have been isolated under hydrothermal conditions as phase-pure samples and their crystal structures determined from single crystal X-ray diffraction. [Fe(2)(HPO(4))(2)(C(2)O(4))(H(2)O)(2)] x 2 H(2)O, I, is a polymorph of a known phase and differs in the local arrangement of hydrophosphate, oxalate and coordinated water about iron, presenting a mer orientation of three coordinated phosphates, rather than fac as previously seen. The structure of I is three-dimensionally connected with similar network connectivity to the known phase but different overall topology. [Fe(2)(HPO(4))(2)(C(2)O(4))(H(2)O)(2)], II, has a layered structure constructed from octahedral Fe(III) centres coordinated by hydrophosphate, oxalate and water in a fac arrangement. The amount of water used in synthesis is one of the key experimental parameters in stabilising one phase over the other. Thermogravimetric analysis shows that both I and II ultimately collapse into dense tridymite type FePO(4) above 600 degrees C and variable temperature powder XRD shows that this occurs via crystalline intermediate phases. Variable temperature magnetisation measurements show that both materials order antiferromagnetically at low temperatures, with similar Néel temperatures (approximately 29 K) despite their long-range structural differences.

Negative Poisson's ratios in siliceous zeolite MFI-silicalite.

Brillouin scattering measurements of the single-crystal elastic properties of the as-made zeolite silicalite mid R:(C(3)H(7))(4)NFmid R:(4)[Si(96)O(192)]-MFI provides the first experimental evidence for on-axis negative Poisson's ratios (auxeticity) in a synthetic zeolite structure. MFI laterally contracts when compressed and laterally expands when stretched along x(1) and x(2) directions in the (001) plane (nu(12)=-0.061, nu(21)=-0.051). The aggregate Poisson's ratio of MFI, although positive, has an anomalously low value nu=0.175(3) compared to other silicate materials. These results suggest that the template-free MFI-silicalite [Si(96)O(192)] might have potential applications as tunable sieve where molecular discriminating characteristics are adjusted by application of stress along specific axes.

Synthesis of hybrid framework materials under "dry" hydrothermal conditions: crystal structure and magnetic properties of Mn(2)(H(2)PO(4))(2)(C(2)O(4)).

An exploration of the manganese oxalate-phosphoric acid-water system under hydrothermal conditions, and using "reagent" quantities only of water, has led to the isolation of a new mixed anion framework material Mn(2)(H(2)PO(4))(2)(C(2)O(4)). This material features continuous chains of cis edge-sharing MnO(6) octahedra, a motif which is unique among mixed phosphate-oxalate materials identified so far. These octahedral chains are linked into a three-dimensional framework via corner-sharing with H(2)PO(4) tetrahedra, with oxalate ions acting as a bis-bidentate ligand in the third direction. Magnetic susceptibility studies show that this material may be modeled as an antiferromagnetic, S = (5)/(2) Heisenberg chain, with weaker coupling between the chains.