Study of spin-ordering and spin-reorientation transitions in hexagonal manganites through Raman spectroscopy.

Spin-wave (magnon) scattering, when clearly observed by Raman spectroscopy, can be simple and powerful for studying magnetic phase transitions. In this paper, we present how to observe magnon scattering clearly by Raman spectroscopy, then apply the Raman method to study spin-ordering and spin-reorientation transitions of hexagonal manganite single crystal and thin films and compare directly with the results of magnetization measurements. Our results show that by choosing strong resonance condition and appropriate polarization configuration, magnon scattering can be clearly observed, and the temperature dependence of magnon scattering can be simple and powerful quantity for investigating spin-ordering as well as spin-reorientation transitions. Especially, the Raman method would be very helpful for investigating the weak spin-reorientation transitions by selectively probing the magnons in the Mn(3+) sublattices, while leaving out the strong effects of paramagnetic moments of the rare earth ions.

Quantitation of fatty acid ethyl esters in human meconium by an improved liquid chromatography/tandem mass spectrometry.

This paper reports the development and validation of an improved assay for quantitation of fatty acid ethyl esters (FAEEs) in human meconium using liquid chromatography/tandem mass spectrometry (LC-MS/MS). FAAEs (ethyl laurate, ethyl myristate, ethyl palmitate, ethyl palmitoleate, ethyl stearate, ethyl oleate, ethyl linoleate, ethyl linolenate, and ethyl arachidonate) and the internal standard (I.S.), ethyl heptadecanoate, were separated by reverse phase HPLC and quantified by MS/MS using electrospray ionization (ESI) and multiple reaction monitoring (MRM) in the positive ionization mode. The absolute recovery of FAEEs varied from 55+/-10% for 0.33 nmol/g (100 ng/g) of ethyl linoleate up to 86+/-8% for 1.55 nmol/g (500 ng/g) of ethyl miristate. The LODs and LOQs varied from 0.01 to 0.08 nmol/g and from 0.02 to 0.27 nmol/g, respectively. The assay has been successfully applied to examine the FAEE levels in 81 meconium samples from babies born to mothers reporting alcohol consumption, to varying degrees, during pregnancy.

Effect of RGD-immobilized dual-pore poly(L-lactic acid) scaffolds on chondrocyte proliferation and extracellular matrix production.

Interactions between cell and polymer surface have great implications in tissue engineering. In this study, chondrocyte proliferation and matrix production were examined using porous poly(L-lactide) (PLLA) scaffolds that have different surface characteristics. PLLA scaffolds were prepared using a gas-foaming method, and subjected to surface modifications through plasma treatment and subsequent in situ grafting of hydrophilic acrylic acid (AA). To immobilize peptide ligands, the AA-grafted PLLA scaffolds (PLLA-PAA) were further reacted with either Gly-Arg-Asp-Gly (GRDG) or Gly-Arg-Gly-Asp (GRGD) to produce PLLA-PAA-GRDG or PLLA-PAA-GRGD scaffold, respectively. The average porosities of the scaffolds were more than 90%, and their pore sizes ranged from 200 approximately 300 to 10 approximately 50 microm for large and small pores, respectively. The concentrations of each bound component were 2.14 x 10(-4) mmol/cm(2) for AA, 1.87 nmol/g for GRDG, and 1.68 nmol/g for GRGD. When chondrocytes were seeded onto the different PLLA scaffolds, cell adhesion and proliferation were highly affected as the substrate types vary. The RGD-immobilized scaffolds resulted in higher cellularity and better accumulation of total glycosaminoglycan than the others. Histological staining of Safranin O showed that the deposited extracellular matrix was more intense and widely distributed in the PLLA-PAA-GRGD scaffold. The present data suggest that immobilization of RGD peptide on the AA-grafted PLLA scaffold can be an effective tool for chondrocyte attachment and proliferation, and that it may also be helpful to facilitate cartilaginous tissue formation.

Poly (4-vinylimidazole) as nonviral gene carrier: in vitro and in vivo transfection.

We explored poly(4-vinylimidazole) (P4V) as a nonviral gene carrier. We show that P4V can form DNA condensates of small size (<110 nm) using a dye-exclusion assay with ethidium bromide and dynamic light scattering, and that the complexes form in a pH-sensitive manner, due to the amphotericity of the polymer. P4V was demonstrated to lead to transfection in vitro as effectively as polyethyleneimine (PEI), but at lower cytotoxicity, under conditions where higher amounts of either polymer are required, using luciferase and green fluorescent protein as examples. Transfection in vivo was also explored, using a gene encoding yellow fluorescent protein and human osteoprotegerin injected in the tail vein of the rat. Transfection was observed, both at the gene and protein levels in lung and spleen tissue. Transfection in vivo appeared to be at least as effective using P4V as with PEI. Based upon this good transfection and low cytotoxicity, P4V seems to show promise as a nonviral gene transfer vector.

High transfection efficiency of poly(4-vinylimidazole) as a new gene carrier.

Poly(4-vinylimidazole) (P4V) was obtained by free radical polymerization of 4-vinylimidazole (4V) prepared by decarboxylation of urocanic acid. P4V formed a complex with DNA that exhibited higher transfection effiency on Hela cells than polyethylenimine (PEI), through the proton sponge mechanism of the imidazole groups in the side chain of the P4V, and low cell toxicity.