Synthesis and evaluation of novel polysaccharide-Gd-DTPA compounds as contrast agent for MRI

Macromolecular conjugates of two kinds of natural polysaccharides, that from Panax quinquefolium linn (PQPS) and Ganoderma applanatum pat (GAPS), with gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) have been synthesized and characterized by means of FTIR, elementary analysis and ICP-AES. Their stability was investigated by competition study with Ca2+, EDTA (ethylenediaminetetraacetic acid) and DTPA. Polysaccharide-bound complexes exhibit T-1 relaxivities of 1.5-1.7 times that of Gd-DTPA in D2O at 25degreesC and 9.4T. MR imaging of Sprague-Dawley (SD) rats showed remarkable enhancement in rat liver and kidney after i.v. injection of these two complexes: liver parenchyma 60.9+/-5.6%, 57.8+/-7.4% at 65-85 min; kidney 144.9+/-14.5%, 199.9+/-25.4% at 10-30 min for PQPS-GdDTPA, GAPS-Gd-DTPA at gadolinium dose of 0.083 and 0.082 mmol/kg, respectively. Our preliminary in vivo and in vitro study indicates that the two kinds of polysaccharide-bound complexes are potential tissue-specific contrast agents for MRI.

Reactive compatibilization of polyamide 6 with isocyanate functionalized ethylene-propylene copolymer

Reactive compatibilization of ethylene-propylene copolymer functionalized with allyl (3-isocyanato-4-tolyl) carbamate (TAI) isocyanate (EPM-g-TAI) and polyamide 6 (PA6) was investigated in this paper, FTIR analysis revealed the evidence of a chemical reaction between the end groups of PA6 and EPM-g-TAI. Thermal, rheological, morphological, and mechanical properties of the resultant system were examined, DSC analysis indicated that the crystallization of PA6 in Pa6/EPM-g-TAI blends was inhibited, due to the chemical reaction that occurs at the interface of PA6 and EPM-g-TAI. Rheological measurement showed that complex viscosity and storage modulus of PA6/EPM-g-TAI were both dramatically enhanced compared to those of PA6/EPM at the same blending composition. After examining the morphology of both blending systems, smaller particile sizes, more homogeneous distribution of domains and improved interfacial adhesion between matrix and domains were observed in the compatibilized system. Mechanical properties such as tensile strength. Young's modulus, flexural strength and modulus, as well as notched and un-notched impact strength of PA6/EPM-g-TAI blends were also found to improve gradually with increasing the content of grafted TAI.

Functionalization of an ethylene-propylene copolymer with allyl (3-isocyanate-4-tolyl) carbamate

An ethylene-propylene copolymer (EPM) was functionalized with an iso cyanate-bearing unsaturated monomer, allyl(3-isocyanate-4-tolyl) carbamate (TAI), with dicumyl peroxide as an initiator in a xylene solution. Fourier transform infrared (FTIR) was used to confirm the formation of EPM-g-TAI. The peak at 2273 cm(-1), characteristic of -NCO groups in EPM-g-TAI, revealed evidence of grafting. The grafting degree was determined with both chemical titration and FTIR. The grafting degree could be adjusted, and the maximum was over 6 wt % without any gelation. The molar mass distribution of EPM-g-TAI was narrower than that of EPM. The rheological behavior of both EPM-g-TAI and EPM was investigated with a rotational rheometer. The apparent viscosity of EPM-g-TAI was higher than that of EPM and increased with an increasing grafting degree of TAI. Surface analysis by contact-angle measurements showed that contact angles of EPM-g-TAI samples to a given polar liquid decreased with an increasing grafting degree of TAI. We also obtained the dispersion component of the surface free energy (gamma(S)(d)), the polar component of the surface free energy (gamma(S)(d)), and the total surface free energy (gamma(S) = gamma(S)(d) + gamma(S)(p)) of the grafted EPM. These parameters increased with the enhancement of the grafting degree, which gave us a quantitative estimation of the polar contribution of the grafted TAI to the total surface free energy of EPM-g-TAI.

Layer-by-layer assembly of multilayer films composed of avidin and biotin-labeled antibody for immunosensing

Protein multilayers composed of avidin and biotin-labeled antibody (bio-Ab) were prepared on gold surface by layer-by-layer assembly technology using the high specific binding constant (K-a: approximate to 10(15) M-1) between avidin and biotin. The assembly process of the multilayer films was monitored by using real-time BIA technique based on surface plasmon resonance (SPR). The multilayer films were also characterized by electrochemical impedance spectroscopy (EIS) and reflection absorption Fourier transform infrared spectroscopy (FTIR). The results indicate that the growth of the multilayer is uniform. From response of SPR for each layer, the stoichiometry S for the interaction between avidin and bio-Ab is calculated to be 0.37 in the multilayer whereas 0.82 in the first layer. The protein mass concentration for each layer was also obtained. The schematic figure for the multilayer assembly was proposed according to the layer mass, concentration and S value. The utility of the mutilayer films for immunosensing has been investigated via their subsequent interaction with hIgG. The binding ability of the multilayer increased for one to three layers of antibody, and then reach saturation after the fourth layer. These layer-by-layer constructed antibody multilayers enhance the binding ability than covalently immobilized monolayer antibody. This technology can be also used for construction of other thin films for immunosensing and biosensor.

Strontium-based initiator system for ring-opening polymerization of cyclic esters

An amino isopropoxyl strontium (Sr-PO) initiator, which was prepared by the reaction of propylene oxide with liquid strontium ammoniate solution, was used to carry out the ring-opening polymerization (ROP) of cyclic esters to obtain aliphatic polyesters, such as poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA). The Sr-PO initiator demonstrated an effective initiating activity for the ROP of epsilon-caprolactone (epsilon-CL) and L-lactide (LLA) under mild conditions and adjusted the molecular weight by the ratio of monomer to Sr-PO initiator. Block copolymer PCL-b-PLLA was prepared by sequential polymerization of epsilon-CL and LLA, which was demonstrated by H-1 NMR, C-13 NMR, and gel permeation chromatography. The chemical structure of Sr-PO initiator was confirmed by elemental analysis of Sr and N, H-1 NMR analysis of the end groups in epsilon-CL oligomer, and Fourier transform infrared (FTIR) spectroscopy. The end groups of PCL were hydroxyl and isopropoxycarbonyl, and FTIR spectroscopy showed the coordination between Sr-PO initiator and model monomer gamma-butyrolactone. These experimental facts indicated that the ROP of cyclic esters followed a coordination-insertion mechanism, and cyclic esters exclusively inserted into the Sr-O bond.

Arabinogalactan as a carrier for contrast agent in magnetic resonance imaging

Arabinogalactan-Gd-DTPA was synthesized by the reaction of diethylenetriaminepenta-acetic acid (DTPA) bisanhydride with polysaccharide in dry DMSO and characterized by FTIR, elemental analysis and ICP-AES. Its stability was investigated by competition with Ca2+, EDTA, DTPA. The t(1)-relaxivity is 8.06 mmol(-1) . L . s(-1) in D2O, 8.48 mmol(-1) . L . s(-1) in 0.725 mmol . L-1 BSA, respectively. t(1)-weighted MR imaging of rat kidney and liver showed a remarkable enhancement post injection of Arabinogalactan-Gd-DTPA. The results indicate that the arabinogalactan-Gd-DTPA is a potential contrast agent for MRI.

Phenanthroline-functionalized MCM-41 doped with europium ions

Organo-functionalized MCM-41 containing non-covalently linked 1,10-phenanthroline (denoted as Phen-MCM-41) was synthesized by template-directed co-condensation of tetraethoxysilane and the modified phenanthroline (denoted as Phen-Si). XRD, FTIR, UV/VIS spectroscopy as well as luminescence spectroscopy were employed to characterize Phen-MCM-41. No disintegration or loss of the Phen-Si during the solvent extraction procedure could be observed. When monitored by the ligand absorption wavelength (272 nm), the undoped MCM-41 produces a broad band emission centered at 450 run, whereas europium (III) doped Phen-MCM-41 displays the emission of the Eu3+, i.e., D-5(0) --> F-7(J) (J = 0, 1, 2, 3, 4) transition lines due to the energy transfer from the ligands to Eu3+ as well as a broad band emission centered at 442 nm.

Miscibility and hydrogen-bonding interactions in blends of carbon dioxide/epoxy propane copolymer with poly (p-vinylphenol)

The miscibility and hydrogen-bonding interactions of carbon dioxide and epoxy propane copolymer to poly(propylene carbonate) (PPC)/poly(p-vinylphenol) (PVPh) blends were investigated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The single glass-transition temperature for each composition showed miscibility over the entire composition range. FTIR indicates the presence of strong hydrogen-bonding interassociation between the hydroxyl groups of PVPh and the oxygen functional groups of PPC as a function of composition and temperature. XPS results testify to intermolecular hydrogen-bonding interactions between the oxygen atoms of carbon-oxygen single bonds and carbon-oxygen double bonds in carbonate groups of PPC and the hydroxyl groups of PVPh by the shift of C-1s peaks and the evolution of three novel O-1s peaks in the blends, which supports the suggestion from FTIR analyses.

Carbon ceramic electrodes bulk-modified with nanoparticles of ferrocenebutyrate-intercalated Mg-Al layered double hydroxide

Ferrocenebutyrate-intercalated layered double hydroxide (FcLDH) was prepared by the coprecipitation method and characterized by PXRD, FTIR, TEM and elemental analysis. FcLDH nanoparticles in deionized water were deposited onto the surface of graphite powder to yield graphite powder-supported FcLDH, which was subsequently dispersed into methyltrimethoxysilane-derived gels to fabricate surface-renewable, stable, rigid carbon ceramic electrodes containing the electroactive ferrocenyl group. Cyclic voltammetric study revealed that peak currents of the FcLDH-modified electrode were diffusion-con trolled in 0.1 mol l(-1) KCl aqueous solution. In addition, the formal potential of the modified electrode is related to the activity of chloride ion with a Nernst slope of 56 mV per decade.

Reactive reinforcement of the interface of poly(ether sulfone)/poly(phenylene sulfide) polymer blend by PMR-POI

The effect of polymerization of monomer reactant-polyimide (POI) as the interfacial agent on the interface characteristics, morphology features, and crystallization of poly(ether sulfone)/poly(phenylene sulfide) (PES/PPS) blends were investigated using a scanning electron microscope, FTIR, WAXD, and XPS surface analysis. It was found that the interfacial adhesion was enhanced, the particle size of the dispersed phase was reduced, and the miscibility between PES and PPS was improved by the addition of POI. It was also found that POI was an effective nucleation agent of the crystallization for PPS.

Synthesis of phenyl/amino-capped tetraaniline by chemical and electrochemical methods

Phenyl/amino-capped tetraaniline was prepared by chemical oxidation coupling and electrochemical cyclic voltammetry methods. The MacDiarmid's method of oxidation coupling was improved. The aqueous HCl was replaced with a mixture solution of HCl and acetone and (NH4)(2)S(2)O(0)8 was used as oxidant instead of FeCl3. The reaction displays a higher yield and the product tetraaniline has a higher purity owing to the improvement. In the mixture solution system, tetraaniline can be synthesized by electrochemical cyclic voltammetry method. The mechanism by which tetraaniline was prepared from p-amino diphenylamine was proposed. The product was characterized by MALDI-TOF MS and FTIR.

Study on the transesterification of poly(beta-hydroxybutyrate) and poly(epsilon-caprolactone)

The transesterification of poly(beta-hydroxybutyrate) (PHB) and poly(epsilon-caprolactone) (PCL) was carried out by using stannous octoate as catalyzer in liquid phase. The effects of reaction conditions on the transesterification, including reaction temperature, reaction time and catalyzer content, were investigated. The sequence distribution, crystallization behavior and thermal stability of PHB-co-PCL copolyesters were studied by C-13-NMR, FTIR, DSC, WAXD and TGA. The results showed that the transesterification of PHB with PCL was confirmed to produce a block copolymer, and enhancing reaction temperature and increasing reaction time were advantageous to the transesterification. With the increase in PCL content in the block copolymer, the crystallization behavior of PHB-co-PCL copolyesters changed evidently. On the other hand, the introduction of PCL segment into PHB chains did not change its crystalline structure; moreover, thermal stability of PHB-co-PCL copolyesters was a little improved in air, comparing with that of pure PHB.

Carbon ceramic electrodes modified with sub-micron particles of new methylene blue (NMB) intercalated alpha-zirconium phosphate

New methylene blue-intercalated a-zirconium phosphate (NMBZrP) was synthesized in the presence of n-butylamine and characterized by powder XRD, FTIR, TEM and elemental analysis. Sub-micron particles of NMBZrP in deionized water were apt to deposit onto the surface of graphite powder to yield graphite powder-supported NMBZrP, which was subsequently dispersed into methyltrimethoxysilane-derived gels to fabricate surface-renewable, stable, rigid carbon ceramic electrodes containing new methylene blue. Cyclic voltammetric studies revealed that peak currents of the NMBZrP-modified electrode were surface-confined at low scan rates but diffusion-controlled. at high scan rates. In addition, NMBZrP immobilized in a carbon ceramic matrix presented a two-electron, three-proton redox process in acidic aqueous solution in the pH range from 0.52 to 3.95.

The kinetics of the thermal decomposition of poly(3-hydroxybutyrate) and maleated poly(3-hydroxybutyrate)

The thermal decomposition mechanism of maleated poly(3-hydroxybutyrate) (PHB) was investigated by FTIR and H-1 NMR. The results of experiments showed that the random chain scission of maleated PHB obeyed the six-membered ring ester decomposition process. The thermal decomposition behavior of PHB and maleated PHB with different graft degree were studied by thermogravimetry (TGA) using various heating-up rates. The thermal stability of maleated PHB was evidently better than that of PHB. With increase in graft degree, the thermal decomposition temperature of maleated PHB gradually increased and then declined. Activation energy E. as a kinetic parameter of thermal decomposition was estimated by the Flynn-Wall-Ozawa and Kissinger methods, respectively. It could be seen that approximately equal values of activation energy were obtained by both methods.

Characterization and properties of the neutral and doped blends of poly(3-dodecylthiophene) with low-density polyethylene

In this paper, the structures and properties of the neutral and doped blends of poly(3-dodecylthiophene) (P3DDT) with low-density polyethylene (LDPE) were investigated. Wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Fourier transform infrared spectra (FTIR), and scanning electron microscopy (SEM) were used to characterize the structures and morphologies of the blends, and conductivity was also measured. It was found that separate crystallizations occur between P3DDT and LDPE. When the amount of P3DDT is small in the blend, it has the effect of a nucleation reagent and has some influence on the crystal structure. After doping, the interaction force between the molecular chains increases, and leads to a more compact packing and a more uniform dispersion in morphology. Through blending, the thermal stability of pure component could be greatly improved, especially when the P3DDT content is 5 wt %. The conductivity measurements indicate that the conductivity increases with the increase of the P3DDT composition and doping time.