Fabrication and characterization of microstructured and pH sensitive interpenetrating networks hydrogel films and application in drug delivery field

Novel microstructured and pH sensitive poly(acryliac acid-co-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) (P(AA-co-HEMA)/PVA) interpenetrating network (IPN) hydrogel films were prepared by radical precipitation copolymerization and sequential IPN technology. The first P(AA-co-HEMA) network was synthesized in the present of IPN aqueous solution by radical initiating, then followed by condensation reaction (Glutaraldehyde as crosslinking agent) within the resultant latex, it formed multiple IPN microstructured hydrogel film. The film samples were characterized by IR, SEM and DSC. Swelling and deswelling behaviors and mechanical property showed the novel multiple IPN nanostuctured film had rapid response and good mechanical property. The IPN films were studied as controlled drug delivery material in different pH buffer solution using cationic compound, crystal violet as a model drug.

Preparation and Characterization of Nanostructured and High Transparent Hydrogel Films with pH Sensitivity and Application

Novel nanostructured, high transparent, and pH sensitive poly(2-hydroxyethyl methacrylate-co-methacryliac acid)/poly(vinyl alcohol) (P(HEMA-co-MA)/PVA) interpenetrating polymer network (IPN) hydrogel films were prepared by precipitation copolymerization of aqueous phase and sequential IPN technology. The first P(HEMA-co-MA) network was synthesized in aqueous solution of PVA, then followed by aldol condensation reaction, it formed multiple IPN nanostructured hydrogel film. The film samples were characterized by IR, SEM, DSC, and UV-vis spectrum. The transmittance arrived at 93%. Swelling and deswelling behaviors showed the multiple IPN nanostructured film had rapid response. The mechanical properties of all the IPN films improved than that of PVA film. Using crystal violet as a model drug, the release behaviors of the films were studied.

Reduction of Eu3+ to Eu2+ in MAl2Si2O8 (M = Ca, Sr, Ba) in air condition

In general, the reduction of Eu3+ to Eu2+ in solids needs an annealing Process in a reducing atmosphere. in this paper, it is of great interest and importance to find that the reduction of Eu3+ to Eu2+ can be realized in a series of alkaline-earth metal aluminum silicates MAl2Si2O8 (M = Ca, Sr, Ba) just in air condition. The Eu2+-doped MAl2Si2O8 (M = Ca, Sr, Ba) powder samples were prepared in air atmosphere by Pechini-type sol-gel process. It was found that the strong hand emissions of 4f(6)5d(1)-4f(7) from Eu2+ were observed at 417, 404 and 373 nm in air-annealed CaAl2Si2O8, SrAl2Si2O8 and BaAl2Si2O8, respectively, under ultraviolet excitation although the Eu3+ precursors were employed. In addition, under low-voltage electron beam excitation, Eu2+-doped MAl2Si2O8 also shows strong blue or ultraviolet emission corresponding to 4f(6)5d(1)-4f(7) transition.

Synthesis of biodegradable thermo- and pH-responsive hydrogels for controlled drug release

Novel intelligent hydrogels composed of biodegradable and pH-sensitive poly(L-glutamic acid) (PGA) and temperature sensitive poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (PNH) were synthesized and characterized for controlled release of hydrophilic drug. The influence of pH on the equilibrium swelling ratios of the hydrogels was investigated. A higher PNH content resulted in lower equilibrium swelling ratios. Although temperature had little influence on the swelling behaviors of the hydrogels, the changes of optical transmittance of hydrogels as a function of temperature were marked, which showed that the PNH part of hydrogel exhibited hydrophobic property at temperature above the lower critical solution temperature (LCST). The biodegradation rate of the stimuli-sensitive hydrogels in the presence of enzyme was directly proportional to the PGA content. Lysozyme was chosen as a model drug and loaded into the hydrogels.

Facile, Efficient Copolymerization of Ethylene with Bicyclic, Non-Conjugated Dienes by Titanium Complexes Bearing Bis(beta-Enaminoketonato) Ligands

Copolymerizations of ethylene with 5-vinyl-2-norbornene or 5-ethylidene-2-norbornene under the action of various titanium complexes bearing bis(beta-enaminoketonato) chelate ligands of the type, [(RN)-N-1=C(R-2)CH=C(R-3)O](2)TiCl2 (1, R-1=Ph, R-2=CF3, R-3=Ph; 2, R-1=C6H4F-p, R-2=CF3, R-3=Ph; 3, R-1=Ph, R-2=CF3, R-3=t-Bu; 4, R-1=C6H4F-p, R-2=CF3, R-3=t-Bu; 5, R-1=Ph, R-2=CH3, R-3=CF3; 6, R-1=C6H4F-p, R-2=CH3 R-3=CF3), have been shown to occur with the regioselective insertion of the endocyclic double bond of the monomer into the copolymer chain, leaving the exocyclic vinyl double bond as a pendant unsaturation. The ligand modification strongly affects the copolymerization behaviour. High catalytic activities and efficient co-monomer incorporation can be easily obtained by optimizing the catalyst structures and polymerization conditions.

Synthesis, Structural Characterization, and Olefin Polymerization Behavior of Vanadium(III) Complexes Bearing Tridentate Schiff Base Ligands

Vanadium(III) complexes bearing tridentate salicylaldiminato ligands (2a-f) [OC6H4CH=NL]VCl2(THF) (L = CH2CH2OMe, 2a; CH2CH2NMe2, 2b; CH2C5H4N, 2c; 8-C9H6N (quinoline), 2d; 2-MeSC6H4, 2e; 2-Ph2PC6H4, 2f) and tridentate beta-enaminoketonato ligands [OC6H8CH=N-2-Ph2PC6H4]VCl2(THF) (2g) and [O(Ph)C=CHCH=N-2-Ph2PC6H4]VCl2(THF) (2h) were prepared from VCl3(THF)(3) by treating with 1.0 equiv of the deprotonated ligands in tetrahydrofuran (THF). These complexes were characterized by FTIR and mass spectrometry as well as elemental analysis. Structures of complexes 2e, 2f, and 2h were further confirmed by X-ray crystallographic analysis. These complexes were investigated as catalysts for olefin polymerization in the presence of organoaluminum compounds. On activation with Et2AlCl, complexes 2a-h exhibited high catalytic activities toward ethylene polymerization (up to 20.64 kg PE/mmol(v) center dot h center dot bar) even at high temperature, suggesting these catalysts possess high thermal stability.

Copolymerizations of ethylene with alpha-olefin-omega-ols by highly active vanadium(III) catalysts bearing [N,O] bidentate chelated ligands

The copolymerizations of ethylene with polar hydroxyl monomers such as 10-undecen-1-ol, 5-hexen-1-ol and 3-buten-1-ol were investigated by the vanadium(III) catalysts bearing bidentate [N,O] ligands (1, [PhN=C(CH3)CHC(Ph)O]VCl2(THF)(2): 2, [PhN=CHC6H4O]VCl2(THF)(2); 3, [PhN=CHC(Ph)CHO]VCl2(THF)(2)). The polar monomers were pretreated by alkylaluminum before the polymerization. High catalytic activities and efficient comonomer incorporations can be easily obtained by changing monomer masking reagents and polymerization conditions in the presence of diethylaluminium chloride as a cocatalyst. The longer the spacer group, the higher the incorporation of the monomer. Under the mild conditions, the incorporation level of 10-undecen-1-ol reached 13.9 mol% in the resultant copolymers was obtained. The reactivity ratios of copolymerization (r(1) = 41.4, r(2) = 0.02, r(1)r(2) = 0.83) were evaluated by Fineman-Ross method. According to C-13 NMR spectra, polar units were located both on the main chain and at the chain end.

Different microstructures of ss-NaYF4 fabricated by hydrothermal process: Effects of pH values and fluoride sources

beta-NaYF4 microcrystals with a variety of morphologies, such as microrod, hexagonal microprism, and octadecahedron, have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of beta-NaYF4 seeds and two important external factors, namely, the pH values in the initial reaction solution and fluoride sources, are responsible for shape determination of beta-NaYF4 microcrystals. It is found that the organic additive trisodium citrate (Cit(3-)) as a shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of the anisotropic geometries of various beta-NaYF4 microcrystals. The possible formation mechanisms for products with various architectures have been presented. A systematic study on the photoluminescence of Tb3+-doped beta-NaYF4 samples with rod, prism, and octadecahedral shapes has shown that the optical properties of these phosphors are strongly dependent on their morphologies and sizes.

pH-dependent protein conformational changes in albumin : gold nanoparticle bioconjugates: A spectroscopic study

The conformational changes of bovine serum albumin (BSA) in the albumin:gold nanoparticle bioconjugates were investigated in detail by various spectroscopic techniques including UV-vis absorption, fluorescence, circular dichroism, and Fourier transform infrared spectroscopies. Our studies suggested that albumin in the bioconjugates that was prepared by the common adsorption method underwent substantial conformational changes at both secondary and tertiary structure levels. BSA was found to adopt a more flexible conformational state on the boundary surface of gold nanoparticles as a result of the conformational changes in the bioconjugates. The conformational changes at pH 3.8, 7.0, and 9.0, which corresponded to different isomeric forms of albumin, were investigated, respectively, to probe the pH effect on the conformational changes of BSA in the bioconjugates. The results showed that the pH of the medium influenced the changes greatly and that fluorescence and circular dichroism studies further indicated that the changes were larger at higher pH.

Preparation and luminescent properties of rare earth ions in M2B5O9Cl : Re(M = Ca, Sr, Ba; Re=Eu, Tb)

M2B5O9X: Re(M = Ca, Sr, Ba; X = Cl, Br; Re = Eu, Th) phosphors were synthesized via solid state method. The products were characterized with X-ray powder diffraction and luminescence spectrometer. The luminescent properties as well. as the influences of the matrix composition and other doping ions on the luminescence of the rare earth ions of the co-doped phosphors were investigated. The coexistence of Eu3+, Eu2+ and Th3+ were observed in these matrices. The phenomenon may be explained by the electron transfer theory. The sensitization of Ce3+ ion improves the intensity of emission of Eu2+, and Tb3+. The competition between electron transfer among conjugate rare earth ions and energy migration might be the reasons for the observation. We predict a novel trichromatic phosphor co-doped with Eu3+ Tb3+ in M2B5O9X.

Structural diversity of lanthanide-amino acid complexes under near physiological pH conditions and their recognition of single-stranded DNA

We reported here four structures of lanthanide-amino acid complexes obtained under near physiological pH conditions and their individual formula can be described as [Tb-2(DL-Cys)(4)(H2O)(8)]Cl-2 (1), [Eu-4(mu(3)-OH)(4)(L-Asp)(2)(L-HAsp)(3)(H2O)(7)] Cl center dot 11.5H(2)O (2), [Eu-8-(L-HVal) (16)(H2O)(32)]Cl-24 center dot 12.5H(2)O (3), and [Tb-2(DL-HVal)(4)(H2O)(8)]Cl-6 center dot 2H(2)O (4). These complexes showed diverse structures and have shown potential application in DNA detection. We studied the interactions of the complexes with five single-stranded DNA and found different fluorescence enhancement, binding affinity and binding stoichiometry when the complexes are bound to DNA.

PH-Dependent syntheses and structures of two Copper(II)/Phenanthroline/p-Sulfonatocalix[4]arene supramolecular compounds with 1D water-filled channels

Two copper-organic framework supramolecular assemblies of p-sulfonatocalix[4]arene and 1,10-phenanthroline Cu-2[C12H8N2][C28H20S4O16][H2O](23.5) (1) and Cu-3[C12H8N2](3)[C28H19S4O16]Cl[H2O](17.6) (2) were obtained by pH-dependent synthesis at room temperature. Both structures show ID water-filled channels (rectangular shape in I and triangular in 2) with the solvent-accessible volume occupying 30.8% (1) and 24.2% (2) of the unit-cell volume, respectively. The calixarene molecules in both structures assume analogous cone shapes of C-2 nu symmetry instead of the conventional C-4 nu symmetry. Their connecting to different amounts of copper/phenanthroline cations leads to the formation of different structures.

Self-assembly of polypeptide-containing ABC-type triblock copolymers in aqueous solution and its pH dependence

Self-assembling of novel biodegradable ABC-type triblock copolymer poly(ethylene glycol)-poly(L-lactide)-poly(L-glutamic acid) (PEG-PLLA-PLGA) is studied. In aqueous media, it self-assembles into a spherical micelle with the hydrophobic PLLA segment in the core and the two hydrophilic segments PEG and PLGA in the shell. With the lengths of PEG and PLLA blocks fixed, the diameter of the micelles depends on the length of the PLGA block and on the volume ratio of H2O/dimethylformamide (DMF) in the media. When the PLGA block is long enough, morphology of the self-assembly is pH-dependent. It assembles into the spherical micelle in aqueous media at pH 4.5 and into the connected rod at or below pH 3.2. The critical micelle concentration (cmc) of the copolymer changes accordingly with decreasing solution pH. Both aggregation states can convert to each other at the proper pH value. This reversibility is ascribed to the dissociation and neutralization of the COOH groups in the LGA residues. When the PLGA block is short compared to the PEG or PLLA block, it assembles only into the spherical micelle at various pH values.

Controlled organization of silver nanoparticles into network assemblies by tuning pH values

We demonstrate the pH-induced assembly of 2-mercaptosuccinic acid-functionalized silver nanoparticles (MSA-Ag NPs) in the absence of hard or soft template. Two-dimensional (2D) and three-dimensional (3D) networks of silver NPs were achieved by tuning pH of the medium. The assembly process was monitored using atomic forces microscopy. The key factor affects the formation of network of silver NPs may be intermolecular hydrogen bonding between two carboxylic acid groups of MSA on two adjacent silver NPs.