Characterization of polysuccinate and hydroxyapatite‐based nanocomposites containing poly(ester‐anhydride) microspheres

Repair and regeneration of bone defects with particular shape may be enhanced by in situ forming biomaterials which can be used in minimal invasive surgery. This study is aimed to prepare novel in situ forming biodegradable nanocomposites based on poly(3‐allyloxy‐1,2‐propylene) succinate (PSAGE) and nanosized hydroxyapatite (HA). These nanocomposite materials contain poly(ester‐anhydride) (PEA) microspheres embedded in a polyester matrix prepared by crosslinking PSAGE with oligo(1,2‐propylene maleate) and methacrylic monomers. Methyl methacrylate and one of hydrophilic oligo(ethylene glycol) methacrylates with different functionality and various length of oligooxyethylene chains were used as polymerizable diluents. Incorporation of microspheres which degrade faster than crosslinked polyester matrices enables formation of porous structure in situ. The obtained materials are liquid before curing and harden in several minutes with moderate exothermic effect. The effect of the composition of nanocomposite materials on selected properties, such as water sorption, mechanical strength, porosity and hydrolytic degradation process, was investigated. Rheological behavior and injectability of liquid formulations were studied. Analysis by energy dispersive spectroscopy confirmed the presence of characteristic features of HA in the nanocomposite materials. The morphology of the cured nanocomposites subjected to hydrolytic degradation was evaluated by scanning electron microscopy. The MTS cytotoxicity assay was carried out for extracts from crosslinked materials using hFOB1.19 cells. It was found that the extracts exhibit a dose‐dependent cytotoxic response. Copyright © 2014 John Wiley & Sons, Ltd.     

TiO2 and Al2O3 nanoporous oxide layers decorated with silver nanoparticles—active substrates for SERS measurements

Self-organized nanoporous oxide layers (TiO₂, Al₂O₃) exhibiting specific properties, obtained by anodic oxidation at a constant voltage in neutral electrolyte, may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as a stable platform for detecting various organic compounds. This paper presents the influence of the size of the nanotubes/nanopores and the structure of the porous oxide layers on the SERS enhancement factor, E _F. We used pyridine and mercaptobenzoic acid as probe molecules, since they have a large cross-section for Raman scattering. To characterize the morphology and structure of the oxide layer substrates, before and after vacuum vapor deposition of silver nanoparticles, we applied scanning electron microscopy, X-ray diffraction and surface analytical techniques: AES, XPS and SERS. The results obtained show that for the same amount of Ag (0.02 mg/cm²) the size of the nanopores significantly affects the E _F, which reaches, at a properly chosen nanopore size, distinctly higher values than that characteristic of a standard silver surface roughened by electrochemical cycling, i.e. E _F?>?10⁶. The new Ag/MeO _x –NT composites layer, ensure a good reproducibility of the SERS measurements and exhibit stability over a limited period of time.     

Fullerene derived molecularly imprinted polymer for chemosensing of adenosine-5′-triphosphate (ATP)

For molecular imprinting of oxidatively electroactive analytes by electropolymerization, we used herein reductively electroactive functional monomers. As a proof of concept, we applied C₆₀ fullerene adducts as such for the first time. For that, we derivatized C₆₀ to bear either an uracil or an amide, or a carboxy addend for recognition of the adenosine-5′-triphosphate (ATP) oxidizable analyte with the ATP-templated molecularly imprinted polymer (MIP-ATP). Accordingly, the ATP complex with all of the functional monomers formed in solution was potentiodynamically electropolymerized to deposit an MIP-ATP film either on an Au electrode of the quartz crystal resonator or on a Pt disk electrode for the piezoelectric microgravimetry (PM) or capacitive impedimetry (CI) determination of ATP, respectively, under the flow-injection analysis (FIA) conditions. The apparent imprinting factor for ATP was ∼4.0. After extraction of the ATP template, analytical performance of the resulting chemosensors, including detectability, sensitivity, and selectivity, was characterized. The limit of detection was 0.3 and 0.03 mM ATP for the PM and CI chemosensor, respectively. The MIP-ATP film discriminated structural analogues of ATP quite well. The Langmuir, Freundlich, and Langmuir–Freundlich isotherms were fitted to the experimental data of the ATP sorption and sorption stability constants appeared to be nearly independent of the adopted sorption model.     

Directional coupler wavelength selective filter based on dispersive Bragg reflection waveguide

A new type of wavelength selective filter, based on high differential dispersion between two coupled waveguides, is presented. The Bragg Reflection Waveguide displays high effective refractive index dispersion, due to the interaction of the guided mode with the two confining Bragg reflectors. When coupled with a weakly guided buried channel silica waveguide, a very narrow bandwidth filter (<1 nm) can be easily produced, in a shorter length, with respect to directional couplers made with standard step index channel waveguides. The complete design methodology, fabrication and characterization are presented.     

Factor analysis of transient spectra. Free radicals in cyclic dipeptides containing methionine

Factor analysis is introduced and applied to resolving puzzling behavior in the free-radical chemistry of the cyclic dipeptide cyclo-(D-Met-L-Met). Previously, spectral analysis of the transient absorption spectra, following the hydroxyl radical-induced oxidation of cyclo-(D-Met-L-Met), failed to match expectations seen when transient conductivity was used to monitor the same reaction sequence. In the current work, factor analysis is used to show that a radical cation is formed via the stabilization of the oxidized sulfur through the formation of two-centered three-electron bonds with the lone pairs on oxygen. This previously undetected radical resolves the discrepancy between transient absorption and transient conductivity observations.     

The DSC Study of PA 6, Polyamides and Copolyamides

The DSC method was used to obtain more information on changes of thermal properties connected with different comonomers bound in the (co)polymer chains. The copolyamides propered were block ones which were less crystalline and compatible with poly-ε-caprolactam. The results have confirmed the crystalline nature of polyamides and copolyamides. This revised version was published online in August 2006 with corrections to the Cover Date.     

2,2′‐Isopropyl­idene­diphenol

The planar benzene rings in the title compound, C₁₅H₁₆O₂, are inclined at an angle of 82.61 (9)° to one another. There are two intra­molecular hydrogen bonds of types O—H⋯π and C—H⋯O. The mol­ecules are linked by strong O—H⋯O hydrogen bonds into a one‐dimensional network, which is compared with that of related compounds.     

3‐(1‐Pyridinio)propane­sulfonate and 3‐(benzyl­dimethyl­ammonio)propane­sulfonate monohydrate

3‐(1‐Pyridinio)propane­sulfonate, C₈H₁₁NO₃S, and 3‐(benzyl­dimethyl­ammonio)propane­sulfonate monohydrate, C₁₂H₁₉NO₃S·H₂O, used as additives during protein refolding and crystallization, both crystallize in the monoclinic system in the P2₁/c space group, with one mol­ecule (or one set of mol­ecules) per asymmetric unit. The solvent water mol­ecule present in the second crystal structure results in the formation of a dimer through hydrogen bonds. The conformation of the propane­sulfonate moiety is similar in both structures.     

Tb2Ni2Mg3: a new structure type derived from the Ru3Al2B2 type

Single crystals of diterbium dinickel trimagnesium, Tb₂Ni₂Mg₃, were synthesized from the elements by induction melting. The novel compound crystallizes in the space group Cmmm with one Mg atom of site symmetry mmm and the Tb, Ni and other Mg atom in m2m positions. This ternary compound represents a new structure type that is derived from Ru₃Al₂B₂ by way of Wyckoff site distribution. The two‐layer structure of Tb₂Ni₂Mg₃ is a new representative of a homologous linear structure series of general formula R′_k+nX_2nR′′_2m+k based on structural fragments of the α‐Fe, CsCl and AlB₂ structure types. The Tb atoms in the structure are enclosed in 17‐vertex polyhedra, while rhombododeca­hedra and distorted rhombododeca­hedra surround the Mg atoms, and equatorially tricapped trigonal prisms form around the Ni atoms. All inter­atomic distances indicate metallic type bonding.