Viscoelasticity,mechanical properties,and in vivo biocompatibility of injectable polyvinyl alcohol/bioactive glass composite hydrogels as potential bone tissue scaffolds

Abstract

An injectable composite hydrogel composed of polyvinyl alcohol (PVA) and bioactive glass (BG) particles were synthesized by a physical crosslinking approach. The morphology, mechanical properties, and viscoelasticity of the PVA/BG composite hydrogel were characterized. Scanning electronic microscopy (SEM) showed uniform and homogeneous distribution of BG particles throughout the composite hydrogel. The incorporation of 2.5?wt% of BG particles in the composite hydrogel formulations, enhanced the static compressive strength and static elastic modulus by 325% and 150%, respectively. The storage molds (G′) was greater than the loss modules (G′′) at all the frequency range studied, which revealed a self-standing elastic composite hydrogel with a smooth injectability. The PVA/BG composite hydrogel was also implanted subcutaneously in the dorsal region of adult male rats. After 4?weeks of implantation, no inflammatory cells were seen within and around the implant, which indicated that the composite hydrogel was biocompatible. The properties of the synthesized injectable PVA/BG composite hydrogel demonstrate its capability toward bone regeneration.     

Effects of humidity and temperature during irradiation on the response of blue PMMA dosimeter

Effects of relative humidity conditions in the irradiation chamber and of temperature of the chamber on the response of 3 mm thick light blue poly (methyl methacrylate) sheets have been studied. The response was measured spectrophotometrically at 402, 450, 596 and 612 nm. The response of the dosimeter is independent of the relative humidity (12–97%) during irradiation if the response is measured within 24 h of irradiation. If the response is measured after longer storage time, the absorbance at 402 and 450 nm increases significantly. At these two wavelengths the response of the dosimeter is also independent of the temperature of the irradiation chamber in the range of 0 to 40 °C. However, at higher temperatures (60, 80 °C), the response is not uniform.     

Isotope shift studies in the spectra of Gadolinium in UV region and term shifts of high even levels of Gd I

Isotope shift Δσ(¹⁵⁶Gd?¹⁶⁰Gd) is reported in 70 spectral lines of neutral gadolinium atom (Gd I) in the 3290- 3920 Å region providing isotope shift data in UV lines of Gd I spectrum for the first time. The measurements were carried out on a photoelectric recording Fabry-Perot Spectrometer using highly enriched isotopic samples of gadolinium. Term isotope shifts ΔT(¹⁵⁶Gd?¹⁶⁰Gd) have been evaluated for 48 high lying even parity energy levels of Gd I using this data; new ΔT values have been obtained for 24 levels. Electronic configurations 4f⁷5d6s6p, 4ff⁷5df²6p and 4f⁸5d6s assigned earlier to these even levels have been either confirmed or configuration mixing pointed out in some of these levels. Probable assignment of 4f⁸5d6s configuration to 8 even levels between 32 930 and 35 500 cm^-1 have been confirmed.     

Unique cascade ring-opening/cyclization reaction of azlactones and DBU or DBN: Synthesis of new pyrrolam A analogues

1-Azabicyclo[3.3.0]oct-3-en-2-one derivatives were synthesized efficiently through the facile cascade reaction of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) with arylidene azlactones. This research provides a straightforward procedure for the synthesis of a novel class of multicyclic semi-alkaloids which shows good antimicrobial activity. Under catalyst-free, mild, and solventless condition, a wide range of fused tricyclic derivatives was obtained in high yields.     

Studies on novel thermally stable segmented polyurethanes based on thiourea-derivative diols

Novel thermoplastic segmented poly(urethane-thiourea)s (PURs) were synthesized via one-step polymerization from aromatic diols containing sulfur (thiourea linkage) in the main-chain, including terephthaloyl bis (3-(2-hydroxopyridyl) thiourea) (TBHPT) and terephthaloyl bis (3-(5-naphtholyl) thiourea) (TBNT), along with 1,4-phenylene diisocyanate (PDI) as hard segment and 20, 50 and 80 mol% polyethylene glycol (PEG) as a soft segment. The prepared chain extenders and polymers were characterized by conventional methods, and physical properties such as η_inh, solubility, thermal stability and thermal behavior were studied. Easily processable PURs with excellent thermal stability were obtained by incorporating 20 mol% PEG in the soft segment. Thermogravimetric analysis indicated that poly(urethane-thiourea)s were fairly stable above 500 °C and own high glass transition temperatures about 263-266 °C. These polymers also showed partially crystalline structures. Ultimately, weight average molecular weights (M_w) of PURs were up to 109 × 10³. Compared to typical polyurethanes, PURs exhibited better thermal stability and T_g’s owing to rigid hard segment structure.     

Synthesis,crystal structure,and antimicrobial studies of <Emphasis Type="Italic">trans</Emphasis>-[Pd(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>(imidazolidine-2-thione)<Subscript>2</Subscript>]Cl<Subscript>2</Subscript> · 3.5H<Subscript>2</Subscript>O

The palladium(II) complex, [Pd(PPh₃)₂(Imt)₂]Cl₂ · 3.5H₂O (I) (Imt = imidazolidine-2-thione), has been synthesized and characterized by IR, NMR, and X-ray crystallography. An upfield shift in the >C=S resonance of Imt in the ¹³C NMR spectrum and a downfield shift in the N-H resonance in ¹H NMR are consistent with the sulfur coordination of Imt to palladium(II). In the crystal structure of I, the central palladium atom is coordinated to two thione sulfur atoms of Imt and to two phosphorus atoms possessing a square-planar environment with the average cis and trans bond angles of 89.60° and 167.31°, respectively. The title complex was screened for antimicrobial effects, and the results showed that it exhibits moderate activities against gram-negative bacteria (E. coli, P. aeruginosa). The complexes also exhibited significant activities against yeast (C. albicans, S. serevisaiae).     

Development of a simple extraction and clean-up procedure for determination of organochlorine pesticides in soil using gas chromatography–tandem mass spectrometry

A procedure based on QuEChERS extraction and a simultaneous liquid–liquid partition clean-up was developed. The procedure involved extraction of hydrated soil samples using acetonitrile and clean-up by liquid–liquid partition into n-hexane. The hexane extracts produced were clean and suitable for determination using gas chromatography–tandem mass spectrometry (GC–MS/MS). The method was validated by analysis of soil samples, spiked at five levels between 1 and 200 μg kg⁻¹. The recovery values were generally between 70 and 100% and the relative standard deviation values (%RSDs) were at or below 20%. The procedure was validated for determination of 19 organochlorine (OC) pesticides. These were hexachlorobenzene (HCB), α-HCH, β-HCH, γ-HCH, heptachlor, heptachlor epoxide (trans), aldrin, dieldrin, chlordane (trans), chlordane (cis), oxychlordane, α-endosulfan, β-endosulfan, endosulfan sulfate, endrin, p,p′-DDT, o,p′-DDT, p,p′-DDD and p,p′-DDE. The method achieved low limits of detection (LOD; typically 0.3 μg kg⁻¹) and low limits of quantification (LOQ; typically 1.0 μg kg⁻¹). The method performance was also assessed using five fortified soil samples with different physico-chemical properties and the method performance was consistent for the different types of soil samples. The proposed method was compared with an established procedure based on Soxtec extraction. This comparison was carried out using six soil samples collected from regions of Pakistan with a history of intensive pesticide use. The results of this comparison showed that the two procedures produced results with good agreement. The proposed method produced cleaner extracts and therefore led to lower limits of quantification. The proposed method was less time consuming and safer to use. The six samples tested during this comparison showed that soils from cotton growing regions contained a number of persistent OC residues at relatively low levels (<10 μg kg⁻¹). These residues were α-HCH, γ-HCH, heptachlor, chlordane (trans), p,p′-DDT, o,p′-DDT, p,p′-DDD, p,p′-DDE, β-endosulfan and endosulfan sulfate.     

Benign synthesis of carboxamide ligands,H2Me2bqb and H2Me2bpb. Preparation,characterization and electrochemistry of Ni(II) complexes: The crystal structure of [Ni(Me2bqb)]

A novel and highly efficient approach for the synthesis of H₂Me₂bqb and H₂Me₂bpb using ionic liquid as an environmentally benign reaction medium has been developed, eliminating the need for the pyridine as a toxic solvent. The Ni(II) complex of the dianionic ligand Me₂bqb²⁻, [Me₂bqb²⁻ = 1,2-bis(quinoline-2-carboxamide)-4,5-dimethyl-benzene dianion], has been synthesized and characterized by elemental analyses and spectroscopic methods, and the crystal and molecular structure of [Ni(Me₂bqb)] (1), has been determined by X-ray crystallography. The complex exhibits distorted square-planar NiN₄ coordination geometry with two short and two long Ni–N bonds (Ni–N ∼1.85 and ∼1.96 Å, respectively). The electrochemical behavior of [Ni(Me₂bqb)] (1), has been studied by cyclic voltammetry and compared with the analogous complex, [Ni(Me₂bpb)] (2).     

Kinetics and mechanism of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) by N-bromosuccinimide in aqueous acidic medium

The kinetics of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) complex by N-bromosuccinimide (NBS) in aqueous acid and H₂O–MeOH solvent mixtures were studied spectrophotometrically over the 20–40 °C range, 0.1–0.5 mol dm^?3 ionic strength, 2.2–2.8 pH range and 0–40 wt% MeOH–H₂O solvent mixtures for a range of NBS and complex concentrations. The rate shows first-order dependence on both [NBS] and [complex] and decreases with pH over the range studied. The protonated form of N-bromosuccinimide was identified as the main reactive species. An inner-sphere mechanism involving free radicals is proposed.     

Selective Lanthanides Sequestration Based on a Self‐Assembled Organosilica

In this paper, we investigate the cation‐exchange properties of a self‐assembled hybrid material towards trivalent ions, lanthanides (La³⁺, Eu³⁺, Gd³⁺, Yb³⁺) and Fe³⁺. The bis‐zwitterionic lamellar material was prepared by sol–gel process from only 3‐aminopropyltriethoxysilane (APTES), succinic anhydride, and ethylenediamine. In ethanol heated under reflux, the exchange ethylenediammonium versus Ln³⁺ proved to be complete by complexometry measurements and elemental analyses, one Cl^? ion per one Ln^III remaining as expected for charge balance. In aqueous solution at 20 °C, the material was found to be selective towards lanthanide in spite of the similarity of their ionic radii. The cation uptake depends on the nature of the salt, the difference between two lanthanides reaching up to 20 % in some cases. Finally, ion‐exchange reaction with FeCl₃ was chosen as a probe to get more information on the material after incorporation of trivalent ions. Based on Mössbauer spectroscopic investigations on the resulting material in conjunction with the XRD analysis of materials containing trivalent ions, a structural model was proposed to describe the incorporation of trivalent ions by exchange reaction within the original zwitterionic material.