Piezoelectric Performance of Microcellular Polypropylene Foams Fabricated Using Foam Injection Molding as a Potential Scaffold for Bone Tissue Engineering

Abstract

Piezoelectric properties and adequate porosity play important roles in bone tissue engineering. In this paper we describe the fabrication of piezoelectric polypropylene (PP) foam using injection molding to be utilized as a potential cost-effective scaffold for bone tissue engineering. One-side mechanical skin removal from the foam was used to investigate the effect of the solid skin on the piezoelectric performance. The microcellular structure, relative density, crystalline structure, mechanical properties, piezoelectric properties under repeated impact pressure and biocompatibility of the scaffolds were investigated using scanning electron microscopy (SEM), water displacement method, differential scanning calorimetry (DSC), uniaxial tension tests, piezoelectric tests and MTT assays, respectively. Uniform spherical cells, with an average size of 75?µm and a density of 1.23?×?10⁶ cells/cm^?3, suitable for bone regeneration, were imaged by SEM. The DSC results showed β crystals formation in the PP foam during the foaming process which would be valuable for mechanical properties. The foaming process did not reduce the mechanical properties significantly. The foaming process promoted the piezoelectric responses by 134, 922, and 87%, respectively, for the PP samples with 3, 2 and 1?mm thickness. The biocompatibility test suggested improved cellular biocompatibility by foaming. Overall, the results demonstrated the development of a cost-effective scaffold for tissue engineering.     

Phase‐selective crystallization of nickel phosphate VSB‐5 with (2‐hydroxyethyl) trimethylammonium hydroxide as template

Several nickel phosphate molecular sieves were synthesized by conventional heating (CH) and microwave assisted hydrothermal (MAH). Nickel phosphate VSB‐5 (Versailles Santa Barbara‐5) was synthesized with conventional oven for 72 h or with microwave for 1 h and followed by conventional oven for 48 h in the presence of (2‐hydroxyethyl) trimethylammonium hydroxide as template. The phase transformation is observed by variation of CH time for the synthesis of nickel phosphate molecular sieves. At CH time of 24 h, the VSB‐5 crystal together α‐Ni₂P₂O₇, Ni₂P₄O₁₂ and unknown phases were produced but the pure VSB‐5 crystal was obtained in the CH time of 48 h or more. At high content of nickel, a mixture of α‐Ni₂P₂O₇, Ni₂P₄O₁₂ phases and small amount of VSB‐5 crystal, was achieved but pure VSB‐5 crystal was obtained in the lower level of nickel and other phases are vanished. An efficient ultrasonic‐assisted aging was found for the synthesis of nickel phosphate molecular sieve, in which by ultrasonic mixing of 0.5 h followed microwave of 1 h, the CH time is significantly reduced from 48 to 24 h. The morphology of nickel phosphate crystals is highly influenced in the presence of ethylene glycol as co‐solvent. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrogen Bonds of Peptide Group in Four Acetamide Derivatives: DFT Study of Oxygen and Nitrogen NQR and NMR Parameters

A computational study was conducted to examine hydrogen bond (HB) properties of peptide group in four derivatives of acetamide by density functional theory (DFT) calculations of nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) parameters at the sites of oxygen and nitrogen nuclei of peptide groups. The available crystalline structures of four derivatives; 2,2,2-trifluoro-N-(2-hydroxy-5-nitrophenyl)acetamide, N-(2-acetylphenyl)acetamide, 2-chloro-N-(4-nitrophenyl) acetamide, and N-(4-fluorophenyl)acetamide were obtained from literature. Following the influence of HB interactions, calculations were done on non-hydrogen bonded (single) and hydrogen bonded (cluster) models of derivatives. The results revealed different behaviors of peptide group in contributing to HB interactions in different derivative structures. HB interactions are the strongest in 2-chloro-N-(4-nitrophenyl)acetamide. However, the strengths of HB interactions in all of the four derivatives are still less than that of acetamide. The calculations are done at the level of B3LYP method and 6-311++G** standard basis set using GAUSSIAN 98 package of program.     

2-Aminopyrazine-functionalized MCM-41 nanoporous silica as a new efficient heterogeneous ligand for Cu-catalyzed allylic C–H bonds oxidation of olefins

Research on Chemical Intermediates - In spite of the importance of the application of allylic C–H bond oxidation of olefins in organic synthesis and existence of the numerous reports, lots of...     

Chiral bisoxazoline ligands with a biphenyl backbone: development and application in catalytic asymmetric allylic oxidation of cycloolefins

A simple and efficient method for the synthesis of chiral biphenylbisoxazoline ligands was developed. The bishydroxylamide precursors of ligands showed a dynamic atropselective resolution effect in the crystallization process. When biphenylbisoxazoline ligands were coordinated to tetrakis(acetonitrile)copper(I) hexafluorophosphate, it resulted in the formation of only a single diastereomer complex (S,aS,S), which behaved as a catalyst for the enantioselective allylic oxidation of cycloolefins. The enantioselectivity, yield, and rate of this reaction were optimized under different conditions, such as a change of solvents, temperature, and additives and also using various copper salts. The use of SBA-15 mesoporous silica as an additive played a crucial role in increasing the efficiency of the reaction.     

Homogenization of a composite medium with a thermal barrier

In this work, we consider a heat transfer problem between two periodic connected media exchanging a heat flux throughout their common interface. The interfacial exchange coefficient λ is assumed to tend to zero or to infinity following a rate λ=λ(ε) when the size εof the basic cell tends to zero. Three homogenized problems are determined according to the value of δ=lim_ε→0λ/ε. Copyright © 2004 John Wiley & Sons, Ltd.     

A Comparative Study of Anti-Candida Activity and Phenolic Contents of the Calluses from Lythrum salicaria L. in Different Treatments

In the study, anti-Candida activity and phenol contents of Lythrum salicaria L. calli and wild species have been evaluated. The seeds of L. salicaria (Lythraceae), collected from Lahidjan City in the north of Iran, were cultured in Murashige and Skoog medium (MSM) with a supplement, gibberellin, to germinate. Callus inductions were performed from segments of seedling on MSM containing different concentrations of plant growth regulators, 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP). The activity of calluses extracts, wild plant, gallic acid, and 3,3′,4′-tri-O-methylellagic acid-4-O-β-d-glucopyranoside (TMEG) as the main phenolic compounds against Candida albicans was assessed using cup plate diffusion method. The total phenols contents of calli and wild plant extracts were analyzed using Folin–Ciocalteu reagent. The callus formation in MSM supplemented with various concentrations of 2,4-D and BAP were 0–100 %. Anti-Candida activity of callus extract which obtained from MSM supplemented with 2,4-D and BAP (1 mg?dm^?3) was similar to the wild plant extract. Minimum inhibitory concentration values of gallic acid and TMEG were obtained as 0.312 and 2.5 mg?cm^?3, respectively. Gallic acid equivalent values in all treatments were from 0 to 288 μg GAE mg^?1. Phenolic contents of plant aerial parts (331?±?3.7 μg GAE mg^?1) and the callus, which developed in MSM including 1 mg?dm^?3 of both 2,4-D and BAP, showed the same phenolic value and exhibited anti-Candida extract activity.     

Luminol/H2O2/KSCN/CuSO4 Oscillating Chemiluminescence System in the Presence of Complexing Agents

The oscillating system luminol/H₂O₂/KSCN/CuSO₄ with (2‐hydroxyethyl)trimethylammoniumhydroxide (2‐HETMAOH) was investigated by using luminometry technique. Temperature and solvent effects on the behavior of the oscillating system were studied. The influences of complexing agents such as ethylenediaminetetraacetic acid (EDTA) and methionine were also investigated for this system. All experiments were performed by using the luminometer technique in a batch reactor.