Porous composites of hydroxyapatite‐filled poly[ethylene‐co‐(vinyl acetate)] for tissue engineering

A novel porous composite of hydroxyapatite/poly[ethylene‐co‐vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X‐ray microcomputed tomography (µCT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X‐ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non‐cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3‐(4,5‐dimethylthiazol)‐2‐yl]‐2,5‐diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. Copyright © 2010 Society of Chemical Industry     

Review: Investigation of Partially Pre-mixed Charge Ignitions (PPCI) Engine Mode

This paper embraces the key points of unpolluted internally combusted engine emissions. Core objective is focused on the recent effort to improve compression ignition(CI) and spark ignition(SI) engine to have fuel-efficient and minimized pollutant emissions. There are many advanced internal combustion engines to overcome the challenges of conventional compression ignition engines of the high level of particulate matter(PM) and oxides of nitrogen emission. One of the latest options on which many ...     

Preparation and characterization of novel semi‐interpenetrating 2‐hydroxyethyl methacrylate‐g‐chitosan copolymeric microspheres for sustained release of indomethacin

A novel semi‐interpenetrating (semi‐IPN) graft copolymer of 2‐hydroxyethyl methacrylate (HEMA) with chitosan (CS) has been prepared in the form of microspheres, using water‐in‐oil (W/O) emulsion technique. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X‐ray diffractometry (X‐RD) to confirm the crosslinking and polymorphism of indomethacin (IDM). The X‐RD and DSC techniques indicated a molecular‐level dispersion of IDM in the IPN matrix. Scanning electron micrographs (SEM) taken at the cross section of the microspheres have shown rough surfaces around the microspheres. The sustained release characteristics of the matrices for IDM, an anti‐inflammatory drug, were investigated in pH 7.4 media. Particle size and size distribution of the microspheres were studied by laser light diffraction particle size analyzer. The drug was released in a sustained manner for up to 12 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

ZnO–SnO2 nanocubes for fluorescence sensing and dye degradation applications

ZnO–SnO₂ nanocubes were used as promising material for efficient sensing of p-nitrophenol and faster photocatalytic degradations of dyes like methyl orange (MO), methylene Blue (MB) and acid orange 74 (AO74). ZnO–SnO₂ nanocubes were prepared by the facile solution process at 50 °C using Zn(NO₃)₂·6H₂O and SnCl₂·2H₂O as a precursor in the presence of ethylenediammine. The synthesized material was examined for its morphological, structural, crystalline, optical, vibrational, and compositional studies by using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. FESEM studies revealed the formation of well-defined ZnO–SnO₂ nanocubes where the structural examinations revealed the formation of a crystalline tetragonal rutile phase for SnO₂ with some crystal sites doped with Zn. The as-synthesized nanocubes were explored for their photocatalytic activities towards three different dye viz. MO, MB, and AO74. Practically, complete degradation of AO74 was seen within 4 minutes of photo-irradiation in the presence of 0.05 g ZnO–SnO₂ nanocubes. However, 97.17% and 41.63% degradations were observed for MB and MO within 15 and 60 minutes, respectively. All the dye degradation processes followed the pseudo-first-order kinetic model. Moreover, the as-synthesized nanocubes were utilized to fabricate highly sensitive and selective fluorescent chemical sensor for the detection of p-nitrophenol (PNP). ZnO–SnO₂ nanocubes showed a very low detection limit of 4.09 μM for the detection of PNP as calculated according to the 3σ IUPAC criteria. Further, the as-synthesized ZnO–SnO₂ nanotubes were found to be highly selective for p-nitrophenol as compared to the other two isomers.     

Synthetic and Biological Studies of Sesquiterpene Polygodial: Activity of 9‐Epipolygodial against Drug‐Resistant Cancer Cells

Polygodial, a terpenoid dialdehyde isolated from Polygonum hydropiper L., is a known agonist of the transient receptor potential vanilloid 1 (TRPV1). In this investigation a series of polygodial analogues were prepared and investigated for TRPV1‐agonist and anticancer activities. These experiments led to the identification of 9‐epipolygodial, which has antiproliferative potency significantly exceeding that of polygodial. 9‐Epipolygodial was found to maintain potency against apoptosis‐resistant cancer cells as well as those displaying the multidrug‐resistant (MDR) phenotype. In addition, the chemical feasibility for the previously proposed mechanism of action of polygodial, involving the formation of a Paal–Knorr pyrrole with a lysine residue on the target protein, was demonstrated by the synthesis of a stable polygodial pyrrole derivative. These studies reveal rich chemical and biological properties associated with polygodial and its direct derivatives. These compounds should inspire further work in this area aimed at the development of new pharmacological agents, or the exploration of novel mechanisms of covalent modification of biological molecules with natural products.     

Chitosan/poly(dimethylaminoethylmethacrylate-co-hydroxyethylacrylate) based semi-IPN hydrogels and silver nanocomposites: Synthesis,evaluation of amoxicillin release studies,and antibacterial studies

To fabricate new smart materials that can deliver both the pharmaceutically active molecules and metal nanoparticles, we have formulated chitosan-based semi-IPN hydrogels and their silver nanocomposites (Ag NCs) along with amoxicillin (AMX). Semi-IPN hydrogels and their Ag NCs were synthesized from chitosan, dimethylamino ethyl methacrylate and 2-hydroxyethyl methacrylate via simple-free radical polymerization method and reducing with NaBH₄. The resultant formulations were evaluated for in vitro release of AMX, anti-bacterial studies and DNA cleavage studies. The hydrogels with AMX-derived silver nanoparticles (Ag NPs) show better ability to cleave DNA and anti-microbial activity than individual AMX and Ag NPs.     

Ethanol dehydration activity on hydrothermally stable LaPxOy catalysts synthesized using CTAB template

Nanocrystalline LaP_xO_y with various starting P to La ratios from 0.5 to 2.0 catalysts were prepared by a sol?Cgel method using cetyl trimethylammonium bromide (CTAB) as template. The catalysts were thoroughly characterized by N₂ physisorption, powder X-ray diffraction (XRD), temperature programmed desorption (TPD) of NH₃, solid state ³¹P and ¹H nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM) techniques. XRD results indicate the presence of predominantly monazite LaPO₄ with minor amounts of (??3.0 wt%) rhabdophane LaPO₄ phase in the samples with starting P/La ratios of 1.0 and 1.5. NH₃-TPD results show an increasing trend in the total acidity with increase in P/La ratio. These catalysts were tested in the selective ethanol dehydration in the temperature range between 250 and 400?°C. The catalyst activity (??mol/h/m²) is increased with P/La ratio and the catalyst with highest P/La ratio of 2.0 exhibiting the highest ethanol dehydration activity. The ethanol conversion increased with reaction temperature, reaching 100% at 350?°C and remains unchanged at higher temperatures. On the other hand, the ethylene selectivity is also increased up to 350?°C and then decreased with further increase of reaction temperature. At a P/La ratio of 2, the CTAB templated LaP_xO_y catalyst showed higher catalytic activities compared to the LaP_xO_y by hydrothermal method without any template.     

Tailor-made fumed silica-based nano-composite polymer electrolytes consisting of BmImTFSI ionic liquid

In this work, nano-sized fumed silica (SiO₂) was embedded in poly(methyl methacrylate) (PMMA)?Cpoly(vinyl chloride) (PVC) blend with 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl imide) (BmImTFSI) as ionic liquid. These composite polymer electrolytes (CPEs) were prepared by solution casting technique. The samples followed Arrhenius behavior in the temperature-dependence of ionic conductivity and further proved the ionic hopping mechanism in the polymer electrolyte. It is suggested the formation of three-dimensional polymer network among the aggregates weakens the interaction of polar group of the polymer backbone and initiates the ionic decoupling process. The mobile ions from adjacent sites would occupy this vacant site and reform the interactive bond with the polymer backbone whereby the ionic hopping mechanism is generated. The activation energy (E _a) is further determined. The higher the ionic conductivity, the lower the activation energy. The maximum ionic conductivity of (8.26?±?0.02) mScm^?1 was achieved at 80?°C upon inclusion of 8 wt% of SiO₂. X-ray diffraction (XRD) analysis revealed the higher amorphous region with increasing SiO₂ mass loadings. The coherence length is further determined by using Debye?CScherrer equation. Higher amorphous region in the polymer matrix is conferred by showing the lower coherent length. Scanning electron microscopy (SEM) was applied to examine the morphology of polymer electrolytes. Based on the differential scanning calorimetry (DSC) study, glass transition temperature (T _g) and melting temperature (T _m) were decreased. Highly flexible polymer chain is produced when the T _g was lowered down. On the other hand, thermal stability of polymer electrolytes was increased by SiO₂ dispersion, as depicted in thermogravimetric analysis (TGA).     

Designing polyethylene terephthalate‐based barrier resins

We have studied the efficiencies of commercially available barrier resins used for food packaging and beverage bottle applications and compared them with resins made using copolymer and blending approaches. The effects of various copolymer related parameters that influence oxygen barrier performance and the underlying mechanisms for these effects in PET‐based copolymers and blends were investigated. Using these approaches, it is possible to make highly effective PET‐based copolymers for gas barrier applications. Blending of PET with phenolic and other organic materials shows equivalent barrier performance in PET copolymers having comonomer levels of <8‐mole %. Reduction in oxygen permeation rates results from the reduction or elimination of short range molecular motion of polyethylene terephthalate molecules. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improved transfection efficiency of chitosan‐DNA complexes employing reverse transfection

The present study was designed to systematically compare the conventional and reverse transfection methodologies for chitosan/DNA complexes using a low molecular weight (MW) chitosan. The hydrodynamic diameter of the complexes, measured by Dynamic Light Scattering (DLS) was found to be ～ 216 nm and TEM investigations showed spherical and compact complexes with an average size of 200 nm. The transfection efficiency of chitosan using the two methodologies was assessed by employing reporter gene coding for green fluorescent protein (GFP) and luciferase. More than 50% of HEK 293 cells were transfected when transfection done using reverse transfection strategy at pH 6.5 with 10% serum for 24 h followed by media replenishment with pH 7.4 with 10% serum for an additional 24 h period. Also, the cytotoxicity of chitosan/DNA complexes was also considerably lower than the commercially available transfection reagent lipofectamine. Our investigation concludes that maximal transgene expression levels could be achieved using reverse transfection where the chitosan/DNA complexes are pre‐incubated on the plate surface followed by plating of cells at pH 6.5 with 10% serum for 24h and media resupplemented with pH 7.4 with 10% serum for an additional 24 h period. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012