Use of electrospinning technique for biomedical applications

The electrospinning technique provides non-wovens to the order of few nanometers with large surface areas, ease of functionalisation for various purposes and superior mechanical properties. Also, the possibility of large scale productions combined with the simplicity of the process makes this technique very attractive for many different applications. Biomedical field is one of the important application areas among others utilising the technique of electrospinning like filtration and protective material, electrical and optical applications, sensors, nanofiber reinforced composites etc. Electrospinning assembly can be modified in different ways for combining materials properties with different morphological structures for these applications. The importance of electrospinning, in general, for biomedical applications like tissue engineering drug release, wound dressing, enzyme immobilization etc. is highlighted in this feature article. The focus is also on the types of materials that have been electrospun and the modifications that have been carried out in conventional electrospinning apparatus keeping in view the specific needs for various biomedical applications.     

Vinyl-functionalized gold nanoparticles as artificial monomers for the free radical copolymerization with methyl methacrylate

Vinyl-functionalized gold nanoparticles (AuNP) were prepared by surface polymerization of vinyl-functionalized ligands induced by carboxy-functionalized radical initiators followed by vinyl-transformation of the carboxy-group. These AuNP were regarded as artificial molecules as they were used as comonomers for the free radical copolymerization with methyl methacrylate (MMA). Successful copolymerization was proven by gel permeation chromatography (GPC) and by thermogravimetrical analysis (TGA). Further analysis of the novel hybrid material was carried out by transmission electron microscopy (TEM) and by atomic force microscopy (AFM) to proof the presence of AuNP and their arrangement.     

Attenuation Characteristics and Sensitivity Analysis for Coplanar Waveguide

The behaviour of attenuation losses in Coplanar waveguides (CPW) is studied for quasi-planar transmission lines with constant characteristic impedance (Z₀) and resistivity, having different geometry's. This behavior helps in making a suitable choice of the type of structure and its dimensional parameters depending upon the application. Minimization of loss for a chosen substrate thickness, conductivity and impedance is analyzed. Dispersion characteristics of CPW have been plotted for various metallization thicknesses. A sensitivity analysis for effective dielectric constant with respect to various dimensional parameters of CPW is presented.     

Single‐Molecule Imaging Reveals that Small Amyloid‐β1–42 Oligomers Interact with the Cellular Prion Protein (PrPC)

Oligomers of the amyloid‐β peptide (Aβ) play a central role in the pathogenesis of Alzheimer’s disease and have been suggested to induce neurotoxicity by binding to a plethora of cell‐surface receptors. However, the heterogeneous mixtures of oligomers of varying sizes and conformations formed by Aβ42 have obscured the nature of the oligomeric species that bind to a given receptor. Here, we have used single‐molecule imaging to characterize Aβ42 oligomers (oAβ42) and to confirm the controversial interaction of oAβ42 with the cellular prion protein (PrP^C) on live neuronal cells. Our results show that, at nanomolar concentrations, oAβ42 interacts with PrP^C and that the species bound to PrP^C are predominantly small oligomers (dimers and trimers). Single‐molecule biophysical studies can thus aid in deciphering the mechanisms that underlie receptor‐mediated oAβ‐induced neurotoxicity, and ultimately facilitate the discovery of novel inhibitors of these pathways.     

Removal of basic dyes from aqueous solution by low-cost adsorbent: Wood apple shell (Feronia acidissima)

The adsorption of two basic dyes, methylene blue (MB) and crystal violet (CV) on wood apple shell (WAS) were investigated using a batch adsorption technique. A series of experiments were undertaken in an agitated batch adsorber to assess the effect of the system variables such as solution pH, dye concentration and temperature. Removal of dyes was observed to be most effective at higher pH. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The results showed that Langmuir equation fits better than the Freundlich equation. It was observed that the WAS adsorbent showed higher adsorption capacity for crystal violet (130 mg/g) than methylene blue (95.2 mg/g). The FTIR studies indicate that the interaction of dye and WAS surface is via the nitrogen atoms of the adsorbate and oxygen groups of the adsorbent. The adsorption of dyes onto WAS proceeds according to a pseudo-second-order model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also calculated. The studies show that WAS, a lignocellulosic inexpensive material, can be an alternative to other expensive adsorbents used for dye removal in wastewater treatment.     

Development of biosensor for phenol detection using agarose–guar gum based laccases extracted from Pleurotus ostreatus

Laccases from Pleurotus ostreatus was extracted from the Shaken flask cultures of Pleurotus ostreatus grown at 25°C with continuous agitation (110 rpm.) in baffled 1000 mL Erlenmeyer flasks containing 200 mL medium. The basal GYP medium used for cultures contained 20 g glucose l^?1, 5 g yeast extract l^?1, 5 g peptone from casein l^?1, and 1 g MgSO₄.7H₂O l^?1. The pH was adjusted to 5.0 with H₃PO₄ before sterilization. The kinetics of oxidation reactions catalyzed by laccases was studied using 2,2′‐azino‐bis (3‐ethylbenzthiazoline‐6‐sulphonic acid). The laccases showed lower specific activity and higher activity in nonpolar organic solvents. A biosensor using laccases was constructed for the determination of phenol. The enzyme was extracted from Pleurotus ostreatus and entrapped in agarose–guar gum composite biopolymer matrix. Phenol was determined by direct reduction of biocatalytically liberated quinone species at ?0.1 V versus Ag/AgCl (3M KCl). The response was found to be linear and concentration dependent.It has a shelf life of more than 2 months when stored at 4°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Tape casting of nickel manganite NTC ceramics for chip thermistors

Tape casting is a reliable route for mass production of precise miniature NTC chip sensors. The present paper describes the development work in tape casting of nickel manganite based NTC formulations. The most suitable dispersion condition of the powder in MEK–ethanol solvent system was determined by rheological and sedimentation studies. The optimized slurry composition for obtaining defect-free tapes was achieved by controlling the amounts of organic additives. The sintered chip samples exhibited 98% theoretical density with an over all shrinkage of 17%.     

Predetermined overall thermal transfer value coefficients for Composite, Hot-Dry and Warm-Humid climates

This paper attempts to formulate Overall Thermal Transfer Value (OTTV) coefficients for Composite, Hot-Dry and Warm-Humid climates, the three main tropical climates in India. Four existing air-conditioned office buildings - two mid-rise and two high-rise were modeled as case studies using eQuest v.3.6, which is a DoE2.2, based building energy simulation tool. Based on the study of building envelope, loads, operation and HVAC system characteristics of these case study buildings, a hypothetical high-rise, 16 storey office building, octagonal in plan was created for parametric studies. 98 types of opaque exterior wall constructions and 93 types of glass constructions were varied sequentially in parametric runs to obtain results for hourly wall conduction, glass conduction and glass radiation heat flow in eight orientations for each of the climate type. These hourly results were processed to obtain annual heat gain intensities for each parametric case for all three modes of heat transfer. Regression analysis was used to obtain the OTTV coefficients - TD_eq, DT and SF for the three climates. A new OTTV equation is obtained and presented. The set of coefficients obtained were verified by calculating the OTTV for the four case study buildings, for various parametric runs. The computed OTTV for the four case study buildings exhibits good linear correlation with the annual space cooling plus heating energy use in three climates.     

Synthesis,characterization and properties evaluation of copolymers of 2,3,4,5,6‐pentafluorostyrene and N‐phenylmaleimide

Copolymers of 2,3,4,5,6‐pentafluorostyrene (PFS) having a combination of high hydrophobicity and high glass transition temperature (T_g) are reported here for the first time. The copolymerization was carried out using N‐phenylmaleimide (NPM) as the comonomer and azobisisobutyronitrile (AIBN) as the initiator under both conventional thermal heating and microwave heating. The initial copolymerization rate was found to be higher under microwave heating than under thermal heating. The copolymerization parameters were determined using the Fineman–Ross method and were found to be r₁ (NPM) = 0.28 and r₂ (PFS) = 0.86. Increased incorporation of NPM in the copolymers led to an increase in T_g of the copolymers without significantly affecting the hydrophobicity of poly(2,3,4,5,6‐pentafluorostyrene). Thermal stability of the copolymers is also reported. Copyright © 2005 Society of Chemical Industry     

Transformations in Sol-Gel Synthesized Nanoscale Hydroxyapatite Calcined Under Different Temperatures and Time Conditions

Nano-hydroxyapatite (HAP) has been synthesized using sol-gel technique. Calcium nitrate tetrahydrate and potassium dihydrogen phosphate were used as precursors for calcium and phosphorus, respectively. A detailed study on its transformation during calcination at two crucial temperatures has been undertaken. The synthesized nanopowder was calcined at 600 and 800?°C for different time periods. The results revealed that the obtained powders after calcining at 600 and 800?°C are composed of hydroxyapatite nanoparticles. The nano-HAP powders were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA), and BET surface area analyzer techniques. The results indicate that crystallite size as well as crystallinity of synthesized HAP nanopowders increase with increase in calcination temperature as well as calcination time, but the effect of temperature is more prominent as compared to that of calcination time. TEM micrograph revealed the presence of majority of HAP powder particles as agglomerates and a few as individual particles. It also revealed that HAP produced after sintering at 600?°C is 26-45?nm in size, which is well in agreement with the crystallite size calculated using XRD data. TGA study showed the thermal stability of the as-synthesized nano-HAP powder. The BET surface area decreased with increase in calcination temperature and time. The results clearly demonstrate the significant role of calcination parameters on the characteristics of nano-HAP powders.