Glyceryl Behenate and Its Suitability for Production of Aceclofenac Solid Lipid Nanoparticles

The aim of this study was to explore the use of glyceryl behenate (GB) as a candidate lipid for the production of solid lipid nanoparticles (SLN) using the anti-inflammatory drug, aceclofenac, as an example. SLN were produced using the Gasco microemulsion method with three different lipids, namely GB, glyceryl palmitostearate (GP) and cetyl alcohol (CA). The prepared SLN were subjected to determination of entrapment, zeta potential, particle size, in vitro dissolution, entrapment efficiency and biodistribution. Stable SLN of GB having size 245 ± 5 nm were prepared with a polydispersity index of 0.470. The size range was higher with other lipids i.e., CA and GP. It was found that as the drug lipid molar concentration was raised, particles with a smaller size were obtained irrespective of the nature of the lipid. The surfactant poloxamer 188 gave best results when used at a concentration of 2.5% w/v of dispersion. The study recommends GB as a suitable candidate for the production of SLN.     

Novel Microwave-Assisted Synthesis of Nickel/Carbon (Ni/C) Nanocomposite with Tannin as the Carbon Source

Abstract

Metal/carbon nanocomposites find use in many potential applications, in areas such as batteries, catalysts, inks, polymer additives, and solar cells. Nickel/carbon nanocomposites are widely used as heterogeneous catalysts in oil processing and other catalytic reactions. Here we describe a novel microwave-assisted synthesis of nickel/carbon nanocomposites, achieved within a few minutes, starting from nickel salts and a renewable high-content carbon source, tannin. The carbon precursor is Quebracho tannin, which is a renewable-resource material obtained from the hot-water extraction of Schinopsis lorentzii and Schinopsis balansae, which are indigenous to Argentina and Paraguay. The process involves a simultaneous carbonization of the carbon precursor as well as the reduction of nickel ions to elemental nickel nanoparticles in an ambient atmosphere. Thus, this technique provides a fast, easy, and economical way to produce nickel/carbon nanocomposites without requiring the need for hydrogen or inert gas during the transformation. This technique could be used to synthesize a wide range of other metal/carbon nanocomposites and therefore holds tremendous economic promise. The nanocomposites have a high surface area and may be suitable as high efficiency catalysts.     

Antihypertensive and natriuretic effects of CGS 30440, a dual inhibitor of angiotensin-converting enzyme and neutral endopeptidase 24.11

Dual angiotensin-converting enzyme (ACE)/neutral endopeptidase (NEP) inhibitors, by decreasing angiotensin-II production and by preventing the degradation of atrial natriuretic peptide (ANP), may be useful for the treatment of hypertension and congestive heart failure. The thiol dipeptide CGS 30440 (prodrug of CGS 30008, IC50: ACE/NEP = 19/2 nM) administered to rats (10 mg/kg p.o.) inhibited lung tissue ACE activity by 98% and 61% at 1 and 24 hr (P < .001) and inhibited the angiotensin-I pressor response by 75 to 90% for more than 6 hr. Renal tissue NEP activity was reduced by 80% at 1 hr and 73% at 24 hr (P < .001). In rats supplemented with exogenous ANP, CGS 30440 (1 mg/kg p.o.) elevated the concentration of circulating ANP (133%, P < .025) for 4 hr and increased the excretion of urine (300%, P < .001), sodium (194%, P < .025) and cyclic GMP (238%, P < .005). CGS 30440 (10 mg/kg p.o.) administered to hypertensive rats with aortic ligation between the renal arteries (mean arterial blood pressure, 209 +/- 4 mm Hg) produced a 48 mm Hg blood pressure reduction (P < .001) within 4 hr. CGS 30440 given to cynomolgus monkeys at 2 mg/kg inhibited plasma ACE activity by 96% within 1 hr (P < .001), and this inhibition was maintained for 7 and 21 days in monkeys receiving the compound orally at 2.5 mg/kg b.i.d. These studies demonstrate that CGS 30440 is an orally active agent which produces tissue ACE and NEP inhibition in rats and plasma ACE inhibition in primates and suggest that the compound may be useful in the treatment of hypertension and congestive heart failure.     

Diffusion of phosphorus in CdTe

The diffusion of phosphorus in CdTe was measured as a function of anneal time and temperature in the temperature range 600–900°C. The diffusion anneals were carried out in evacuated silica capsules mainly with traces of radioactive phosphorus in the capsule along with sufficient cadmium metal to maintain a saturated vapor pressure over the CdTe slice throughout each anneal. The concentration profiles were measured using a radiotracer sectioning technique. Diffusion anneals were carried out also using other conditions, including some with excess tellurium in the capsule in place of the cadmium. The diffusion profiles were single component. The standard erfc function gave satisfactory fits to the profiles which were Fickian in nature except for short anneal times at intermediate temperatures. When the diffusivity was plotted on an Arrhenius graph, a straight line was obtained giving an activation energy of 2.0 eV. The surface concentration at each temperature was independent of time and varied in value between 1.5×10¹⁶ cm⁻³ at 600°C to 1×10¹⁸ cm⁻³ at 900°C. When the results were plotted on an Arrhenius graph, the results gave a straight line with an activation energy of 1.3 eV.     

Non-equilibrium synthesis of new materials

Over the last few decades it has become apparent that metallic materials produced by conventional casting processes have reached their limit. Some improvements have been obtained by rapidly cooling bulk alloys but major increases have required the development of rapid solidification processes. However, more radical approaches, such as mechanical alloying (MA) and physical vapour deposition (PVD), are also being explored and these are the subject of this paper. This paper describes the physical basis behind the development of MA and PVD in the Structural Materials Centre and presents the results of some materials development programmes on aluminium, magnesium and titanium based materials.     

Nanostructural physical and chemical information derived from the unit cell scattering amplitudes of a spider dragline silk

Characterizing the nanostructures of spider major ampullate (dragline) silks is an important step in understanding the origin of their high mean strength and toughness, and for producing polymeric analogs that mimic these properties. Here we present transmission electron microscopy (TEM) diffraction patterns and an accompanying structure factor analysis for the dragline silk of Latrodectus hesperus (black widow spider). The chemical and physical composition of crystalline regions in this silk fiber was studied by manipulating the positions and size of amino acid side groups in a theoretical model, and comparing the expected unit cell scattering amplitudes with experimental electron diffraction patterns. The results suggest that—in addition to the smaller amino acid side groups such as alanine, glycine and serine—some of the bulkier amino acid side groups such as tyrosine and leucine are included in the crystalline fraction of the major ampullate silk. The structure factor analysis also demonstrates a marked sensitivity of the respective diffraction spot intensities to a slight change in both side group position and side group bulkiness. These observations point to a unique function for TEM in characterizing silk and other polymers.     

Greatly Enhanced Thermal Contraction at Room Temperature by Carbon Nanotubes

A crosslinked polyarylamide polymer exhibits novel photothermal behavior, that is, reversible giant contraction in response to near infrared irradiation in addition to normal thermal expansion. Such reversibility is seldom found in a polymeric system. Due to the amphiphilic nature of the benzocyclobutene‐containing triblock copolymer precursor with polyarylamide interacting strongly with few‐walled carbon nanotubes (FWCNTs), they are dispersed extremely well in the polymer solution at a loading up to at least 5 wt%. Also, strained carbon double bonds on FWCNTs can directly form covalent linkages with the benzocyclobutene groups on the polymer chains via cyclo‐addition. The incorporation of FWCNTs increases mechanical stiffness two‐fold. Exploiting the ability of FWCNTs to effectively convert photon energy into heat and to provide conductive pathways, the NIR‐induced unexpected contraction stress can be further increased dramatically. The systematic study suggests that there is an optimal CNT concentration. At 3 wt% FWCNTs, the enhancement factor for contraction stress is almost 24: 166 kPa with 3 wt% FWCNTs versus 7 kPa without FWCNTs. The colossal photothermal contraction stress generated by this new composite film at ambient condition upon NIR stimulation can lead to the development of new NIR actuators, for example, for biological applications, and create new material platforms for green energy conversion.     

Measurements and Analysis of Photochemical Oxidants and Trace Gases in the Rural Troposphere of the Southeast United States

Ambient concentrations of photochemical oxidants (O₃, PAN, HNO₃, H₂O₂) and various trace species including reactive nitrogen compounds as well as total NO_y were measured during June and early July 1992 at a rural site, SONIA, in the central Piedmont region of North Carolina, as a part of the Southern Oxidants Study. The measurements were made in an effort to provide a comprehensive understanding of tropospheric photochemistry in the rural Southeastern United States. NO_y, NO₂, and NO showed diurnal variations with maxima in the morning between 0600 and 0900 EST. The maximum NO_y, NO, and NO₂ concentrations reached were 14.5, 5.4, and 7.8 ppbv, respectively. The mean NO_y concentration was found to be 2.63 ± 1.72 ppbv (n = 819) with an average daily maximum of 3.6 ppbv. The mean concentrations of NO and NO₂ for the entire period of measurement were found to be 0.18 ± 0.37 ppbv (n = 794) and 1.31 ± 0.99 ppbv/(n = 769). H₂O₂, HNO₃, and PAN showed diurnal variation with maxima in the afternoon and minima at night. Mean concentrations were found to be 0.52 ± 0.36 ppbv (n = 312), 0.67 ± 0.33 ppbv (n = 250), and 0.41 ± 0.24 ppbv (n = 578). The NO_x/NO_y ratio was used as an indicator of the chemical age of airmasses and the ratio showed strong positive correlations with the photochemical oxidants HNO₃ (r = 0.76), PAN (r= 0.68), and O₃ (r = 0.79) measured at the site. The relationship between the accumulation rate of O₃ and the deviation from the photostationary state was examined based on the measured PSS constant obtained from the values of [O₃], [NO], and [NO₂] measured at the site.