Mucoadhesive, syringeable drug delivery systems for controlled application of metronidazole to the periodontal pocket: In vitro release kinetics, syringeability, mechanical and mucoadhesive properties

Novel mucoadhesive formulations containing hydroxyethylcellulose (HEC; 3 and 5%, w/w) or Carbopol (3 and 5%, w/w), polycarbophil (PC; 1 and 3%, w/w) and metronidazole (5%, w/w) at pH 6.8 were designed for the treatment of periodontal diseases. Each formulation was characterised in terms of hardness, compressibility, adhesiveness and cohesiveness (using Texture Profile Analysis), drug release, adhesion to a mucin disc (measured as a detachment force using the texture analyser in tensile mode) and, finally, syringeability (using the texture analyser in compression mode). Drug release from all formulations was non-diffusion controlled. Drug release was significantly decreased as the concentration of each polymeric component was increased, due to both the concomitant increased viscosity of the formulations and, additionally, the swelling kinetics of PC following contact with dissolution fluid. Increasing the concentrations of each polymeric component significantly increased formulation hardness, compressibility, adhesiveness, mucoadhesion and syringeability, yet decreased cohesiveness. Increased product hardness, compressibility and syringeability were due to polymeric effects on formulation viscosity. The effects on cohesiveness may be explained both by increased viscosity and also by the increasing semi-solid nature of products containing 5% HEC or Carbopol and PC (1 or 3%). The observations concerning formulation adhesiveness/mucoadhesion illustrate the adhesive nature of each polymeric component. Greatest adhesion was noted in formulations where neutralisation of PC was maximally suppressed. For the most part, increased time of contact between formulation and mucin significantly increased the required force of detachment, due to the greater extent of mucin polymer hydration and interpenetration with the formulations. Significant statistical interactions were observed between the effects of each polymer on drug release and mechanical/mucoadhesive properties. These interactions may be explained by formulatory effects on the extent of swelling of PC. In conclusion, the formulations described offered a wide range of mechanical and drug release characteristics. Formulations containing HEC exhibited superior physical characteristics for improved drug delivery to the periodontal pocket and are now the subject of long-term clinical investigations. (C) 1997 Elsevier Science B.V.

The mechanical and rheological characterisation of implantable medical devices formulated from binary mixtures of cellulose derivatives

This study highlights the potential associated with utilising multi-component polymeric gels to formulate materials that possess unique rheological and mechanical properties. The synergistic effect* and interaction between hydroxyethylcellulose (HEC) and sodium carboxymethylcellulose (NaCMC), polymers which are commonly employed as drug delivery platforms for implantable medical devices (1), have been determined using dynamic, continuous shear and texture profile analysis. * The difference between the actual response of a binary mixture and the sum of the two components comprising the mixture Increases in polymer concentration resulted in an increase in G', G? and ?' whereas tan d decreased. Similarly, significant increases were also apparent in continuous shear and texture analysis. All binary mixtures showed positive synergy values which may suggest associative interaction between the two components.

Risk assessment of potentially toxic elements in agricultural soils and maize tissues from selected districts in Tanzania

A field survey was conducted to investigate the contamination of potentially toxic elements (PTEs) arsenic (As), lead (Pb), chromium (Cr), and nickel (Ni) in Tanzanian agricultural soils and to evaluate their uptake and translocation in maize as proxy to the safety of maize used for human and animal consumption. Soils and maize tissues were sampled from 40 farms in Tanzania and analyzed using inductively coupled plasma-mass spectrometry in the United Kingdom. The results showed high levels of PTEs in both soils and maize tissues above the recommended limits. Nickel levels of up to 34.4 and 56.9mgkg(-1) respectively were found in some maize shoots and grains from several districts. Also, high Pb levels >0.2mgkg(-1) were found in some grains. The grains and shoots with high levels of Ni and Pb are unfit for human and animal consumption. Concentrations of individual elements in maize tissues and soils did not correlate and showed differences in uptake and translocation. However, Ni showed a more efficient transfer from soils to shoots than As, Pb and Cr. Transfer of Cr and Ni from shoots to grains was higher than other elements, implying that whatever amount is assimilated in maize shoots is efficiently mobilized and transferred to grains. Thus, the study recommended to the public to stop consuming and feeding their animals maize with high levels of PTEs for their safety.

Effect of impeller speed on mechanical and dissolution properties of high-shear granules

Impeller speed is one of the most crucial process variables that affect the properties of the granules produced in a high-shear granulator. Several reports can be found in literature that discuss the influence of impeller speed on the granules size. For instance some researchers like Knight report an increase of granule size with impeller speed [1] and [2], while others (Scheaefer et al. and Ramaker et al.) observed a decrease of granules size with increasing impeller speed [3] and [4]. However there is limited work reported in literature on the effect of the impeller speed on the mechanical properties of granules. Mechanical properties are important as they affect the performance of the granules on the other downstream process such as transportation and handling. The work reported here serves to address the missing in knowledge gap regarding the influence of impeller speed on mechanical properties granules. How the granulation system responds to the changes in the impeller speeds depends on binder that is used in the process. For this reason the two extreme cases, of a low viscosity binder system and high viscosity binder system are considered in this research. For low viscosity binder system it was observed that the granule size decreased with increasing impeller speed whilst for the high viscosity binder system the opposite was observed by Knight [1]. The granule strength, the Young's modulus and yield strength of the high viscosity granules increased with increasing impeller speed where as the opposite trends were observed for the low viscosity binder granules.

Influence of nanoclays on mechanical and barrier properties of hydrogenated acrylonitrile butadiene rubber nanocomposites

In this research, two different methods have been investigated for optimising the preparation of hydrogenated acrylonitrile butadiene rubber/clay nanocomposites. Commercially available organoclay (Cloisite 20A) has been considered for the preparation of rubber nanocomposites. A detailed analysis has been made to investigate the morphological structure and mechanical behaviour at room temperature and at elevated temperature. Also the influence of organoclays on permeability has been studied. Structural analysis indicates very good dispersion for a low loading of 5 parts per hundred (phr) amount of nanoclays. Significant improvements in mechanical properties have been observed with the addition of organoclays at both room and elevated temperatures. Even with the low level of addition of nanoclays, there was a remarkable reduction in permeability. © Institute of Materials, Minerals and Mining 2011.

Why are you tall while others are short? Agricultural production and other proximate determinants of global heights

We analyze the proximate determinants of the biological standard of living from a global perspective, namely high-quality nutrition and the disease environment during the nineteenth and twentieth centuries. Until the mid-twentieth century, the local availability of cattle, meat, and milk per capita and the local disease environment mainly determined the stature of the population – and, by implication, how long they lived and how healthy they were. During the late twentieth century, the trade of agricultural products and health-promoting technologies increased in relative importance; hence, the local availabilities became less decisive in explaining height differences.

Nanocomposite-Coated Open-Cell Foams with Tunable Mechanical and Multifunctional Properties

No abstract available

Structure, mechanical, and electrical properties of high-density polyethylene/multi-walled carbon nanotube composites processed by compression molding and blown film extrusion

The structure and properties of melt mixed high-density polyethylene/multi-walled carbon nanotube (HDPE/MWCNT) composites processed by compression molding and blown film extrusion were investigated to assess the influence of processing route on properties. The addition of MWCNTs leads to a more elastic response during deformations that result in a more uniform thick-ness distribution in the blown films. Blown film composites exhibit better mechanical properties due to the enhanced orientation and disentanglement of MWCNTs. At a blow up ratio (BUR) of 3 the breaking strength and elongation in the machine direction of the film with 4 wt % MWCNTs are 239% and 1054% higher than those of compression molded (CM) samples. Resistivity of the composite films increases significantly with increasing BURs due to the destruction of conductive pathways. These pathways can be recovered partially using an appropriate annealing process. At 8 wt % MWCNTs, there is a sufficient density of nanotubes to maintain a robust network even at high BURs.

Effect of poly ethylene glycol on the mechanical and thermal properties of bioactive Poly (ε–caprolactone) melt extrudates for pharmaceutical applications

This paper investigates the effects of polyethylene glycol (PEG), on the mechanical and thermal properties of nalidixic acid/ploy ε-caprolactone (NA)/PCL blends prepared by hot melt extrusion. The blends were characterized by tensile and flexural analysis, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction. Experimental data indicated that the addition of NA caused loss of the tensile strength and toughness of PCL. Thermal analysis of the PCL showed that on addition of the thermally unstable NA, thermal degradation occurred early and was autocatalytic. However, the NA did benefit from the heat shielding provided by the PCL matrix resulting in more thermally stable NA particles. Results show that loading PEG in the PCL had a detrimental effect on the tensile strength and toughness of the blends, reducing them by 20-40%. The partial miscibility of the PCL-PEG system, causes an increase in Tg. While increases in the crystallinity is attributed to the plasticisation effect of PEG and the nucleation effect of NA. The average crystal size increased by 8% upon PEG addition.

Changes in cannabis and tobacco use trajectories from age 17 to age 23

Much like the first volume published in 2011, the second volume of this anthology series gathers a selection of analyses which are empirically based on the data of the Swiss panel study TREE (Transitions from Education to Employment). The contributions of this volume carry on the investigation of the critical transitions during youth and young adulthood, drawing on sociological, economic, psychological and pedagogical research questions and thus highlighting the analytic and pluri-disciplinary research potential of the TREE data. One of the topical foci is the long-term influence of social origin on education and labour market pathways, particularly with regard to access to higher education.

Waxing Ornamental : Reading a Poetics of Excess in Virginia Woolf’s Orlando and Djuna Barnes’s Nightwood

Ce mémoire de maîtrise porte sur une poétique de l’excès dans Orlando de Virginia Woolf et Nightwood de Djuna Barnes comme une stratégie combattant la tendance qu’a le modernisme à dévaloriser l’écriture des femmes comme étant trop ornementale. J’expose comment Ezra Pound, T.S. Eliot, et Wyndham Lewis tentent de récupérer la notion du détail afin d’affirmer une poétique masculin. Je fais appel également aux oeuvres de l’architecte autrichien Adolf Loos qui souligne sa dénonciation de l’ornement comme régressif. Dans Orlando et Nightwood, je considère l’excès associé au corps. Je soutiens que, dans ces textes, les corps dépassent les limites de la représentation moderniste. Je considère aussi comment Orlando et Nightwood font apparaître la narration comme ornement et écrivent excessivement l’histoire et le temps. Pour conclure, je propose une façon de lire l’excès afin de reconceptualiser le potentiel de production de la signification dans des textes modernistes.