Systematic screening of compressed ODT excipients:cellulosic versus non-cellulosic

The successful development of compressed ODTs utilises low compression forces to create a porous structure whereby excipients are added to enhance wicking/swelling action or provide strength to the fragile tablet framework. In this work, a systematic investigation comparing materials from two different categories was employed to understand their functionality in binary mixture tablets of the most commonly used diluent mannitol. Cellulose based excipients such as HPC (SSL-SFP), L-HPC (NBD-022) and MCC (Avicel PH-102) were compared with non-cellulosic materials such as PEO (POLYOX WSR N-10) and Crospovidone (XL-10). Pure excipient properties were studied using Heckel Plot, compressibility profile, SEM and XRPD, whereas the prepared binary mixture compacts were studied for hardness, disintegration time and friability. Results from our investigation provide insight into differences encountered in product performance of ODT upon inclusion of additional materials. For example, non-cellulosic excipients Polyox and Crospovidone showed higher plasticity (Py values 588 and 450MPa) in pure form but not in binary mixtures of mannitol. Cellulosic excipients, nonetheless, offer faster disintegration (<30 sec) specifically L-HPC and MCC tablets. Disintegration time for tablets with fully substituted-HPC was prolonged (200-500 sec) upon increasing concentration between 1-10% due to gelation/matrix formation. It can be concluded that despite the reasonably good plasticity of both cellulosic and non-cellulosic excipients in pure form, the mechanical strength in binary mixtures is negatively impacted by the fragmentation/fracture effect of mannitol. © 2014 Bentham Science Publishers.

Microscale mesoarrays created by dip-pen nanolithography for screening of protein-protein interactions

Using microarrays to probe protein-protein interactions is becoming increasingly attractive due to their compatibility with highly sensitive detection techniques, selectivity of interaction, robustness and capacity for examining multiple proteins simultaneously. The major drawback to using this approach is the relatively large volumes and high concentrations necessary. Reducing the protein array spot size should allow for smaller volumes and lower concentrations to be used as well as opening the way for combination with more sensitive detection technologies. Dip-Pen Nanolithography (DPN) is a recently developed technique for structure creation on the nano to microscale with the capacity to create biological architectures. Here we describe the creation of miniaturised microarrays, 'mesoarrays', using DPN with protein spots 400× smaller by area compared to conventional microarrays. The mesoarrays were then used to probe the ERK2-KSR binding event of the Ras/Raf/MEK/ERK signalling pathway at a physical scale below that previously reported. Whilst the overall assay efficiency was determined to be low, the mesoarrays could detect KSR binding to ERK2 repeatedly and with low non-specific binding. This study serves as a first step towards an approach that can be used for analysis of proteins at a concentration level comparable to that found in the cellular environment.

Wear and corrosion of mechanical seals

Mechanical seals are used extensively to seal machinery such as pumps, mixers and agitators in the oil, petrochemical and chemical industries. The performance of such machinery is critically dependent on these devices. Seal failures may result in the escape of dangerous chemicals, possibly causing injury or loss of life. Seal performance is limited by the choice of face materials available. These range from cast iron and stellited stainless steel to cemented and silicon carbides. The main factors that affect seal performance are the wear and corrosion of seal faces. This research investigated the feasibility of applying surface coating/treatments to seal materials, in order to provide improved seal performance. Various surface coating/treatment methods were considered; these included electroless nickel plating, ion plating, plasma nitriding, thermal spraying and high temperature diffusion processes. The best wear resistance, as evaluated by the Pin-on-Disc wear test method, was conferred by the sprayed tungsten carbide/nickel/tungsten-chromium carbide deposit, produced by the high energy plasma spraying (Jet-Kote) process. In general, no correlation was found between hardness and wear resistance or surface finish and friction. This is due primarily to the complexity of the wear and frictional oxidation, plastic deformation, ploughing, fracture and delamination. Corrosion resistance was evaluated by Tafel extrapolation, linear polarisation and anodic potentiodynamic polarisation techniques. The best corrosion performance was exhibited by an electroless nickel/titanium nitride duplex coating due to the passivity of the titanium nitride layer in the acidified salt solution. The surface coating/treatments were ranked using a systematic method, which also considered other properties such as adhesion, internal stress and resistance to thermal cracking. The sealing behaviour of surface coated/treated seals was investigated on an industrial seal testing rig. The best sealing performances were exhibited by the Jet-Kote and electroless nickel silicon carbide composite coated seals. The failure of the electroless nickel and electroless nickel/titanium nitride duplex coated seals was due to inadequate adhesion of the deposits to the substrate. Abrasion of the seal faces was the principal wear mechanism. For operation in an environment similar to the experimental system employed (acidified salt solution) the Jet-Kote deposit appears to be the best compromise.

Computer-aided design, synthesis and screening of potential anti-microbial compounds

The work presented in this thesis falls into three main categories: The design and synthesis of potential anti-tuberculosis drugs targeting a mycobacterial esterase and the enzyme dUTPase; synthesis and anti-microbial SAR studies on a set of carboxamidrazones; synthesis and anti-microbial SAR studies on a set of thiosem icarbazones.

Analysis of variables measured in the visual screening of University of Birmingham freshmen and a critical review of visual screening methods and approach

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Systematic screening of compressed ODT excipients : cellulosic versus non-cellulosic

The successful development of c ompressed ODTs utilises low compression force s to create a porous structure whereby excipients are added to enhance wicking/swelling action or p rovide strength to the fragile tablet framework. In this work, a systematic investigation comparing materials from two different categories was employed to understand their functionality in binary mixture tablets of the most commonly used diluent mannitol. Cellulose based excipients such as HPC (SSL-SFP), L-HPC (NBD -022) and MCC (Avicel PH -102 ) were compared with non -cellulosic materials such as PEO (POLYOX WSR N -10) and Crospovidone (XL -10). P ure excipient properties were studied using Heckel Plot, compre ssibility profile, SEM and XR PD, w hereas the prepared binary mixture compacts were studied for hardness, disintegration time and friability. Results from our investigation provide insight into differences encountered in product performance of ODT upon inclusion of additional materials. For example, non -cellulosic excipients Polyox and Crospovidone showed higher plasticity (Py values 588 and 450 MPa) in pure form but not in binary mixtures of mannitol . Cellulosic excipients, nonetheless, offer faster disintegration (

Synthesis and screening of potential antimicrobial compounds

Tuberculosis (TB), an infection caused by human pathogen Mycobacterium tuberculosis, continues to kill millions each year and is as prevalent as it was in the pre-antimicrobial era. With the emergence of continuously-evolving multi-drug resistant strains (MDR) and the implications of the HIV epidemic, it is crucial that new drugs with better efficacy and affordable cost are developed to treat TB. With this in mind, the first part of this thesis discusses the synthesis of libraries of derivatives of pyridine carboxamidrazones, along with cyclised (1,2,4-triazole and 1,2,4-oxadiazole) and fluorinated analogues. Microbiological screening against M. tuberculosis was carried out at the TAACF, NIAID and IDRI (USA). This confirmed the earlier findings that 2-pyridyl-substituted carboxamidrazones were more active than the 4-pyridyl-substituted carboxamidrazones. Another important observation was that upon cyclisation of these carboxamidrazones, a small number of the triazoles retained their activity while in most of the remaining compounds the activity was diminished. This might be attributed to the significant increase in logP value caused by cyclisation of these linear carboxamidrazones, resulting in high lipophilicity and decreased permeability. Another reason might be that the rigidity conferred upon the compound due to cyclisation, results in failure of the compound to fit into the active site of the putative target enzyme. In order to investigate the potential change to the compounds’ metabolism in the organism and/or host, the most active compounds were selected and a fluorine atom was introduced in the pyridine ring. The microbiological results shows a drastic improvement in the activity of the fluorinated carboxamidrazone amides as compared to their non fluorinated counterpart. This improvement in the activity could possibly be the result of the increased cell permeability caused by the fluorine. In a subsidiary strand, a selection of long-chain , -unsaturated carboxylic esters, -keto, -hydroxy carboxylic esters and -keto, -hydroxy carboxylic esters, structurally similar to mycolic acids, were synthesised. The microbiological data revealed that one of the open chain compound was active against the Mycobacterium tuberculosis H37Rv strain and some resistant isolates. The possible compound activity could be its potential to disrupt mycobacterial cell wall synthesis by interfering with the FAS-II pathway.

Toward the discovery of vaccine adjuvants:coupling in silico screening and in vitro analysis of antagonist binding to human and mouse CCR4 receptors

Background Adjuvants enhance or modify an immune response that is made to an antigen. An antagonist of the chemokine CCR4 receptor can display adjuvant-like properties by diminishing the ability of CD4+CD25+ regulatory T cells (Tregs) to down-regulate immune responses. Methodology Here, we have used protein modelling to create a plausible chemokine receptor model with the aim of using virtual screening to identify potential small molecule chemokine antagonists. A combination of homology modelling and molecular docking was used to create a model of the CCR4 receptor in order to investigate potential lead compounds that display antagonistic properties. Three-dimensional structure-based virtual screening of the CCR4 receptor identified 116 small molecules that were calculated to have a high affinity for the receptor; these were tested experimentally for CCR4 antagonism. Fifteen of these small molecules were shown to inhibit specifically CCR4-mediated cell migration, including that of CCR4+ Tregs. Significance Our CCR4 antagonists act as adjuvants augmenting human T cell proliferation in an in vitro immune response model and compound SP50 increases T cell and antibody responses in vivo when combined with vaccine antigens of Mycobacterium tuberculosis and Plasmodium yoelii in mice.

Tissue engineering of co-cultured skin substitutes using biocomposite membranes based on collagen and polycaprolactone

The preparation and characterisation of collagen: PCL, gelatin: PCL and gelatin/collagen:PCL biocomposites for manufacture of tissue engineered skin substitutes are reported. Films of collagen: PLC, gelatin: PCL (1:4, 1:8 and 1:20 w/w) and gelatin/collagen:PCL (1:8 and 1:20 w/w) biocomposites were prepared by impregnation of lyophilised collagen and/or gelatin mats by PCL solutions followed by solvent evaporation. In vitro assays of total protein release of collagen:PCL and gelatin: PCL biocomposite films revealed an expected inverse relationship between the collagen release rate and the content of synthetic polymer in the biocomposite samples that may be exploited for controlled presentation and release of biopharmaceuticals such as growth factors. Good compatibility of all biocomposite groups was proven by interaction with 3T3 fibroblasts, normal human epidermal keratinocytes (NHEK), and primary human epidermal keratinocytes (PHEK) and dermal fibroblasts (PHDF) in vitro respectively. The 1:20 collagen: PCL materials exhibiting good cell growth curves and mechanical characteristics were selected for engineering of skin substitutes in this work. The tissue-engineered skin model based on single-donor PHEK and PHDF with differentiated confluent epidermal layer and fibrous porous dermal layer was then developed successfully in vitro proven by SEM and immunohistochemistry assay. The following in vivo animal study on athymic mice revealed early complete wound healing in 10 days and good integration of co-cultured skin substitutes with adjacent mice skin structures. Thus the co-cultured skin substitutes based on 1:20 collagen: PCL biocomposite membranes was proven in principle. The approach to skin modelling reported here may find application in wound treatment, gene therapy and screening of new pharmaceuticals.

The application of knowledge based expert systems to mechanical engineering design

Investigation of the different approaches used by Expert Systems researchers to solve problems in the domain of Mechanical Design and Expert Systems was carried out. The techniques used for conventional formal logic programming were compared with those used when applying Expert Systems concepts. A literature survey of design processes was also conducted with a view to adopting a suitable model of the design process. A model, comprising a variation on two established ones, was developed and applied to a problem within what are described as class 3 design tasks. The research explored the application of these concepts to Mechanical Engineering Design problems and their implementation on a microcomputer using an Expert System building tool. It was necessary to explore the use of Expert Systems in this manner so as to bridge the gap between their use as a control structure and for detailed analytical design. The former application is well researched into and this thesis discusses the latter. Some Expert System building tools available to the author at the beginning of his work were evaluated specifically for their suitability for Mechanical Engineering design problems. Microsynics was found to be the most suitable on which to implement a design problem because of its simple but powerful Semantic Net Knowledge Representation structure and the ability to use other types of representation schemes. Two major implementations were carried out. The first involved a design program for a Helical compression spring and the second a gearpair system design. Two concepts were proposed in the thesis for the modelling and implementation of design systems involving many equations. The method proposed enables equation manipulation and analysis using a combination of frames, semantic nets and production rules. The use of semantic nets for purposes other than for psychology and natural language interpretation, is quite new and represents one of the major contributions to knowledge by the author. The development of a purpose built shell program for this type of design problems was recommended as an extension of the research. Microsynics may usefully be used as a platform for this development.

Dynamic behaviour of rotary mechanical seals

This thesis covers both experimental and computer investigations into the dynamic behaviour of mechanical seals. The literature survey shows no investigations on the effect of vibration on mechanical seals of the type common in the various process industries. Typical seal designs are discussed. A form of Reynolds' equation has been developed that permits the calculation of stiffnesses and damping coefficients for the fluid film. The dynamics of the mechanical seal floating ring have been investigated using approximate formulae, and it has been shown that the floating ring will behave as a rigid body. Some elements, such as the radial damping due to the fluid film, are small and may be neglected. The equations of motion of the floating ring have been developed utilising the significant elements, and a solution technique described. The stiffness and damping coefficients of nitrile rubber o-rings have been obtained. These show a wide variation, with a constant stiffness up to 60 Hz. The importance of the effect of temperature on the properties is discussed. An unsuccessful test rig is described in the appendices. The dynamic behaviour of a mechanical seal has been investigated experimentally, including the effect of changes of speed, sealed pressure and seal geometry. The results, as expected, show that high vibration levels result in both high leakage and seal temperatures. Computer programs have been developed to solve Reynolds' Equation and the equations of motion. Two solution techniques for this latter program were developed, the unsuccesful technique is described in the appendices. Some stability problems were encountered, but despite these the solution shows good agreement with some of the experimental conditions. Possible reasons for the discrepancies are discussed. Various suggestions for future work in this field are given. These include the combining of the programs and more extensive experimental and computer modelling.

Effects of fibre reinforcement on the mechanical properties of brushite cement

In this study the effect of structure and amount of polyglactin fibre incorporation into a brushite forming calcium phosphate cement system and the effect of mechanical compaction on the fibre modified system were investigated. In comparison the effect of resorbable polycaprolactone surface coating of cement specimens was investigated. The results showed that, apart from the mechanical properties of the reinforcing material, the structure of the incorporated fibres, regular or random, is crucial for the resulting flexural strength and modulus of elasticity. Fibre reinforcement could also be combined with mechanical compaction of the cement/fibre composite paste leading to a possible 7-fold increase in flexural strength or an almost 5-fold increase in modulus of elasticity. Reinforcement of the tensile surface of cement grafts may ultimately improve strength where required, especially in conjunction with bone fixation devices. © 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A collagen IV matrix is required for guinea pig gastric epithelial cell monolayers to provide an optimal model of the stomach surface for biopharmaceutical screening

The surface epithelial cells of the stomach represent a major component of the gastric barrier. A cell culture model of the gastric epithelial cell surface would prove useful for biopharmaceutical screening of new chemical entities and dosage forms. Primary cultures of guinea pig gastric mucous epithelial cells were grown on filter inserts (Transwells®) for 3 days. Tight-junction formation, assessed by transepithelial electrical resistance (TEER) and permeability of mannitol and fluorescein, was enhanced when collagen IV rather than collagen I was used to coat the polycarbonate filter. TEER for cells grown on collagen IV was close to that obtained with intact guinea pig gastric epithelium in vitro. Differentiation was assessed by incorporation of [ 3H]glucosamine into glycoprotein and by activity of NADPH oxidase, which produces superoxide. Both of these measures were greater for cells grown on filters coated with collagen I than for cells grown on plastic culture plates, but no major difference was found between cells grown on collagens I and IV. The proportion of cells, which stained positively for mucin with periodic acid Schiff reagent, was greater than 95% for all culture conditions. Monolayers grown on membranes coated with collagen IV exhibited apically polarized secretion of mucin and superoxide, and were resistant to acidification of the apical medium to pH 3.0 for 30 min. A screen of nonsteroidal anti-inflammatory drugs revealed a novel effect of diclofenac and niflumic acid in reversibly reducing permeability by the paracellular route. In conclusion, the mucous cell preparation grown on collagen IV represents a good model of the gastric surface epithelium suitable for screening procedures. © 2005 The Society for Biomolecular Screening.