Browsing by Author "Armitage, David"
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Item Metadata only Chemical, corrosion and topographical analysis of stainless steel implants after different implantation periods.(2008) Chrzanowski, W.; Armitage, David; Knowles, J.; Szade, J.; Korelacki, W.; Marciniak, J.Item Metadata only Degradation studies on biodegradable nanocomposite based on polycaprolactone/polycarbonate (80:20%) polyhedral oligomeric silsesquioxane.(Wiley, 2009) Raghunath, J.; Georgiou, G.; Armitage, David; Nazhat, S.; Sales, K.; Butler, P. E.; Seifalian, A.Item Metadata only Development of aqueous ternary nanomatrix films: a novel ‘green’ strategy for the delivery of poorly soluble drugs(Elsevier, 2016-11-05) Kola-Mustapha, A.; Armitage, David; Abioye, A. O.Aqueous polymeric films have potentially great values in drug development, particularly in controlled drug release and taste masking strategies. However the progressive polymer-particle coalescence that occurs randomly during film formation, curing and storage may render the film less permeable leading to erratic and unpredictable drug release profile. The focus of this study was to investigate the impacts of the in situ formation of polymer-drug nanoconjugate, at the interfacial nano-domains of two oppositely charged polymers, on the mechanism of film formation and to prepare aqueous ternary polymer-drug-polymer nanomatrix films as a novel green strategy for the delivery of ibuprofen, a model poorly soluble drug. Composite and Layer-by-Layer films were prepared by aqueous casting technique using the concept of combined polymer-drug self-assembly and polyelectrolyte complexation. The plain and drug-loaded nanomatrix films were characterized using SEM, AFM, FTIR, DSC and TGA. Ibuprofen formed spherical core-shell microstructures (4.55 - 9.73 μm) in gellan film. However in the presence of cationic dextran (Ddex), nanoconjugates (61.49±5.97 - 447.52±37.51 nm) were formed within the core of the film matrix. The composite films exhibited reduced tensile strength and lower elastic modulus with optimal conjugation efficiency of 98.14±1.19%, which correlates with higher dissolution efficiency (99.76%) compared to 47.37% in layer-by-layer (LbL) films, dictated by Ddex concentration. Generally, the mechanism of drug release was by Fickian diffusion, however anomalous transport or polymer relaxation was also observed at higher concentration of Ddex. This study demonstrated the potential application of aqueous drug-loaded nanomatrix films as controlled drug delivery strategy for ibuprofen, a model poorly soluble drug.Item Metadata only A DNA nanostructure for the functional assembly of chemical groups with tunable stoichiometry and defined nanoscale geometry(Wiley Blackwell, 2009) Mitchell, Nick; Schlapak, Robert; Kastner, Markus; Armitage, David; Chrzanowski, W.; Riener, Johannes; Hinterdorfer, Peter; Ebner, Andreas; Howorka, StefanItem Metadata only Effect of surface treatment on the bioactivity of nickel–titanium.(Elsevier, 2008) Chrzanowski, W.; Abou Neel, E.; Armitage, David; Knowles, J.Item Embargo Electrospun PVP-indomethacin constituents for transdermal dressings and drug delivery devices(Elsevier, 2014-07) Rasekh, M.; Karavasili, Chirstina; Soong, Yi Ling; Bouropoulos, Nikolaos; Morris, M. A.; Armitage, David; Li, Xiang; Fatouros, Dimitrios; Ahmad, Z.A method in layering dressings with a superficial active layer of sub-micrometer scaled fibrous structures is demonstrated. For this, polyvinylpyrolidone (PVP) - indomethacin (INDO) fibres (5% w/v PVP, 5% w/w indomethacin, using a 50:50 ethanol-methanol solvent system) were produced at different flow rates (50μL/min and 100μL/min) via a modified electrospinning device head (applied voltage varied between 15±2kV). We further assessed these structures for their chemical, physical and morphological properties using SEM, AFM, DSC, XRD, FTIR and HPLC-UV. The average diameter of the resulting 3D (∼500nm in height) PVP-INDO fibres produced at 50μL/min flow rate was 2.58±0.30μm, while the diameter almost doubled (5.22±0.83μm) when the flow rate was doubled. However, both of these diameters were appreciably smaller than the existing dressing fibres (∼30μm), which were visible even when layered with the active spun fibres. Indomethacin was incorporated in the amorphous state. The encapsulation efficiency was 75% w/w, with complete drug release in 45minutes. The advantages are the ease of fabrication and deposition onto any existing normal or functionalised dressing (retaining the original fabric functionality), elimination of topical product issues (application, storage and transport), rapid release of active and controlled loading of drug content (fibre layer). Electrospun PVP-indomethacin constituents for transdermal dressings and drug delivery devices.Item Metadata only Impaired bacterial attachment to light activated Ni–Ti alloy.(Elsevier, 2010) Chrzanowski, W.; Valappil, S.; Dunnill, C.; Abou Neel, E.; Lee, Kevin; Parkin, I.; Wilson, Michael; Armitage, David; Knowles, J.Item Metadata only In vitro studies on the influence of surface modification of Ni-Ti alloy on human bone cells.(Wiley Liss, 2010) Chrzanowski, W.; Abou Neel, E.; Armitage, David; Zhao, X.; Knowles, J.; Salih, V.Item Embargo A multi-faceted approach to determining the efficacy of metal and metal oxide nanoparticles against bacterial biofilms(2018-10-01) Tejpal, Jyoti; Cross, R. B. M.; Owen, Lucy; Paul, Shashi; Jenkins, R. O.; Armitage, David; Laird, KatieAntibacterial efficacy of nanoscale silver, copper (II) oxide and zinc oxide were assessed against Pseudomonas aeruginosa and Staphylococcus aureus biofilms in solution and on surfaces. Using a Center for Disease Control biofilm reactor, minimum biofilm reduction concentrations, the coefficient of determination (R2) and log(10) reductions were determined. Atomic absorption spectroscopy, scanning electron microscopy and confocal laser scanning microscopy were used to assess the disruption of the biofilms. The efficacy of thin films of zinc oxide and silver deposited via magnetron sputtering and thermal evaporation respectively was also assessed. Minimum biofilm reduction concentrations of zinc oxide or silver nanoparticles were 256 or 50 µg/ml for P. aeruginosa and 16 or50 µg/ml for S. aureus respectively. When tested in combination the nanoparticles concentrations were at least halved resulting in significant (p ≤0.05) biofilm reductions of 3.77 log(10) - 3.91 log(10). Biofilm growth on thin films resulted in reductions of up to 1.82 log(10). The results suggest that nanoparticle suspensions and thin films of zinc oxide and may have potential as antimicrobial treatments for hard to eliminate biofilms in a clinical environment.Item Metadata only Nanomechanical evaluation of nickel–titanium surface properties after alkali and electrochemical treatments.(2008) Chrzanowski, W.; Abou Neel, E.; Armitage, David; Lee, Kevin; Walke, W.; Knowles, J.Item Metadata only Nanoscale DNA tetrahedra improve biomolecular recognition on patterned surfaces.(Wiley, 2012) Schlapak, Robert; Danzberger, J.; Armitage, David; Morgan, D.; Ebner, Andreas; Hinterdorfer, Peter; Pollheimer, P.; Gruber, H. J.; Schaffler, F.; Howorka, StefanItem Metadata only Reduction of surface contamination and biofilms of Enterococcus sp and Staphylococcus aureus using a citrus-based vapour.(W. B. Saunders, 2012) Laird, Katie; Armitage, David; Phillips, C.Item Metadata only Selective protein and DNA adsorption on PLL-PEG films modulated by ionic strength.(Royal Society of Chemistry, 2009) Schlapak, Robert; Armitage, David; Saucedo-Zeni, N.; Chrzanowski, W.; Caruana, D.; Howorka, Stefan; Hohage, M.Item Metadata only Semipermeable poly(ethylene glycol) films: the relationship between permeability and molecular structure of polymer chains(Royal Society of Chemistry, 2009) Schlapak, Robert; Armitage, David; Caruana, D.; Howorka, StefanWe describe size-selective semipermeable poly(ethylene glycol) (PEG) films which avoid the nonspecific absorption of large proteins but permit the passage of small target molecules. The size threshold for permeation through the PEG films on indium-tin oxide surfaces was characterised using cyclovoltammetry and redox-active probes of 0.3 and 0.6 nm diameter. The permeation was dependent on the molecular weight of PEG and the different conformational preferences of the polymer chains. PEG 5000 D with a looped and dynamically changing structure provided a porous and easily permeable meshwork for the passage of small molecules. In contrast, parallel aligned and helical PEG 500 chains represented a denser molecular sieve which is only permeable for small molecules 0.3 nm in size. By describing the relationship between the molecular structure and an important physiochemical property of surface-tethered PEG films, our findings on controllable semipermeable interfaces may be exploited for electrical sensor surfaces.Item Metadata only Surface modification of microspheres with steric stabilizing and cationic polymers for gene delivery.(ACS, 2008) Davies, O.; Head, L.; Armitage, David; Pearson, E.; Davies, M.; Marlow, M.; Stolnik, S.Item Metadata only Surface preparation of bioactive Ni–Ti alloy using alkali, thermal treatments and spark oxidation.(Springer, 2008) Chrzanowski, W.; Abou Neel, E.; Armitage, David; Knowles, J.