- Co-Founder and Chief Technical Officer of Arterius Limited, Leeds, United KIngdomedit
Research is continually under way to improve biocompatibility performance in biomaterials. This article discusses a technique for the covalent attachment of heparin and other drugs onto a variety of polymer and metal surfaces. It offers... more
Research is continually under way to improve biocompatibility performance in biomaterials. This article discusses a technique for the covalent attachment of heparin and other drugs onto a variety of polymer and metal surfaces. It offers the potential to improve haemocompatibility and lubricity in a number of medical device applications as well as new drug-delivery systems.
Research Interests: Materials Science, Drug delivery, Nanotechnology, Polymers, Lubrication, and 15 moreMedicine, Adsorption, Hemorheology, Biocompatibility, Humans, Heparin, Pubmed, Blood, Drug Delivery Systems, Medical Device Technology, Anticoagulants, Metals, Lubricity, Biocompatible Materials, and Equipment Design
Research Interests:
Drugs which inhibit platelet function have been coupled to a variety of polymers and the effects of these adducts on platelet aggregation have been examined (prostaglandin analogue BW 245C, dipyridamole and theophylline)
Research Interests:
Research Interests:
Much headway is being made in the quest to improve biocompatibility and reduce restenosis related to the use of stents. This article reviews the research data involving stent coatings and surface treatments techniques. It also describes... more
Much headway is being made in the quest to improve biocompatibility and reduce restenosis related to the use of stents. This article reviews the research data involving stent coatings and surface treatments techniques. It also describes recent work in surface modification of metallic stents and covalent coupling of drugs that employs a novel bonding process.
Research Interests:
A permanent, molecular level layer, water based surface modification technology has been developed that can be applied to the external and internal polymer surfaces of high value catheters. Its characteristics, advantages and applications... more
A permanent, molecular level layer, water based surface modification technology has been developed that can be applied to the external and internal polymer surfaces of high value catheters. Its characteristics, advantages and applications are discussed here.
Research Interests:
Research Interests:
Research Interests:
Despite good results in reducing in-stent restenosis during cardiac stenting procedures, a number of issues in the application of drug-eluting stents still challenge the industry. These include drug-elution kinetics and long-term... more
Despite good results in reducing in-stent restenosis during cardiac stenting procedures, a number of issues in the application of drug-eluting stents still challenge the industry. These include drug-elution kinetics and long-term biocompatibility. Some of the latest developments in these areas are described here.
Research Interests:
A method of bonding together a polymer and bitumen comprises the steps of functionalising the surface of each material and bonding the modified materials with a crosslinking agent. The modification of the polymer and bitumen is preferably... more
A method of bonding together a polymer and bitumen comprises the steps of functionalising the surface of each material and bonding the modified materials with a crosslinking agent. The modification of the polymer and bitumen is preferably performed by treating the respective materials with an oxidising solution, such as chromic acid comprising potassium dichromate, water, and sulphuric acid. The polymer may be in the form of strips derived from a recycled plastics or rubber material. A particulate material is also disclosed, wherein the material comprises modified polymer particles bonded to modified bitumen with a crosslinking agent. The resulting product may be mixed with aggregates, such as gravel, cement, or pulverised fuel ash. The particulate material is stated to be used as chippings or for surface dressing, wherein the surface is a road, airfield, or pavement.
Research Interests:
Research Interests:
The invention relates to a metal surface, glass or ceramics treated to improve its compatibility with biological materials such as blood or blood related products. Treatment involves covalent bonding of the surface by functionally... more
The invention relates to a metal surface, glass or ceramics treated to improve its compatibility with biological materials such as blood or blood related products. Treatment involves covalent bonding of the surface by functionally catalytic molecules, each of which has at least one alkoxysilane group which can form at least one covalent first link by reaction with the oxide or hydroxide of said surface and within another group you can participate in a free radical polymerization. The free radical polymerization from said functional molecule is then affected to build chains biocompatible polymers and / or hydrophilic. The compatibility of the metal surface with biological materials can be further enhanced by links with bioactive molecules such as heparin or heparin derivative molecules with the polymer chains. Suitable metal surfaces are those of medical devices such as heat exchangers, valves and coronary and peripheral guidewires used in angioplasty.
Research Interests:
Purpose The ArterioSorb$$^{\rm{{TM}}}$$ TM bioresorbable scaffold (BRS) developed by Arterius Ltd is about to enter first in man clinical trials. Previous generations of BRS have been vulnerable to brittle fracture, when expanded via... more
Purpose The ArterioSorb$$^{\rm{{TM}}}$$ TM bioresorbable scaffold (BRS) developed by Arterius Ltd is about to enter first in man clinical trials. Previous generations of BRS have been vulnerable to brittle fracture, when expanded via balloon inflation in-vivo, which can be extremely detrimental to patient outcome. Therefore, this study explores the effect of variable ring length and strut width (as facilitated by the ArterioSorb$$^{\rm{{TM}}}$$ TM design) on fracture resistance via analysis of the distribution of equivalent plastic strain in the scaffold struts post expansion. Scaffold performance is also assessed with respect to side branch access, radial strength, final deployed diameter and percentage recoil. Methods Finite element analysis was conducted of the crimping, expansion and radial crushing of five scaffold designs comprising different variations in ring length and strut width. The Abaqus/Explicit (DS SIMULIA) solution method was used for all simulations. Direct compari...
Research Interests:
Research Interests:
A method of treating an article having oxide or hydroxide on its surface, said method comprising the steps of: priming said surface by contacting with an alkoxysilane in an aprotic organic solvent in the presence of an acid catalyst to... more
A method of treating an article having oxide or hydroxide on its surface, said method comprising the steps of: priming said surface by contacting with an alkoxysilane in an aprotic organic solvent in the presence of an acid catalyst to molecules alkoxysilane react with oxide or hydroxide of said surface to form covalent bonds, the alkoxysilane one or more amino, hydroxyl, carboxylic acid or anhydride comprising acid; and covalently coupling a polymer to said surface through said barley alkoxysilane.
Research Interests:
The accurate material modelling of poly-l-lactic acid (PLLA) is vital in conducting finite element analysis of polymeric bioresorbable scaffolds (BRS) to investigate their mechanical performance and seek improved scaffold designs. To... more
The accurate material modelling of poly-l-lactic acid (PLLA) is vital in conducting finite element analysis of polymeric bioresorbable scaffolds (BRS) to investigate their mechanical performance and seek improved scaffold designs. To date, a large variety of material models have been utilised, ranging from simple elasto-plastic models to high fidelity parallel network models. However, no clear consensus has been reached on the appropriateness of these different models and whether simple, less computationally expensive models can serve as acceptable approximations. Therefore, we present a study which explored the use of different isotropic and anisotropic elasto-plastic models in simulating the balloon expansion and radial crushing of the thin-strut (sub-100 μm) ArterioSorbTM BRS using the Abaqus/Explicit (DS SIMULIA) solution method. Stress-strain data was obtained via tensile tests at two different displacement rates. The use of isotropic and transversely isotropic elastic theories was explored, as well as the implementation of stress relaxation in the plastic regime of the material. The scaffold performance was quantified via its post-expansion diameter, percentage recoil and radial strength. The in-silico results were validated via comparison with in-vitro data of an analogous bench test. Accurately predicting both the post-expansion scaffold shape and radial strength was found to be challenging using the in-built Abaqus models. Therefore, a novel user-defined material model was developed via the VUMAT subroutine which improved functionality by facilitating a variable yield ratio, dependent upon the plastic strain as well as stress relaxation in overly strained elements. This achieved prediction of the radial strength within 1.1% of the in-vitro results and the scaffold's post-expansion diameter within 6.7%. A realistic multi-balloon simulation strategy was also used which confirmed that a mechanism exists in the PLLA which facilitates the extremely low percentage recoil behaviour observed in the ArterioSorbTM BRS. This could not be captured by the aforementioned material property models.
Research Interests:
AIMS To assess acute performance of the 95-µm ArterioSorb oriented poly L-lactic acid (PLLA) scaffold in comparison with the Xience metallic drug-eluting stent (DES) in porcine coronary arteries. METHODS AND RESULTS In 15... more
AIMS To assess acute performance of the 95-µm ArterioSorb oriented poly L-lactic acid (PLLA) scaffold in comparison with the Xience metallic drug-eluting stent (DES) in porcine coronary arteries. METHODS AND RESULTS In 15 nonatherosclerotic Yucatan mini pigs, ArterioSorb in 3.0/14 mm and Xience in 3.0/15 mm were implanted in 25 and 15 vessels, respectively. Acute performance was evaluated by using quantitative coronary angiography (QCA) and optical coherence tomography (OCT). Following three-dimensional reconstruction of coronary arteries, endothelial shear stress (ESS) was quantified using non-Newtonian steady-flow simulation. Acute recoil measured by QCA was comparable in the two arms. Post-procedural flow and scaffold/stent area by OCT did not differ between the two devices. ESS post-procedure was comparable between ArterioSorb and Xience (2.21±1.97 vs. 2.25±1.71 Pa, p=0.314). CONCLUSIONS Acute recoil, luminal dimensions and ESS in ArterioSorb oriented-PLLA scaffold with thin struts of 95 µm were comparable to Xience metallic DES.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Segmented poly(ether-urethanes) have been shown to be particularly suitable for a wide range of biomedical applications on account of their good elastomeric and other mechanical properties and their relative compatibility with blood.... more
Segmented poly(ether-urethanes) have been shown to be particularly suitable for a wide range of biomedical applications on account of their good elastomeric and other mechanical properties and their relative compatibility with blood. Consequently several commercial poly(ether-urethanes) have been exploited for the manufacture of prostheses such as artificial hearts and arteries and extracorporeal circulatory systems.1,2 Attainment of the highest possible degree of haemocompatibility of the polymers is essential in certain applications such as small-boar arterial prostheses of internal diameter 4 mm or less. The work we now describe was undertaken as part of the development of such a prosthesis and required chemical modification of commercial poly(ether-urethanes) rather than the investigation of new types with potentially improved properties.
Research Interests:
Synthetic methods available for improving the haemocompatibility of polymer surfaces are outlined. The present paper is concerned mainly with ”passivation“ techniques and some of the chemical routes by which they may be effected. Uses of... more
Synthetic methods available for improving the haemocompatibility of polymer surfaces are outlined. The present paper is concerned mainly with ”passivation“ techniques and some of the chemical routes by which they may be effected. Uses of isocyanatoethyl methacrylate as a functionalising reagent and for grafting to polymers are discussed with examples of its applications in the syntheses of (a) monomers from α-amino acids and peptides, and the amino-sugars D-glucamine and D-glucosamine, and (b) macromers from poly(ether urethanes) and from the hydroxylic macromolecules poly(ethylene glycol), poly(tetrahydrofuran), poly (vinyl alcohol) and dextran. Grafting of monomers and macromers to functionalised polymers is considered. A series of grafts to polyurethane elastomers have been synthesised and tested for blood-platelet adhesion (a measure of passivation) by a simple procedure which is outlined. All the graft copolymers tested show significantly reduced platelet adhesion compared to the base polyurethane. In particular, a Pellethane-poly D-glucamine graft is probably the most inert material towards platelets which we have examined.
Research Interests:
A biocompatible and highly lubricous hydrophilic coating has been developed for intermittent urinary catheters. The coating has additives incorporated into it, which reduce the drying out of the catheter when it is inserted into the... more
A biocompatible and highly lubricous hydrophilic coating has been developed for intermittent urinary catheters. The coating has additives incorporated into it, which reduce the drying out of the catheter when it is inserted into the urethra, and antimicrobial agents can be incorporated into it to minimise the trauma associated with catheterisation.
Research Interests:
ABSTRACT The success of percutaneous coronary intervention (PCI) has been limited by restenosis and stent thrombosis. Delayed or incomplete endothelial regeneration is believed to be a key factor responsible for these events. Developing a... more
ABSTRACT The success of percutaneous coronary intervention (PCI) has been limited by restenosis and stent thrombosis. Delayed or incomplete endothelial regeneration is believed to be a key factor responsible for these events. Developing a stent with an accelerated healing profile may be of benefit. We aimed to evaluate the feasibility and safety of seeding a bare metal stent (BMS) with human trophoblastic endovascular progenitor cells (hTEC) derived from human embryonic stem cells.
Research Interests:
The synthesis is described of a macroporous electrostatically-spun poly(ether urethane) membrane, functionalised to show molecular recognition of uracil derivatives.
Research Interests:
Research Interests:
Research Interests:
Approximately 30 new derivatives of theophylline and dipyridamole have been prepared and examined as potentiators of the inhibition of platelet aggregation induced by the prostaglandin analogue BW 245C. Potentiating activity has been... more
Approximately 30 new derivatives of theophylline and dipyridamole have been prepared and examined as potentiators of the inhibition of platelet aggregation induced by the prostaglandin analogue BW 245C. Potentiating activity has been found to be sensitive to molecular size and also to the presence of specific groups. Polymeric adducts based on dextran, poly(ethylene glycol) or poly(N-vinyl pyrrolidone), and aliphatic esters with alkyl chain-lengths greater than 7 are inactive in potentiation. Derivatives containing carboxyl groups are also inactive. Potentiation is discussed in terms of platelet membrane penetration and extra- and intra-cellular processes. The latter are invoked to account for the enhanced potentiation shown by dipyridamole and derivatives when aggregation is induced by PAF-acether rather than ADP. One derivative of particular interest is the adduct of theophylline with 1,2,5,6-diisopropylidene-D-glucose, containing a furanose ring. This is a more active potentiator than theophylline itself, possibly owing to its molecular resemblance to cAMP. On conversion to the pyranose form all activity is removed.
Research Interests: Materials Engineering, Chemical Engineering, Chemistry, Long Term Potentiation, Polymers, and 12 moreMedicine, Platelet aggregation, Sheep, Animals, Theophylline, Poly Ethylene Glycol, Molecular weight, Structure activity Relationship, Prostaglandin E2, Molecular Structure, Drug synergism, and Platelet Aggregation Inhibitors
Research Interests:
Research Interests:
Research Interests:
Research Interests: Biomedical Engineering, Computational Fluid Dynamics, Optical coherence tomography, Medicine, Patterns, and 15 moreComputer Simulation, Animals, Blind, Impact, Fusion, Everolimus, Percutaneous Coronary Intervention, Outcomes, Coronary Angiography, Cardiovascular Imaging, Coronary Circulation, Materials Testing, Coronary Arteries, Cardiovascular medicine and haematology, and Coronary Vessels
Research Interests:
... BY CLEMENT H. BAMFORD*~ AND KADEM G. AL-LAMEET Department of Inorganic, Physical and Industrial Chemistry, University of Liverpool, Liverpool L69 3BX Received 31st October, 1983 ... Methyl methacrylate was purified as described by... more
... BY CLEMENT H. BAMFORD*~ AND KADEM G. AL-LAMEET Department of Inorganic, Physical and Industrial Chemistry, University of Liverpool, Liverpool L69 3BX Received 31st October, 1983 ... Methyl methacrylate was purified as described by Bamford and L ~ II ~ . ~ ...
Research Interests:
As the use of coronary stents continues to expand worldwide, in-stent restenosis remains a major clinical problem for interventional cardiologists. However, recent clinical trials have shown that the drug-eluting stents are the most... more
As the use of coronary stents continues to expand worldwide, in-stent restenosis remains a major clinical problem for interventional cardiologists. However, recent clinical trials have shown that the drug-eluting stents are the most promising method for reducing the restenosis and allowing the injured vessel to heal. Further development work is focused on investigating the use of this technology with a range of drugs for the inhibition of restenosis.
Research Interests:
Research Interests:
Research Interests:
We have studied the inhibition of ADP-induced platelet aggregation in sheep platelet-rich plasma by water-soluble polymers bound to the prostaglandin analogue 5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)hydantoin ('BW... more
We have studied the inhibition of ADP-induced platelet aggregation in sheep platelet-rich plasma by water-soluble polymers bound to the prostaglandin analogue 5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)hydantoin ('BW 245' C, (I). The use of unambiguous modes of binding this antiplatelet drug to polymers has enabled us to study some structural features which influence inhibitory activity. Evidence is adduced which indicates that the chemical mechanisms responsible for inhibition by free and coupled BW 245 are similar. The most important observation is a remarkable synergism demonstrated by the greatly enhanced activity of a mixture of a polymer coupled to BW 245 with the uncoupled parent polymer. In some cases (e.g., with high-molecular-weight dextran) the effect may reach (and possibly exceed) two orders of magnitude. The influence of polymer molecular weights and 'cross-polymer' effects have both been examined. A mechanism has been proposed to account for these phenomena, involving adsorption of the added (inactive) polymer on to the platelet membranes, facilitating interaction of the polymer-bound drug with receptors, made more accessible by alteration to the surface geometry. This mechanism is based on physical processes, unlike other explanations of synergistic behaviour, e.g., that of prostaglandins used in conjunction with non-polymeric drugs. The observed dependences of synergistic effects upon polymer molecular weight and type and distribution of drug molecules along chains are typical 'polymer' phenomena which are all consistent with the proposed mechanism.