Medical technology - a question of convergence

As the initial group of students complete their projects at the UK’s first medical device doctoral training centre we take a look at some of the top devices coming out of this convergence of expertise.

There is a growing realisation that the medical device technologies of the future will be increasingly dependent on the convergence of engineering, science and medicine.  For example, in 2006 the UK Technology Strategy Board (TSB) - the pre-eminent national body tasked with ensuring a cohesive approach to research and technology development in the UK - identified bioscience and healthcare as one of its six key areas. Within that the TSB has accorded medical devices priority status, especially:
• Converging technologies – convergence of the physical with the biological leading to new and combined functionalities.
• Diagnosis and screening technologies together with the development and monitoring
of more targeted therapies.
• Regenerative medicine – methods to induce the body to regenerate healthy functional tissue and to provide replacement parts.
• Assistive technologies – devices and technologies that aid rehabilitation and support for independent life in the community.

Such technologies are not only of importance as a source of national wealth creation and employment but also to healthcare end users, e.g. clinical staff and patients.

The Strathclyde Institute of Medical Devices (SIMD) was launched in October 2006 in response to the recognition that effective innovation in medicine and healthcare technology is required to address the world’s healthcare problems in the 21st Century. The convergence of engineering, science and medicine is key and SIMD is ideally placed to pioneer the complex, team approaches that will be needed to deliver new research and products to the healthcare end users.

The Institute draws upon teams and technologies developed within the UK’s first Medical Devices Doctoral Training Centre (DTC), at the University of Strathclyde. The DTC, founded in 2003 and funded by the Engineering and Physical Sciences Research Council (EPSRC) Life Sciences Interface Programme, works in partnership with the DTI-funded Health Technologies KTN and is supported by a core group of departments across the University’s Faculties of Science and Engineering. These groups include drug delivery, orthopaedics, prosthetics, medicinal chemistry and neuroprosthetics.

Wound bed monitor There are currently no devices on the market capable of monitoring wound moisture levels either at the wound/dressing interface or within the dressing itself despite the accepted clinical need for optimal moisture levels during wound healing. A wound bed monitor capable of monitoring wound moisture levels has now been developed at the University of Strathclyde. A hand held meter/disposable sensor array is under development through Scottish Enterprise’s Proof of Concept Fund.

In addition some projects also involve external academic groups at the Universities of Glasgow and Paisley and Imperial College, London as well as the NHS (from Greater Glasgow and Clyde Health Board and Addenbrookes Hospital in Cambridge).

A unique characteristic of the DTC in Medical Devices is that it recruits highly qualified physical scientists and engineers and introduces them to life sciences, medical engineering and medical science in a masters level package in the first year of their 4 years Eng. D degree before they embark on an interdisciplinary medical device related research project.

Each 3 year research project is co-supervised by academic staff from different scientific disciplines. Additionally, all projects have the involvement of clinical groups or medical industry companies. This ensures that the science explored and technology developed is rooted in an area of clinical or commercial need relevant to healthcare.

Currently there are around 25 DTC interdisciplinary projects in operation with a further ten starting over the summer. The current projects span a very broad range of medical device applications – including diagnostics, rehabilitation engineering (e.g. prosthetics and orthotics), drug delivery, cell and tissue engineering and pioneering “brain computer interface” work - neuroprosthetics. A neuroprosthesis, for example a robotic arm controlled through their brain activity, will ultimately allow people with severe paralysis to carry out everyday tasks that the rest of the population take for granted. The first five projects will be completed this autumn and their uniquely talented students are in great demand in academic, industrial and consultancy sectors.

Some current examples of projects which are leading to new and exciting technologies and products are given below and illustrate the interdisciplinary approach adopted by SIMD and the DTC.
A team led by Professor Patricia Connolly, director of both the DTC and the SIMD, has developed a novel, patented, technology which allows the moisture level of a wound to be measured using a non-invasive wound dressing monitor. At present there is no way of measuring the moisture balance at the wound-dressing interface other than to remove the dressing for inspection. This can, however, disrupt the healing process and cause unnecessary pain to the patient.
There are 3 million patients with chronic wounds - leg ulcers, venous ulcers, diabetic ulcers, pressure sores etc - in the UK, where the cost of wound care is estimated to be £1bn per annum. Optimum moisture balance at the wound-dressing interface is a key element in wound healing.
The clinical system which is now under development as part of the Scottish Enterprise Proof of Concept Fund comprises a simple, disposal, sensor that can be used with a wide range of currently available dressings and a small hand-held meter which the carer, patient or nurse can use as required to monitor the condition of the wound and obtain guidance as to when the dressing should be changed.
Another example of a successful interdisciplinary project relates to drug-eluting stent technology. This drug delivery project draws upon both pharmaceutical and materials technology expertise. The worldwide coronary stent market was over US$5 billion in 2005 and the opportunity for a novel drug-eluting stent with superior performance to competitor products is high.

Stent implantation is a highly effective treatment for restoring blood flow through an atherosclerotic artery. However, restenosis (i.e. re-narrowing of the diseased artery) occurs in a significant proportion of patients, which requires renewed surgery and in some cases needs by-pass surgery which is associated with much higher risks. Current drug-eluting stents (DES) have reduced restenosis rates, following percutaneous coronary revascularisations, to less than 10%.  However, concerns have been raised about the long term safety and efficacy of these devices due to their reliance on potent anti-proliferative agents. Specifically, the effect on endothelial cell function in the long term is unclear.

Scientists at the University of Strathclyde have developed several novel DES technologies. The most advanced involves the use of VAN 10-4 (a patented small molecule which has successfully cleared regulatory toxicological testing) which has shown significant promise in the in vivo model employed thus far. Key advantages of these approaches over current drug-eluting stents include the efficacy of the therapeutic agents, improvement of the drug delivery system, the lack of detrimental effects on endothelial cell function and its application in high-risk individuals, e.g. diabetic patients.

Non-invasive extraction and analysis of blood-circulating molecules There is a need for more minimally-invasive diagnostic systems for a variety of healthcare applications. For example, control of blood glucose levels through glucose measurement and insulin injection can reduce the occurrence of complications in type 1 diabetes. Methods such as the “finger-stick” technique have proven expensive, cumbersome and painful to use. Reverse iontophoresis research at the University of Strathclyde’s EPRSC funded Doctoral Training Centre (DTC) has pioneered a portable and programmable device capable of simultaneous transdermal extraction of several molecules important for diagnostics including glucose and lactate without the need for blood samples.

Further early stage interdisciplinary research is on-going in the development of an “intelligent” stent - a stent that incorporates a sensor, which will be capable of continuously monitoring in-stent restenosis, and transmitting this data to a device outside the body.
 
At present restenosis is monitored principally through angiography and the
measurement of pressure and flow proximal and distal to the stent. These are sensitive indicators of the presence of restenosis. Angiography is a good qualitative
assessment method. The ratio of pressure proximal and distal to the stent is known as
the fractional flow reserve (FFR) and is a quantitative measure of whether significant
restenosis has occurred. However, the problem with these measurements is that they involve catheterisation, and are only carried out if the patient presents with recurrent anginal symptoms. A method by which restenosis could be measured non-invasively would allow continuous monitoring of the degree of restenosis. Thus restenosis could be diagnosed and treated earlier, for example, by a change of drug, or increased dose.

Another early stage medical device technology, this time drawing upon expertise from the University’s medical diagnostics and pharmaceutical science communities, relates to non-invasive extraction and analysis of blood-circulating molecules. This device, based on the reverse iontophoresis technique, detects blood glucose, and potentially many other molecules, as effectively as current “finger-stick” based methods used in the control of type 1diabetes, but with much greater convenience and usability. Finger-stick methods of glucose measurement, a precursor to insulin injection to control type 1 diabetes, have proven expensive, cumbersome and painful to use.

A full listing of current DTC projects can be found on the Institute’s webpages, http://www.strath.ac.uk/simd/.

Alan Lindsay. Alan is the Industrial Manager for the Strathclyde Institute of Medical Devices, University of Strathclyde, Glasgow. He has extensive commercial research and research management experience from within both the corporate and SME sectors.