Researchers at IT Sligo are leading a €1 million EU-funded project that could pave the way for more people to receive better and cheaper medical implants faster. According to the team involved in Bio-PolyTec, greater use of bioresorbable polymer material is set to have a significant impact the future development of implantable medical devices, with important benefits for patients and manufacturers.
Bioresorbable polymers have key advantages over traditional metal implants. They naturally break down into non-toxic by-products and are gradually replaced by the patient’s own tissue, leading to improved patient recovery and fewer follow-up operations.
“Bioresorbable materials have been used for a whole host of different devices and are increasing in popularity – for example, cardiovascular stents are increasingly moving in the direction of becoming totally bioresorbable,” said Dr Marion McAfee from the Centre for Precision Engineering, Materials and Manufacturing (PEM) at IT Sligo, co-ordinator of the Bio-PolyTec project.
“The stent performs its temporary function of mechanical support to the artery, restoring blood flow and allowing the arterial wall to heal,” she continued. “Over time, the material breaks down – typically into carbon dioxide, water and lactic acid – when we no longer need it.”
The materials are seeing increasing application in treatment of trauma and sports injuries, including internal bone fixation devices (screws, plates and pins) and reattachment of ruptured ligaments (suture anchors). “Bone needs loading to heal,” explained McAfee, “so if you have metal in there taking some of the load, the bone doesn’t really regenerate with the same strength. But with resorbable implants, the bone takes over the strain as the implant is resorbed. In addition, you don’t need more surgery to take out the implants afterwards.”
The downside of bioresorbable implants at the moment is the cost of manufacturing them. Bioresorbable polymers generally have to undergo processing at high temperatures and pressures to form them into the implant shape required. Unfortunately, this tends to cause the materials to degrade.
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“There is a lot of trial and error in the manufacturing of these devices,” according to McAfee, who also lectures in the Department of Mechanical & Electronic Engineering at IT Sligo. “It can take a long time to work out what process conditions result in satisfactory performance of the product – and a change in the batch of raw material can throw things off completely. Scrap rates are typically 25-30% and the material is hugely expensive, so this can be a barrier to successful commercialisation. There are lots of patented implant ideas out there that haven’t come to fruition as a result.”
An advantage of bioresorbable implants is that they can be impregnanted with drugs or other bio-active particles, which are slowly released as the polymer resorbs. This can help improve biocompatibility, aid regeneration of the body’s own tissue, prevent implant-site infection and even provide a new way to achieve controlled drug delivery specifically to a target site of the body.
Unfortunately, the introduction of additives can make the processing of the material even more complex. Joe Molloy, the technical director at IPC Polymers – a manufacturer of polymer compounds for the medical industry based in Kilbeggan, County Westmeath and a partner in the Bio-PolyTec project – said the ability to monitor and control the dispersion of additives in a polymer is an important technological development. “Having the additive well-dispersed in the polymer is key for the performance of a medical implant, but it can be expensive and time-consuming to achieve.”
Bio-Poly Tec aims to develop novel instrumentation and control technology to rapidly optimise process set-up and reduce scrap rates to a target 5%. “Using the Fibre-optic probes and spectroscopy hardware of our German partner FOS Messtechnik, we’re developing new sensors to detect product quality online during processing so manufacturers will know straight away if the product is okay or not,” explained IT Sligo Post-doctoral researcher Dr Darren Whitaker, who is developing methods for monitoring the concentration of degradation products and the dispersion of additives in the melt during processing.
“At present, these are things that have to be analysed in the lab after production and it can take a day or more to get the results – by which time an entire batch may be out of spec. By illuminating the polymer with a light source and analysing the light transmitted or reflected back, we can get rapid feedback on the physical and chemical structure of the material.”
The project, which kicked-off in December 2013, comprises polymer processing, biomaterials and spectroscopy experts at three higher-education Institutes and four companies across Europe. Finnish company Scaffdex manufactures a bioresorbable implant called RegJoint, which is used for the treatment of arthritis in the small joints of the hand and foot. RegJoint is a tissue scaffold that acts as a spacer and is gradually replaced by the patient´s own. The neojoint is living, functional, dense and flexible and it is formed in the shape of the implant between the bone ends and it attaches on the bone tissue.
Tuija Annala, managing director of Scaffdex, said that improving the manufacturing process would help the company to reduce the cost of making RegJoint. “It will also enable us to bring a new product to market,” said Annala. “At present, the development and manufacturing costs of the new device are too high for the clinical end use, so patients are missing out on a potential treatment.”
Bio-PolyTec is just one of the current projects ongoing at IT Sligo’s newly formed Centre of Precision Engineering, Materials and Manufacturing. “Most of our research work is applied,” explained the research centre’s manager, Dr David Tormey. “We work with a range of manufacturing industries from within Ireland and Europe, addressing challenges in precision engineering and manufacturing as well as developing novel functional materials.”
For more information see www.pemcentre.ie and www.biopolytec.eu.