Medical Devices: Material innovations enable medical device breakthroughs

August 8, 2018

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Rubber materials like silicones are aiding in the improvement of medical devices for the healthcare sector, says Angelica Buan in this report.

Modern medical devices aid in early detection and treatment of diseases, as well as help in improving the quality of life of patients with disabilities. This increasing adoption of medical devices in the healthcare system is leading to further market growth, which Lucintel, in its medical device market report, predicted to reach nearly half a trillion dollars by 2023, growing at a CAGR of 4.5% from 2018.

Lucintel adds that the major drivers for the growth of this market are the higher rates of healthcare expenditure, technological development, ageing population and chronic diseases.

Focus in obtaining the highest levels of comfort, safety and performance of medical devices is leading to more improvements in the design and functionality of the devices; and materials play a key role in enabling this objective.

Biocompatible/electrically conductive silicones

Medical implants are man-made devices or tissues that are placed inside or on the surface of the body to replace missing or damaged part of the body as in prosthetics; or to deliver medication, monitor body functions, or provide support to organs and tissues.

Driven by rising incidence of chronic diseases and advancements in technologies and surgical outcomes, the global market for medical implants is inclined to grow at a CAGR of 7% between 2017 to 2023, as projected by Cooked Research Reports.

Materials used for implants vary and should comply with stringent materials standard. Biocompatibility is a vital criterion for implantable materials, which medical grade silicone is suitable for.

Silicone rubber has been the material of choice for implantable devices, owing to its high chemical inertness, durability, tensile strength, availability in a wide range of durometers, wide temperature range, and ease of moulding by many methods has made the material a mainstay of medical devices of all types, but especially for long-term implants, according to a whitepaper published by US-based medical silicone components & assemblies manufacturing company ProMed.

silicone-rubber

Conductive silicone rubber has gained traction in the automotive, oil and gas, and electrical and electronics sectors, says the Minnesota-headquartered firm that has also published a whitepaper on electrically conductive silicone rubber.

Now, the material, owing to its lightweight, flexibility, durability and high thermal and electrical conductance, is likewise finding applications in the medical devices segment. ProMed said that it has partnered with several companies experimenting with conductive silicone medical products in the R&D stage.

Electrically conductive silicones have been used in automotive and industrial applications such as radio frequency shielding and sealing. Until now, the use in medical devices has long been hampered by the purity, cost, and processing challenges of the two traditional additives used to make silicone electrically conductive, namely carbon black and silver coated glass spheres.

Due to the purity, size and robustness of carbon nanotubes, its use as an additive enables silicone raw material manufacturers to offer electrically conductive silicones that are capable of meeting some of the basic material testing requirements (including USP Class VI) for medical devices. Moreover, they are price competitive with silvercoated microspheres, and as durable and stable in suspension as carbon black, while being much more pure, thus enabling innovative conductive medical device applications, ProMed furthered.

Biomarking implants with tomato DNA

For years, a French company sold breast implants made of cheap industrial silicone components. Headlined news when it broke in 2010, this scandal is still keeping the courts busy today. Now, a research team at the German Fraunhofer Institute for Applied Polymer Research IAP has come up with a method to prevent this sort of fraud. It gives manufacturers the opportunity to counterfeit-proof implants – by tagging them with encapsulated tomato DNA.

Joachim-Storsberg

Product counterfeiting has become a growing problem for manufacturers, with fakes being usually inferior and seriously harm patients’ health and even jeopardise lives. “Counterfeiters generally buy high-quality individual components from reputable suppliers and stretch them with cheap silicone, which costs a fraction of the premium material. Product pirates turn huge profits,” says Dr Joachim Storsberg, a scientist at the Fraunhofer IAP.

Storsberg and his team have developed patented DNA sequences as permanent markers to positively identify breast implants. This gives manufacturers the opportunity to tag products with a counterfeit-proof marker and thereby enhance patient safety. Tomato DNA makes the perfect marker, as various experiments have substantiated.

“We isolated genomic DNA (gDNA) from tomato leaves and embedded it in the silicone matrix. We used approved siloxanes, which are building blocks for silicone products, to manufacture breast implants,” explains Storsberg. The researchers managed to demonstrate the extracted DNA’s temperature stability in pilot experiments. They vulcanised the gDNA in the host silicone at 150 degrees for five hours and then tested it with a polymerase chain reaction (PCR), a technique to amplify DNA, and with a special analytical method call gel electrophoresis. The DNA remained stable and did not degrade.

Storsberg says the advantage of tomato DNA is that it costs next to nothing and is suitable as a counterfeit-proof marker for many polymer-based implants such lens implants.

Medical-grade LSR growing, too

NuSil-brand

Meanwhile, medical-grade liquid silicone rubbers (LSRs) are widely used for a broad range of implantable medical devices, including cardiovascular, neurological, urological, ophthalmic and aesthetic applications, according to US medical and space-grade LSR manufacturer Nusil. Typically, LSRs are used to fabricate cured devices outside the body, and then the device is implanted via surgery.

A latest innovation in its roster of LSR specialised range, NuSil, an Avantor brand, has a patented technology that allows medical device manufacturers to create devices that can be cured in-situ. Nusil said: “The new in-situ cure LSR solution for implantable devices is a prefilled, sterilisable dispensing system that enables specific uncured LSRs to be cured in-situ.”

Designed specifically to allow sterilisation of the uncured medical grade LSR, the NuSil packaging solution features a double-cartridge prefilled dispensing system. Each cartridge in the dispenser has a gas-permeable plunger seal, allowing the ethylene oxide steriliser to pass through to the contents of the barrels as well as the entire system assembly.

The solution, which features disposable syringes in sizes ranging from 5 ml to 75 ml, is engineered for use in complete surgical kits and allows one-step sterilisation of LSR components and packaging.

Nusil also offers an advanced line of lubricious silicones for use with medical devices. Medical devices can benefit from high-performance, biocompatible silicone lubricants to reduce friction. Other desirable properties of lubricious silicones for medical devices include oxidative resistance, chemical inertness and hydrophobicity. NuSil says its lubricious silicones are available in a broad portfolio of off-the-shelf solutions including selflubricating elastomers as well as dispersions, fluids and greases.

A pulse for efficient heart devices

Heart disease is a top cause of death worldwide. Incidence and mortality rates from cardiovascular diseases (CVDs) are increasing every year. The World Health Organisation (WHO) estimates that yearly, 17.7 million people die from CVDs, accounting for 31% of all deaths worldwide.

Demand for medical devices specialising in the early detection, management and treatment of CVDs is at an all-time high, given the prevalence of so-called lifestyle diseases that are taking a toll on the heart’s health.

The global CVD device market is anticipated to reached over US$59 billion by 2022, growing at a CAGR of nearly 7% from 2017 and value of US$42 billion, according to Research and Markets.

An important medical device for CVD patients is the pacemaker, an electrically-charged medical device, which has undergone tremendous changes over the years since the first models of pacemakers in the 1950s that were huge and plugged externally or were hung around the neck of the patient. Modern pacemakers are more compact, comprising a pulse generator and wires that send electrical signals to the heart; and are implantable.

Pacemakers and related hardware are constantly being upgraded to offer safer and better patient outcomes. Along this line, surgical trainings have also improved to adopt simulation as a key tool for surgeons to ensure patient safety.

In specialties such as cardiovascular surgery, training using simulators is compulsory and demand for surgical training simulators is rapidly growing, according to Toyoda Gosei, Japanese manufacturer of rubber and plastic automotive parts and optoelectronic products. The firm partnered with EBM, a Waseda University launched start-up, to develop and promote a simulator that helps surgeons to efficiently improve their surgical skills.

EBM, established in 2006, has been involved in training simulator development and system creation for both domestic Japanese and overseas markets, principally in the field of cardiac surgery.

The partners, who began collaborating in 2017, have built a prototype Super BEAT surgical training simulator that can reproduce the beating of the heart with extreme accuracy using e-Rubber, an artificial muscle that functions with electricity.

Super-BEAT

In EBM’s current BEAT simulator, the movement of the heart is simulated with the use of a shape-memory alloy that expands and contracts by heating. The high-end version of this simulator uses e-Rubber, which expands and contracts rapidly in response to electricity switching on and off. Regulation of fine movement is also possible to mimic states such as complex heartbeat patterns due to arrhythmia or the rapid heartbeat of children, allowing reproduction of an environment closer to that of actual surgery. Improvement of Super BEAT is ongoing, and sales are targeted in the fall of 2019.

An equally vital cardiac device, a defibrillator is used to deliver therapeutic shock to a patient’s heart in life-threatening conditions, including ventricular fibrillation, cardiac arrhythmia, and pulseless ventricular tachycardia, to depolarise heart muscles and restore its normal electric impulse.

Allied Market Research in its report covering the periods 2014 to 2022 forecasts the global market size for defibrillators to garner over US$15.6 trillion by 2022, growing at a CAGR of 6.5% during the report period. The automated external defibrillator (AED) is the most commonly used external defibrillator, clinching more than two-thirds of external defibrillator market revenue share in 2015.

As with increasing use, the defibrillator has to advance and overcome certain challenges that impact its effectiveness. One such challenge is to deliver enough current to the heart without burning the patient’s skin – a formidable barrier with a typical impedance of 500 kilo ohm/sq cm.

A team of bioengineering students from Rice University in Texas, US, has found a way around that problem with an add-on pad for the defibrillator.

3D-printed-plastic

The Zfib add-on is a 3D printed plastic frame with a rubber backing that allows the user to press 180 tiny needles into a patient’s chest without having to touch the needles. The needles collect current from the side of the pad that touches the skin and deliver it to the patient. Indicators on top of the device turn green when enough pressure is applied.

The add-on reduces the skin’s impedance by 72%, and thus, should increase a patient’s chance of survival and reduce the odds that the patient will need multiple shocks, the team said.

Low cost option for prosthetics

The rising prevalence of lifestyle related diseases, and incidences of trauma and accidental injuries factor significantly in the growth of the global orthopaedic prosthetics market.

Modern prosthetics, however, are no longer using metals, iron or wood materials. Common materials used nowadays are Kevlar, titanium, and carbon-fibre, which render low-weight and high-strength features to prosthetics. Innovative materials such as rubbers are also utilised for additional functionality and for aesthetics to make an artificial limb look, feel and function like a natural body part. The cost to get an artificial limb varies and can be costly.

Researchers from the Massachusetts Institute of Technology (MIT) have developed a simple, low-cost, prosthetic foot that is custom-designed based on the patient’s body weight and size, to allow users to walk more fluidly. Their work has been published in the ASME Journal of Mechanical Design.

The MIT team, in producing the low-cost prosthesis, is providing an affordable option for amputees in lower and middle income countries. The carbon-fibre passive foot prosthetics would easily cost US$1,000 to US$10,000, while the more high-tech ones can cost even more.

The custom-designed nylon prosthesis is based on a design framework developed by researchers that provides a quantitative way to predict a patient’s biomechanical performance based on the mechanical design of the prosthetic foot.

prosthetic-foot_01

The prototype has no ankle or metatarsal joint, and is just one big structure, and thus, makes it simple and affordable to manufacture. To test the prosthetic, the researchers produced several feet for volunteers in India.

The team is currently collaborating with Vibram, an Italian manufacturer of rubber outsoles for footwear, to design a life-like cover for the prosthesis, which will also give the foot some traction over slippery surfaces. The MIT researchers plan to test the prosthetics and coverings on volunteers in India.

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(Last Updated: 16 Aug 2018)

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