How plastics are transforming the implantable medical devices space
Innovation has long been a driving factor in the progression of various industrial sectors across the globe. The healthcare sector, particularly with regards to medical devices, is likely to gain lucrative benefits from novel solutions and technology, be it through the modification of existing devices, or the implementation of strategic alliances and initiatives for product development. In recent years, this innovative drive has been increasingly apparent in the implantable medical devices industry.
Implantable medical devices, also known as IMDs or medical implants, are devices created using synthetic materials, designed to be placed inside the human body for medical purposes, often for a long-term duration. These devices can be used as replacements for body parts such as knees or hips, for delivery of medication like pain relief, for supervision and regulation of regular body functions including heart rate, as well as for offering support to tissues and organs.
Implants can be either inert or active, depending on their purpose. The inert ones are intended for use as structural support, generally in the form of stents or surgical meshes. On the other hand, active medical implants are built to interact with the body, for instance by responding to changes in heart rhythm via electrical shocks.
Certain implantable medical devices are designed to be “smart”, in that, they can connect to and communicate with systems outside of the body, these include devices such as neurostimulators, pacemakers, and implantable defibrillators, among others, which can monitor and deliver treatment automatically in response to any changes in the body.
The implantable medical devices market growth is mainly characterised by steady evolution and the emergence of advanced techniques and devices. A notable example of this is the progress of the cardiac pacing field. Pacemakers have undergone decades of transformation and have become progressively smaller in size, whilst featuring added functional capabilities.
In the quest to develop smaller and more sophisticated medical implant technologies, entities in the medical device domain are rapidly adopting various materials that can help reduce device profiles without any compromise on durability, flexibility, strength, and biocompatibility. One such material currently in use is plastic.
Plastics and their use in IMDs
Polymers have been suitable alternatives for metal components in medical applications for several years. This burgeoning popularity is attributed to a host of beneficial characteristics, the most significant being the biocompatibility of the material. The human body’s extracellular fluid, which comprises of isotonic saline solution, often displays extreme hostility to metal materials, which can lead to their degradation. However, this degrading effect is not largely associated with polymers, which is why many synthetic high-molecular-weight polymers are used extensively in the development of modern medical devices.
In terms of weight, thermoplastics account for almost 90% of global plastic usage. Unlike their thermoset counterparts, thermoplastics for medical devices can undergo processing sans loss of properties, making them highly sought-after materials for the development of implantable medical devices in recent years. Some of the most common thermoplastics used for medical applications include:
- Polyethylene, also known as polythene, which demonstrates strong potential for use in prosthetics development, especially in the form of Ultra-High Molecular Weight Polyethylene (UHMWP).
- Polypropylene, which is used for applications that require radiation stabilisation and autoclave sterilisation, given the product’s resistance to high temperatures.
- Acrylonitrile Butadiene Styrene (ABS), which can be used as metal substitutes in structural parts, owing to features such as rigidity and high resistance to both impact and heat.
- Polycarbonate, which is used for the development of medical tubing and other devices, due to strong UltraViolet (UV) and heat-resistant properties as well as transparency.
The impact of polymers on the medical device industry
Metal was considered the preferred material for healthcare applications for decades, as conventional plastic materials could not offer the same combination of chemical resistance, high modulus, and sterilisation process-compatibility that metal provided. Polymer technology has come a long way since then, however, with numerous plastic materials delivering metal-like properties and facilitating the fabrication of more integrated and complex medical device parts.
Healthcare OEMs are also becoming more attuned to the merits of using thermoplastics for medical devices and are rapidly making the shift from metal to plastic, by investing heavily to bring more polymer-based advanced medical devices to market.
Some high-performance plastics are now able to deliver similar strength properties as that of metals at ambient temperature, in addition to further advantages such as better aesthetics, cost-benefits as well as ergonomic enhancements like robust grip options.
To illustrate, high-performance medical polymers such as PolyEther Ether Ketone (PEEK) are used extensively in the production of implantable medical devices, showing particularly high potential in orthopaedic implants. PEEK is a strong, flexible, safe, and bioinert thermoplastic, which is suitable for medical applications and is a superior alternative to metal, ceramic, and other resorbable materials.
With this in mind, Germany-based specialty chemicals firm Evonik, in 2020, introduced its new range of implant-grade PEEK filament, dubbed Vestakeep i4 3DF, as a part of its 3D printing materials portfolio. The new material, which complies with ASTM F2026 standards for surgical implants, facilitates the manufacturing of 3D plastic medical implants, via Fused Filament Fabrication (FFF) technology, and demonstrates superior application potential in the maxillofacial and orthopaedic surgery domains.
The rising focus on silicone as a suitable implantable medical device material
Medical device producers have also shown considerable interest in silicone as an ideal medical implant material for a long time, given the ease of moulding, vast temperature range, high tensile strength, durability, and wide range of available durometers, among other characteristics. However, what truly makes silicone the ideal match for medical devices, especially combination products, is its robust biocompatibility. Silicone is highly compatible with body fluids and tissue, demonstrates low tissue response once implanted, and helps deter the growth of bacteria and other contaminants. Furthermore, medical-grade silicone materials are subjected to strict biocompatibility and purity testing, which makes them suitable for integration in long-term medical implants.
A major application area for medical-grade silicones like Lliquid Silicone Rubber (LSR) is in drug-eluting implantable medical devices. These silicones can be compounded with Active Pharmaceutical Ingredients (APIs) such as hormones or cancer drugs, prior to moulding. These APIs can then be released steadily over time into targeted areas of the patient’s body, once the moulded implant is placed. Drug-eluting silicone-based IMDs can sustain the required API level in the patient’s body at a consistent pace and for longer durations of time, as compared to delivery through injection or pills. Additionally, since these implants are generally placed close to the targeted tissue or organ, relatively lower API concentrations are required since they can reach the targeted area directly.
There have been several prolific advancements over the years in silicone-based IMDs, including the creation of a novel technology by noted additive manufacturing company Spectroplast, which has transformed the industrial landscape for 3D printed products by using silicone as a key material in high-precision 3D printing for medical devices. The technology, which addresses the ever-growing need for time and cost-effective prototyping and mass manufacturing of customisable silicone-based medical devices, can be used to create next-gen products such as customised hearing aids, dental implants, bespoke silicon-based IMDs for heart valves as well as anatomically accurate medical models for surgical training purposes.
How the use of bioplastics is making medical devices more eco-friendly
Sustainability is the need of the hour across the globe. Plastic is considered to be one of the most notorious contributors to environmental degradation, with major global shifts taking place to ban fossil-based plastics, single-use disposable plastics such as plastic bags and straws, as well as the use of plastics that develop longer-lasting microplastic residues.
In the medical sector, however, the role of plastics is highly integral, which has prompted massive research efforts worldwide to develop more sustainable polymer technologies, designed for use in medical applications. Studies suggest that between the period of 2030-2040, nearly 25-30% of plastics across the world will be bio-based.
Given these circumstances, many global medical industry players are leaning towards adopting more environmentally friendly products, thus opening lucrative avenues for innovative efforts by companies such as Arctic Biomaterials. An example of such an effort is the company’s 2016 breakthrough in medical device innovation, with the development of a material combining the strengths of plastic and glass fibres, by fusing the two together using a proprietary adhesion layer. The resulting material established the entity as a leading presence in the medical devices’ domain, by demonstrating high heat resistance and superior strength for medical and technical purposes.
A team of researchers from the University of Birmingham made similar progress, with the development of a novel thermoplastic biomaterial, which possesses not just high toughness and strength properties, but is also easier to shape and process compared to its counterparts. The material, which is a type of nylon equipped with shape memory characteristics, can be moulded and stretched as needed, returning to its original shape upon application of heat, making it ideal for bio-based medical implants such as bone replacements, where the flexibility of implant materials plays a key role in minimally invasive surgical procedures.
Technological advancements are triggering the invention of novel materials, technologies, and ideas across the medical industry, designed to surpass the existing concepts. With plastics held in such high regard as key medical-grade materials, alongside the emergence of modern techniques such as insert moulding, injection moulding, and the like, it is becoming easier and easier for medical device manufacturers to create precision tools that can be mass-produced without compromising on efficiency or quality. This widespread adoption and acceptance of various material technologies in the implantable medical devices industry are thus indicative of revolutionary innovations that have changed and will continue to change the healthcare landscape even in the years to come.