Exploring the World of Medical Biomaterials

Biomaterials Steven Gibney, PhD The rapid development of new biomaterials is changing the healthcare landscape. Biomaterials are materials designed to safely interact with biological systems to support, improve or replace natural processes. In 2022, the biomaterials market reached $155 billion and is predicted to grow by 15.5% over the next two decades.1 This investment is helping to unlock new treatment strategies, from advanced prostheses and implantable devices to cutting-edge drug delivery systems and tissue regeneration techniques. This listicle will explore the different types of biomaterials, highlight their diverse properties and discuss how they are being applied to accelerate advanced medical treatments. What are biomaterials? A comprehensive definition of a “biomaterial” is difficult to achieve; it has evolved over the years as the field has grown and developed. The most widely accepted description defines a biomaterial as a substance that has been intentionally designed to interact with biological systems, whether for the treatment, augmentation or replacement of a biological function. Significant research into biomaterials began in the late 1960s, with an initial interest in materials that were “inert”. Early applications focused on dental and surgical treatments, such as the use of titanium for orthopedic and dental implants.2 Since then, the number of available biomaterials has grown rapidly. Broadly, biomaterials can be grouped based on their primary material and the properties of that material. Types of biomaterials Metals Metals have played a role in medical implants for over a century, ever since metal plates were first used to fix bone fractures.3 However, early attempts at metal implants often suffered from corrosion issues. This is exemplified by Sherman vanadium steel which, despite its relatively high hardness, displayed poor corrosion resistance when implanted in a biological environment.4 Since then, more EXPLORING THE WORLD OF MEDICAL BIOMATERIALS 2 Listicle advanced metallic materials have been developed, including titanium alloys, stainless steel alloys and cobalt–chromium alloys.5 These metals are biocompatible and corrosion resistant, ensuring any implants made from them will maintain structural integrity. This also makes them safer than their historical counterparts. The properties of metallic biomaterials make them ideal for load-bearing applications that require sufficient strength to withstand constant daily activity. This includes good physical strength, durability and a high elastic modulus. One of the most common applications for metallic biomaterials is artificial joints and orthopedic implants, such as hip and knee replacements.6 On a smaller scale, zincand magnesium-based alloys have been used to create cardiovascular stents, small mesh tubes that are used to expand narrowed or blocked coronary arteries.7 Ceramics Ceramic biomaterials share many properties and applications with their metallic counterparts. This includes their high physical and mechanical strength, resistance to wear and generally good biocompatibility. However, bioceramics have several advantages when compared directly to metallic biomaterials, such as a higher melting temperature, extreme corrosion resistance, improved mechanical properties and a biocompatibility exceeding that of most metals.8 This combination of properties makes ceramic biomaterials well-suited for applications where durability and biocompatibility are crucial. Ceramics such as zirconia, also known as zirconium dioxide, are used extensively in dental implants, where their biocompatibility and resemblance to natural tooth structure make them successful replacements in dental procedures.9 Ceramics such as alumina and hydroxyapatite are employed in bone grafts and joint replacements and can also be used as coatings to reduce the wear and inflammatory response to larger implants.8 Polymers (natural and synthetic) Polymers represent one of the widest categories of biomaterials, encompassing both synthetic polymers, like polyethylene, and natural polymers, such as collagen. Polymeric biomaterials are valued for their versatility; the wide range of unique polymers available makes it possible to tailor their design to meet specific medical needs. Natural polymers have already been the subject of much study. For example, collagen – a natural protein present in skin and other connective tissues – has been widely used in the preparation of biological scaffolds and implants for tissue engineering and regeneration.8 Other natural polymers like fibrin, keratin, fibronectin and laminin have also been investigated as biomaterials for tissue engineering applications.10 Fibrin derived from blood can function as a natural sealant during surgeries, while decellularized matrices created by removing cellular components from tissues provide a framework for tissue regeneration.10,11 The integration of naturally occurring polymers as a biomaterial ensures a seamless interaction with the body, making them extremely biocompatible solutions for tissue repair, regeneration and transplantation. Synthetic polymers, such as nylon, polyethylene and polyester, can be heavily modified and engineered to suit a specific need. Synthetic polymers are also useful substitutes for patients with an allergy to certain natural polymers, as they are less immunogenic. The ability to modify synthetic polymers by adjusting their monomer structure makes it easy to adjust material properties to suit a specific need. This can include tweaking the physical or chemical properties to improve biodegradability, making them more suitable for tissue engineering applications.12 This also makes synthetic polymers valuable for the development of implantable devices, where polymers such as polylactic-co-glycolic acid (PLGA), polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) can be manufac- EXPLORING THE WORLD OF MEDICAL BIOMATERIALS 3 Listicle tured into 3D scaffolds using different methods, such as 3D printing, freeze-drying or electrospinning.13,14 There is similar interest in the use of synthetic polymers for drug delivery applications, where polymers can be used to improve the efficacy of therapeutics, extend the release of compounds or target specific biological systems.15 Composite/hybrid materials Composite or hybrid biomaterials are created by combining different materials to create a product that possesses the optimal properties of their individual components. This ability to create custom combinations of biomaterials unlocks new avenues of interest when designing medical solutions. For instance, a combination of natural collagen and synthetic PLGA can be used to manufacture structures that display unique combinations of physicochemical properties including elasticity and strength, making them suitable for bone and soft tissue regeneration.16 Likewise, ceramic and metal biomaterials can be directly combined or mixed with polymers to create more effective joint replacements or for tissue reconstruction.16,17 The sheer number of possible combinations of biomaterials means that hybrid design is expected to become increasingly popular, allowing researchers to tune the properties of their material to their desired solution. The future of biomaterials Biomaterials have already brought about transformative innovations that have reshaped patient care and disease management. Ongoing research is laying the foundation for groundbreaking developments in biomaterials, from new types of materials to novel applications. This progress will also benefit from wider advances in technology, such as the use of 3D printing for personalized implants and the development of smart biomaterials that dynamically respond to physiological cues. Likewise, the integration of data-driven design and artificial intelligence (AI) solutions will accelerate the design and optimization of key biomaterials. The convergence of multidisciplinary approaches and emerging technologies will no doubt unlock new frontiers in the development and application of biomaterials, contributing to more personalized and effective medical treatments