The word biomaterial is fairly frequently encountered these days. But what exactly is a biomaterial?
A biomaterial is a material designed to interact with the body. Contrary to what the word may implicate, a biomaterial is not necessarily biological or based on bio-related matter. The material itself can be anything from metal to plastic to varieties of composites, but it can also be bio-inspired and derived from nature. The definition of a biomaterial is a material that is designed with the purpose of interacting with the body, i.e., it is designed to reside in a biological environment.
A brief history of biomaterials
Nowadays, biomaterials are widely used throughout medicine, dentistry, and biotechnology. Just 50 years ago, biomaterials, as we think of them today, did not exist. The word “biomaterial” was not used. There were no medical device manufacturers (except for external prosthetics such as limbs, fracture fixation devices, glass eyes, and dental devices), no formalized regulatory approval processes, no understanding of biocompatibility, and certainly no academic courses on biomaterials. However, crude biomaterials have been used, generally with poor to mixed results, throughout history.
The first historical use of biomaterials dates back to 32.000 years ago when ancient Egyptians used sutures made from animal sinew. Cat’s gut was used for suture in the Middle Age in Europe. As a science, however, biomaterials science is only about fifty years old. Biomaterials science is a highly interdisciplinary science with elements of medicine, biology, chemistry, tissue engineering, and materials science. The increasing importance of biomaterials in our society over the past decades can be tracked in a number of ways, including the growth of biomaterials both as an academic discipline and as an important industry. It has experienced steady and strong growth over its history, with many companies investing large amounts of money into the development of new products.
Why and when do we need biomaterials?
The modern applications of biomaterials are wide and multiple. Usually, biomaterials are designed to replace a missing piece of a body part by replicating the structure that is no longer there or to enhance a function that is deteriorating because of age or disease. Some of the most common examples are implants, such as hip joints and heart valves, skin transplants, vascular grafts, and stents. Biomaterials are also used in less invasive contexts, such as wound care. Even contact lenses are a biomaterial!
The function of a biomaterial implanted in the body can be relatively passive – see the heart valves – or may be bioactive, meaning that it actively interacts with some functions of the body. One example of this is hip implants coated with a special material called hydroxyapatite, which helps the integration of the implant with the original bone and has been successfully used for a long time. Biomaterials are also used every day in dental applications, surgery, and drug delivery. For example, a biomaterial with impregnated pharmaceutical products can be placed into the body, which permits the prolonged release of a drug over an extended period of time. Biomaterials are often biodegradable, and some are bio-absorbable, meaning they are eliminated gradually from the body after fulfilling a function.
Some examples - Biomaterials to mend a broken heart
Patients who survive a heart attack (7 out of 10) are left with a non-contractile scar on their heart. The scar will stay. The human heart has no intrinsic regenerative capacity, no capacity to heal itself. The presence of this scar will progress to heart failure, a condition where the heart is no longer able to efficiently pump blood all around the body. Currently, there are no available treatments for the cause of heart failure, only for the symptoms. Therefore, we should do something to prevent this scar from forming. We should act quickly after a heart attack. Biomaterials might be the answer.
Stem cells are undifferentiated cells that have the potential to become specialized adult cells, for example, heart muscle cells. However, if you inject stem cells into the heart, although they have the potential to repair it, they will not stick around. The beating of the heart will flush them away, and studies show that after 24 h they are all gone1.
The main advantage of biomaterials is that they can be delivered alone, but, most importantly, they can be used as a carrier to deliver stem cells. They can help the stem cells to stick around for longer and do their healing job. For example, after very promising results in animal models, there is a large clinical trial in France at the moment where surgeons and scientists are working together to test a combined approach with biomaterials and stem cells. This approach involves the use of stem cells delivered to the damaged heart through either an injectable hydrogel (a semi-solid water-based material of the same texture as contact lenses) or a patch (a sort of plaster)2.
Another study is developing a “patch” from stem cells. This patch could be used to replace damaged muscle tissue after a heart attack. It’s made from a scaffold of the protein collagen and is designed like a sponge with pores that absorb cells into the scaffold3.
Other examples - Biomaterials and stem cells for joints’ health
Cartilage is a pretty incredible substance. It’s strong yet flexible enough to allow adults’ bones to move against each other without injury for decades. But in the process of protecting the bones, the cartilage itself can take become damaged. The issue here is that when we’re adults, our articular cartilage cannot regrow or heal because it doesn’t have any blood vessels, which means oxygenated red blood cells can’t reach the damaged tissue.
Intra-articular injections of stem cells (meaning that the cells are delivered inside the joint) have shown promising results in knee osteoarthritis, and there are currently many clinical trials testing the efficacy of this treatment, not only for the knee joint but also for shoulders and hips4,5,6. As for the heart, these stem cells can be delivered through a biomaterial to make sure that they “stick” and do their job.
Another very useful way in which biomaterials can help cartilage regeneration is growing articular cartilage in a laboratory and then transplanting it in patients. Basically, scientists can construct a nurturing, jelly-like environment in a petri dish using biomaterials. Then, they can introduce special proteins, called growth factors, that help the stem cells decide what they’ll be when they grow up. In this case, you can make them become cartilage cells (called chondrocytes). Doing so, you end up with a tissue-like construct made of a biomaterial scaffold and cartilage cells that you can, relatively easily, implant in patients. This “artificial cartilage” resembles very closely the natural one, and many research groups all around the world are designing and testing the optimal protocol to develop high-quality artificial cartilage7,8,9.
To conclude, these novel treatments for regenerative medicine could revolutionize the way we treat heart attacks, joints pain, but also many other conditions such as congenital defects, neurodegenerative diseases, and many others. Thanks to tissue engineering, people could live longer, healthier lives.