What are biomaterials?
In 2011, I started my journey into the material sciences. As an undergraduate studying materials engineering, I was frequently asked ‘what is materials engineering?’ and ‘what does a materials engineer do?’. I went on to reply that a materials engineer is a professional who studies all types of materials, polymers, metals, ceramics, develops new ones and improves what we currently have. That was a vague answer that satisfied most. When I started my postgraduate degree in Biomaterials, the questions changed to ‘bio? What does bio mean? Is it plastic from plants?’. I believe I cannot answer this one with a brief, vague sentence.
The definition of ‘biomaterial’ is already complex. In my undergraduate course, I was told it was either materials that come from nature or materials that interact with the body. Technically that is not wrong but it’s also too broad and can give a false impression that, if it comes from nature, it can interact harmlessly with the body. So for the sake of this discussion, let’s just say that biomaterials are all materials, either natural or synthetic, that can be applied into or in close contact with the human body.
There are so many applications for these biomaterials. Do you know those medicines that come in capsules? It’s a biomaterial, a polymer, that dissolves when exposed to the acids in the stomach. And the hip replacement implants? A highly advanced metal alloy, with ceramic parts and polymer coating; all biomaterials. Also, the filling in your teeth, a composite material with polymer resin. In my clearly biased opinion, they are fascinating!
Biomaterials need to be biocompatible. Our body is a very chemically reactive machine, full of enzymes, ions, with a whole defence system always fully aware of new threats. Materials that don’t trigger our overly cautious immune system or react with any molecules are called bioinert. The ones that interact with our tissues and cells, having some sort of therapeutic or beneficial effect are called bioactive materials. Needless to say, we do not want materials that cause inflammation or are toxic. However, even materials considered bioinert tend to cause some reaction, so it’s more about how manageable the side effects are.
When we design biomaterials, we want them to be as similar to the tissue they are replacing/complimenting as possible. For instance, orthopaedic implants, such as hip and knee replacements, need to mimic the bone. Mismatch in properties, one being much stronger than the other, can lead to weaker bones. That happens because our cells produce bone according to cues they receive constantly. A knee replacement that is much stronger than bone will absorb all the load resulting from a walk, for example. That means the cells don’t get the mechanical signals that tell them to produce bone, they ‘think’ it’s not necessary. Which turns into weaker bones and a higher risk of fracture. Our body is a living, adaptable machine. We need to be aware of the cascade of events whenever we mess with it.
This is just one example of a problem scientists face when developing biomaterials. There are so many variables to consider in applications such as drug delivery systems, tissue engineering and biosensing. Even though we’ve been using biomaterials for a very long time, recent developments such as nanotechnology, imaging and genetic tools changed the landscape of what we understand and of what we can do. Now when we test a biomaterial in the lab, we’re able to measure gene expression from the cells, which tells us if they’re behaving as we want or expect. We can better imitate natural materials and their hierarchical structure, to try and achieve better biocompatibility.
It’s a bright future ahead for biomaterials. They’re already in the mRNA Covid vaccines (that’s a whole different post) and in so many aspects of our lives. If you want to see more examples of them, do take a look at my Instagram page, where I talk about a different biomaterial related topic every week!
