Question: What is a biomaterial?
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A biomaterial is any material engineered for use in a biological system. Artificial heart valves and joint replacements are well-known examples.
![Designing a biomaterial to treat a brain injury is a challenging process. Designing a biomaterial to treat a brain injury is a challenging process.](/images/transform/v1/crop/frm/silverstone-ct-migration/96526763-733f-48cb-94a3-d7dd5a93f9df/r0_0_1000_666_w1200_h678_fmax.jpg)
Biomaterials must be carefully engineered. To illustrate this, consider the challenges of designing a biomaterial to treat traumatic brain injury. One potential approach involves implanting an artificial scaffold into damaged brain tissue with stem cells. This scaffold directs stem cells in the brain to develop into healthy brain tissue. Stem cells are known for their marvellous ability to turn into any kind of cell, but just the ability to do something doesn't make it happen.
You can think of stem cells as tiny teenagers: full of potential, but they need a kick in the pants to get going. Also like teenagers, stem cells like to conform. They look around their environment, sensing the physical, chemical, and biological properties of the surrounding material to determine where they are and what type of cell they should be. If we want stem cells to develop into brain tissue, we need to design a scaffold to mimic the properties of normal brain tissue. For example, it needs to be squishy because a stiff material would encourage the stem cells to turn into bone.
At the same time, the scaffold needs to be rigid enough to provide physical support. Trying to balance all of these properties simultaneously is where things get difficult. Here we're after a Goldilocks material, not too strong and not too weak. Achieving this balance is vital.
When biomaterial properties are too far from normal, your immune system recognises the materials as foreign, and your immune system has a very strict immigration policy. The immune system will either destroy foreign material, or, if it can't break it down, it will build a wall around it. This is what happens when you get asbestos in your lungs; the asbestos itself is inert, but the walls assembled around the asbestos impair your lungs.
We need to design a scaffold that can guide stem cells into becoming brain cells while convincing the immune system there's nothing to see. There's a lot of exciting development going on in biomaterials now, from nanoscale engineering to 3D printing full organs, bringing together engineers and medical researchers to help tackle challenging medical problems like traumatic brain injury.
Response by: Kiara Bruggeman, Research School of Engineering, the Australian National University
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