The Role of Nanotechnology in Tissue Engineering
Why tissue engineering exists
Our bodies are made up of trillions of cells, each with very specific structures and functions. Every single one of these cells carries out an important task that helps our bodies stay at optimal and resource-efficient state.
As we live our lives, we constantly expose our body to danger, even if we don’t realize it. Everything we do, from walking to sleeping, requires energy, and through this constant energy use many of our cells die. It’s thanks to our bodies natural repair system that we are able to produce more cells and keep them functioning healthily.
I’m sure many of you reading this article have been in a situation that has negatively affected your body, whether it’s getting sick, getting a paper cut, or even having experienced something more severe. The common trait between all these situations is that each time you experience it, the cells in your body die. Usually this isn’t detrimental to us, and we are able to continue on with our daily activities because our body repairs itself.
But when we get into a situation that causes a widespread cellular death-that is, our tissue or even organs stop functioning-we need someway to externally supply our body with the mechanisms to heal itself. This external supplementation can come in many forms, such as physical structural support (eg. cast for broken bones), or medication (allows our body to return to a healthy state by killing an infection).
Unfortunately, many of these external forms of supplementation aren’t perfect, which is why diseases/injuries in general are such a major problem. Especially as illnesses become more complex and require specialized treatment, our current commercial methods become less and less effective. Because of the rising need for more personalized and targeted treatments, the field of tissue engineering was able to proliferate and find its use in many areas of medicine.
The role of scaffolds in tissue engineering
Tissue engineering is a broad subject area which combines many disciplines to accomplish one goal: improving upon or replacing biological tissues. The idea sounds simple, but the process to achieving this can actually be quite complex. There are many hurdles which impede scientists and engineers from creating viable tissues that can be used in the human body, and many of them aren’t quite apparent at first.
The first hurdle is actually ourselves. Our body has a natural defense system called the immune system, which automatically detects and attempts to kill any foreign thing that enters our body, usually a virus or bacterium. However, given that engineered tissues are made up of cells, there’s no reason that our body won’t attack it as well. This means that engineered tissue has to be created in such a way so that our body will “accept” it and not detect it as foreign.
Given that this is the case, it makes the most sense that we need to engineer tissues with the function and geometry that’s most familiar to the body. We can do this by creating structures called scaffolds, which mimic the extracellular microenvironments in our body. Scaffolds help cells used in tissue engineering to grow and be oriented properly, and ultimately be accepted into our body. Obviously these structures are super important, and the scalable production of them has been a topic under intense research.
Three methods to create functional scaffolds
Scaffolds have to meet certain requirements to be optimal for the body, like having certain thicknesses, various reactivities, biodegradability, etc. To meet these requirements, scaffolds have to be created with insane precision and detail (it is mimicking our cellular structures and interactions after all), up to the nanometer scale. And here is where nanotechnology comes in.
There are three main nanotechnological methods to create scaffolds: Self assembly, phase separation, and electrospinning. With tissue engineering being something that many people will want to take advantage of, it is important that these methods are simple and can be recreated outside of a lab for larger-scale production.
Let’s start with the first one: self assembly. I’m sure many of you reading this article have heard this term before. For those that don’t know, it is essentially the natural process of atoms bonding together to create larger structures. With recent advances in the nanotechnology field, many scientists have manipulated this process to have atoms assemble in desirable ways, usually to improve the form or function of whatever they’re making. In this case, the goal is to create an artificial extracellular microenvironment, which can be done my manipulating the self assembly process to hopefully create one.
The downside to this method is that it’s very complex. Creating scaffolds usually requires lots of lab equipment and skilled lab workers to piece small particles together correctly. This makes it hard for this process to be scaled up to be commercially available for people around the world. Although the end result of the self-assembly process can be very desirable, it’s just too hard to recreate outside of a lab.
This brings us to our next technique: phase separation. As the name suggests, this process involves separating a solution into different phases (solid, liquid, gas, etc.) to extract newly formed polymers. This can be done simply by changing the temperature of the solution or adding a non-solvent to it to create a gel. This makes the solution thermodynamically unstable, causing it to separate into two parts: a polymer-poor phase and a polymer-rich phase. By adding water, the solvent can be extracted. The simplicity of this process compared to many others means it doesn’t require complex lab equipment, making it promising for scalable production. In terms of cost, phase separation is fairly cheap. Unfortunately, this process is limited to a small number of materials, meaning that this process can’t be used to create many tissues/microenvironments that already exist within the human body.
Evidently, we need a process that meets the criteria of being precise, scalable, and simple, and this is where electrospinning comes in. The great thing about this technique is that it’s extremely simple, cost-effective, and doesn’t require any overly complicated procedures or equipment. This process works by having a capillary tube filled with a polymer solution. When the capillary tube is next to a ground (e.g. the earth), an electric charge is sent through the tube by a high voltage battery. Once the force of the electric charge overcomes the force of the meniscus holding the liquid in the tube, the liquid shoots out, kind of like a mini jet stream. The electronic attraction causes the polymer jet stream to direct itself towards the ground. The polymer jet also starts to spin in mid air, creating a loop shape. This is because of the charges in the electromagnetic field between the capillary tube and the ground.
One of the amazing things about electrospinning is that the entire process practically happens on its own. This allows for more active manipulation of various components in the setup, like moving the capillary tube in certain patterns or changing the voltage, or even using a different polymer solution altogether. All of this results in different materials of different attributes, which can be applied to different microenvironments in the body. The only downside to this process is that it lacks some accuracy.
However, given all the technological advances we have made in the last few decades, this surely won’t be a long standing issue. The field of tissue engineering is quite promising, and holds huge potential for the future of medicine and nanotechnology. With huge amounts of research and experimentation going towards this area, there’s definitely going to be more exciting advances that will change our life for the better,
Thank you for reading this article! If you want more information, check out some of the links below.
Works Cited:
- Phase Separation. (n.d.). Retrieved February 24, 2019, from https://www.sciencedirect.com/topics/chemistry/phase-separation
- Sill, T. J., & Von Recum, H. A. (2008, February 20). Electrospinning: Applications in drug delivery and tissue engineering. Retrieved February 26, 2019, from https://www.sciencedirect.com/science/article/pii/S0142961208000203
- L. M., & H. J. (2005). Synthetic biomaterials as instructive extracellular microenvironments for morphogenesis in tissue engineering. Retrieved February 20, 2019, from https://www.nature.com/articles/nbt1055
