Biomaterials in Medicine

Most medical devices are made of metals, plastics, and other synthetic elements.

What’s the issue with that?

Well, your body is made of organic biomaterials.

So that means that inorganic medical devices automatically will be incompatible with your biological systems. What if we could do medicine using biomaterials?

We’ve survived this long using inorganic materials you might say. And yes, that’s true, but there are a lot of other benefits to using organic materials.

  1. Compatibility — The more similar the two things you put together, the more likely they are to integrate.
  2. Flexibility — Your body and biological processes are flexible and can move and mold and shape around other things.
  3. Insertion and Removal — If it’s natural and flexible, it will be easier to add into the body. If/when it needs to be removed, it could be broken down by your natural bodily functions.
  4. Environment — Using natural materials is usually more environmentally friendly than synthetic things.

So then what is this biomaterial?

What is a hydrogel?

If you’ve ever seen those little pellets you put in water that swell up to be a jello like substance, that’s a hydrogel.

Contact lenses are also hydrogels.

It’s made from a 3d network of polymers that, when exposed to water, swell. You can think of it kind of like a net shape. When it’s dehydrated, it’s small and squished, but when you add water, the inside fills and the water is trapped.

This net is formed using cross linkages. Imagine if you combined string with connector pieces.

Cross-linking process

The strength of a hydrogel comes from its covalent bonds. It also has many hydrophilic groups (polar, water-loving sections) such as amines(-NH₂), carboxyls (-COOH), alcohols (-OH), amides(-CONH₂), sulfos (-SO₃H).

Drug Delivery

Hydrogels can be used for targeted drug delivery. Inside the net, you can add drug particles and use the hydrogel as a carrier to deliver the drug.

This method can be more targeted than simply injecting the drug independently because hydrogels can be engineered to respond to their environment. Hydrogel can swell or unswell in response to external stimuli like the presence of a particular chemical.

What hydrogels can be used for:

Hydrogels are still in the research phase so a lot of these studies that came out in the past few months.

Smart Hydrogels:

Making hydrogels respond to their outside environment is key to having targeted effects. Light, temperature, and pH were mentioned above, but going even further, scientists are embedding DNA or proteins into the hydrogel network. DNA can be used for molecular recognition and the proteins effectively give the hydrogel their own functionality.

Pollution:

Hydrogels can be added to water sources and used to suck up pollutants. Currently though, hydrogels are still too expensive to be used on such a large scale.

Wound Dressings:

A number of companies are looking into using hydrogel bandages or wound dressings. Since they’re a natural material, they can prove more sensitive to the wound. It preserves moisture, and additional healing properties like medicine can be added into the dressing.

Hydrogels x Cancer:

MIT Researchers used PEG-PLA copolymers mixed with cellulose to carry chemotherapy drugs. The hydrogel is injected, attracts the tumor cells, delivers chemotherapy, and mops up or absorbs the dead cells. The filled hydrogel can now fill in the cavity left behind to repress further growth.

This uses a non invasive injection to deliver the chemotherapy to a very targeted group of cells and limits the accidental killing of healthy cells. It also enables you to vary dosing rates over time depending on the number of tumor cells.

Hydrogels x GI Tract:

Hydrogels were used to create a bariatric balloon and esophageal stent. In the case of the bariatric balloon, the patient swallowed the light sensitive hydrogel and when it reached the GI tract, it swelled up. When doctors wanted to remove it, they exposed it to a small light that caused it to deflate.

Instead of needing to insert a tube from the throat into the stomach and pumping the balloon up, this process is much simpler.

Hydrogels x Osteoarthritis:

Osteoarthritis is when the cartilage in the joints break down and currently there isn’t a cure. Researchers tried injecting hydrogels into the joint to stabilize it and stop deterioration.

The hydrogel itself was actually found to stimulate new cartilage cell growth and repair. Combining stem cells with the hydrogel accelerated the process even more. This was successfully tested in horses and is beginning human trials.

Hydrogels x Spinal Cord:

After a spinal cord injury, cystic cavities often form, but scientists found that hydrogels can be used to fill the cavities and even support regrowth. It soothed the severed axons to prevent further damage. In 2017 clinical trials in rats, when hydrogels were injected into cystic cavities the cavities shrank! This is really exciting because the spinal cord is thought to not be able to regrow.

In Summary:

  • Hydrogels are like a polymer net that can swell and deflate on cue
  • They can carry drugs to targeted locations
  • Hydrogels are being researched for use in a variety of applications from cancer to spinal cord injuries

I hope enjoyed learning about some real time applications of hydrogels. If you work with hydrogels or you’re interested in this article and want to talk, you can contact me at kiranamak@gmail.com.

At 17 years old, I love learning and am interested in materials science, education, and environmental sustainability.