New biomaterial mimics human tissue, fights bacteria

Scientists at UNSW Sydney have created a new biomaterial that could change the way human tissue can be grown in the lab and used in medical procedures, which they have described in the journal Nature Communications.

The material belongs to a family of substances called hydrogels, the essence of the ‘squishy’ substances found in all living things, such as cartilage in animals and in plants like seaweed. The properties of hydrogels make them very useful in biomedical research because they can mimic human tissue, allowing cells to grow in a laboratory.

There are also human-made hydrogels that are used in commodity products ranging from food and cosmetics to contact lenses and absorbent materials, and more recently in medical research to seal wounds and replace damaged tissue. While they might function adequately as space fillers that encourage tissue growth, synthetic hydrogels fall short in recreating the complex properties of real human tissue.

UNSW scientists have now developed a lab-made hydrogel that behaves like natural tissue, with a number of surprising qualities that have implications for medical, food and manufacturing technology. Associate Professor Kris Kilian said the hydrogel material is made from very simple, short peptides, which are the building blocks of proteins.

“The material is bioactive, which means that encapsulated cells behave as if they are living in natural tissue,” said Kilian, from UNSW’s School of Materials Science & Engineering and School of Chemistry.

“At the same time, the material is antimicrobial, meaning that it will prevent bacterial infections. This combination lands it in the sweet spot for materials that might be useful in medicine. The material is also self-healing, which means that it will reform after being squished, fractured, or after being expelled from a syringe. This makes it ideal for 3D bioprinting, or as an injectable material for medicine.”

The discovery began during the COVID-19 lockdown, when UNSW PhD student Ashley Nguyen was looking for molecules that self-assemble — where they spontaneously arrange themselves without human intervention — using computer simulations, and stumbled upon the concept of ‘tryptophan zippers’. These are short chains of amino acids with multiple tryptophans that act as a zipper to promote self-assembly, which have been dubbed ‘Trpzip’.

“I was excited to identify a unique peptide sequence using computational simulations that might form a hydrogel,” Nguyen said.

“After we returned to the lab, I synthesised the top candidate and was thrilled to see it actually form a gel.”

Nguyen said new hydrogel has the potential to be an ethical alternative to widely used natural hydrogels, which require harvesting from animals.

“Also, animal-derived materials are problematic for use in humans because of the negative immune response that occurs,” she said. “With Trpzip, we have a synthetic material that not only shows potential in many areas where natural materials are currently used, but also could outperform them in others, such as clinical research.”

To test the viability of Trpzip in biomedical research, Kilian’s team partnered with Dr Shafagh Waters from UNSW’s School of Biomedical Sciences, who usually uses with Matrigel — a hydrogel harvested from mouse tumours — for the culture of patient tissue in her research. Waters explained that Matrigel has some disadvantages in research use because every batch is different, so a chemically defined alternative would be cheaper and more uniform.

The next phase of the team’s research will involve partnering with industry and clinical scientists to test the utility of Trpzip gels in tissue culture and explore applications like 3D bioprinting and stem cell delivery. With the natural materials business being a billion-dollar industry, Kilian is keen to explore pathways to commercialisation.

“We think that Trpzip hydrogels and materials like it will provide a more uniform and cost-effective alternative to animal-derived products,” he said. “It would be a tremendous outcome if our material reduced the number of animals used in scientific research.”

Image caption: The ‘Trpzip’ material will reform after being squished, fractured or expelled from a syringe. Image credit: UNSW Sydney.