A UNSW professor has created a type of fabric that replicates bone tissue, with potential for wide-ranging medical, commercial and safety applications. By Michele Tydd.
Biology-inspired smart fabrics
In 2013 students at a weaving course in the United States were surprised to discover the ambitions of one of their classmates. While they had their sights set on stylish sofa throws or rugs, biomedical engineer Professor Melissa Knothe Tate wanted to replicate the natural weave of the tissue around human bones. The Jacquard loom used in the classes was to become a critical component in Tate’s research into a future generation of smart materials inspired by nature.
“I thought it was important I learn the weaving process, so I squeezed in a road trip to the tomato fields in Chico, California, to classes recommended by the company that made my laboratory loom,” says Tate, who is University of New South Wales Paul Trainor Chair of Biomedical Engineering.
The quirky world-first technology her team used to develop the smart materials is now at the stage where Australian and international patents are pending. “The potential medical, safety and commercial applications range from more efficient compression sleeves to bulletproof vests. We even have a company interested in our material for a new range of steel-belt radial tyres,” she says.
The first wave of smart fabrics was pioneered by Professor Gordon Wallace’s team from the University of Wollongong in the 1990s, which created “intelligent” conductive polymers. These could sense and respond to stimuli and were used to create clothing such as the widely publicised smart bra for sportswomen.
“They have done fantastic work with polymers that shrank and expanded under electricity or battery power,” says Tate. “The novel aspect of our work is that the smart properties are intrinsic to the materials themselves.
“When they are stretched or strained from normal human movement, they exert a pressure wave on the body part such as arm or a leg. They basically harness energy in the body’s own movement to generate the required pressure gradients.
“We see these patterns in real tissues and we work backwards to develop the algorithms to achieve the same textile with the same pattern of mechanical strains.”
The research, recently published in Nature’s Scientific Reports, is focused on the periosteum, the protective tissue sleeve around most of the body’s bones.
“It’s hyper-elastic tissue which is super stretchy and soft,” says Tate.
These properties derive mainly from the proteins collagen and elastin that also give the tissue its strength. These particular protein fibres proved too elusive for the first weave prototypes so were replaced with similar easier-to-obtain natural fibres.
“Periosteum doesn’t seem that strong but it gives our bones turbo strength,” says Tate. “The way we know is that if you take the periosteum off a bone in mechanical testing machines, it breaks at a much much lower load level than it does with it on. So it’s these sorts of smart materials that we’re trying to emulate here. They can be soft and stretchy like periosteum, but also stiffen under load.
“For example, if we wanted to make a bulletproof textile to protect the wearer, it would need to have strain-stiffening properties under extremely high-impact loads. But it would also need to be soft and wearable for the user under normal conditions,” she says.
In essence the process involves mimicking nature’s own cellular spinning and weaving in situ.
To do that, the team rely on high-resolution microscopes and optics to map the cellular structure of the natural tissue they want to replicate and then it is scaled up and woven with meticulous precision.
The Jacquard loom, with its punch-card technology similar to that used in the first commercial computers, was considered the go-to machine for this project.
“The loom I have in my lab is amazing,” says Tate. “It has five computer motherboards, so essentially the logic boards from five computers run the lifting and dropping of the hooks. We can control … 5000 different threads to make up the desired pattern.”
Tate is also using the technology to create soft surgical implants that deliver stem cells and healing agents to tissue defects, essentially mimicking the periosteum’s role as a smart habitat for stem cells, guiding the cells to injured tissue at the right time
This stem cell work is significant in that it improves our understanding of bone formation, according to biomedical engineer Greg Forman, the CEO of Cellform in Dallas, Texas.
“Biologic research for the past 30 years has focused on creating bone-growth substitutes,” says Forman. “It was first theorised that to grow new bone to fill gaps in bone defects you first had to fill it with an osteoconductive material so bone could grow into, around and over it to fill it with new bone growth.
“These materials would need to be absorbed by the body and replaced with bone, a long process that differs greatly from material to material.”
Forman says Tate has shown for the first time from a cellular level how bone grows from the periosteum inwards.
“Her artificial periosteum with its flow properties is a valuable insight into understanding how bone forms for future research,” he says.
Another research spinoff is a pilot project that involves weaving a compression sleeve prototype for women suffering lymphoedema after breast cancer surgery. Lymphoedema is a painful condition caused by fluid accumulation in the limbs after draining nodes or glands have been removed from the armpit.
“It is interesting how little is known about the properties of the existing sleeves and how they work and if they work, and also are they being properly applied,” says Tate.
She says tests on current sleeves show significant weaknesses.
“We are putting a huge effort into first understanding how current compression sleeves work and secondly trying to redesign them so they are both comfortable and efficient.”
Tate grew up in an itinerant family with three siblings, a naval engineer father and a journalist mother who later became a teacher and counsellor.
“My father wanted me to go into electrical engineering but I was much more visually orientated, and very into art and literature,” she says. “I’m more the creative type.”
Tate did earn a degree in mechanical engineering but combined it with a degree in biology at Stanford University.
“I found a position in a Stanford lab very early on that was doing fascinating research into the relationship between physical activity and bone strength and health,” she says.
It provided Tate with a valuable apprenticeship for the work she is doing now, especially with a mentor such as Professor Dennis Carter, who was the founder of the mechanobiology movement in the United States.
Tate says she eventually wants to weave biodegradable tissues for joint replacements and repairs.
“I’ve wanted to do this since I wrecked my shoulder in a mountain biking accident early in 2013.
“Before that, I was working on basic science approaches to guide cells to weave tissues naturally. Now we are directly applying these cellular principles to weave scaled-up textiles on a loom.”
While she thrives on work and problem-solving, Tate sets a steady, patient pace.
“Both the long-term basic research and more applied research with solid results in the short term provide the foundation for the big discoveries and innovative technologies 20 years on,” she says.
“It’s a bit like a good stock portfolio in which you need a lot of breadth and depth with short- and long-term performance in mind, and that’s the way we should also organise our research portfolios.”
This article was first published in the print edition of The Saturday Paper on February 4, 2017 as "Looming success".
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