But a company in Cambridge, Massachusetts, called Vaxess Technologies plans to sidestep this common fear by abandoning stainless steel needles and switching to silk.
The silk protein acts as a preservative, so there’s no need to keep it on ice at a doctor’s office. ‘It’s similar to what happens when you freeze something,’ said Vaxess founder and chief executive Michael Schrader. ‘It’s room-temperature freezing.’ In testing, Vaxess found that flu vaccines stored in a silk patch at room temperature remained viable three years later.
No more need for a ‘cold chain’, the costly network of refrigerators between manufacturing plants and medical clinics required by so many vaccines. Indeed, there’d be no need to get vaccinated at a clinic at all. Patients could vaccinate themselves.
‘We would mail you a patch,’ said Schrader. ‘It looks like a nicotine patch, only much smaller. You wear the patch for five minutes, then take it off and throw it away.’
Having completed a successful phase one clinical trial of the silk patches in late 2022, Schrader hopes to bring them to market by 2028.
It’s hardly the sort of product we’d usually associate with silk, the tough, luxurious, and luminous fabric that has delighted people for at least 5,000 years. But silk is proving to be far more valuable than its early Chinese cultivators could have imagined.
Much of what we now understand about silk was discovered at Silklab, a branch of the department of engineering at Tufts University in Medford, a suburb of Boston. Here a visitor encounters silken lenses that project words and images when bathed in laser light; surgical gloves coated in silk that display a warning if they’ve been contaminated with pathogens; tiny silken screws that are strong enough to repair a broken bone, only to dissolve entirely once the injury is healed.
For Silklab director Fiorenzo Omenetto, silk is not a fashion statement. It’s a set of microscopic Lego blocks that he and his colleagues are pulling apart and reassembling into an array of unexpected products.
‘We make everything,’ said Omenetto. ‘We make plastics, we make edible electronics, we make coatings for food.’
Silk isn’t everything at Silklab. Omenetto and his colleagues experiment with a variety of similar molecules, known as structural proteins. They’re found all over the place, shaping and strengthening plant and animal tissues. There’s the keratin in hair, collagen that holds our organs together, and more.
But for Omenetto, silk comes first. And his team has found an array of new uses for a fiber that humans have been cultivating for millennia.
Legend has it that the wife of the Yellow Emperor, who reigned around 2700 BC, was sipping hot tea under a mulberry tree when the cocoon of a silkworm fell into her cup. The hot liquid dissolved the cocoon’s sticky coating and caused the silk underneath to unravel, revealing its extraordinary beauty and strength. Then again, Chinese archeologists in 2017 found traces of silk in the soil under bodies in tombs 8,500 years old. The traces could be wild silk, but they could also suggest that sericulture – silk farming – may have begun much earlier.
A gray moth called Bombyx mori is the source of the silk. Centuries of selective breeding have created moths that reproduce at an exceptional rate – up to eight generations per year, compared to just three for wild silk moths. Domestication has wrought other changes; their wings are so stubby that the moths can barely fly, and the female moths are born already fat with as many as 500 eggs ready for immediate fertilization by a male.
In about ten days, the eggs hatch into silkworms, tiny caterpillars that are only about two or three millimeters in size. They mature quickly; given proper care, the worms will grow to 10,000 times their birth weight in about a month.
Theirs is a monotonous diet – they eat only the leaves of mulberry trees, and quite a lot of them. The recipe for one pound of silk: start with about 3,000 worms, gradually add 220 pounds of clean, fresh mulberry leaves, and wait about a month.
That’s when the silkworms begin to spew forth the cocoons that will shield them from harm as they develop into moths. The silk emerges from two glands called spinnerets located near the worm’s jaws. The stuff is almost entirely made of a protein called fibroin. The worm emits two streams of fibroin, then coats them in a gooey protein called sericin.
For up to three days, the silkworm’s head weaves back and forth as it wraps itself in silk. The finished cocoon is no bigger than a chocolate-covered almond, yet its silk forms a continuous thread a kilometer long.
To get at the silk, humans boil the cocoons, killing the worm inside and stripping away the sericin. Then the silk fiber is unspooled.
The stuff is stronger than a steel wire of equal thickness, stronger even than the Kevlar fibers found in bullet-resistant vests. In fact, one of the first such vests, developed by Chicago Catholic priest Casimer Zeglen in 1897, was woven of silk. It worked, too.
Spider silk is actually stronger than that produced by silkworms. But nobody’s been able to successfully domesticate spiders, which have an unfortunate habit of eating one another. Happily, silkworms have been getting along well with humans and one another for quite a few centuries. (...)
One Silklab spinoff, Boston-based Mori, has raised over $82 million in investment capital, and has begun signing contracts with food distributors for a product that turns silk into a food preservative.
Keeping meats and vegetables flavorful is largely a matter of keeping oxygen and bacteria out and moisture in. A plastic wrapper can accomplish this, but supermarkets aren’t going to wrap each apple or banana. Apart from the cost and inconvenience, it would generate vast amounts of plastic waste.
One Silklab spinoff, Boston-based Mori, has raised over $82 million in investment capital, and has begun signing contracts with food distributors for a product that turns silk into a food preservative.
Keeping meats and vegetables flavorful is largely a matter of keeping oxygen and bacteria out and moisture in. A plastic wrapper can accomplish this, but supermarkets aren’t going to wrap each apple or banana. Apart from the cost and inconvenience, it would generate vast amounts of plastic waste.
But in 2016, Omenetto and Kaplan joined with Benedetto Marelli, an associate professor at the Massachusetts Institute of Technology, to demonstrate that merely dipping the food in a solution of silk and water leaves behind a film that holds in moisture and keeps out air and bacteria. On average, fruit and vegetables coated in silk protein can remain fresh at room temperature for one week longer than unwrapped food. And unlike plastic wrap, there’s no waste. It’s not even necessary to wash off the silk coating; it’s flavorless, nontoxic, and biodegradable. (...)
Today’s skin care ingredients are mostly synthetic compounds supplied by petrochemical companies. Not dangerous in themselves, the manufacture of these synthetics often involves the use of toxins like cyanide and heavy metals. Besides, many of these chemicals eventually end up in our food and water.
‘We don’t necessarily know if they’re biodegradable,’ Altman said. ‘We don’t know where they end up.’
Altman and Lacouture’s new company, Evolved by Nature, developed a version of silk protein that substitutes for claudin, a different protein that occurs naturally in human skin. Over time, claudin tends to erode, making our skin more vulnerable to moisture loss. Evolved by Nature’s skin barrier is designed to deliver a dose of silk protein to fill in the gaps. (...)
But Altman said skin care is only the beginning. Silk protein, he said, makes an excellent substitute for petrochemical coatings used in a vast array of products.
The stuff’s everywhere, Altman said. ‘There’s a layer on your glasses. There’s a coating on a trillion dollars of textiles produced every year. In every house, architectural surfaces. In every car, on every piece of leather.’
His company’s future product road map includes custom silk protein for coating fabrics and leather. Because it’s not a medical application, these coatings needn’t be made of the finest silk. Altman said his company could thrive on silk producers’ leftover scraps. ‘Evolved by Nature could generate a billion dollars in revenue’, he said, ‘and never use anything but the trash of the sericulture industry.’
‘We don’t necessarily know if they’re biodegradable,’ Altman said. ‘We don’t know where they end up.’
Altman and Lacouture’s new company, Evolved by Nature, developed a version of silk protein that substitutes for claudin, a different protein that occurs naturally in human skin. Over time, claudin tends to erode, making our skin more vulnerable to moisture loss. Evolved by Nature’s skin barrier is designed to deliver a dose of silk protein to fill in the gaps. (...)
But Altman said skin care is only the beginning. Silk protein, he said, makes an excellent substitute for petrochemical coatings used in a vast array of products.
The stuff’s everywhere, Altman said. ‘There’s a layer on your glasses. There’s a coating on a trillion dollars of textiles produced every year. In every house, architectural surfaces. In every car, on every piece of leather.’
His company’s future product road map includes custom silk protein for coating fabrics and leather. Because it’s not a medical application, these coatings needn’t be made of the finest silk. Altman said his company could thrive on silk producers’ leftover scraps. ‘Evolved by Nature could generate a billion dollars in revenue’, he said, ‘and never use anything but the trash of the sericulture industry.’
by Hiawatha Bray, Works in Progress | Read more:
Images: Wikimedia; Library of Congress
