Tag Archives: organ transplants

Say goodbye to crunchy (ice crystal-laden) in ice cream thanks to cellulose nanocrystals (CNC)

The American Chemical Society (ACS) held its 2022 Spring Meeting from March 20 – 24, 2022 and it seems like a good excuse to feature ice cream.

Adding cellulose nanocrystals prevents the growth of small ice crystals (bottom left) into the large ones (top left) that can make ice cream (right) unpleasantly crunchy. Scale bar = 100 μm. Credit: Tao Wu

A March 20, 2022 news item on phys.org introduces an ice cream presentation given at the meeting on Monday, March 20, 2022,

Ice cream can be a culinary delight, except when it gets unpleasantly crunchy because ice crystals have grown in it. Today, scientists report that a form of cellulose obtained from plants can be added to the tasty treat to stop crystals cold—and the additive works better than currently used ice growth inhibitors in the face of temperature fluctuations. The findings could be extended to the preservation of other frozen foods and perhaps donated organs and tissues

A March 20, 2022 ACS press release, which originated the news item, provides more details about crunchy ice cream and how it might be avoided,

Freshly made ice cream contains tiny ice crystals. But during storage and transport, the ice melts and regrows. During this recrystallization process, smaller crystals melt, and the water diffuses to join larger ones, causing them to grow, says Tao Wu, Ph.D., the project’s principal investigator. If the ice crystals become bigger than 50 micrometers — or roughly the diameter of a hair — the dessert takes on a grainy, icy texture that reduces consumer appeal, Wu says. “Controlling the formation and growth of ice crystals is thus the key to obtaining high-quality frozen foods.”

One fix would be to copy nature’s solution: “Some fish, insects and plants can survive in sub-zero temperatures because they produce antifreeze proteins that fight the growth of ice crystals,” Wu says. But antifreeze proteins are costlier than gold and limited in supply, so they’re not practical to add to ice cream. Polysaccharides such as guar gum or locust bean gum are used instead. “But these stabilizers are not very effective,” Wu notes. “Their performance is influenced by many factors, including storage temperature and time, and the composition and concentration of other ingredients. This means they sometimes work in one product but not in another.” In addition, their mechanism of action is uncertain. Wu wanted to clarify how they work and develop better alternatives.

Although Wu didn’t use antifreeze proteins in the study, he drew inspiration from them. These proteins are amphiphilic, meaning they have a hydrophilic surface with an affinity for water, as well as a hydrophobic surface that repels water. Wu knew that nano-sized crystals of cellulose are also amphiphilic, so he figured it was worth checking if they could stop ice crystal growth in ice cream. These cellulose nanocrystals (CNCs) are extracted from the plant cell walls of agricultural and forestry byproducts, so they are inexpensive, abundant and renewable.

In a model ice cream — a 25% sucrose solution — the CNCs initially had no effect, says Min Li, a graduate student in Wu’s lab at the University of Tennessee. Though still small, ice crystals were the same size whether CNCs were present or not. But after the model ice cream was stored for a few hours, the researchers found that the CNCs completely shut down the growth of ice crystals, while the crystals continued to enlarge in the untreated model ice cream.

The team’s tests also revealed that the cellulose inhibits ice recrystallization through surface adsorption. CNCs, like antifreeze proteins, appear to stick to the surfaces of ice crystals, preventing them from drawing together and fusing. “This completely contradicted the existing belief that stabilizers inhibit ice recrystallization by increasing viscosity, which was thought to slow diffusion of water molecules,” adds Li, who will present the work at the meeting.

In their latest study, the scientists found that CNCs are more protective than current stabilizers when ice cream is exposed to fluctuating temperatures, such as when the treat is stored in the supermarket and then taken home. The team also discovered the additive can slow the melting of ice crystals, so it could be used to produce slow-melting ice cream. Other labs have shown the stabilizer is nontoxic at the levels needed in food, Wu notes, but the additive would require review by the U.S. Food and Drug Administration.

With further research, CNCs could be used to protect the quality of other foods — such as frozen dough and fish — or perhaps to preserve cells, tissues and organs in biomedicine, Wu says. “At present, a heart must be transplanted within a few hours after being removed from a donor,” he explains. “But this time limit could be eliminated if we could inhibit the growth of ice crystals when the heart is kept at low temperatures.”

Interesting to see that this research into ice cream crystals could lead to new techniques for organ transplants.

Globe and Mail discovers nanomedicine

Business writer, Nick Rockel, has an October 4, 2011 article titled, Nano-technology [sic] coming to the doctor’s office, in The Globe and Mail newspaper. Dr. Jillian Buriak and her colleague, Dr.Lori West (my latest posting about their work was April 28, 2011) were heavily featured in it. From the Oct. 4, 2011 article in The Globe and Mail,

One of Dr. Buriak’s key collaborators on the transplantation project is Lori West, a U of A [University of Alberta] professor of pediatrics, surgery and immunology. Dr. West, a renowned cardiac transplant expert, is known for her discovery that children younger than two will not reject a heart from a donor with a different blood type.

That’s because the immune system is still developing during infancy. Even more remarkably, if a baby with Type A blood gets a Type B heart, it will develop a lifelong tolerance for B and AB blood.

The U of A team “functionalized” so-called stealth nano-particles with the antigens, or markers, that blood cells use to recognize each other. In animal tests, it introduced these particles into the bloodstream in an attempt to teach the body to tolerate every blood type.

Dr. Buriak, who hopes to move to more advanced models by 2015, says the nano-particles could eventually join the standard set of shots that children receive. “Later, if you ever had to have an organ transplant or a transfusion, you wouldn’t have to wait for the right one – you could just take any of them.”

Buriak’s and West’s strategy for avoiding organ rejection contrasts with the strategy used by a joint (Swedish/UK/US) team, which I featured in an August 2, 2011 posting about their work transplanting a synthetic windpipe coated with stem cells harvested from the patient receiving the new organ.

Rockel’s article goes on to provide descriptions of other nanomedicine initiatives (a mix of Canadian- and US-based projects). He employs the usual ‘war against disease’ rhetorical style common to articles about any kind of medicine even when he’s including a ‘kinder, gentler’ quote such as,

People keep asking when her field will deliver a killer app like the cure for cancer, Dr. Buriak says. “But what nanotechnology has done more than anything else is bring people together who normally would never talk to each other,” she explains. [emphases mine]

As one would expect from a business writer, the article concludes with a list of three commercially available nanomedicne products. I wish Rockel had stated whether or not he’s done additional research into these products since this list is culled from the Project on Emerging Nanotechnologies (PEN) database. As I’ve noted before (my July 26, 2011 posting) there is no oversight provided by PEN nor does the organization require any description of how the product is nanotechnology-enable, as they openly admit.

I’m glad to see more coverage of nanotechnology and that writers from many specialties are learning about it. As for why I described Nick Rockel as a business writer, here’s his description of his work,

Market forces are one thing, but you can’t force somebody to read about the markets. Nick Rockel helps you connect with your audience. A veteran writer and editor, Nick knows how to grab people’s attention by giving them access to the financial and investment world. Whether it’s hedge funds or herding behaviour, he presents complex subjects in clear and simple terms, without any jargon or bafflegab. Most important, Nick finds the story behind the numbers and makes it resonate with readers.

He advertizes himself as providing Financial Wrting, Editing & Research.