Chemists design shape-changing nanomaterials with biochemical potential

Chemists have developed nanomaterials that inspire them to shape movement – from flat sheets to tubes and back to sheets again – in a controllable way. The Journal of the Chemical Society of America published a description of the nanomaterials, developed at Emory University and capable of a range of biochemical applications, from controlled drug delivery to compression engineering.

The nanomaterial, which is in the form of a leaf 10,000 times thinner than the width of a human hair, is made of synthetic collagen. Naturally occurring collagen is the most abundant protein in humans, making the new material highly biodegradable.

“No one has made collagen before with the shape-shifting properties of our nanomaterials,” says Vincent Conticello, senior discovery author and Emory professor in biomolecular chemistry. “We can turn it from leaves to tubes and back just by changing the pH, or acidic density, in its environment.”

The Emory Office of Technology Transfer has applied for a temporary patent for the nanomaterials.

The first authors to be discovered are Andrea Merg, a former postdoctoral fellow in Conticello’s lab now at the University of California Merced, and Gavin Touponse, who did the work as an Emory undergraduate and is now the medical school at Stanford. The work was a collaboration between Emory and scientists from the Argonne National Laboratory, the Paul Scherrer Institute in Villigen, Switzerland, and the Center for Cellular Imaging and NanoAnalytics at the University of Basel.

Collagen is the main structural protein in the connective tissue of the body, such as cartilage, bones, tendons, ligaments and skin. It is also abundant in blood vessels, the gut, muscles and other parts of the body.

Collagen taken from other mammals, such as pigs, is sometimes used for wound healing and other medical applications in humans. Conticello Laboratory is one of only a few dozen worldwide with a focus on developing synthetic collagen suitable for applications in biomedicine and other complex technologies. Such synthetic “designer” biomaterials can be controlled in ways that natural collagen cannot.

“As far back as 30 years ago, it became possible to control the collagen sequence,” Conticello says. “The field has really boosted steam, however, in the last 15 years as a result of advances in crystals and an electronic microscope, which allows us to better study structures at the nano-scale. . “

The development of Emory’s new motion-shaped nanomaterial was a “lucky disaster,” Conticello says. “There was an element of luck and an element of design.”

The collagen protein is made up of a triple helix of wood that wraps around each other like a three-layered rope. The strands are not flexible, are firm like pencils, and pack together tightly in a crystalline layer.

Conticello’s lab has been working with collagen sheets he developed for a decade. “One sheet is a large, two-dimensional crystal, but because of the way the peptides are packed it looks like a whole bunch of pencils folded together,” Conticello explains. “Half of the pencils are in the package with their instructions marking and the other end marking their scratches.”

Conticello wanted to try to update the collagen sheets so that each side was limited to one action. To advance the pencil simulation, one surface of the sheet would be the main points and the other surface would be a eraser. The ultimate goal was to develop collagen sheets that could be integrated with a medical device by making one surface compatible with the machine and the other surface compatible with action proteins in the body .

When the researchers engineered these different types into single collagen sheets, however, they were surprised to find that it made the sheets bend up like scrolls. They then discovered that the shape movement was reversible – they could control whether a leaf was flat or examined simply by changing the pH of the solution it contained. They also showed that they could adjust the sheets to form a movement at a certain pH. levels in a way that can be controlled at the molecular level by design.

“It’s particularly interesting that the situation around which the movement is taking place is a psychological state,” Conticello says. “That opens up the opportunity to find a way to load a drug into a collagen tube under controlled, laboratory conditions. Then the collagen tube could be pressed to unfurl and the Molecular release of existing drug molecules after entering the pH environment of human cells. “

Emory scientists who contributed to the measurement and characterization of the new nanomaterials and who co-authored the paper include chemistry professors Brian Dyer and Khalid Salaita; chemistry graduate students Alisina Bazrafshan and Helen Siaw; and Arthur McCanna from Robert P. Apkarian ‘s Cross Integrated Electric Microscopy.

###

Co-authors from the Paul Scherrer Institute helped identify the three-dimensional structure of the crystalline assemblages and further analyzed the nanomaterials. They include Jan Pieter Abrahams, Thorsten Blum and Eric van Genderen. Xiaobing also contributed Zuo from Argonne National Laboratory as co-author of the project.

The work was supported by funding from the National Science Foundation, the Swiss National Science Foundation and the National Institutes of Health.