Chemists invent shape-changing nanomaterials with biomedical potential

Chemists have developed nanomaterials that can cause shape changes from flat sheets to tubes and back to sheets in a controllable way. The Journal of the American Chemical Society has published a description of nanomaterials developed at Emory University that have potential for a variety of biomedical applications, from sustained-release drug delivery to tissue engineering.

Sheet-like nanomaterials are 1 / 10,000th the width of human hair and are made of synthetic collagen. Naturally occurring collagen is the most abundant protein in humans, making new materials essentially biocompatible.

“To date, no one has made collagen with the shape-changing properties of our nanomaterials,” said Vincent Conticello, senior author of the discovery and professor of biomolecular chemistry Emory. I will. “By simply changing the pH or acid concentration in the environment, you can convert or restore a sheet to a tube.”

The Emory Technology Transfer Authority has applied for a provisional patent for nanomaterials.

The first authors of the findings are Andrea Melg, a former postdoctoral fellow at the Conticero Lab at the University of California, Merced, and Gavin Tupons, who worked as an undergraduate student at Emory University and is now at Stanford University School of Medicine. The work was a collaboration between Emory and scientists at the Argonne National Laboratory, the Paul Scheller Institute in Villigen, Switzerland, and the Center for Cell Imaging and Nanoanalysis at the University of Basel.

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

Collagen from other mammals, such as pigs, may be used for human wound healing and other medical applications. Conticello’s lab is one of dozens of labs in the world focused on developing synthetic collagen suitable for applications in biomedical and other complex technologies. Such synthetic “designer” biomaterials can be controlled in ways that natural collagen cannot control.

“Going back 30 years, it became possible to control the sequence of collagen,” says Conticello. “But advances in crystallography and electron microscopy have really gained momentum in this area over the last 15 years, allowing us to better analyze structures at the nanoscale.”

Conticero says the development of new shape-changing nanomaterials at Emory was an “accident”. “It had an element of luck and an element of design.”

Collagen proteins are made up of triple helix of fibers that wind around each other like a triple-stranded rope. The strands are inflexible, as hard as a pencil, and tightly packed into an array of crystals.

Conticello Lab has been working on collagen sheets developed for 10 years. “The sheet is one large two-dimensional crystal, but the peptide packing method makes it look like a bundle of pencils,” explains Conticello. “Half of the pencils in the bundle have the leads facing up, and the other half have the eraser edges facing up.”

Conticero sought to improve the collagen sheet so that each side was restricted to one function. Taking the pencil analogy further, one side of the sheet becomes the lead point and the other side becomes the eraser. The ultimate goal is to develop a collagen sheet that can be integrated with medical devices by making one surface compatible with medical devices and the other surface compatible with functional proteins in the body. did.

But when researchers designed these different types of surfaces into a single collagen sheet, they were surprised to find that it caused the sheet to roll like a scroll. Next, we discovered that the transition of shape change is reversible. Whether the sheet is flat or scrolling can be controlled by simply changing the pH of the solution. We also demonstrated that the sheet can be adjusted to change shape at a specific pH. Level in a way that can be controlled at the molecular level through design.

“It’s especially interesting that the state in which the transition occurs is a physiological state,” says Conticello. “This opens up the possibility of finding ways to load therapeutic agents into collagen tubes under controlled laboratory conditions. Collagen tubes contain drug molecules after entering the pH environment of human cells. Can be adjusted to spread and emit.

Emory’s scientists who contributed to the measurement and characterization of new nanomaterials and co-authored the treatise include professors of chemistry, Brian Dier and Khalid Salita. Alisina Bazrafshan and Helen Siaw; Robert P. Apkarian Integrated Electron Microscopy Core Arthur McCanna, graduate students in chemistry.