Their cells of cephalopods like squid and octopuses can change in incredible ways to create living camouflage. Researchers have now taken some of these unique characteristics and transferred them to human cells. Reporting in Nature Communications, the scientists were able to engineer human cells that can ramp up their transparency and the way they scatter or deviate light.
"For millennia, people have been fascinated by transparency and invisibility, which have inspired philosophical speculation, works of science fiction, and much academic research," said the lead study author Atrouli Chatterjee, a graduate student at the University of California Irvine (UCI). "Our project, which is decidedly in the realm of science, centers on designing and engineering cellular systems and tissues with controllable properties for transmitting, reflecting, and absorbing light."
This work was conducted in the lab of Alon Gorodetsky, a UCI associate professor of chemical & biomolecular engineering who has studied the color-changing abilities of cephalopods and how they might benefit humans for years.
A female Doryteuthis opalescens squid can evade a predator by changing a stripe on their bodies from almost clear to opaque white. The researchers took some of the molecules that are involved in this camouflaging technique and added them to human cells. When human embryonic kidney cells were engineered to express a protein called reflectin, the protein took on a disordered form in the cytoplasm. These structures enabled the cells to change how they scattered light.
"We were amazed to find that the cells not only expressed reflectin but also packaged the protein in spheroidal nanostructures and distributed them throughout the cells' bodies," said study author Gorodetsky. "Through quantitative phase microscopy, we were able to determine that the protein structures had different optical characteristics when compared to the cytoplasm inside the cells; in other words, they optically behaved almost as they do in their native cephalopod leucophores."
The researchers were also able to switch the cellular reflections on and off with external stimuli. Cells that were exposed to higher levels of sodium were found to scatter more light, causing them to stand out more.
"Our experiments showed that these effects appeared in the engineered cells but not in cells that lacked the reflectin particles, demonstrating a potential valuable method for tuning light-scattering properties in human cells," Chatterjee said.
We're not going to see cell-based human camouflage on store shelves anytime soon, but this research may have real-world applications right now.
"This project showed that it's possible to develop human cells with stimuli-responsive optical properties inspired by leucophores in cephalopods, and it shows that these amazing reflectin proteins can maintain their properties in foreign cellular environments," Gorodetsky said. Reflectin might also make a useful marker in biomedical research or diagnostics.