Human Cells Engineered with Squid-Like Transparency

Researchers at the University of California, Irvine have engineered human cells to have similar transparent abilities as octopuses, squids, and other sea creatures. In a paper published yesterday in Nature Communications, the team described how they drew inspiration from cephalopod skin to endow mammalian cells with tunable transparency and light-scattering characteristics.

For this study, the group drew inspiration from the way female Doryteuthis opalescens squids can evade predators by dynamically switching a stripe on their mantle from nearly transparent to opaque white. The researchers then borrowed some of the intercellular protein-based particles involved in this biological cloaking technique and found a way to introduce them into human cells to test whether the light-scattering powers are transferable to other animals.

This species of squid has specialized reflective cells called leucophores, which can alter the how they scatter light. Within these cells are leucosomes, membrane-bound particles that are composed of proteins known as reflectins, which can produce iridescent camouflage.

In their experiments, the researchers cultured human embryonic kidney cells and genetically engineered them to express reflectin. They found that the protein would assemble into particles in the cells' cytoplasm in a disordered arrangement. They also saw through optical microscopy and spectroscopy that the introduced reflectin-based structures caused the cells to change their scattering of 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 Alon Gorodetsky, a co-author on this study. "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."

While invisible humans are still firmly in the realm of science fiction, Gorodetsky said his group's research can offer some tangible benefits in the near term. "This project showed that it's possible to develop human cells with stimuli-responsive optical properties inspired by leucophores in celphalopods, and it shows that these amazing reflectin proteins can maintain their properties in foreign cellular environments. " He added that the new knowledge also could open the possibility of using reflectins as a new type of biomolecular marker for medical and biological microscopy applications.