The first stage of the "zombie cell" only moderately heated, the cell is now pure silica and needed a gold coating for a scanning electron microscope to image it. | Photo courtesy of Sandia National Laboratories
“Zombie” mammalian cells that may function better after they die have been created by researchers at Sandia National Laboratories and the University of New Mexico (UNM).
The simple technique coats a cell with a silica solution to form a near-perfect replica of its structure. The process may simplify a wide variety of commercial fabrication processes from the nano- to macroscale. It’s also allowing scientists to preserve cells down to the minor grooves of its DNA.
The work uses the cells as templates, or molds, on which to deposit silica. From the living cell, this process creates hardened silica structures that look the same as the previously living cell, but can survive greater pressures and temperatures than flesh ever could, and can perform some functions better than when they were alive.
Right now, it’s very challenging for researchers to build structures at the nanometer scale. But, think for a minute if we don’t need to build these components. Instead, researchers could find cells that possess the right machinery, and then use them as a mold to copy the part. In the future, using chemistry or surface patterning, they may even be able to tell cells to form whatever shape they need.
The construction process is relatively simple: Take some free-floating mammalian cells, put them in a petri dish and add silicic acid. The silicic acid, for reasons still partially unclear, enters without clogging and in effect embalms every organelle in the cell from the micro- to the nanometer scale.
The silica forms a kind of permeable armor around the protein of the living cell, allowing researchers to use the cell as a catalyst at temperatures and pressures undreamed of by nature.
By heating the silica to relatively low heat (400 C), the organic material of the cell — its protein — evaporates and leaves the silica in a kind of three-dimensional Madame Tussauds wax replica of a formerly living being. The difference is that instead of modeling the face, say, of a famous criminal, the hardened silica-based cells display internal mineralized structures with intricate features ranging from nano- to millimeter-length scales.
This means taking a soft, potentially valuable biological material and converting it to a fossil that researchers can shelve indefinitely.
By heating the silica to high temperatures, experiments show the cell can be reverse molded. In other words, in the same way that burning wood in air leaves a residue of structureless soot, the zombie heating method results in a high-quality carbon structure. Subsequent dissolution of the underlying silica support decreased the cell’s electrical resistance by approximately 20 times. Such materials would have substantial utility in fuel cells, decontamination and sensor technologies.
Summing up, lead researcher Bryan Kaehr, a Sandia materials scientist, offers what may be the first distinction in scientific literature between a mummy cell and a zombie cell. “King Tut was mummified,” he said, “to approximately resemble his living self, but the process took place without mineralization [a process of fossilization]. Our zombie cells bridge chemistry and biology to create forms that not only near-perfectly resemble their past selves, but can do future work.”