Scientists 3-D printed a tiny elephant inside a cell
The elephant is among the first structures ever printed inside living cells
Scientists 3-D printed microstructures, hardened with the use of a microlaser, within human cells (shown).
A tiny elephant establishes a new stomping ground for 3-D printing: inside cells.
For the first time, scientists have 3-D printed objects within living cells, including a 10-micrometer long elephant and tiny “barcodes” that could help track individual cells. Remarkably, many of the cells lived to tell the tale, researchers reported in a paper submitted June 16 at arXiv.org.
“It’s amazing to see that some of the cells actually do survive,” says biophysicist Kerstin Göpfrich of Heidelberg University in Germany, who wasn’t involved with the research. “Honestly, I wouldn’t have thought this. If you told me I would have been like, ‘Nah, never.’”
The researchers used a technique called two-photon polymerization, in which a liquid resin called a photoresist solidifies when it absorbs two photons from a laser simultaneously. The laser’s light is focused enough to produce that double whammy only in a small volume. That makes it possible to create incredibly detailed microstructures by moving the location of the laser’s focus.
To make structures inside a cell, physicist Matjaž Humar and colleagues injected cells with photoresist. Then they 3-D printed the structures and let the remaining photoresist dissolve. The technique is novel and exciting, says optical physicist Malte Gather of the University of Cologne in Germany, who was not involved with the research. “And there’s the elephant inside the cell,” he adds, “which of course is a very nice symbol.” The large is contained within the little.
Scientists have previously implanted trinkets in cells via the process of phagocytosis, in which a cell swallows up a foreign object. But only certain varieties of cells are keen gobblers. 3-D printing has the advantage of working in other types of cells.
But stabbing a cell and pumping liquid into it is a potentially deadly insult, especially because many photoresists are toxic. To boost the odds of survival, Humar and colleagues combed through existing photoresists, choosing one more cell-friendly. Upon 3-D printing, some cells survived, going about their business unperturbed. Some even underwent cellular division, splitting into two and bequeathing a 3-D-printed heirloom to one of the daughter cells. Humar, of the Jožef Stefan Institute in Ljubljana, Slovenia, declined to comment on the work, as the paper is awaiting publication in a scientific journal.
Even with the precautions, many of the cells died within 24 hours. “It seems to be related simply to the fact that cells don’t like having liquids injected into them, and that’s a prerequisite for the 3-D printing,” Gather says.
Better photoresists or injection techniques might improve the success rate. And scientists could eliminate the injurious injection entirely by using a photoresist that can cross cell membranes, Göpfrich says.
In addition to printing barcode-like patterns, the researchers printed a microlaser, another possibility for labeling cells. The microlaser consists of a tiny sphere that, when illuminated, confines and amplifies light, emitting laser light. Subtle variations in the sizes of the spheres will affect the emitted light, which could give each cell a distinct light signature. Microlasers could also be used to sense conditions within a cell that would alter the light emitted, Gather says, such as the presence of certain biomolecules bound to its surface.
Humar and colleagues propose creating microlevers, springs or barriers within cells to study forces within them. Tiny structures could be fashioned to isolate parts of a cell and study their function.
Scientists aren’t sure yet how the technique will be useful, but it opens up possibilities, Göpfrich says. “It’s a way to interact with cells without genetically modifying them.”
