The behavior of cells strongly depends on their environment. If they are to be researched an manipulated, it is crucial to embed them in suitable surroundings. Aleksandr Ovsianikov is developing a laser system, which allows living cells to be incorporated into intricate taylor-made structures, similar to biological tissue, in which cells are surrounded by the extracellular matrix. This technology is particularly important for artificially growing biotissue, for finding new drugs or for stem cell research.
At first, the cells are suspended in a liquid, which mainly consists of water. Cell-friendly molecules are added, which react with light in a very special way: a focused laser beam breaks up double bonds at exactly the right places. A chemical chain reaction then causes the molecules to bond and create a polymer.
This reaction is only triggered when two laser photons are absorbed at the same time. Only within the focal point of the laser beam the density of photons is high enough for that. Material outside the focal point is not affected by the laser. “That is how we can define with unprecedented accuracy, at which points the molecules are supposed to bond and create a solid scaffold”, explains Ovsianikov.
Guiding the focus of the laser beam through the liquid, a solid structure is created, in which living cells are incorporated. The surplus molecules which are not polymerized are simply washed away afterwards. This way, a hydrogel structure can be built, similar to the extracellular matrix which surrounds our own cells in living tissue. Ideas from nature are imitated in the lab and used for technological applications. This approach, called ‘bio-mimetics’ plays an increasingly important role, especially in materials science. Aleksandr Ovsianikov is confident that in many cases, this technology will render animal testing unnecessary and yield much quicker and more significant results.
Stem cell research is a particularly interesting field of application for the new technology. “It is known that stem cells can turn into different kinds of tissue, depending on their environment”, says Aleksandr Ovsianikov. “On top of a hard surface, they tend to develop into bone cells, on a soft substrate they may turn into neurons.” In the laser-generated 3D structure the rigidity of the substrate can be tuned so that different types of tissue can be created.