Using laser beams it’s now possible to fix molecules to an exactly desired placement in a three dimensional material. This new method can be used to precisely grow biological tissue or to create micro sensors.
There are many different processes available to create three dimensional objects on a micrometer scale, but great precision doing so has until now been lacking. Now the chemical properties of a material can be tuned at the micrometer level. Researchers from the Vienna University of Technology developed a method that makes it possible to attach molecules at an exactly desired position.
When this is used with biological tissues being grown, the method allows “the positioning of chemical signals, telling living cells where to attach.” There is also some hope that the technique will improve sensor technology: “A tiny three dimensional ‘lab on a chip’ could be created, in which accurately positioned molecules react with substances from the environment.”
“3-D-photografting” is the name the researchers gave the new method. The researchers involved in the project have previously been involved in the development of new types of 3-D-printers. 3-D printers have limitations on the micro scale, and wouldn’t be useful for the same types of applications that “3-D-photografting”would: “Putting together a material from tiny building blocks with different chemical properties would be extremely complicated,” says Aleksandr Ovsianikov. “That is why we start from a three dimensional scaffold and then attach the desired molecules at exactly the right positions.”
“The scientists start with a so-called hydrogel — a material made of macromolecules, arranged in a loose meshwork. Between those molecules, large pores remain, through which other molecules or even cells can migrate. Specially selected molecules are introduced into the hydrogel meshwork, then certain points are irradiated with a laser beam. At the positions where the focused laser beam is most intense, a photochemically labile bond is broken.”
By doing that, there are highly reactive intermediates created which attach on the locally level to the hydrogel almost immediately. “The precision depends on the laser’s lens system, at the Vienna University of Technology a resolution of 4 µm could be obtained.”
“Much like an artist, placing colors at certain points of the canvas, we can place molecules in the hydrogel — but in three dimensions and with high precision,” says Aleksandr Ovsianikov.
Chemical Signals for Cells
It’s possible to artificially grow biological tissue using this method. Similar to a vine climbing a scaffold, cells need some scaffold at which they can attach. In a natural biological tissue, “the extracellular matrix does the trick by using specific amino acid sequences to signal the cells, where they are supposed to grow. In the lab, scientists are trying to use similar chemical signals. In various experiments, cell attachment could be guided on two dimensional surfaces, but in order to grow larger tissues with a specific inner structure (such as capillaries), a truly three dimensional technique is required.”
3-D photografting is useful for more than just bio-engineering, fields as diverse as photovoltaics or sensor technology could benefit. And for these different applications different molecules can be used. When working with very limited space, “molecules can be positioned which attach to specific chemical substances and allow their detection.” Using this it will be possible to create a microscopic three-dimensional “lab on a chip”.
Source: Vienna University of Technology
Image Credits: Vienna University of Technology, TU Vienna