'3D photografting' method uses laser beams to precisely attach molecules

Researchers at the Vienna University of Technology have developed a method that uses a laser beam to fix biological molecules at exactly the right position in a 3D material, and on a micrometer scale.

3D pattern produced by photografting (180 µm wide). Fluorescent molecules are attached to the hydrogel, resulting in a microscopic 3D pattern
3D pattern produced by photografting (180 µm wide). Fluorescent molecules are attached to the hydrogel, resulting in a microscopic 3D pattern

Researchers at the Vienna University of Technology (Vienna, Austria) have developed a method that uses a laser beam to fix biological molecules at exactly the right position in a 3D material, and on a micrometer scale. The work is promising for artificially growing biological tissue or for creating biosensors.

Dubbed "3D photografting," the method begins with a hydrogel—a type of scaffold made of macromolecules arranged in a loose meshwork. Between those molecules, there are large pores through which other molecules or cells can migrate.

3d Photografting News 1 Web
In 3D photografting, a laser shines into the hydrogel (yellow), attaching molecules to it at specific points in space (green). (Images courtesy of the Vienna University of Technology)

Then, specially selected molecules are introduced into the hydrogel meshwork and a laser beam irradiates certain points. At the positions where the focused laser beam is most intense, a photochemically labile bond is broken. That way, highly reactive intermediates are created, which locally attach to the hydrogel quickly. The precision depends on the laser’s lens system; the researchers' system was able to obtain 4 µm resolution.

The researchers' method can be used to artificially grow biological tissue: Like a climbing plant clinging to a trellis, cells need a scaffold to which they attach. In natural tissue, the extracellular matrix accomplishes this by using specific amino acid sequences to signal to the cells where they are supposed to grow. In the lab, scientists are trying to use similar chemical signals. Cell attachment could be guided on 2D surfaces, but in order to grow larger tissues with a specific inner structure (such as capillaries), a 3D technique is required.

3D pattern produced by photografting (180 µm wide). Fluorescent molecules are attached to the hydrogel, resulting in a microscopic 3D pattern3D pattern produced by photografting (180 µm wide). Fluorescent molecules are attached to the hydrogel, resulting in a microscopic 3D pattern
3D pattern produced by photografting (180 µm wide). Fluorescent molecules are attached to the hydrogel, resulting in a microscopic 3D pattern.

Depending on the application, different molecules can be used. 3D photografting is not only useful for biomedical engineering, but also for photovoltaics or sensor technology.

The researchers' work has been published in Advanced Functional Materials; for more information, please visit http://onlinelibrary.wiley.com/doi/10.1002/adfm.201290098/abstract.

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