TU Wien 3D prints human tissue on a chip in a bid to eliminate animal testing

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Researchers at TU Wien have fabricated ‘artificial human tissue on a chip’ using a multi-photon lithography technique that could eliminate the need for animal testing in the future.

The laser-based method allows researchers to guide individual cells to specific locations in a hydrogel to form reproducible specialized tissue systems. These tissues can then be examined under precisely controlled conditions on a chip, which holds promise for pharmaceutical research, such as testing the effectiveness of new drugs.

Schematic illustration of the multiphoton lithography process. Image via Scientific Reports.

AM as an alternative to animal testing

In recent years, advances in bioprinting and tissue engineering technologies have offered increasingly viable alternatives to the use of animal models in experimental medical research. While viable patient-specific tissues for testing drug efficacy remain largely experimental at this time, significant progress is being made towards this goal.

For example, bioprinter maker CELLINK is committed to advancing its research into cruelty-free cellular test models, while the University of Stuttgart is working to develop bioprinted skin models at the microscopic scale to test the effectiveness of anti-cancer drugs.

Elsewhere, Fluicell’s Biopixlar platform produces highly complex neural models that could offer future applications for clinical drug screening, while UpNano’s NanoOne Bio system hopes to reduce the number of animal experiments with its 3D printed cell culture microstructures.

More recently, the Institute of Bioengineering of Catalonia (IBEC) announced that it is coordinating the EU-funded BRIGHTER project, with the aim of developing new 3D bioprinting processes to reduce animal testing in fields of tissue engineering and regenerative medicine.

A scientist experiments using MatTek's in vitro cell technology.
CELLINK has acquired in vitro technology specialist MatTek with the aim of creating a humane drug testing model. Photo via MatTek.

Making “human tissue on a chip”

The creation of tissue structures in a laboratory often begins with living cells embedded in a hydrogel, usually a biocompatible material with properties very similar to those of biological tissue. Cells can migrate through the hydrogel and form tissue, but the ability to precisely control this process and direct cells to a predetermined plane has so far been difficult.

Using a laser, multiphoton lithography techniques can create complex 3D microstructures with feature sizes as small as 100 nm in photosensitive materials. The method has proven to be a suitable tool to precisely control the microenvironment of cells by modifying the biochemical and biophysical properties of the hydrogel matrix in which they are encapsulated.

According to Professor Aleksandr Ovsianikov, head of the 3D printing and biofabrication research group at TU Wien, the success of the team’s technique is due to the addition of “special molecules” that change the physical properties of the hydrogel when activated by a laser.

At the precise point of contact with the laser, the hydrogel becomes softer and more permeable, allowing the creation of predetermined paths through the hydrogel along which cells can migrate.

“The molecule couples to the network of the hydrogel, at this point the network becomes more hydrophilic,” explained Simon Sayer of TU Wien. “This changes the physical properties, and in this way it is possible to create a 3D pattern through which cells can pass more easily than elsewhere.”

Leveraging their multiphoton lithography process, the researchers created star-shaped patterns (left), into which cells can grow (right).  Image via TU Wien.
Leveraging their multiphoton lithography process, the researchers created star-shaped patterns (left), into which cells can grow (right). Image via TU Wien.

As a result, the researchers were able to produce star- or lattice-shaped cellular structures in the hydrogel that mimic biological functions such as blood vessels. These tissue structures can then be placed on a chip of a few centimeters and be precisely supplied with specific nutrients or pharmaceutical compounds. How the tissues interact with each other can then be observed, allowing the team to gather important information about the effect of different drugs without the need for animal testing.

“But that only works if we can precisely control the properties of these tissues,” said Tommaso Zandrini, also from TU Wien. “Firstly, these experiments need to be reproducible, so if you want multiple tissue samples with exactly the same microstructure, and secondly, you also need to be able to connect the different samples precisely – for example, if you’re studying the interaction between a small piece of heart muscle tissue and a small piece of liver tissue.

By leveraging their multi-photon lithography technique, the TU Wien team is able to precisely understand the interaction between different tissues, as structures such as blood vessels can be printed in exactly the right place, while allowing greatly increase the complexity of custom fabric swatches. .

Further information on the study can be found in the document entitled: “Guiding cell migration in 3D using high-resolution photografting”, published in the journal Scientific Reports. The study is co-authored by S. Sayer, T. Zandrini, M. Markovic, J. Van Hoorick, S. Van Vlierberghe, S. Baudis, W. Holnthoner and A. Ovsianikov.

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Featured image shows Leveraging their multiphoton lithography process, the researchers created star-shaped patterns (left), into which cells can grow (right). Image via TU Wien.

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