Biological tissue from the 3D printer
The medicine of the future is biological: Destroyed tissue will be replaced by biologically functional tissue from the 3D printer. A team of researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB has been developing and optimising bio-inks suitable for additive production for years in cooperation with the University of Stuttgart. By varying the composition of the biomaterial, the researchers can expand their portfolio to include bone and vascularisation inks. The researchers have thus laid the foundations for the production of bone-like tissue structures using capillary networks.
3D printing has not only found its way into production, but is also becoming increasingly important in regenerative medicine: 3D printing can be used to create tailor-made biocompatible tissue frameworks that will replace irreparably damaged tissue in the future. A team of researchers at the Fraunhofer IGB in Stuttgart is also working on producing biological implants in the laboratory using 3D printing methods. Layer by layer, the scientists print liquids consisting of biopolymers such as gelatine or hyaluronic acid, aqueous nutrient medium and living cells until a 3D object is created whose shape was previously programmed. These bio inks remain flowable during printing, after which they are irradiated with UV light and cross-linked to hydrogels, i.e. water-containing polymer networks.
Targeted chemical modification of biomolecules
The biomolecules can be chemically modified so that the resulting gels have different strengths and swellabilities. Thus, the properties of natural tissues can be reproduced – from solid cartilage to soft fatty tissue. The spectrum of adjustable viscosity is broad. “At 21 degrees room temperature, gelatine is as solid as a jelly – so it cannot be printed. To prevent this from happening and to enable us to process it independently of the temperature, we mask the side chains of the biomolecules that are responsible for gelling the gelatine,” explains Dr. Achim Weber, head of the group “Particulate Systems and Formulations,” one of the challenges of the process.
Another hurdle: To prevent the gelatine from flowing at a temperature of around 37 degrees, it must be chemically crosslinked. To achieve this, it is functionalized twice: As an alternative to the non-crosslinkable, masking acetyl groups that prevent gelation, the research team integrates crosslinkable groups into the biomolecules – a unique approach in the field of bioprinting. “We formulate inks that offer optimal conditions for different cell types and tissue structures,” said Dr. Kirsten Borchers, responsible for the bioprinting projects in Stuttgart.
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