A group of researchers from the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) is working on bioink that will allow biologically functional tissue to be 3D-printed to replace irreparably damaged tissue. The researchers hope to use this ink to print implantable tissues that integrate with the human body much faster than is currently possible.
3D printing is a technology that is increasingly being embraced, particularly in industry. Here, the manufacturing technique is used to produce personalised products, print spare parts for cars directly for a customer so that less stock needs to be held and even print entire houses, among other things.
Biocompatible tissue structures
However, additive manufacturing is also being looked at with interest in the medical sector. One example is the bioink that the Fraunhofer IGB has been working on for several years. With it, the researchers hope to pave the way for the development of biocompatible tissue structures capable of repairing irreparable tissue.
The researchers use a 3D printing technology in which objects are printed layer by layer. The bioink used is a liquid composed of biopolymers such as gelatine, hyaluronic acid and living cells. This ink is liquid during the printing process and is converted to a hydrogel after printing using UV radiation.
By modifying the chemical appointment of this hydrogel, researchers can, among other things, modify its structure. This makes it possible to mimic the structure of natural tissues. For example, harder hydrogels can be used for cartilage and softer hydrogels for adipose tissue.
Bone cells and blood vessels
In addition, in collaboration with the University of Stuttgart, the Fraunhofer IGB recently created two new hydrogels: a stiffer gel with mineral components to mimic bone cells and a softer gel without mineral components to allow blood vessels to grow in capillary structure. Using this material, the researchers have produced a bioink for bone.
With this material, the researchers do not so much want to print bone tissue directly, but hope that the cells in this ink will allow new bone tissue to grow. The key here, according to the researchers, lies in using a special mix of the mineral hydroxyapatite and biomolecules. "The best artificial environment for cells is one that makes it as close as possible to natural conditions in the body. This is why the role of the tissue matrix in our printed tissue is fulfilled by biomaterials that we create from elements of the natural tissue matrix," says Dr Kirstin Borchers, responsible for bioprinting projects at the University of Stuttgart.
Vascular ink
In addition, the researchers have developed vascular ink that can be used to form tissue structures that provide space for blood vessels. The material thus created contains openings through which blood vessels can grow. An implant based on this material can therefore be more easily integrated with a patient's blood vessels than a traditional implant. "It would probably not be possible to print larger tissue structures successfully without vascular ink," says Dr Achim Weber, head of the Particle-Based Systems and Formulations Group at the Fraunhofer Institute.
In their latest project, researchers at the Fraunhofer IGB are focusing on a bioink that allows cartilage repair. "Regardless of the type of cell we isolate from human tissue and allow to multiply in a laboratory, we need to create a suitable environment in which they can perform their specific functions for long periods of time," explains bioscientist Lia Rebers.
Other bioink projects
Fraunhofer IGB and Stuttgart University are not the only parties working on bioink for human tissue. US Rice University, for example, announced in April that it had printed osteochondral tissue using a 3D printer. With this, the researchers hope to provide relief for patients with osteochondral injuries, where both bone and cartilage are damaged.
Additionally, in February, a 3D-printed skull roof was implanted in a dog by the University Clinic for Companion Animals at Utrecht University. This skull roof is made of titanium and fitted with a porous rim, where bone can grow into the implant to integrate it into the skull.
The School of Engineering at the Okanagan campus of the American University of British Columbia also developed two bioinkts in 2017. These inks are intended for printing artificial organs, something the researchers say could potentially solve the global shortage of donor organs. They are a gelatine-based hydrogel made from skin cells of cold-water fish and a hydrogel based on cold-soluble gelatine.
Author: Wouter Hoeffnagel
Source: Fraunhofer Institute for Interfacial Engineering and Biotechnology
