Biofabrication

Melt electrowriting is a 3D printing technology that electrostatically sustains a molten fluid jet  over a translating collector stage. MEW allows the 3D printing of new biomaterials with nano- and microscale structures for a variety of applications, including biomedical. The MEW printers are custom-built research level devices. They can fabricate fine structured scaffolds using a broad range of polymers.

MEW is particularly pertinent to biomedical engineers as materials for clinical, research and in vitro applications. It produces fine and flexible lattices that are cell invasive and unique, and incredibly variable. For further information on this technology, feel free to read the increasing literature listed below.

Contact:
Jun.-Prof. Dr. Tomasz Jüngst
Telephone +49(0)931 201-74081
tomasz.juengst@uni-wuerzburg.de

A bioink is defined as “a formulation of cells suitable for processing by an automated biofabrication technology that may also contain biologically active components and biomaterials” (Groll et al. 2019). The automated fabrication technology the FMZ is mainly utilizing is extrusion-based bioprinting. Bioink development at the FMZ (approach see figure 3) is focused on the combination of cells and biomaterials, more specifically the synthesis of hydrogel-based inks made from fully synthetic as well as modified natural polymers. According to the chosen polymers the applied synthetic techniques include cationic and anionic polymerizations of glycidols and polyoxazolines and subsequent polymer analogue sidechain modifications. For the natural polymers, different polysaccharides and proteins are used as starting materials to introduce further cross-linkable side functions. All synthesized and modified polymers are chemically characterized using the in-house available techniques (e.g. NMR, GPC, FT-IR, Raman, MALDI-TOF) to determine molecular weights, degree of modification and degradation or the branching geometry of synthesized materials.

After their synthesis the materials are investigated for their suitability as bioink components for the different below described techniques. This means that the hydrogel forming materials are crosslinked via radical polymerization, thiol-ene chemistry or reversible imine formation and then studied for their mechanical stability as well as swelling and degradation properties. Techniques applied for this are dynamic mechanical analysis, gravimetric evaluation as well as oscillation rheology.

Overall strategies for our bioink development are the investigation of new materials for bioinks, the optimization of existing materials using macromolecular chemistry and the development of materials for new printing approaches, as described below.

Contact:
Prof. Dr. Jürgen Groll
Telephone +49(0)931 201-73610
fmz-office@uni-wuerzburg.de

Dr. habil Jörg Tessmar
Telephone +49(0)931 201-73720
joerg.tessmar@uni-wuerzburg.de

Figure 3: Overview of bioink development at FMZ

In bioprinting additive manufacturing is used to make bioengineered structures from living and non-living materials. The three most frequently applied techniques are inkjet printing, laser induced forward transfer and extrusion-based bioprinting. The main focus of the department is on extrusion-based bioprinting where biomaterials inks or hydrogel-based bioinks are processed. In most of our printers, the material is loaded into a cartridge and dispensed through a fine needle tip using pressurized air. The printer can be programmed to coordinate cartridge movement and dispensing in a way that 3D constructs can be fabricated in a layer-by-layer fashion. At the FMZ we have a variety of commercially available bioprinters that are used to access the printability of bioinks and biomaterial inks and to develop tissue models.

Besides using commercially available systems we also modify printers and develop new bioprinting techniques. One example is the convergence of microfluidics and bioprinting for the design of new printing approaches.

A big challenge in bioprinting is the online evaluation of the process. We addressed it in a collaboration with the University of Lübeck that is sponsored by the BMBF. Besides the print fidelity also information about the chemical structure and the status of the cells are analyzed via optical coherence tomography and RAMAN spectroscopy. Ideally, we are aiming to achieve information about e.g. cell viability using non-invasive techniques like optical coherence microscopy.

Contact:
Jun.-Prof. Dr. Tomasz Jüngst
Telephone +49(0)931 201-74081
tomasz.juengst@uni-wuerzburg.de