3D bioprinting is similar to conventional 3D printing, but instead of printing plastic filaments, 3D bioprinting integrates living cells with biomaterial inks to allow controlled layer-by-layer deposition. Bioprinted living structures have promising potential in various applications in regenerative and personalised medicine, drug discovery and cosmetics.
The main component of 3D bioprinting is the bioink, or biomaterial ink. However, each bioprinting technique demands specific ink properties. For extrusion-based 3D bioprinting, the ink must exhibit unique rheological properties such as shear-thinning, yield stress, and recovery behaviour. Similar rheological behaviour governing the performance of biomaterial inks can also be found in everyday life examples, such as in shampoo, ketchup and toothpaste.
“Ketchup flows slowly and stays in place without spilling off the food. But instead of using viscosity enhancers familiar to the food industry, we utilised chemistry to improve the flow behaviour of the inks,” Hatai Jongprasitkul explains.
Specific crosslinking or processing techniques are essential to maintain the shape fidelity of the printed structure during printing. The sufficient crosslinking of each printed layer allows the structures to support their own weight when printing the higher layers.
“We optimised printing outcomes by utilising various non-covalent crosslinking mechanisms, including temperature, ionic crosslinking, coordination complexes, and pH modulation,” he says.
Jongprasitkul’s thesis explores a variety of polymer types and functionalisations to analyse a diverse range of crosslinking types, including methacrylation and catechol conjugation. Briefly, temperature-induced gelation is prominent in polypeptide-based biomaterial inks, such as gelatin and collagen. The printability of alginate and gellan gum-based biomaterial inks can be enhanced via ionic crosslinking. Another notable method involves extending crosslinking techniques with catechol-conjugated biomaterial inks, facilitating metal-catechol complexes and hydrogen bonding triggered by pH changes.
The study emphasised that the methacrylation of the ink alone does not allow the extensive utilisation of these diverse non-covalent crosslinking methods. Thus, Hatai’s mission is to explore the polymer properties and their various functionalisations to develop novel biomaterial inks suitable for extrusion-based printing. Furthermore, Hatai employs these non-covalent interactions as primary crosslinking methods, followed by photocrosslinking as a secondary crosslinking – a strategy he calls the two-step crosslinking technique.
“Apart from bioprinting, these inks possess remarkable tunability, paving the way for their potential use in self-healing, injectable, tissue adhesive and physiological stimuli-responsive hydrogels. In addition, we have collected a set of printability assessment tools to ensure that these newly developed inks meet the minimum requirements for specific printing methods,” Jongprasitkul says.
Public defence on Friday 20 October
The doctoral dissertation of MSc (Tech) Hatai Jongprasitkul in the field of biomaterials and tissue engineering titled Tailoring the Printability of Photocrosslinkable Polypeptide and Polysaccharide-based Bioinks for Extrusion-based 3D Bioprinting will be publicly examined at the Faculty of Medicine and Health Technology at Tampere University at 12.00 on Friday 20 October 2023 in the Tietotalo auditorium TB109 (address: Korkeakoulunkatu 1, Tampere). The Opponent will be Professor Anna Finne-Wistrand from KTH Royal Institute of Technology, Sweden. The Custos will be Professor Minna Kellomäki from Tampere University, Finland.
The doctoral dissertation is available online.
The public defence can be followed via a remote connection.
Photo: Dr. Vijay Singh Parihar