3D printing biomaterials for regenerative medicine

There have been many advances in the field of 3D printing or additive manufacturing in the last years, and particularly 3D printing living organs is a hot topic. While directly printing living organ is not (yet) possible, researchers in the field of tissue engineering are using biocompatible materials to print 3D structures also known as scaffolds. These scaffolds are used together with stem cells and placed into a bioreactor or in a patient, where the organ or tissue can grow. Materials for such applications have to be biocompatible, biodegradable and provide appropriate conditions to house cells. On top of that, the material should be ‘printable’. We have been working with gellan gum composites that showed promising results as a scaffold material1. Gellan gum samples are made by pouring hot polymer solution into a mould, where the solution cools down and gels into a hydrogel. Rheological studies of gellan gum2 showed how we can tailor gelation by changing the amount of Ca2+ ions. Addition of Ca2+ ions will increase temperature of gelation as well as increase the visco(elasti)city of the initial solution. Ca2+ ions can be added in the form of CaCl2 or by dissolution of bioactive glass (BAG) particles in the gellan gum solution. A specific type of 3D printing technique called ‘fused deposition modelling’ (FDM) was chosen as the most appropriate. This technique works by adding layer by layer of material that is usually in a form of a filament. Since gellan gum could not be made into a filament, we had to modify the printer to print it. The idea was to keep the suspension of gellan gum hot in a syringe, which would then cool down as it exits from the syringe needle (see Figure 1). By adjusting temperature in the syringe, changing the amount of Ca2+ ions, adding forced cooling at the nozzle, etc. we can drastically improve printing capabilities.