Tissue printing or “bioprinting”
The cells used for printing are combined with a suitable support material, i.e. the so-called biomusteeseen. The appropriate material is selected according to both the cell type and the desired tissue and its desired properties. The cells must be able to grow, divide and move, i.e. the support material. In a typical bioprinting technique, the cells and bioart ink are combined in a sterile syringe and then extruded through a narrow die or needle. The printing process is controlled by a three-dimensional “floor plan” (.stl or .gcode file) that provides instructions for printing layer by layer. At its simplest, the models can be, for example, teardrop-shaped “droplets”, in which case only a suitably sized dose of the cell-biomass mixture is squeezed out of the die. Indeed, such models are very clever when it comes to studying, for example, cell-cell interactions or migration in a support medium, or when wanting to create large repetition sets in a “tissue model”.
Cellink’s HepG2 3D Bioprinting
The morphology of printed and three-dimensionally grown cells is often very similar to the native morphology of native cells (Figure 1.). Similarly, gene expression profiles are more reminiscent of native space than their 2-dimensionally grown counterparts. This may be due to the fact that the cells can both grow, move and interact in three dimensions in all directions, while receiving support from a support material suitable for their growth. In addition, the bio-ink itself can promote cell growth and function, including, for example, cell medium molecules suitable for that cell type. Three-dimensional tissue printing allows the researcher, for example, to create their own unique models, perform drug screenings with 3D cultures, and grow, for example, organoids, tumors, etc. in a reliably reproducible manner.
How to get started?
Ordinary 3D printers cannot be used for tissue printing because they are designed to print completely different types of materials (e.g., different grades of plastic) nor would they be sterile enough to print living cells. Therefore, a device designed specifically for this purpose is needed. In addition, a support material suitable for the cell type of interest, i.e. biomass, is needed. An easy way to test the suitability of bio-ink for your own cells is to order a suitable substance from the manufacturer and try to grow the cells in it. In general, the cells themselves tolerate the printing process well, so if the cells “feel comfortable” in the bio-ink already in the initial test, they can safely switch to printing.
The latest generation of tissue printers are very user-friendly: the built-in computer, touch screen, easy-to-approach interface, ready-made printing formulas and good support provide a pleasant and easy user experience. Support for the bioprinting community is also available online: for example, Bioverse allows you to share your own or download print templates, ask questions, and share publications (THE 3D BIOPRINTING COMMUNITY). Even when creating models, you can easily get started with “low-threshold” CAD programs, such as TinkerCAD.
Selection of bio-ink
Basically, you can print anything that can only be squeezed out of the syringe nozzle. In most cases, a hydrogel is chosen in which the cells thrive. However, the chemical properties of the bio ink, the printing pressure, the temperature, the size of the nozzle, etc. affect the printability, and it is a good idea to take these factors into account when printing different structures. Often, the easiest way to start is to choose a commercial and well-tested bio-ink. For these, there are usually ready-made instructions for use, which get well into traffic (More about biofumes). There are different for different cell & tissue types