Bioprinting allows the fabrication of complex biological constructs for tissue engineering. Combine this with 3D printing, and it's possible to create functional 3D tissue and organs using computer-aided design (CAD) software and 3D printing.
3D printing using existing technology was extended to create 3D bioprinting in the first decade of the 21st century. Its development has continued, with companies such as Manchester BIOGEL (MBG) creating complex biological scaffolds from biological materials relevant to the function of the required tissues. 3D printing for transportable organs has seen significant investment and breakthroughs in organ and tissue regenerative ability.
In the 1980s, it was discovered that extracellular matrix in cell behaviour was fundamental to cell cultures that in 3D would mimic key tissue factors more effectively than 2D in vivo monolayers.
The four stages of bioprinting
A healthy tissue or organ resembling the required results is scanned into CAD. CT or MRI scanning is used.
Using CAD, create a base model to generate printing instructions for a replica structure.
Results are printed layer by layer using a bioink. Bioinsk contains living cells that mix with microgels to provide a suitable environment to keep the cells alive and create a living 3D tissue or organ structure. The bioink must be selected to provide the correct scaffold structure for the tissue/organ replicated type.
A bioreactor then incubates the organ by simulating the environment in which it would typically live. Depending on the requirements of the organ, this step may not be required. However, the resulting organ must be kept viable until it is needed for transplant or research.
Tissue, bones or organs are highly individual, and no two will be identical. Bioprinting and additive manufacturing allows different components and parts to be built separately and assembled into complex structures more accurately than any manufacturing or mould process.
Items with a hierarchical structure can be created using bioprinting, something that previously had been impossible. Biomimicry is one approach used to replicate the function of a body part around a scaffold if the form required is the same as the original. This method relies on a bioreactor for maturation. Autonomous self-assembly allows embryonic organ development. If relevant embryonic elements are in place, this leads to natural development without a scaffold. Lastly, the mini tissue approach combines Biomimicry and Autonomous self-assembly, created cultured cells that make up bio ink. Layers of the mini tissues are then printed together, where they will self-assemble into the target organ.
3 Main Bioprinting Methods
- Extrusion – bioinks are extruded to create 3D structures through nozzles. They are perhaps the simplest to use, a cost-effective and reproducible technique used by those already working with 3D cell culture.
- Inkjet – the start of the bioprinting concept. Droplets of dilute solutions are dispensed in non-contact printing through microvalve, piezoelectric or thermal printing processes. It is high speed and low cost but lacks precision and needs a low viscosity bio-ink.
- Laser – a laser energy source deposits biomaterials onto substrates. It is compatible with a broad range of viscous bioinks, and the resolution can be microscaled. It is a more costly and time-consuming option.
Success is dependent on the selection of a suitable bioink. The bioink is capable of forming and maintaining the structure of the printed organ or tissue. Curing and additional functions must also be considered. Physical bio ink properties can affect cell behaviour and the success of tissue transplant in vivo. Its viscosity can stress cells during the printing process.
PeptiInks® Innovative Bioink Solutions
The range of peptide hydrogels is explicitly designed for successful 3D bioprinting cell cultures. Suitable for any extrusion-based printing, they are shear thinning and engineered with chemical and mechanical properties that mimic native cellular microenvironments. This specialism allows successful tissue cell type growth of any kind.
The control of polymerisation processes through cell layer printing with an option to print the bioink without cells is seen by researchers as an attractive advantage. They are artificially made, which allows for low cost, well defined easy replication. They offer a future beyond that of currently available bioinks.