Biofabrication: From additive manufacturing to bioprinting

In biofabrication, researchers aim to produce three-dimensional (3D) constructs for the regeneration of various tissues or organs and for the use as in vitro models. The origin of biofabrication can be found in additive manufacturing (AM) and self-assembly techniques. Whereas AM enables the fabrication of biological constructs in a controlled manner with an intricate pore network and geometrical complexity, self-assembly allows the fabrication of larger constructs by exploiting cell-cell interaction and the concept of tissue liquidity, ultimately resulting in the fusion of smaller cellular aggregates. Nowadays classical techniques like 3D printing and fused deposition modeling have become more advanced in producing complex scaffolds with instructive hierarchical and/or surface properties. Latest technological advances in bioprinting, magnetic levitation and acoustic assembly further increase the ability to control cell deposition. These biological constructs can be made out of a variety of biomaterials ranging from metals, ceramics and thermoplastics in case of instructive scaffolds able to steer cell activity and tissue regeneration, to hydrogels in case of bioinks for bioprinting. Recent advances in biofabrication show significant progress in the development of 3D in vitro models for pharmaceutical and physiological studies, as well as new functional therapies for tissue engineering and regenerative medicine. Yet, many challenges, such as nutrient supply, mimicking the cell environment, mechanical properties and the chance of immune rejection still exist today and should be tackled in the coming years to translate biofabrication strategies to the clinic.