Biofabrication of Tissue Scaffolds

Tissue engineering is an emerging interdisciplinary field that applies the principles of life science and engineering to produce engineered tissues for the repair and replacement of damaged tissues or organs [1]. In tissue engineering, tissue scaffolds play a crucial role. A tissue scaffold is a three-dimensional (3D) structure made from biological materials and bio‐ materials, which is used to facilitate cell/tissue growth and the transport of nutrients and wastes while degrading gradually itself. To fabricate such tissue scaffolds, a number of fab‐ rication techniques have been developed and reported in the literature and these techniques can generally be classified into two categories: conventional and advanced. Conventional techniques [2], including solvent-casting, particulate-leaching, and freeze drying, can build scaffolds with interconnected porous structures. However, they offer little capacity to pre‐ cisely control pore size, pore geometry, pore interconnectivity, and spatial distribution of pores or allow for the construction of internal channels within the scaffolds. Ideally, scaf‐ folds should not only provide a supporting structure but also the chemical, mechanical, and biological signals required to respond to environmental stimuli. As an alternative to conven‐ tional scaffold fabrication methods, advanced fabrication techniques have recently been de‐ veloped in tissue engineering, such as electrospinning [3], a nanotechnology-based fabrication technique, and rapid prototyping [4], a class of techniques by which a 3D scaf‐ fold is fabricated by laying down multiple, precisely formed layers in succession. With the development of such advanced tissue engineering fabrication techniques, the new concept of "biofabrication" has emerged. Biofabrication is defined as the production of complex liv‐ ing and non-living biological products from raw materials, such as living cells, molecules, extracellular matrices, and biomaterials. It has the potential to be the manufacturing para‐ digm of the 21st century and makes a significant contribution to the development of tissue engineering strategies [5].