Three-dimensional bioprinting is not only about cell-laden structures

Abstract

In this review, we focused on a few obstacles that hinder three-dimensional (3D) bioprinting process in tissue engineering. One of the obstacles is the bioinks used to deliver cells. Hydrogels are the most widely used bioink materials; however, they are mechanically weak in nature and cannot meet the requirements for supporting structures, especially when the tissues, such as cartilage, require extracellular matrix to be mechanically strong. Secondly and more importantly, tissue regeneration is not only about building all the components in a way that mimics the structures of living tissues, but also about how to make the constructs function normally in the long term. One of the key issues is sufficient nutrient and oxygen supply to the engineered living constructs. The other is to coordinate the interplays between cells, bioactive agents and extracellular matrix in a natural way. This article reviews the approaches to improve the mechanical strength of hydrogels and their suitability for 3D bioprinting; moreover, the key issues of multiple cell lines coprinting with multiple growth factors, vascularization within engineered living constructs etc. were also reviewed.

Microfluidic Fabrication of Biomimetic Helical Hydrogel Microfibers for Blood‐Vessel‐on‐a‐Chip Applications

“…To improve the robustness of bioprinted constructs, composite hydrogels have been created incorporating synthetic polymers either alone or with natural polymers, allowing greater control over degradation rates and elastic moduli [72][73][74]. The bioactivity and cell binding of synthetic polymers has also be increased through surface functionalisation with bioactive molecules such as peptides, arginylglycylaspartic acid (RGD) and hyaluronan [51,75,76].…”

A bioprinting printing approach to regenerate cartilage for microtia treatment

“…Bioprinting has already simplified the solution to fabricate an exact replica of the contralateral ear cartilage and the challenge now is to provide the required internal architecture or biological cues to better mimic the native cartilage and allow integration/vascularisation [134]. Studies now are leaning towards depositing multiple tissue types or materials into a single construct, as well as using multiple fabrication techniques to produce the scaffold [135,136].…”

Liver microsystems in vitro for drug response

“…The liver is composed of orderly-aligned hepatocytes and non-parenchymal cells within ECM. Hydrogels, such as collagen [5–11, 13, 35], agarose [12, 15], PEG [12, 19, 23] and GelMA [19, 21, 24, 28], are widely used in liver microsystems as the engineered ECM [74–76] to support the initial growth of cells. In studies of drug response, the source of hepatocytes and the cell types of non-parenchymal cells are crucial [75, 77, 78].…”