Study of hydrogels for 3D printing of constructs with strong interfacial bonding
Date of Issue2018-11-07
Hydrogels are the most appealing candidates of biomaterials for bioprinting. In this field of bioprinting, the lack of suitable hydrogels remains a major challenge. Thus, choosing appropriate hydrogels is the key to successfully print self-supporting 3D constructs. Most importantly, the design criteria regarding the bioinks and the obtained constructs should be made clear in advance. Therefore, the first task of this study is to clarify the design criteria regarding the important properties of a potential bioink and the generated 3D construct, including rheological, interfacial, structural, biological, and degradation properties, which are crucial for printing of complex and functional 3D structures. A method is developed for evaluating the printability of a candidate hydrogel through simulating its rheological behaviors before, during, and after printing. After that, two novel strategies are proposed in order to obtain multilayered hydrogel constructs with strong interface bonding. In the first strategy, trisodium citrate (TSC) acts as a chelating agent to remove the superficial Ca2+ at each layer. The subsequent post-crosslinking of constructs in a calcium chloride bath will further create the crosslinks and enhance the adhesion between adjacent layers. The second strategy for improving the adhesion between printed layers of a construct is to exploit the interaction between two oppositely charged hydrogels. On the basis of these two strategies, the exciting results have been obtained, which include strong interfacial bonding between two layers of the printed structures, good shape fidelity of the printed constructs, suitable structural integrity of the constructs, and excellent biocompatibility for the bioprinted constructs. It is hoped that the above-mentioned specific considerations for 3D printable hydrogels and their 3D printed constructs could help the researchers in selecting or developing a suitable hydrogel for bioprinting.