Hydrogels for Bioprinting: A Systematic Review of Hydrogels Synthesis, Bioprinting Parameters, and Bioprinted Structures Behavior

Abstract

Nowadays, bioprinting is rapidly evolving and hydrogels are a key component for its success. In this sense, synthesis of hydrogels, as well as bioprinting process, and cross-linking of bioinks represent different challenges for the scientific community. A set of unified criteria and a common framework are missing, so multidisciplinary research teams might not efficiently share the advances and limitations of bioprinting. Although multiple combinations of materials and proportions have been used for several applications, it is still unclear the relationship between good printability of hydrogels and better medical/clinical behavior of bioprinted structures. For this reason, a PRISMA methodology was conducted in this review. Thus, 1,774 papers were retrieved from PUBMED, WOS, and SCOPUS databases. After selection, 118 papers were analyzed to extract information about materials, hydrogel synthesis, bioprinting process, and tests performed on bioprinted structures. The aim of this systematic review is to analyze materials used and their influence on the bioprinting parameters that ultimately generate tridimensional structures. Furthermore, a comparison of mechanical and cellular behavior of those bioprinted structures is presented. Finally, some conclusions and recommendations are exposed to improve reproducibility and facilitate a fair comparison of results.

Printability, Durability, Contractility and Vascular Network Formation in 3D Bioprinted Cardiac Endothelial Cells Using Alginate–Gelatin Hydrogels

“…Overall, our results suggest that optimising bioprinting parameters was key to the printability and long durability of patches as opposed to the bioprinting platform used (for example, by optimisation pre-testing to determine the ideal flow rate, nozzle speed and temperature settings which were different for each system to work optimally with our hydrogels). It is known that bioprinting parameters and the concentration of AlgGel hydrogels are established determinants of printability and durability (Mancha Sánchez et al, 2020); our study supports this and also adds the finding that the bioprinting system itself was not a strong influencing factor.…”

3D Bioprinting of In Vitro Models Using Hydrogel-Based Bioinks

“…Due to this reversible interaction between inter and intra polymer chains, they usually show a shear-thinning behavior [ 50 ]. Typically, a mixture of polymer solution as bioink and desired cells to load cross-links or polymerizes by relatively cell-friendly reagent and condition [ 51 , 52 , 53 , 54 ]. Appropriate materials should be carefully chosen for the desired purpose, since each material for the hydrogel bioink has intrinsic characteristics.…”

A Review of Recent Advances in 3D Bioprinting With an Eye on Future Regenerative Therapies in Veterinary Medicine

“…Hydrogels can be derived from natural sources such as gelatin, fibrin or collagen, or synthetically derived (examples include polyethylene glycol and Pluronic® F-127) ( 26 ). Currently, Alginate is the most often used material in 3D bioprinting processes; however, synthetic sources have gained recent attention due to their lower batch-to-batch variation and higher level of control over factors such as degradation and mechanical stability ( 27 , 28 ). Hydrogels derived from a mixture of natural and synthetic sources are called hybrid bioinks.…”

“…Post-bioprinting, hydrogels are cross-linked via thermal, chemical or physical methods to increase their structural integrity. These methods as well as additional hydrogel characteristics have been reviewed elsewhere ( 28 ).…”