Research on the printability of hydrogels in 3D bioprinting

Abstract

As the biocompatible materials, hydrogels have been widely used in three- dimensional (3D) bioprinting/organ printing to load cell for tissue engineering. It is important to precisely control hydrogels deposition during printing the mimic organ structures. However, the printability of hydrogels about printing parameters is seldom addressed. In this paper, we systemically investigated the printability of hydrogels from printing lines (one dimensional, 1D structures) to printing lattices/films (two dimensional, 2D structures) and printing 3D structures with a special attention to the accurate printing. After a series of experiments, we discovered the relationships between the important factors such as air pressure, feedrate, or even printing distance and the printing quality of the expected structures. Dumbbell shape was observed in the lattice structures printing due to the hydrogel diffuses at the intersection. Collapses and fusion of adjacent layer would result in the error accumulation at Z direction which was an important fact that could cause printing failure. Finally, we successfully demonstrated a 3D printing hydrogel scaffold through harmonize with all the parameters. The cell viability after printing was compared with the casting and the results showed that our bioprinting method almost had no extra damage to the cells.

Structured Macroporous Hydrogels: Progress, Challenges, and Opportunities

“…However, this technique still requires extraction of residual (unpolymerized) monomer following gelation and, as a raster-based technique, is extremely slow for making anything but very small scaffolds. More promising is free-form printing techniques that can directly print a 3D gel structure in a single processing step using one of four approaches: (a) simple extrusion and deposition of preformed hydrogel tubes; [89] (b) printing and simultaneous rapid photocrosslinking of (meth)acrylated prepolymer solutions to convert the liquid-like prepolymer into a gel (also known as 3D printing stereolithography); [90] (c) printing a polyelectrolyte into a counterion solution (e.g., sodium alginate into a calcium ion bath) [91] to facilitate near-instantaneous ionotropic gelation; or (d) extrusion of thermoresponsive gelling pairs (e.g., sodium alginate/gelatin [92] ) on a cooled or heated support that induces gelation on contact. Stereolithography has been particularly commonly exploited in this context given its capacity for processing different polymers.…”

“…[178] The use of in situ gelation chemistries in 3D printing is still in its infancy, aside from the ionotropic alginate-calcium gelation mechanism that forms the basis of most existing hydrogel 3D printers. [139,179,180] Thermogelation by printing on a heated platform (e.g., methacrylamide-PEG-based triblock copolymer hydrogels [181] ) or a cooled platform (e.g., sodium alginate/ gelatin [92] ) has also been demonstrated, although suffers from drawbacks associated with the stability of the resulting structures outside of the controlled temperature environment, the capacity to print thicker structures further away from the temperature-controlled base, and a lack of flexibility regarding the hydrogel components in order to facilitate the required thermogelation. Combinations of physical gelation with UV photopolymerization have also been demonstrated.…”

3D printing for drug manufacturing: A perspective on the future of pharmaceuticals

“…Another consideration is the viscosity, surface tension, and temperature-dependent properties of hydrogels. These factors are crucial for finding or synthesizing materials that are appropriate for 3D printing [62,72] . A final limitation of practically all hydrogels that should be considered is the geometric precision during the 3D printing process.…”

Extrusion-Based 3D Printing of Photocurable Hydrogels in Presence of Flavin Mononucleotide for Tissue Engineering

“…However, all materials for scaffolding as well as products of their biodegradation must be nontoxic both to the cells and surrounding tissues. One of the attractive candidates for those scaffolds are various hydrogels based on biocompatible macromolecules [6], such as hyaluronic acid and its derivatives [7], as hyaluronic acid (nonsulfated glycosaminoglycan) is one of the major native component of the human extracellular matrix for connective, epithelial, and neural tissues.…”