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International Journal of Bioprinting Bioprinting cell-laden protein-based hydrogel

Figure 4. Bioink considerations needed to obtain cell-laden protein-based hydrogel (PBH) construct.

extraction method is of great importance when a PBH is have a storage modulus greater than the loss modulus
developed. The characteristics of protein-based materials in order to maintain their shape, indicating more
are significantly affected by the extraction technique and viscoelastic behavior and thus greater printability. High
the utilized raw material, mainly due to the structure, protein concentration aids in minimizing post-printing
molar mass distribution, composition, and functional shrinkage caused by ambient conditions; hence, better
properties of these materials [168] . Of note, protein integrated mechanical properties are obtained [169-172] .
molecules are entangled above a critical molecular weight, Although augmenting the bioink’s concentration
resulting in a proportional relationship between viscosity via enhancing the viscosity reduces the distortion,
and molecular weight [168] . increasing the concentration of PBHs diminishes the
The presence and density of cells impact the micro-roughness of the bioprinted scaffolds [25] .
rheological and mechanical features of inks. As a result In the bioprinting fabrication method, viscosity
of incorporating cells into a cell-barren gel-phase describes the resistance of a bioink to deformation.
bioink, as well as increased cellular density, decreased Extruding bioinks with high viscosities and maintaining
degree of crosslinking, liquid viscosity, and final their shape post-printing are possible; however,
mechanical properties were observed [169] . Following this, encapsulated cells can be afflicted during the extrusion
rheological characteristics of the bioinks affect cellular process because the deforming forces are high [173] . Another
viability during bioprinting; therefore, shear-thinning problem is associated with the release of shear forces after
bioinks are more desirable because they shield cells and printing, which raise viscosity and inhibit the flow of
enable high-resolution printing simultaneously. Indeed, printed constructs. On the other hand, the lower viscosity of
hydrogels should protect cells from exerted shear forces bioinks leads to less nozzle clogging and allows the mixing
when the bioink is printed through the bioprinters’ of cells, but it can also result in poor feature definition
nozzles. After gelation, cell-laden hydrogels must since the bioinks cannot retain their shape subsequent to

Volume 9 Issue 6 (2023) 482 https://doi.org/10.36922/ijb.1089