Optimization of the Rheological Properties of Self-Assembled Tripeptide/Alginate/Cellulose Hydrogels for 3D Printing

Abstract

3D printing is an emerging and powerful technique to create shape-defined three-dimensional structures for tissue engineering applications. Herein, different alginate–cellulose formulations were optimized to be used as printable inks. Alginate (Alg) was chosen as the main component of the scaffold due to its tunable mechanical properties, rapid gelation, and non-toxicity, whereas microcrystalline cellulose (MCC) was added to the hydrogel to modulate its mechanical properties for printing. Additionally, Fmoc-FFY (Fmoc: 9-fluorenylmethoxycarbonyl; F: phenylalanine; Y: tyrosine), a self-assembled peptide that promotes cell adhesion was incorporated into the ink without modifying its rheological properties and shear-thinning behavior. Then, 3D-printed scaffolds made of Alg, 40% of MCC inks and Fmoc-FFY peptide were characterized by scanning electron microscopy and infrared spectroscopy, confirming the morphological microstructure of the hydrogel scaffolds with edged particles of MCC homogeneously distributed within the alginate matrix and the self-assembly of the peptide in a β-sheet conformation. Finally, the cytocompatibility of the scaffolds was tested in contact with the MG63 osteosarcoma cells, confirming the absence of cytotoxic components that may compromise their viability. Interestingly, MG63 cell growth was retarded in the scaffolds containing the peptide, but cells were more likely to promote adhesive interactions with the material rather than with the other cells, indicating the benefits of the peptide in promoting biological functionality to alginate-based biomaterials.

Improving Chitosan Hydrogels Printability: A Comprehensive Study on Printing Scaffolds for Customized Drug Delivery

“…Since the material has to pass through the nozzle tip, it is necessary that it has an adequate viscosity behavior as a function of shear stress [ 43 ]. The 3D printing process chosen for the present study, an extrusion-based method, and according to previous studies, shows that it is mandatory that the materials used for this type of process present a shear-thinning behavior for the hydrogel be able to extrude through the nozzle tip [ 44 , 45 , 46 , 47 ].…”

Rheology as a Tool for Fine-Tuning the Properties of Printable Bioinspired Gels

“…Identification of the linear viscoelastic regime allows to obtain yield strain—the minimum value of deformation before starting the flow as a viscous fluid ( G ″ > G ′). The yield strain is correlated with the values required to be selected for the force pushing the syringe piston or pressure for pneumatic 3D printing [ 35 ].…”

“…There were developed various numerical and analytical fluid dynamics models to describe the cells’ effect on material flow, taking into account the influence of the mechanical forces inside of the printing head on the cell viability [ 20 , 25 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Thus, it was established that the rheology and dynamics of the ink formulations and the applied shear stress represent a critical key factor to judge the material’s printability, printing resolution, and ink integrity [ 20 , 35 , 36 , 37 ]. The applied shear stress and shear-thinning behavior under well-established conditions of shear rates must be examined for determining the printability of bioinks.…”

Peptide-Based Hydrogels: New Materials for Biosensing and Biomedical Applications

“…Under the same conditions and at neutral pH, NI-GFF self-assembled into a stable hydrogel, whereas NI-FFG did not. Das Hernández-Sosa et al used different alginate–cellulose formulations for employing them as bioinks in 3D hydrogel-based scaffolds [ 29 ]. In these structures, alginate (Alg) acts as the main component, because of its fast gelation and tunable mechanical properties, and cellulose modulates the mechanical properties of the printing.…”