Core/shell Printing Scaffolds For Tissue Engineering Of Tubular Structures

Abstract

Three-dimensional (3D) printing of core/shell filaments allows direct fabrication of channel structures with a stable shell that is cross-linked at the interface with a liquid core. The latter is removed post-printing, leaving behind a hollow tube. Integrating an additive manufacturing technique (like the one described here with tailor-made [bio]inks, which structurally and biochemically mimic the native extracellular matrix [ECM]) is an important step towards advanced tissue engineering. However, precise fabrication of well-defined structures requires tailored fabrication strategies optimized for the material in use. Therefore, it is sensible to begin with a setup that is customizable, simple-to-use, and compatible with a broad spectrum of materials and applications. This work presents an easy-to-manufacture core/shell nozzle with luer-compatibility to explore core/shell printing of woodpile structures, tested with a well-defined, alginate-based scaffold material formulation. Video Link The video component of this article can be found at https://www.jove.com/video/59951/ Additive manufacturing (AM, such as 3D bioprinting) is increasingly involved in the fabrication of 3D constructs using biological or biocompatible materials to create scaffolds suitable for TE. Several AM approaches are being used and developed in parallel (e.g., ink jet-and microextrusionbased methods, different types of lithographic techniques) to produce scaffolds that mimic native tissues in their architecture, biochemistry, and functionality. The individual techniques exhibit certain advantages and disadvantages 28 , which is why various modifications being explored

Polysaccharide-Based Bioink Formulation for 3D Bioprinting of an In Vitro Model of the Human Dermis

“…Following the bioprinting process implemented by our group [36], 4-layer hSF cell-laden scaffolds with 3D architecture were achieved using a layer-by-layer fabrication approach ( Figure 1). For this purpose, we used the VitaPrint 3D bioprinter (Institute IRNAS, Maribor, Slovenia), which enables the formation of pores of a chosen size, shape and pore density in z-direction, and extrusion nozzles (Nordon EFD, East Providence, RI, USA) with 0.25 mm diameter.…”

“…Before bioprinting was initiated, a cylinder-shaped scaffold with a 10 mm diameter and a height of 0.8 mm were modeled using the Autodesk software (Autodesk Inc., San Rafael, CA, USA). The pore size was pre-defined in a g-code generator software (Slic3r 1.2.9, open access program published under GNU Affero General Public License) [36] and was set to a constant 30% infill across the scaffold.…”

“…defined in a g-code generator software (Slic3r 1.2.9, open access program published under GNU Affero General Public License) [36] and was set to a constant 30% infill across the scaffold. The formulation used in this study was previously partially optimized [24,36,37] and herein modified to serve the specific needs to prepare the bioink formulation (e.g., the water part was exchanged with the cell growth media, the concentration of the used calcium chloride solution for cross-linking had to be reduced, etc.). The preparation procedure was as follows.…”

“…For the determination of viscosity profiles, the shear rate (Γ) was continuously increased from 0.01 to 1000 s −1 , comprising 31 measuring points per 10 s for a total duration of 310 s. The analysis method and curve fitting were performed according to the Carreau-Yasuda model [38]. The formulation used in this study was previously partially optimized [24,36,37] and herein modified to serve the specific needs to prepare the bioink formulation (e.g., the water part was exchanged with the cell growth media, the concentration of the used calcium chloride solution for cross-linking had to be reduced, etc.). The preparation procedure was as follows.…”

“…Therefore, bioinks shear-thinning properties are necessary to compensate for these high shear stresses, results from the mentioned (desired) bioinks high viscosity. Herein, an already partially tested bioink formulation [24,36,37] was further optimized to serve the specific needs of skin model bioprinting. The crucial changes in the formulation had to include the exchange of the "water part" with the cell growth media (ADMEM + 5 wt.% FBS), as well as adjustments (decreasing) in the calcium chloride concentration, which was used for cross-linking.…”