The Technique of Thyroid Cartilage Scaffold Support Formation for Extrusion-Based Bioprinting

Abstract

During biofabrication, a tissue scaffold may require temporary support. The aim of this study was to develop an approach of human thyroid cartilage scaffold temporal support formation. The scaffold 3D-model was based on DICOM images. XY plane projections were used to form scaffold supporting part. To verify the technique, collagen hydrogel was chosen as the main scaffold component. Gelatin was applied for the supporting part. To test the applicability of the approach, a model of thyroid cartilage scaffold with the support was printed. The scaffold corresponded to a given model, although some discrepancy in geometry was observed during verification by computed tomography.

Keywords: 3D-bioprinting; Cartilage; Collagen; Computer-aided design/Computer-aided manufacturing; Gelatin.

Figure 1

Thyroid cartilage model formation. (A) The area of interest at DICOM image (marked in red). (B) Model solid body. (C and D) Support material location (yellow). Scale bar – 1 cm.

Figure 2

The process of support creation. (A) Cross-sections with 2 mm step. (B) The volume formed by extruding of each slice to the base. (C) The complete support model obtained by subtracting the thyroid cartilage model from the model in Figure 1(A).

Figure 3

The effect of cross-section number on the quality of supporting part of the scaffold. (A) Dependence of the overall volume (model quality) and a number of polygons (model complexity) on the step of the cross-section in the range of 0.5÷8 mm. (B) Volume increases for each new slice (from the bottom one) and area of each section for 2 mm step.

Figure 4

Assessment of wall thickness of the support and optimization options. (A-C) Areas with thickness <0.52 cm for options with 0.5, 2.0, and 8 mm slice step, respectively. (D-G). The result of procedures 1, 2, and 3 applying the support with 2.0 mm step (b). (H). Areas with thickness <1.03 cm for the support with 2.0 mm step underwent double modification according to procedure 1 (g).

Figure 5

The thyroid cartilage scaffold with the support. (A) In the beginning of biofabrication: The white component was collagen, while the transparent component was gelatin. (B) Immediately after the printing: On the left side, the additional printing element, required for normalization of pressure in a syringe after changing the dispenser at each new layer.

Figure 6

Thyroid cartilage scaffold with the support. (A) The input model (marked in blue) and the printed object CT-reconstruction (red). (B) The conforming volume (blue). (C) The redundant volume (green). (D) The missing volume (orange).

Figure 7

Estimation of viability rat chondrocytes in collagen scaffold through staining (A) On the 3^rd and (B) 7^th days of incubation. The green indicates live cells, while the red indicates dead cells. Composite images were made of 10 layers. Scale bar – 100 μm.