Additive Manufacturing of Patient-Customizable Scaffolds for Tubular Tissues Using the Melt-Drawing Method

Abstract

Polymeric fibrous scaffolds for guiding cell growth are designed to be potentially used for the tissue engineering (TE) of tubular organs including esophagi, blood vessels, tracheas, etc. Tubular scaffolds were fabricated via melt-drawing of highly elastic poly(l-lactide-co-ε-caprolactone) (PLC) fibers layer-by-layer on a cylindrical mandrel. The diameter and length of the scaffolds are customizable via 3D printing of the mandrel. Thickness of the scaffolds was varied by changing the number of layers of the melt-drawing process. The morphology and tensile properties of the PLC fibers were investigated. The fibers were highly aligned with a uniform diameter. Their diameters and tensile properties were tunable by varying the melt-drawing speeds. These tailorable topographies and tensile properties show that the additive-based scaffold fabrication technique is customizable at the micro- and macro-scale for different tubular tissues. The merits of these scaffolds in TE were further shown by the finding that myoblast and fibroblast cells seeded onto the scaffolds in vitro showed appropriate cell proliferation and distribution. Human mesenchymal stem cells (hMSCs) differentiated to smooth muscle lineage on the microfibrous scaffolds in the absence of soluble induction factors, showing cellular shape modulation and scaffold elasticity may encourage the myogenic differentiation of stem cells.

Keywords: additive manufacturing; melt-drawing; scaffold; tissue engineering; tubular tissues.

Figure 1

Schematic illustration of dimension and properties customization for scaffolds for tubular tissues [24,25,26,27,28,29,30] by using melt-drawing.

Figure 2

(a) Dynamic frequency sweep test at 150 °C. Inset illustrates the zero-shear viscosities at different temperatures; (b) Melt-drawing ability analysis of PLC at different melt temperatures and melt-drawing speeds.

Figure 3

(a,b) Pictures of PLC scaffolds with different dimensions; (c) Illustration of elasticity of PLC scaffold in the radial direction.

Figure 4

(a) SEM images of PLC scaffolds fabricated with different melt-drawing speeds; (b) Graphical illustration on the effect of melt-drawing speeds on the fiber diameters from theoretical and experimental. Effect of melt-drawing speeds on the crystallinity of PLC is included in the graph.

Figure 5

(a) Stress–strain curves for PLC rings with different melt-drawing speeds; (b) Relationship between Young’s modulus, UTS, and maximum elongation with crystallinity of PLC.

Figure 6

(a) Real-time cell proliferation of A10 on the TCPS (control) and the scaffold V_3.77 with initial cell seeding of 2500 cells/scaffold. Inset: water contact angle of PLC scaffold; (b) OM images of L929 cell growth and distribution on V_0.94 scaffold for day 1, 3 and 6. SEM images showing the L929 cells elongation and alignment on the scaffold after 6 days of culture.

Figure 7

Cy3 labeled CD44 (red; positive marker for hMSCs), AlexaFluor 488 labeled CD31 (green; negative marker for hMSCs), DAPI nuclear staining (blue) and overlaid fluorescent image of immuno-stained cellular components (merged) for the hMSCs on control (TCPS) (a) and microfibers (b). Cy3 labeled SM actin (red), DAPI nuclear staining (blue) and overlaid fluorescent image of immuno-stained cellular components (merged) for the hMSCs on microfibers are shown in (b); (c) SEM images of the hMSCs on the microfibers show that cells can attach well on the microfibers.