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Research Papers

Bioprinting Endothelial Cells With Alginate for 3D Tissue Constructs

[+] Author and Article Information
Saif Khalil

Laboratory for Computer-Aided Tissue Engineering, Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104sok22@drexel.edu

Wei Sun1

Laboratory for Computer-Aided Tissue Engineering, Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104sunwei@drexel.edu

1

Corresponding author.

J Biomech Eng 131(11), 111002 (Oct 16, 2009) (8 pages) doi:10.1115/1.3128729 History: Received February 06, 2008; Revised November 17, 2008; Published October 16, 2009

Advanced solid freeform fabrication (SFF) techniques have been an interest for constructing tissue engineered polymeric scaffolds because of its repeatability and capability of high accuracy in fabrication resolution at the scaffold macro- and microscales. Among many important scaffold applications, hydrogel scaffolds have been utilized in tissue engineering as a technique to confide the desired proliferation of seeded cells in vitro and in vivo into its architecturally porous three-dimensional structures. Such fabrication techniques not only enable the reconstruction of scaffolds with accurate anatomical architectures but also enable the ability to incorporate bioactive species such as growth factors, proteins, and living cells. This paper presents a bioprinting system designed for the freeform fabrication of porous alginate scaffolds with encapsulated endothelial cells. The bioprinting fabrication system includes a multinozzle deposition system that utilizes SFF techniques and a computer-aided modeling system capable of creating heterogeneous tissue scaffolds. The manufacturing process is biologically compatible and is capable of functioning at room temperature and relatively low pressures to reduce the fluidic shear forces that could deteriorate biologically active species. The deposition system resolution is 10μm in the three orthogonal directions XYZ and has minimum velocity of 100μm/s. The ideal concentrations of sodium alginate and calcium chloride were investigated to determine a viable bioprinting process. The results indicated that the suitable fabrication parameters were 1.5% (w/v) sodium alginate and 0.5% (w/v) calcium chloride. Degradation studies via mechanical testing showed a decrease in the elastic modulus by 35% after 3 weeks. Cell viability studies were conducted on the cell encapsulated scaffolds for validating the bioprinting process and determining cell viability of 83%. This work exhibits the potential use of accurate cell placement for engineering complex tissue regeneration using computer-aided design systems.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Bioprinting fabrication system; (b) schematic of a multinozzle deposition system with 3D motion setup for biopolymer deposition in SFF of tissue engineered scaffolds

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Figure 2

Image of a freeform fabricated porous 3D alginate scaffold

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Figure 3

Fraction initial fluorescent reading (normalized) versus incubation day for 1%, 1.5%, 2%, and 3% (w/v) sodium alginate disks using 0.5% (w/v) calcium chloride (n=6)

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Figure 4

Fraction initial fluorescent reading (normalized) versus incubation day for constant 1.5%, (w/v) sodium alginate disks using 0.5%, 1%, and 2%, (w/v) calcium chloride solutions (n=6)

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Figure 5

Elastic modulus versus the degradation time for 1.5% (w/v) alginate disk and scaffold using 0.5% (w/v) calcium chloride solutions (n=6)

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Figure 6

Results of the elastic modulus versus the degradation time for 1.5% (w/v) alginate disks with and without encapsulated RHECs at 500,000 cells/ml using 0.5% (w/v) calcium chloride solutions (n=6)

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Figure 7

Effect of the maximum shear stress on the percentage of live cells using 1.5% (w/v) of sodium alginate for the bioprinting process (n=6)

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Figure 8

Incubation day versus the fluorescent reading fraction initial for 1.5% (w/v) sodium alginate bioprinted scaffold using 0.5% (w/v) calcium chloride and initial cell density of 500,000 cells/ml (n=6)

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Figure 9

Bioprinting fabrication window for sodium alginate and calcium chloride concentrations

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Figure 10

Optical image of a bioprinted scaffold on day 14 of incubation time

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Figure 11

Fluorescent LIVE/DEAD assay image of a bioprinted scaffold on day 14 of incubation

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