3D PRINTING AND NANOMANUFACTURING - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 42

2.4.1 SCAFFOLD-BASED APPROACH TO TISSUE CONSTRUCTS
Human osteoblast-like (SaOS-2) cells were seeded on nanocomposite scaffolds produced using SLS
with Ca-P/PHBV and CHA/PLLA nanocomposite spheres in order to evaluate biomimetic environ-
ment ( Duan et al. , 2010 ). The Ca-P/PHBV nanocomposite scaffolds were sintered at 15 W laser power,
1257 mm/s scan speed, and part bed temperature of 35°C. For CHA/PLLA scaffolds, the nanocom-
posites were sintered with a laser power of 15 W using the same scanning speed at a part bed tempera-
ture of 45°C. The pore size was designed to be 0.8 mm 3 . The porosities of fabricated structures were
62.6 ± 1.3% (Ca-P/ PHBV) and 66.8 ± 2.5% (CHA/PLLA), respectively, although the porosity of the
designed model was calculated to be 52.7% using a computer program. Alkaline phosphatase (ALP)
activity was measured, since ALP is an enzyme used as a biomarker of the osteogenic phenotype. It can
catalyze the hydrolysis of phosphate esters at alkaline pH and influences on the bone matrix mineraliza-
tion. ALP activity kept increasing until 7 days after seeding, but decreased between 7 days and 14 days.
This is because ALP is an early marker for osteogenic differentiation and it decreases with initiation of
the mineralization process ( Kim et al. , 2006 ). There was no significant difference in cell proliferation
and ALP activity between two nanocomposite scaffolds.
Human fetal femur-derived cells were cultured in poly (D,L)-lactic acid (PLA) scaffolds in vitro and
in vivo to evaluate the scaffold fabricated with SLS ( Kanczler et al. , 2009 ). PLA powder mixed with
carbon black was sintered with a continuous wave fiber diode laser having an energy density of about
100 ± 20 W/cm 2 . The scan speed was 3 mm/s. Cell proliferation and histological characteristic were
evaluated after 7 days of cell culturing. A PLA scaffold containing human fetal femur-derived cells
after 24 h cell culture was subcutaneously implanted in female MF-1 nu/nu immunodeficient mice.
After 28 days, the tissue scaffold in vivo was evaluated by staining for Acian blue/ Sirius red and for
the expression of type I collagen. This study provided a platform for the differentiation of human fetal
femur-derived cells to generate new cartilaginous and osteogenic matrices.
A biomedical titanium bone scaffold was fabricated using SLS ( Liu et al. , 2013 ). The laser was
tuned at laser power of 15 W and a scanning speed of 100 mm/s. The scaffold showed a 142 MPa
compressive strength after post-heat treatment at 800°C and proved suitable biocompatibility after
cultivation of human osteogenic sarcoma cells (MG63).
A laser-based stereolithography was employed to create predesigned internal architecture and po-
rosities of scaffold with PEGDMA ( Mapili et al. , 2008 ). The 3D scaffold was fabricated using Nd:YAG
laser having laser energy of ∼ 10 mJ/pulse. The scanning speed on x - y direction was about 50 m m/s.
Measured pore size and wall thickness of microfabricated scaffolds were ∼ 425 and ∼ 200 m m, respec-
tively. PEG acrylates were modified with the peptide arginine-glycine-aspartic acid (RGD) or the
ECM component heparin sulfate, and was later contained within the scaffold to enhance cell adhesion
and allow spatial sequestration of heparin-binding growth factor. After the modification, murine bone-
marrow stromal cells were seeded and cultured on the scaffolds for 24 h. Cell attachment was evaluated
using confocal fluorescence images.
The biohybrid actuator was fabricated using laser-based SLA with PEGDA ( Chan et al. , 2012 ). The
cantilever-shaped actuator was created by using commercial apparatus. The fabricated cantilever beam
measured 2 mm wide, 4 mm long, and 0.45 mm thick. Cardiomyocytes were seeded on the cantilever
and bending of the actuator was measured to analyze the traction forces created by cells.
2PP was used to fabricate woodpile scaffold with PEGDA ( Zhang and Chen, 2011 ). The power of
the Ti:sapphire femtosecond laser (wavelength 800 nm) was adjusted by rotating a beam attenuator.
The woodpile consisted of 1 m m wide lines with spacing of 8 m m. The distance between layers was