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The mussel-inspired assisted apatite mineralized on PolyJet material for artificial bone scaffold
products, such as artificial pelvis . (4) The manufacturing (Objet/Stratasys, USA) with MED610 biocompatible
[5]
of customized implants: The implants were fabricated by photopolymers (Objet/Stratasys, USA). The objects
3D printing technology and can be used for long-term were printed with a thickness of 3 mm and a diameter
implantation. Cases: 3D printed bioresorbable airway of 6 mm for the evaluation of mechanical properties and
splint for tracheobronchomalacia , 3D printed skull with a thickness of 3 mm and a diameter of 6 mm for the
[6]
implant , hip , pelvis , jaw and so on. biological test. The uncured photopolymers were washed
[10]
[7]
[8]
[9]
Although 3D printing in modern medicine had many away, and the objects were post cured under UV light to
practical cases and has a lot of advantages, it still has obtain fully cured objects. In addition, the objects were
many challenges that need to be solved. First, the washed again for cell culture.
biocompatible materials for 3D printing in the market
are limited and the materials cannot satisfy the specific 2.2 PDA Coating and HA Mineralization
needs of desired strength, flexibility, and hardness. In The PDA was deposited onto the MED610 3D printed
addition, the polymerization of 3D printable materials objects by direct immersion coating. The objects were
usually involved with hot and organic solvents. The immersed in a solution of dopamine hydrochloride (Acros
materials did not have good biocompatibility and cannot Organics) (2 mg/mL in 10 mM Tris, pH 8.5) for PDA
be used in biomedical and tissue engineering. Although coating, shaken at 25 rpm for 12 h at room temperature,
some natural materials such as collagen or gelatin have and then rinsed several times with deionized water
been applied in 3D printing technology , they cannot
[11]
provide good mechanical properties and the strength and dried. For HA crystal mineralization, the objects
are usually increased by toxic cross-linking agents. were treated with calcium and phosphate solution. 10×
Therefore, developing new biocompatible materials or simulated body fluid (SBF) solution was chosen to initiate
new strategies to enhance the biocompatibility of printed uniform nucleation and growth. A stable stock solution of
objects is a very important issue. NaH PO .H O (1.198 g), NaCl (58.44 g), KCl (0.375 g),
2
4
2
In the current year, scientists have devoted considerable CaCl ·2H O (1.016 g), and MgCl ·6H O (3.675 g) at pH of
2
2
2
2
attention to polydopamine (PDA)-related research . about 4.1 was prepared and then added NaHCO 0.84 g)
[12]
3 (
PDA has the excellent adhesive force to bind with various was added to adjust the pH to about 6.3. The objects were
substrates containing plastics, oxides, noble metals, immersed in 10×SBF at room temperature for 1 h.
ceramics and so on, and it can also supply secondary 2.3 Characterization
reactivity for conjugating molecules [13-15] . It provides a
new strategy through simple chemistry to modify various Using X-ray diffractometry (XRD; Bruker D8 SSS,
substrates and increase the function and biocompatibility Karlsruhe, Germany) at 30 kV and 30 mA with a scanning
of substrates [16-18] . In 2014, Wu’s group showed self- speed of 1o/min., the phase composition of the objects with
assembled Ca-P/PDA composite nanolayers can modify or without coatings was analyzed and the concentration
the surface of materials and provide the bioactivity of the measured elements was given in atomic percent.
for bone regeneration . In our previous study, we Besides, the scanning electron microscope (SEM) images
[19]
also demonstrated the angiogenesis and osteogenesis of the samples were obtained with a SEM (SEM; JSM-
of human mesenchymal stem cells (hMSCs) cultured 6700F, JEOL) operated in the lower secondary electron
on the polycaprolactone scaffold with PDA-coated/ image mode at 3 kV accelerating voltage. Furthermore,
hydroxyapatite (HA) precipitate can be promoted . the hardness of the samples was evaluated by the Vickers
[20]
In this study, PDA-coated/HA precipitate was modified hardness test.
on the objects printed with the commercial PolyJet
photopolymers (MED610), which only support short-term 2.4 Cell Proliferation
mucosal-membrane contact of up to 24 h. The modified All samples were immersed in 75% ethanol and
objects had greater biocompatibility and better osteogenesis exposed to UV light for 30 min for sterilization before
ability. These results pointed out that this strategy can cell experiments. The hMSCs were obtained from
increase the biocompatibility of printed objects and facilitate
the development of 3D printing in biomedicine. Sciencell Research Laboratories (Sciencell, Carlsbad,
CA) and cultured with mesenchymal stem cell culture
2. Materials and Methods medium (Sciencell) at 37°C in a 5% CO atmosphere.
2
Cell suspensions at a density of 10 cells/sample were
4
directly seeded on each sample. The cells were cultured
2.1 MED610 3D Printed Object Fabrication on tissue culture plates without materials (control, Ctl)
The 3D printed objects were through SolidWorks (Dassault or the objects with or without coatings for different days
Systemes SolidWorks Corp., USA) and fabricated and the cell viability was evaluated by the PrestoBlue ®
by a Stratasys Objet500 Connex3 PolyJet printer (Invitrogen, NY, USA) assay. The optical density was

84 International Journal of Bioprinting (2019)–Volume 5, Issue 2