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Digital light processing based 3D printing for medical applications
4.3 Bone heart diseases. There are two kinds of artificial
heart valves, including mechanical valves and
Bone is a dynamic vascularized tissue that can biological valves (autograft and allograft). The
repair and remodel itself without leaving scars . mechanical valves lead to the risk of thrombus.
[55]
However, for critical size bone defects, bone The autograft implantation is a complex surgery
replacement or surgical intervention is usually that requires cutting the other part of the
required . Besides the autograft and allografts,
[56]
the implant made by biocompatible metal or patient. On the other hand, the allograft always
causes an immune response. In addition, the
ceramic is an alternative to repair the injured biological valves may fail more than 10 years
bone. However, the inert implant will slowly [58,59]
break down with time. Therefore, active bone after implantation . Thus, a new strategy is
tissue is considered as an ideal implant to replace necessary to be developed to fabricate artificial
the injured part [14,57] . The 3D bioprinting allows myocardium replacements.
precise bone scaffolds to be fabricated and a Some studies have been carried out to
variety of cells arranged in the scaffolds to form develop 3D cardiac tissue in vitro. However,
bionic bone constructs. the cardiomyocyte is usually seeded on or
The bone tissue engineering scaffolds are encapsulated in a simple 3D scaffold in these
[60]
required to fit the defect site, allow transport studies . It is very easy to culture cardiomyocyte
of nutrient and growth factor, and degrade and maintains its viability in vitro. However, the
over time. DLP 3D printing has demonstrated key point of fabricating artificial cardiac tissue is
a very important prospect to construct these obtaining biomimetic structures and promoting
scaffolds. Dean et al. took advantage of the high cardiomyocyte orientation alignment. Liu et al.
accuracy of DLP 3D printing to fabricate tissue- blended human embryonic stem cell-derived
engineered bone scaffolds (Figure 3C i) [51] . The cardiomyocytes (hESC-CMs) into 3D pattern
printed microstructure improved the adhesion, hydrogel constructs by a DLP-based 3D printer
[61]
proliferation, and maturation of the cells. The (Figure 3D) . The DLP-based 3D printing
degradation velocity of the scaffolds can also technology allowed hESC-CMs to mimic the
be adjusted by the microstructure. Recently, multilayered aligned myocardium. Meanwhile,
Lim et al. encapsulated mesenchymal stem cells they printed a customizable cantilever-based force
(MSCs) in hydrogels to obtain bone or cartilage detector to measure the force from the artificial
tissues . They developed a new bioink by cardiac model. Further to this, they encapsulated
[52]
a specific hESC line that is sensitive to calcium.
combining methacrylate polyvinyl alcohol (PVA‐
MA) and GelMA. Using this bioink and a DLP Then, they can detect the calcium transient of the
3D printer, they printed some biologically relevant cardiac model. Recently, this group used DLP-
scaffolds with precise microstructures. The MSCs based 3D printing technology to obtain artificial
encapsulated in printed hydrogels maintain high cardiac tissue and detect the expression of mature
viability (≈90%) after 21 days of culture. Through cardiac marker genes. The work will promote the
staining analysis, osteogenic differentiation, and development of artificial cardiac tissue .
[53]
cartilage-specific ECM were observed in the 4.5 Spinal cord
3D printed hydrogel (Figure 3C ii). The result
indicated potential applications of DLP 3D The spinal cord, together with the brain, is called
printing and the bioink in bone tissue engineering. the central nervous system (CNS). It is a cylindrical

4.4 Heart structure and consists of nerve fibers and associated
tissues. In USA, there are more than 50,000 people
Cardiovascular diseases are the foremost who are suffering from the diseases of spinal cord
cause of death over the world. The heart-valve injury (SCI). Due to the importance of CNS, SCI
replacement is a common treatment for valvular causes significant influence on patients and is hard

20 International Journal of Bioprinting (2020)–Volume 6, Issue 1