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Ng H Y, et al.

media was formed using the same method before having applications of biofabricated vessels. Most constructs
HUVEC endothelized the internal lumen of tunica media do not have the mechanical and physical properties to
[69]
to form the tunica intima . Cell viability and adherence fully replace native blood vessels. Even though we are
were consistent with other related GelMA studies. Even able to replicate the general concentric triple tunica
though 4 to 16% concentrations of GelMA displayed structure with their respective cellular constituents,
varying compressive modulus ranging from 3.1 kPa to our current pool of natural biomaterials is not able
138 kPa with failure stress ranging from 43 kPa to 175 to meet the mechanical and physical requirements
kPa, these values are far from the values from native of native vessels. There remains a need to balance
vessels, which typically have their values in the MPa modification of biomaterials, toxicity and degradability
range. of biomaterials. On the other hand, we have to note that
native vasculature is multi-scalar in nature from the
3. Future Perspectives large arteries to the sub-micron capillaries and to the
The fact that metabolizing cells require continuous venous systems. However, with our current bioprinting
supply of nutrients and oxygen in order to remain technologies, it is very challenging to print sub-micron
viable has inspired many researchers to incorporate capillaries. In addition, vascular networks in our body
an artificial vascular system in a bioengineered tissue do not function independently. Nerve supply networks
construct. However, generation of a stable and viable are intimately connected to our vascular systems and has
vascular network still remains a huge challenge in the a role to play in physiological control of vessels. With
tissue engineering field due the complexity of vascular the emergence of 4D bioprinting, future focus would
architecture. 3D bioprinting has certainly emerged as a certainly be shifted to creating implantable organs with
potential candidate for vascular tissue engineering. Even complete vascular networks or implantable vascular
though numerous studies have reported biofabricating grafts. This may be possible by using a technology that
biomimetic vascularized tissue constructs using 3D has emerged recently, 4D bioprinting, where “time” is
bioprinting technology, we are still far from clinical integrated with 3D bioprinting as the fourth dimension.

Figure 2. Methods employed in 4D bioprinting .
[71]
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