Page 428 - IJB-9-4

International Journal of Bioprinting 3D bioprinting of artificial blood vessel

standard [154] . To enhance mechanical property, the sodium On this basis, more stable and harder gels can be
alginate and carbon nanotubes were mixed in the fibrous obtained by adding photo-cross-linking groups to the
protein/gelatin [154] . hydroxyl groups at the end of Pluronic F-127 [167] . For
Agarose is a natural polysaccharide with a hot gel example, cross-linking acrylates to the hydroxyl group of
temperature of 30 – 40°C [155] . Agarose has good mechanical Pluronic F-127 allows cross-linking under UV to produce
properties since it is inert, it is difficult for cells to attach a stable hydrogel and improve the printing properties,
and proliferate on its surface [156] . The 5% agarose-alginate and the structure can sustain cellular activity for up to
. Some studies have combined Pluronic F-127
14 days
[168]
mixture is more suitable to be used as extruded bioink with collagen and used Irgacure 2959 initiator to prepare
without the additional cross-linking steps or as scarified
material to ensure high structural fidelity [157] . Combining bioink. The bioink shows shear-thinning behavior and has
carboxymethyl-hexanoyl chitosan (CA) hydrogels reversible sol-gel transformation related to temperature. It
(8% w/v) with Pluronic F-127 could build the vessel is relatively tough, elastic, and biocompatible with EC as
structure under the parametric design, which creates vessel well as can be prepared with an average diameter of 0.20 ±
structure by expressing parameters in an algorithm [155,158] . 0.01 mm and an average outer diameter of 0.74 ± 0.01 mm
for the vessel structure [169] .
Nanocellulose refers to three types of nanomaterials:
Bacterial nanocellulose (BNC), cellulose nanofilaments, 3.2.2. Alginate
and CNCs [159] . Among them, BNC can be synthesized by The alginate is a kind of anion (negatively charged)
bacteria, such as gluconacetobacter xylinus, in glucose and hydrophilic polysaccharide derived from the brown
xylose medium and secreted in the form of extracellular seaweed [170] . The properties are the same as those of
polysaccharide to produce structural hydrogels with a GAG and could cross-link with many materials to form
length of about 100 μm and a diameter of about 100 nm [160] . hydrogel [171] . The disadvantages of the alginate hydrogel are
the lack of porosity for nutrient substance exchange and the
3.2 Scarified hydrogels
lack of adhesion properties, along with lower degradation
3.2.1. Pluronic F-127 rate in vivo, making it hard to be exclusively used in
Pluronic F-127 is a kind of synthesized block bioprinting [172] . Normally, the alginate is cross-linked using
2+
copolymers that combine with hydrophilic polyethylene the Ca ions (calcium chloride or calcium sulfate solution)
oxide and two hydrophobic polypropylene oxides on both in ionic cross-linking, which means that the structure is
sides [161] . Below 10°C, Pluronic F-127 is at liquid state reversible under the presence of ionic solution. The shell
but it could self-assemble at room temperature, and the and core of the printing nozzle contain alginate bioink
structure could be dissolved in 4°C cold water to form and calcium chloride solution, respectively, while calcium
hollow structure [162] . Pluronic F-127 is bioinert to many chloride solution can be used as a supporting structure
cells, easy to print, and stress free to cells during formation. for the direct printing of vessels structure [173] . Thus, the
These features make Pluronic F-127 a promising support alginate-Ca hydrogel system is a useful scarified complex
and scarified hydrogel [160,163] . Xu et al. used Pluronic F-127 to form the hollow structure of arterial blood vessel.
as a sacrificial material to form the blood vessel through Gao et al. suspended the SMC and fibroblast in the
a multi-nozzle 3D bioprinting system. After printing, alginate-Ca hydrogel and used two coaxial nozzles on the
Pluronic F-127 was removed to obtain multistage hollow rotating rod to print artificial vessels to form SMC on the
channels for attaching EC, human aortic vascular smooth inner side and fibroblast on the outer side to simulate the
muscle cells, and neonatal dermal fibroblasts, as shown in structure of the vessel [174] , as shown in Figure 10A. The
Figure 9A . The structure and materials could provide ultimate strength of the structure is 0.184 MPa, and the
[66]
better cellular biocompatibility and elastic modulus that survival rate of the cells embedded in the vessel exceeds
are close to natural aorta [164] . A biodegradable multilayered 90% after being cultured for 7 days [174] . Jia et al. also used
bioengineered vascular construct with a curved structure the similar method to prepare the vascular constructs [175] .
was prepared by Liu et al. [165] , as shown in Figure 9B. The The multilayer coaxial nozzle device was used to prepare
gelatin and Pluronic F-127 were used as vessel wall and highly organized perfusion vascular structures containing
scarified materials to build the vessel mold, while the inner EC and MSC. This method could manufacture vessels of a
channel of the structure was seeded with EC; this construct wide range of diameters, with an average outer diameter of
showed better cellular biocompatibility [165] . O’Connell et al. almost 500 – 1500 μm, an average inner about 400 – 1000
used an on-board light exposure strategy that is capable of μm, and a wall thickness of around 60 – 280 μm, which
quick (<1 s) and direct cross-linking when the bioink is allow perfusion, nutrient diffusion, and cell growth [175] .
being extruded from the nozzle [166] . Zhang et al. prepared arterial blood vessel with alginate-Ca

Volume 9 Issue 4 (2023) 420 https://doi.org/10.18063/ijb.740