Page 181 - IJB-9-5

International Journal of Bioprinting Functional materials of 3D bioprinting for wound healing

(quinoline derivatives, doxorubicin, and paclitaxel) [94,95] . biological materials, cells, or other active substances in
The mechanism of antitumor materials killing or a controllable space, so as to repeatedly manufacture 3D
inhibiting cancer cells can be divided into three aspects. functional structures of various shapes and sizes with
Chemotherapy drugs such as doxorubicin and paclitaxel high flexibility [104] . According to the molding principles
inhibit tumor growth by interfering with DNA, RNA, or and printing materials, current bioprinting technologies
protein synthesis of tumor cells. Some photosensitizers such mainly include extrusion-based bioprinting, laser-
as indocyanine green and berberine can induce apoptosis assisted bioprinting, digital light processing-based
of cancer cells by producing ROS or singlet oxygen . In bioprinting, inkjet bioprinting, and microfluidics-assisted
[32]
addition, polyphenols, such as anthocyanin, curcumin, bioprinting [105,106] .
and quercetin, can increase the content of active oxygen
and downregulate cancer cell migration and proliferation Extrusion-based bioprinting is the most popular
by regulating several signaling pathways, such as EGFR/ form of bioprinting that applies mechanical actuation
MAPK signaling pathway . or pneumatic pressure to extrude a bioink from a nozzle
[63]
continuously, and deposit it layer-by-layer to form a 3D
Long-term controlled release of either natural structure [107,108] (Figure 3a). Extrusion bioprinting systems
anticancer drugs or chemotherapy drugs is very important can be classified into screw, piston, and pneumatic type
for tumor treatment. 3D porous scaffolds have been according to their working principles [109] . Compared
widely used in cancer therapy and tissue engineering due with other bioprinting technologies, extrusion-based
to their good capabilities in drug controlled release [96-99] . bioprinting is relatively simple and low-cost, can handle
Zhao et al. designed and developed a multifunctional high-viscosity bioinks, and has excellent compatibility
[32]
biomimetic cellulose nanofiber (CNF) in situ liquid wound with multiple materials (decellularized extracellular matrix
dressing (CNF-ILWD). CNF-ILWD was simultaneously [dECM], microcarriers, polymers, hydrogels, and cell
loaded with photothermal agent (indocyanine green) aggregates) [110] . However, this system suffers from lower
and chemotherapeutic drugs (doxorubicin) during the print resolution (50–400 microns) and longer production
preparation process. NIR, temperature, and pH multiple times due to the small nozzle diameter. Furthermore, when
response switches could efficiently control the drug release the cell density in the ink is too high, the high shear stress
of CNF-ILWD to kill residual tumor cells in wounds and during extrusion reduces the number of viable cells [101,110] .
deep layers of skin, and eliminate bacterial biofilms and
harmful bacteria. Therefore, drug-loaded CNF-based Laser-assisted bioprinting uses an energy source
wound dressings can be used for postoperative tumor (continuous monochromatic laser energy or pulses)
therapy and to promote the repair of infected wounds. The to irradiate a light-absorbing layer, thereby causing
functional material products recently used for skin wound the bioinks to be deposited as droplets on the printing
repair are presented in Table 1. platform by light [111] (Figure 3b). Depending on the laser
source, laser-assisted bioprinting can be subdivided into
Despite the significant advancements in the field laser direct writing (LDW), laser-induced forward transfer
of tissue engineering, a large number of functional or (LIFT), and matrix-assisted pulsed laser evaporation
multifunctional wound healing materials are still afflicted (MAPLE) [112] . Laser-assisted bioprinting has a high system
with problems such as morphological inconsistencies with resolution and open nozzle structure, which can precisely
wounds, difficulty in generating natural vascular networks arrange small volume of cell droplets in 3D spatial
and skin appendages, and difficulty in nutrient and oxygen positions, eliminating the problem of nozzle blockage.
exchange between tissue cells [100,101] . Also, it is hard to meet In addition, as a noncontact printing technology, it can
the diverse needs of wounds in complex situations. In recent prevent cell and bioink contamination to a certain degree.
years, 3D bioprinting technology has emerged as an ideal However, this technology can only select photosensitive
strategy to replace traditional low-precision cell spraying polymers for printing, and photopolymerization requires
and seeding techniques to deposit cells, biomaterials, and additional chemical modification of materials, which
bioactive molecules into precise 3D geometric patterns. limits the extensive use of various biological materials.
Computer control provides tools for the development of In addition, this technology has high maintenance cost
vascular and adnexal regeneration, thereby replicating the and long production time, which leads to low printing
anisotropy of natural skin [102,103] . efficiency and difficulty in printing large tissues and
organs [113,114] .
4. 3D bioprinting technology Digital light processing-based (DLP) 3D bioprinting

3D bioprinting is an advanced additive manufacturing uses a digital micromirror device (DMD) to project
technology, which can distribute bioink containing a designed optical pattern onto an ink container, by

Volume 9 Issue 5 (2023) 173 https://doi.org/10.18063/ijb.757