Page 179 - IJB-9-5

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

Inflammatory response usually exists in the process of quaternary ammonium chitosan (QCSG) and cross-
wound healing, and persistent inflammatory response linked gelatin methacrylate (GM). In addition to good
is one of the major reasons for delayed wound healing. antibacterial properties in vivo/in vitro, the full-thickness
Anti-inflammatory materials can inhibit the production defect repair model of mice infected with methicillin-
or release of anti-inflammatory factors, thereby promoting resistant S. aureus (MRSA) has proven that the conductive
wound healing process. hydrogel can promote wound healing in the repair of
Currently, a variety of anti-inflammatory materials infectious skin tissue.
have been employed to counteract inflammation; for Moreover, in wound care and tissue engineering,
example, paeoniflorin and PDA can inhibit inflammation conductive polymer materials provide electrical stimulation
by promoting the transformation of macrophages at the to activate ion channels by increasing the conductivity
wound site from the pro-inflammatory M1 phenotype to of the wound site, thereby transmitting downstream
the pro-healing and anti-inflammatory M2 phenotype . signals that guide the proliferation and migration of skin
[49]
Aspirin, ibuprofen, and asiaticoside block the synthesis cells, such as keratinocytes and fibroblasts [72,73] . Zhou
of inflammatory mediators (such as prostaglandins and et al. developed a kind of conductive multifunctional
[74]
thromboxane) by inhibiting cyclooxygenase (COX), PGFP scaffold cross-linked by branched polypyrrole@
thereby exerting anti-inflammatory effects . It has polydopamine (PPy@PDA) nanoparticles, aldehyde
[70]
been reported that asiaticoside (AS) not only has anti- F127, and poly(glycerol-amino acid) (PGA) (F127-Phe-
inflammatory activity but also has favorable effects on CHO). PPy@PDA endowed the PGFP scaffold with skin
fibroblast proliferation and collagen synthesis . Seon adhesion behavior, controllable electrical conductivity, and
[71]
et al. used AS to prepare a collagen-AS/εPLL double- photothermochemical tumor therapy. In addition, a full-
[50]
layer scaffold, in which the upper layer was loaded with thickness MRSA-infected wound model showed that this
εPLL with antibacterial effect, and the lower layer was PGFP scaffold could promote collagen deposition, vascular
composed of collagen with AS nanofibers. This scaffold endothelial differentiation, granulation tissue formation,
exhibits anti-inflammatory and bactericidal effects by and accelerate skin regeneration. This multifunctional
adjusting the TLR4/MAPK/NF-kB signaling pathway. scaffold has great potential in multimodal therapy of
Furthermore, a Sprague Dawley (SD) rat model of full- tumor/infection-damaged skin.
thickness inflammation demonstrated that the collagen-
AS/εPLL scaffold could accelerate inflamed full-thickness 3.4. Antioxidants
wound closure and re-epithelialization to promote wound Based on the definition, oxidative stress represents a
repair. Therefore, the collagen-AS/εPLL bilayer scaffolds disproportion between the production and scavenging of
have great application potential in the field of tissue ROS. ROS act as signaling mediators, which are involved
engineering. In addition, a study has shown that cerium in the regulation of growth, differentiation, proliferation,
oxide nanoparticles can eliminate ROS, which plays an autophagy, and apoptosis of many cells. During wound
important role in the inflammatory process, to achieve repair, the controlled level of ROS can moderate the
anti-inflammatory effect . oxidative damage in the wound site and promote epithelial
[51]
cell proliferation (proliferative phase), angiogenesis, and
3.3. Conductive materials tissue repair [75,76] . An overproduction of ROS will disrupt the
Conductive materials refer to carbon nanomaterials, redox balance of cells, leading to a cascade of inflammatory
conductive polymers, and metal nanoparticles with responses that increase tissue damage and hinder wound
[77,78]
electrical conductivity and electrical conductivity healing . Antioxidants can convert ROS into more
above 10 S/m. Conductive polymer materials such as stable molecules, such as water and oxygen, through
−6
polyaniline (PANI), silver nanowires (AgNW), graphene complex catalysis; this explains why antioxidants are also
[79]
oxide (GO), polypyrrole (PPy), polythiophene (PTh), and known as reactive oxygen scavenger . To date, a number
their derivatives (mainly aniline oligomers and poly(3,4- of antioxidants have been used to manage ROS levels.
ethylenedioxythiophene) [PEDOT]) have been widely Antioxidants are mainly divided into enzymatic
used in biomedical fields such as flexible sensors, health antioxidants (low molecular compounds, endogenous
monitoring, wearable devices, drug delivery systems, molecules, including catalase, superoxide dismutase, and
and tissue engineering . Studies have confirmed the glutathione peroxidase) and nonenzymatic antioxidants
[37]
role of conductive materials in skin repair. Liang et al. (with many exogenous and endogenous molecules, such
[52]
developed an injectable antibacterial conductive QCSG/ as PDA, curcumin, polyphenols, and flavonoids) .
[80]
GM/GO hydrogel by using the conductive material GO In the process of skin tissue repair, these antioxidant
functionalized with glycidyl methacrylate-modified materials can accelerate wound healing by controlling

Volume 9 Issue 5 (2023) 171 https://doi.org/10.18063/ijb.757