Page 447 - IJB-9-2

International Journal of Bioprinting Fabrication of 3D functional hydrogel for wound dressings

1. Introduction In order to prevent bacterial infestation, trauma
dressings should have good antimicrobial activity [21,22] .
[1]
Skin, the largest organ and the first barrier of our body , Although antibacterial agents have been widely developed
plays a vital role in protecting our body, but often becomes and used, it has been a big problem to maintain excellent
fragile when encountering different kinds of accidents, biocompatibility while having antibacterial properties .
[22]
such as physical cuts and chemical reagent corrosion Some researchers have chosen to address this problem
injury [2,3] . In addition to the acute wounds caused by by adding antibiotics to the dressing. Antibiotics are
these accidents, chronic wounds such as diabetic foot efficient in destroying bacteria by inhibiting bacterial cell
ulcers (DFU), which are difficult to heal and cause serious wall production or inhibiting protein and nucleic acid
physical damage, have become a major threat to human production within bacteria [23,24] , but the problems caused
health and can lead to amputation and even death [4,5] . As by antibiotics cannot be ignored, and some reports have
a temporary substitute, wound dressings provide durable mentioned that bacterial resistance and bacterial mutations
protection in accelerating wound healing . Traditional are associated with heavy antibiotic use [25,26] . Compared
[6]
wound dressings, such as bandages and gauze, have with antibiotics, biomacromolecular antimicrobial agents
protective effects on wound surface, but often lack of are safer and have sustained antimicrobial properties.
ability to absorb tissue fluid and may cause secondary Chitosan (CS) is the product of the deacetylation of
injuries due to adhesion on the wound surface . To solve chitin, a positively charged alkaline polysaccharide with
[7]
these problems, membrane, sponge, rubber, hydrogel low solubility in water . In order to improve its water
[27]
dressing, and other new dressings [8-11] have been widely solubility, quaternized groups are introduced to obtain
studied and used. Among the dressings described above, quaternized chitosan (QCS). The cationic moieties of
hydrogels can provide a moist environment to promote QCS are preferentially attracted to the negatively charged
skin tissue regeneration and have structural characteristics surfaces of bacteria, resulting in the disruption of bacterial
similar to those of the extracellular matrix, as well as good membranes and efflux of internal material and ultimately
slippery elasticity to avoid secondary injuries caused by in bacteria death [28,29] . At the same time, its low biotoxicity
[12]
lacerations . In addition, with the new modification and and the addition of gelatin and SA as described above
structural design, the hydrogel dressings are endowed ensure that it will not cause damage to skin cells.
with a variety of excellent properties, such as antibacterial,
anti-inflammatory, and antioxidative properties, which are In damaged skin, inflammation-induced over-
beneficial to the four stages of wound repair (hemostasis reactive oxygen species (ROS), including superoxide-free
and coagulation, inflammation, proliferation, and radicals and non-free radical hydrogen peroxides, alter
remodeling) . or degrade extracellular matrix (ECM) proteins, destroy
[13]
skin fibroblasts, and reduce keratinocyte function [30,31] .
Since hydrogel dressings are applied directly to the Hydrogels loaded with free radical scavenging drugs have
skin surface, it is essential to ensure that hydrogels are been shown to significantly improve the wound healing
skin-friendly , which involves the choice of hydrogel process in patients, avoiding oxidative damage [32,33] .
[14]
materials. Gelatin, a protein that partially hydrolyzed However, gelatin, SA, and QCS materials selected above
from collagen, has good biocompatibility and temperature have no antioxidant properties. Fortunately, the antioxidant
sensitivity, and it is favored for its excellent viscoelasticity capacity of hydrogels can be improved by grafting
after solidification at low temperature (below 20°C) . Dou dopamine. As a neurotransmitter secreted by human body,
[15]
et al. introduced gelatin into poly (γ-glutamic acid) by dopamine has good biocompatibility and a large amount of
[16]
physical crosslinking to improve the structural stability and catechol structure, which makes it an excellent free radical
cellular adhesion properties and form an excellent double- eliminator [34,35] .
network bio-based wound dressing. Sodium alginate (SA)
is a harmless natural polysaccharide extracted from brown Due to the accident of wounds, the randomness of the
algae . When a large number of high-valued metal cations size and location of wounds, the dressing could not adapt
[17]
such as Ca , Mg , and Cu exist in the aqueous solution, to the changes of wounds [36,37] . In order to fulfill different
2+
2+
2+
they will be rapidly crosslinked with SA through replacing requirement of patients, 3D printing technology can be
Na to form gel networks . Hence, SA is widely used in introduced to prepare hydrogel dressings according to
+
[18]
hydrogel dressings due to mild reaction conditions . For their wound conditions. Moreover, the simple printing
[19]
example, Chen et al. used sodium alginate as a reducing principle, cheap bioink material, and stable printing
[20]
agent and stabilizer to reduce Ag into silver nanoparticles. equipment make extrusion-based 3D printing conducive
+
[38]
Thereby, the nano-silver-loaded polyvinyl alcohol/sodium to the mass production of wound dressings . In addition,
alginate wound dressings were prepared by using nano- further research on 3D printing technology can pave
silver as an antibacterial agent. the way for the emerging 4D printing technology and
Volume 9 Issue 2 (2023) 439 https://doi.org/10.18063/ijb.689