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International Journal of Bioprinting 3D bioprinting techniques & hydrogels materials

composite alginate hydrogels for osteochondral repair in functional groups, ligands, macromolecular side chains,
future developments. etc. 139,140 Chitosan derivatives demonstrate excellent
biological characteristics. Additionally, as chitosan is
3.1.2. Methacryloyl-modified gelatin hydrogels derived from shellfish or shrimp, the allergic reaction
Methacryloyl-modified gelatin (GelMA) is a gelatin might also impact its clinical transformation. Waibel et al.
derivative composed of methacryloyl side groups evaluated its biosafety, and no adverse effects were found in
(methacrylamide and methacrylate [MA]), with excellent the subjects. Further research is warranted to clarify this
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cell adhesion properties due to its retention of most issue in the future.
functional amino acid motifs (e.g., RGD motifs). 131,132
GelMA hydrogels have excellent biocompatibility, can 3.1.4. Hyaluronic acid hydrogels
load cells, and maintain the controlled release of growth Hyaluronic acid (HA) is an essential constituent of the
factors, as well as the advantage of low immunogenicity, ECM, and its molecular chain is alternately composed of
making them widely used. Jiang et al. fabricated a repeating disaccharide units of β-1,4-D-glucuronate-β-
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3D-printed platelet-rich plasma (PRP)-GelMA hydrogel 1,3-n-acetyl-d-glucosamine. 142,143 Owing to the diversity
scaffold using DMD for osteochondral repair in a of the repeating disaccharide unit, the HA molecule does
rabbit model and compared the therapeutic effects of not induce an immune response. In addition, HA can
different concentrations of PRP on osteochondral repair. cause macrophages to polarize from M1 type to M2 type
They found that 20% of PRP exhibited the strongest by targeting CD44 in vivo, exerting anti-inflammatory
repair effect and could promote the polarization of effects. HA also has inherent properties against certain
144
M2 macrophages. 40 strains and antimicrobial delivery. Coupled with its
outstanding water retention capacity, biodegradability, and
However, Enhancing the mechanical strength of 3D designability, it is extensively utilized in the fields of drug
printed GelMA for soft tissue engineering applications. delivery, cell culture, and regenerative medicine. 145,146
Current methods to enhance their mechanical properties
are mainly through crosslinking with other substances, Nevertheless, its high vulnerability to enzymes
such as nanomaterials and polymers. Dong et al. and weak mechanical properties impede its broader
134
prepared a GelMA-GelMA (G-G) homogeneous double- application. 147 Fortunately, there are numerous
network hydrogel based on DLP 3D printing to improve its multifunctional reactive groups in HA, and diverse
mechanical strength. In addition, hydrogen bonding and HA derivatives can be obtained by employing various
crosslinking between HA and GelMA hydrogel can also play chemical modification and crosslinking strategies to
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a role in enhancing mechanical properties (Figure 2i). enhance their mechanical strength and stability
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(Figure 2i). For instance, HA can be chemically modified
3.1.3. Chitosan hydrogels with photo-crosslinkable functional groups, such as MA,
Chitosan is derived from chitin, which is abundant to facilitate photo-crosslinking between HA molecules.
149
in nature and has satisfactory biocompatibility and A HAMA hydrogel possesses enhanced mechanical
biodegradability. It is an attractive candidate material strength, making it suitable for constructing a variety
136
for tissue engineering. Chitosan hydrogels prepared of hydrogels, such as microparticles, microneedles, and
by enzyme crosslinking can support the proliferation 3D-printed scaffolds. The biological properties of HA
150
of chondrocytes and mesenchymal stem cells can also be improved via oxidation or the introduction of
(MSCs), maintain the phenotype and morphology of sulfhydryl and catechol, etc. 151-153
chondrocytes, and promote the deposition of cartilage
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ECM in vitro. Sheehy et al. verified their capacity to 3.2. Hydrogel composition
support chondrogenesis and hypertrophy of MSCs. The 3.2.1. Hydrogel mixed with bioceramics
chondroblast phenotype of MSCs was well retained after 8 Bioceramic materials, exemplified by calcium carbonate,
weeks of chondrogenesis in vitro. In vivo, it was discovered calcium phosphate, calcium sulfate, and their derivatives,
that it promoted neither vascularization nor endochondral possess excellent mechanical properties, which can
ossification, suggesting that it is a suitable material for compensate for the weak mechanical properties of
articular cartilage engineering. 138 hydrogels. Furthermore, the inherent bone inducibility
154
However, chitosan possesses poor water solubility and conductivity of bioceramics facilitate the proliferation
under physiological conditions and low cell adhesion, and differentiation of MSCs in both scaffold-loaded and
which constitutes the primary reason restricting its bone defect sites, enhancing the repair capacity when
application. Currently, the solubility and cell adhesion combined with hydrogels to form bioinks. 155,156 The
of chitosan derivatives are regulated by introducing common applications of 3D bioprinting of hydrogel in

Volume 10 Issue 6 (2024) 74 doi: 10.36922/ijb.4472