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International Journal of Bioprinting 3D bioprinting techniques & hydrogels materials

3.2.3. Hydrogels made from various molecules constitute a strategy for bone tissue engineering.
composite materials Herein, we will discuss enhancing the biofunctions of
Some researchers have attempted to use two or more hydrogel-mediated osteochondral repair using cells and
composite hydrogels to treat OCDs. Polymeric scaffolds are growth factors.
extensively utilized in bone tissue engineering due to their
biocompatibility, ductility, and customizability. Compared 3.3.1. Mesenchymal stem cells
with other polymers, polycaprolactone (PCL) has greater Mesenchymal stem cells (MSCs) come from a wide
toughness, elasticity, and mechanical strength and is the range of sources and can differentiate into bone cells and
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most prevalently employed synthetic polymer. 168,169 Chen chondrocytes that play important roles in tissue repair.
et al. fabricated a 3D bioprinting biphasic scaffold, where Shim et al. 3D-printed a hydrogel scaffold containing
the cartilage phase scaffold consisted of alginate saline gel human turbinate-derived MSCs (hTMSCs), and the
and PCL, and the bone phase scaffold was loaded with scaffold demonstrated good osteochondral regeneration
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HAP in the PCL. This hybrid scaffold exhibits an ideal in rabbits. Gao et al. uniformly printed human MSCs
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biological response both in the short and long term, and on polymerized poly(ethylene glycol) (PEG)-GelMA,
it has the potential to be used as an interface material for and the scaffold demonstrated remarkable osteogenic and
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cartilage and bone. chondrogenic differentiation. Zhang et al. fabricated a
composite scaffold with HAP and a hydrogel and gradient-
Owing to the deficiency of bone-induced characteristics, loaded BMSCs onto the scaffold in accordance with
the utilization of PCL in bone tissue engineering is osteochondral characteristics, demonstrating favorable
limited. Currently, numerous studies have endeavored osteochondral repair effects in rabbit models. 180
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to coat porous scaffolds with certain natural biological
materials to enhance their cell adhesion. The cartilage Furthermore, chronic inflammation within the joint
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ECM is a special type of natural biological material and reduces chondrogenesis and MSC motility, leading to
also a fiber-reinforced composite material, and it can cartilage matrix interpretation and thus exacerbating
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increase the expression of collagen II and aggrecan in the progression of osteochondral injury. Therefore,
chondrocytes, thereby increasing cell adhesion. Li et al. inhibiting the inflammatory microenvironment is key
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designed a double-layered scaffold; the cartilage layer was for effectively repairing OCDs caused by inflammatory
composed of ECM, polycaprolactone (PCL), and hydrogel, diseases, such as OA. Liu et al. designed a 3D-printed
and the subchondral bone layer was composed of PCL and multilayer hydrogel scaffold loaded with BMSCs. The PCL
polydopamine (PDA) modified with magnesium oxide layer combines with β-TCP for bone regeneration, whereas
(MgO) nanoparticles. The scaffold effectively regenerated PCL/methacrylated hyaluronic acid (MeHA) combines
bone and cartilage simultaneously in rats. 174 with Kartogenin (KGN) for cartilage regeneration.
Diclofenac sodium (DC)-supported hydrogel coating was
Additionally, researchers are applying natural applied to the top of the articular facing stent to inhibit
compounds to bone tissue engineering. Honokiol is the the inflammatory microenvironment (Figure 3i). This
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main bisphenol compound isolated from Magnolia trees composite scaffold can effectively promote osteochondral
and is reported to have a wide range of biological activities repair by promoting the deposition of ECM proteins and
and low cytotoxicity. Zhu et al. used ECM, polyethylene suppressing the production of interleukin-1β.
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glycol diacrylate (PEGDA), and honokiol to develop
hydrogel scaffolds, and the 3D-printed hydrogel scaffolds Promoting cartilage vascularization is also a major
exhibited excellent osteochondral regeneration ability. 176 challenge in bone tissue engineering. Although cartilage
templates are well-vascularized in vivo, vascularization
Owing to the varying advantages and disadvantages begins peripherally, and the central region of cartilage
of different materials, fabricating scaffolds by combining remains vascular-free. To address this issue, Daly et al.
multiple materials can address the various requirements developed a 3D-printed hydrogel scaffold loaded with
of osteochondral repair. However, the complex fabrication MSCs, promoting vascularization after implantation with
process may be a major factor limiting its application. In the the potential to repair large bone defects. 184
future, it is imperative to identify more suitable materials
and simplify the production process (Table 3). In bioprinting, the contact between cells and the cell
contact-dependent signal is blocked due to the trapping
3.3. Enhancement of the biofunctions of effect of the hydrogel, resulting in the loss of their biological
hydrogel-based osteochondral repair activity. The spheroid, a multicellular aggregate with a
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In addition to the recruitment of cells, such as MSCs, or microenvironment similar to native tissue, is an advanced
bioactive factors to promote bone repair, the direct delivery printing unit with the potential to become a bioink for
of homologous or dissimilar MSCs and the stimulation of bone tissue engineering. Its extensive intercellular contact

Volume 10 Issue 6 (2024) 77 doi: 10.36922/ijb.4472