Page 226 - IJB-9-5

International Journal of Bioprinting Hydrogels for 3D bioprinting

properties. In addition, chitosan is also polycationic, and adjusted the rheology of the hydrogel by changing the ratio
its positive charge can generate electrostatic interactions of Sil-MA to adapt to DLP-based printing. Among them,
with negatively charged ECM molecules. Chitosan 30% of Sil-MA has suitable printability and good shape
interacts with the negatively charged cell membrane of recovery. They fabricated a cricoid trachea by DLP-based
microorganisms, causing the death of bacteria. Therefore, printing for in vitro testing. Sil-MA hydrogel provides
this antibacterial property has expanded its application in a suitable environment for the growth of chondrocytes
the medical field [89,90] . and the formation of cartilage in vitro. The scaffold exists
in vitro for up to 4 weeks and degrades up to 50%.
After the chitosan is modified, its performance
will be greatly improved. After being methacrylated,
chitosan can be used as a light-curable material for 4. Nanocomposite hydrogel bioink
printing and crosslinking. Chang et al. synthesized a Despite the continuous investigations on natural and
[91]
water-soluble methacrylated glycol chitosan (MeGC) synthetic hydrogels in recent decades, it is still challenging
and produced an MeGC-based bioink loaded with MG- to prepare tissue engineering scaffolds using single or
63 cells using a visible light curing system with 12 μM mixed hydrogel materials, and some of the problems
riboflavin as a photoinitiator. They made the MeGC include weak mechanical properties, low cell activity,
solution by adjusting the pH of the solution in the first and poor processability. These difficulties have prompted
step; in the second step, MG-63 cells were suspended researchers to find some suitable nanomaterials combined
in a 3% MeGC solution containing 12 μM riboflavin with hydrogels to improve the properties of hydrogels.
and cured at 430–485 nm visible light for 30 to 90 s Nanocomposite hydrogels have a wide range of applications
using a visible light irradiator, and finally the hydrogel in the fields of tissue engineering and regenerative
containing the cells would be 3D-bioprinted. The results medicine . Hassan et al. summarized the methods and
[93]
[12]
showed that the survival and value-added of MeGC-70 applications of nanomaterials in compounding hydrogel
were high, and the rheological properties of the bioink biopolymers. They found that the main natural biopolymers
aqueous solution were optimized. CH materials can not are SA and collagen derivatives. This part reviews the
only be printed in the form of liquid bioink, but can also commonly used nanomaterial composite hydrogels, such
be extruded in the form of solid bioink. Zhang et al. as inorganic nanomaterials, carbon-based nanomaterials,
[88]
used hydrogel particles as the bioink for extrusion- and nanofiber-based materials. A few researchers
based 3D bioprinting. The particles are composed of also use gold nanomaterials mixed with hydrogels as
chitosan methacrylate (CHMA) and freeze-thawed printed bioinks [94,95] .
polyvinyl alcohol (PVA). Under the action of chemical
crosslinking and physical crosslinking, the hydrogel 4.1. Inorganic nanocomposite hydrogel
was manufactured with fast self-healing and adjustable Bioactive glass (BG), hydroxyapatite (HA), and Laponite
mechanical properties (Figure 2A). The CHMA/PVA are common inorganic nanomaterials with osteoinductive
composite hydrogels are broken into particles during properties. Therefore, inorganic nanomaterials are usually
extrusion and then a printable hydrogel is formed through mixed with hydrogels to repair bone and cartilage.
the hydrogen bonding between chitosan and PVA chains. According to related reports, the bioactive ions released
The innovative self-healing hydrogel particles exhibit by the BG during degradation can promote cell adhesion,
excellent shear thinning, gel-sol transition, and good proliferation, and differentiation, and accelerate tissue
yield strength during extrusion printing. Besides, the self- vascularization and increase expansion force. It is currently
supporting scaffold can adequately induce the growth, the only material that can be combined with bone tissues
proliferation, and differentiation of bone marrow-derived and connected with soft tissues . Tissue engineering
[96]
MSCs. In addition to the above modification methods, has developed rapidly in the field of regeneration of hard
mixing chitosan with other polymers, such as PEG, to tissues, such as bone and cartilage, but bone graft therapy
prepare bioinks is also an effective way . is very limited in clinical practice. Bones have strong self-
[39]
regeneration ability, and self-recovery is more successful
3.3.3. Modified silk fibroin for small-scale bone defects. However, for large-scale bone
In addition to gelatin and chitosan, many researchers also defects that cannot be cured on their own, external bone
have modified silk fibroin to improve their mechanical scaffolds are needed to help bone regeneration and healing.
properties and to modulate their degradation rates. It is Bone scaffolds need to meet some specific requirements
usually modified with glycidyl methacrylate (GMA) as a such as bone conduction, controllable pore size, mechanical
photocrosslinked hydrogel for DLP-based printing [34,92] . properties, and biocompatibility similar to natural bone,
Kim et al. prepared SF-based bioink (Sil-MA) and biodegradability, and adsorption capacity .
[97]
[92]
Volume 9 Issue 5 (2023) 218 https://doi.org/10.18063/ijb.759