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Lin, et al.
Table 1. Summary of the characteristic of different materials in 3D bioprinted biodegradable bone repair scaffolds
Materials Features References
Bioceramics Calcium Excellent osteosimilarity, osteoinductive, biocompatibility, [27-33]
phosphate mechanical properties
Hard to degrade, poor toughness
Bioglass Eximious osteogenic properties, biocompatibility [34-37]
Insufficient mechanical strength
Silicate High biocompatibility, osteoinductivity, pro-hard tissue [38,39]
regeneration ability
Poor fracture toughness, too fast degradation
Polymers Natural Good biocompatibility, degradability, printability, high [46-52]
polymers modulus of elasticity
Poor mechanical strength, fast degradation rate, single
material function
synthetic Wide range of material sources, gallows biocompatibility, [53-54]
polymers high mechanical strength
Some materials are difficult to degrade and have no
obvious osteogenic properties
Composites Functional diversity, combination of excellent [62-72]
performance of various materials, wide range of material
selection

prepared by sintering β-TCP ceramic slurry to show good slurry and that hinokitiol-modified scaffolds were also
biocompatibility in biological experiments and provide effective in suppressing cellular inflammatory responses.
richer calcium and phosphorus elements and growth By adding different ratios of graphene to calcium silicate
space for new bone formation after implantation in vivo. powder, Shie et al. showed that the Young’s modulus
[43]
However, β-TCP suffers from low mechanical strength was increased by 47.1% with the addition of 1 wt% of
and very rapid degradation, which limit its development graphene to calcium silicate, and the proliferation and
in the field of bone repair . expression of alkaline phosphatase (ALP), osteogenic,
[37]
Bioglass has good bioactivity, biocompatibility, and and osteogenic-related proteins in hMSCs were superior
promotes bone and soft-tissue regeneration, making it to the expression results of pure calcium silicate.
an excellent material for bone defect repair. One of the
most famous bioactive glass, 45S5, can rapidly bond 2.2. Polymers
to bone and promote bone growth away from the bone- Polymers are long-chain organic materials linked by
implant interface . Fujishiro et al. [39] observed 24 weeks covalent bonds , mainly including natural polymers
[38]
[44]
after surgery in a rat femoral defect experiment and and synthetic polymers such as COL, which are more
found that this bioactive glass accelerated the rate of hydrophilic and can form hydrogels with high water
bone regeneration compared to HA. On the other hand, content [45-47] . The use of polymers in 3D printing not
bioglass has disadvantages such as high brittleness and only achieves more precise customization of the scaffold
poor mechanical strength, which limit its application for geometry, but also minimizes processing costs compared
bone defects in load-bearing areas . Li et al. [41] obtained to other traditional molding methods. At the same
[40]
porous BG scaffolds with controllable mechanical time, due to the lack of mechanical strength and single
strength by modulating the molar ratio of SiO /CaO (90/5 function of natural polymers, research in the field of bone
2
– 60/35), and the characterization results showed that repair has focused on material selection and preparation
the high content of SiO produced more uniform crystal methods for advanced polymer composites [48,49] .
2
particles and dense sintering to improve the mechanical Natural polymers are more widely used in 3D
strength of the scaffolds. printing by virtue of their better bioactivity , mainly
[50]
Compared to bioceramics such as calcium including COL, silk proteins, cellulose, and alginates .
[51]
phosphate, calcium silicate-based biomaterials exhibit COL is the most abundant protein in the human body, and
better biodegradability, and osteoinductive properties. different types of COL bodies are distributed in different
Huang et al. [42] found that Si release and calcium silicate- tissues according to their structure and hierarchical
2+
based materials accelerated the formation of bone-like organization. Its unique triple helix structure is the basis
apatite layers by printing hinokitiol-modified wollastonite for the good stability and mechanical properties of COL

International Journal of Bioprinting (2021)–Volume 7, Issue 4 45