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International Journal of Bioprinting 3D bone: Current & future

hydrogels are often used in DIW, inkjet, LAP, and different chemically modified forms in hydrogels.
DLP bioprinting technologies. 65 In this regard, modified cellulose hydrogels have
good mechanical properties, and cellulose is an
(viii) dECM: dECM provides the most native-like 70
microenvironment for cells as a hydrogel material. It affordable material.
contains all the components of the ECM and growth (x) PEG and its derivatives: PEG is a synthetic
factors commonly found in native tissues; therefore, biocompatible polymer that is highly hydrophilic
it can promote cell proliferation and differentiation. and has a high water-absorbing capacity.
7
The production of dECM is tissue-specific, but the Additionally, its aqueous solution has a low viscosity.
tissue is generally exposed to physical, chemical, In 3D bioprinting, PEGDA and PEG methacrylate
or enzymatic stressors to remove the cellular (PEGDMA) are often used as they are highly
components. These methods can oftentimes be photocurable. PEGDA features rapid and stable
complicated and expensive. In addition, dECM- crosslinking, good mechanical properties, good
based hydrogels are challenging to use for 3D shape retention, high resolution, and high resistance
bioprinting, as they have low viscosity and poor to swelling in the aqueous environment. However,
mechanical properties, making it difficult to regulate PEGDA and PEGMA have low degradation rates and
their temperature-dependent crosslinking and rapid poor cell adhesion, and they are often combined with
degradation. As such, dECM is usually mixed with other organic hydrogel components (e.g., GelMA) or
other hydrogel materials for use in DIW, LAB, and inorganic components (e.g., HA) to improve their
electrospun bioprinters. 66-69 properties. PEG-based hydrogels are commonly
used in DIW, inkjet, and DLP bioprinters. 39,71
(ix) Cellulose: Cellulose is a biocompatible and bioactive
natural hydrophilic polymer. Due to the abundance 4.2.3 Additional inorganic components
of hydroxyl groups and its poor biodegradability, Bone tissue is a complex mineralized tissue with a rigid
cellulose is used not in its natural form but in ECM that is mainly composed of HA. Additionally, the two

Table 5. Materials used in bone 3D bioprinting

Type of Material Benefits Drawbacks Crosslinking 3D printing
material mechanism technique
Hard scaffold Polycaprolactone Good biocompatibility; Slow degradation; poor cell N/A Extrusion
(PCL) 89,90 biodegradable; easy to print adhesion
PEGDA 89,91-94 Biocompatible; fast Poor mechanical properties Photo-crosslinking Extrusion; SLA;
degradation; easy to print DLP
Polylactic acid Biodegradable; Slow degradation; poor cell N/A Extrusion
(PLA) biocompatible; easy to print; adhesion
good mechanical strength
Hydrogel Alginate Low cost; good Low bioactivity; poor cell Ionic crosslinking Extrusion; inkjet;
biocompatibility; adhesion; poor mechanical laser-assisted
biodegradable; low properties; limited stability in the
immunogenicity; shear- presence of antioxidants.; poor
thinning behavior bone conductivity; poor 3D shape
maintenance
Gelatin Biocompatible; Fast degradation; poor mechanical Thermal crosslinking Extrusion; inkjet;
biodegradable; reversible properties; slow gelation laser-assisted
gelation; low cost
Gelatin Biocompatible; High cost; cell damage by Photo-crosslinking Extrusion; DLP;
methacryloyl biodegradable; easy to blue or UV light electrospun
(GelMA) crosslink with photo-
initiators; fast crosslinking;
3D shape maintenance
Chitosan 63 Good biocompatibility; good Fast degradation; poor mechanical Ionic crosslinking; Extrusion; DLP;
cell adhesion; osteogenic properties; high cost photo-crosslinking; laser-assisted
potential self-assembly
(Continued)

Volume 10 Issue 3 (2024) 161 doi: 10.36922/ijb.2056