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International Journal of Bioprinting 3D bioprinting of tissue with carbon nanomaterials

As biomaterial inks do not have cells, they can be subjected Currently, bone tissue engineering (BTE) is considered
to post-printing treatments, such as washing, crosslinking, an alternative to bone grafting in replacing damaged
and UV curing, to make them stronger and biocompatible bones using biomaterials [109-111] . Literature reports have
before cell line studies. In contrast, bioinks possess cells revealed that about 2.2 million patients worldwide
with various bioactive components and biomaterials before undergo bone grafting each year [112] . Hence, 3D
bioprinting. Hence, the components and crosslinking bioprinting of bone tissue is regarded a rapidly evolving
agents involved in bioinks should be biocompatible . technology in this field. In a study, Liu et al. prepared
[91]
Bioinks used in 3D bioprinting can be categorized into a poly(propylene fumarate) (PPF)-based 3D-printed
two types: scaffold-free cell-based and cell-scaffold-based hydrogel incorporating two types of 2D materials—GO
approaches for the creation of tissue- and organ-like and black phosphorous (BP) nanosheets—and examined
structures. In the scaffold-free cell-based approach, living the synergistic effect of these materials on osteogenesis for
cells are printed directly to form neo-tissues and fused into BTE . They used PBB (3D VIPER si2 Stereolithography
[94]
the native functional tissue structures over time. In the System) to construct the 3D scaffold with orthogonal
cell-scaffold-based approach, living cells and biomaterials cubic lattice disks and square pores. Besides, they
are mixed as bioinks; the encapsulated cells migrate and subjected the tissue construct to post-printing treatments
proliferate to fill the space to form a desired tissue structure such as washing with acetone and ethanol as well as UV
in the scaffold matrix . curing for 2 hours to ascertain the biocompatibility and
[92]
A successful bioink with suitable biomechanical stability of the scaffold. GO nanosheets have been found
properties can provide structural integrity of the to enhance cell adherence and protein adsorption in view
printed tissue until the neo-cellular architecture begins of their large surface area, whereas GO layers-wrapped
functioning. According to Bhattacharyya et al., the bioink BP nanosheets continuously released phosphate ions
formulation must meet the following criteria: (1) the cells to the medium through slow oxidation, thus facilitating
to be printed should be selected based on their viability MC3T3 osteoblast differentiation. Immunofluorescence
during in vitro and in vivo measurements; (2) the polymer assay revealed that the 3D PPF-Amine-GO@BP scaffold
matrix or the additives incorporated into the polymeric had a higher cell density on the surface when compared to
composite should be biocompatible, and the additives the 3D PPF-Amine-GO, 3D PPF-Amine-BP, and 3D PPF-
should be bioactive to enhance the physicochemical and Amine scaffolds. The biomineralization and osteogenic
mechanical properties as well as the biofunctionalities of differentiation results indicated that the BP anchored on
the printed gel; (3) the cross-linkage conditions should the GO surface synergistically stimulated cell proliferation
be amicable without stressing the printed cells, and they and osteogenesis, suggesting that the scaffold has the
should not affect the cell survival rate after crosslinking; capacity for bone tissue regeneration.
(4) the bioink layers should be able to maintain structural Cartilage is formed by chondrocytes, which have
stability in the cell culture medium for a long time . In poor regenerative capacity and lack extracellular matrix
[93]
the subsequent sections, we discuss the various CFNs- vascularization. Hence, treating injuries to the cartilage
containing biomaterial inks and CFNs-containing bioinks, can be challenging [113] . Olate-Moya et al. have developed
along with the CFNs’ dimensions utilized, the specification bioconjugated hydrogel-based nanocomposite inks that
of bioprinters, and the biological outcomes in various contain alginate, gelatin, chondroitin sulfate, and GO to
TE applications, as shown in Tables 1 [94-103] and 2 [97, 104-108] , fabricate 3D-printed scaffolds through the microextrusion
respectively. process in EBB for cartilage TE . After printing, the
[95]
alginate chains in the extruded ink were physically
3.1. CFNs-containing biomaterial ink crosslinked with 100 mM calcium chloride (CaCl )
2
3.1.1. Graphene and carbon nanotubes in solution and gelatin chains via a thermotropic process.
biomaterial ink Then, the scaffolds were crosslinked with methacrylated
Graphene-family nanomaterials- and CNTs-incorporated polymers via UV irradiation (365 nm and 9 mW/cm ).
2
printed gels have drawn considerable attention in TE The nanofiller GO enhanced the 3D printability of bioink
owing to their excellent mechanical properties and owing to a faster viscosity recovery during ink extrusion.
high electrical conductivity. Large bone defects caused Due to the templating of the GO liquid crystal, the
by external injury, infections, tumor resection, bone nanocomposite inks produced anisotropic threads. The
resorption, and nonunion fractures are treated with bioconjugated scaffolds displayed higher cell proliferation
autologous or allogeneic bone grafts. However, these rate than pristine alginate, as revealed by the proliferation
treatments have certain drawbacks, including insufficient assay of human adipose tissue-derived MSCs (hADMSCs).
graft quantity, donor site morbidity, and contamination. Furthermore, the immunostaining assay revealed that the

Volume 9 Issue 1 (2023) 186 https://doi.org/10.18063/ijb.v9i1.635