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International Journal of Bioprinting FeS /PCL scaffold for bone regeneration
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self-repair without forming scar tissue when fractured piezoelectric, or microvalve processes . Although this
[19]
through the bone healing process . This process is based technique is relatively inexpensive and has high printing
[4]
on a cascade of events, which include the restoration of speeds, there are some limitations, such as limited bioink
vascularity, recruitment of adjacent cells, ossification, etc. . viscosity and rapid drying of the bioink post-ejection. In
[5]
However, in severe bone fractures, the bone healing the case of laser-assisted systems, laser is used as the energy
process might be disrupted. In order to aid the healing source to deposit bioink . Using laser-based methods,
[20]
of severe bone fractures, the use of bone grafts, such as high printing resolution can be achieved. However, only
autografts, allografts, and xenografts, has been considered photo-crosslinkable bioinks can be used. One of the most
as the ideal method . However, issues including the lack common 3DBP techniques is extrusion-based method,
[6]
of donors, donor site morbidity, and possibility of infection where the bioink is extruded using pneumatic pressure or
still prevail since these grafts are donor tissues [7-9] . mechanical force . Extrusion-based systems compensates
[21]
These shortcomings have compelled the search for an for the limitations of inkjet and laser-based methods. By
alternative, leading to the development of a new field—tissue utilizing the extrusion-based method, heterogeneous
engineering. This field aims to restore or replace damaged structures can be fabricated using various types of
tissues or organs based on the development of biological biomaterials. Another advantage is that extrusion-based
substitutes . Viable cells, scaffolds, and growth factors systems are highly customizable, and recently, they have
[10]
are used to induce tissue development. The bioengineered become more affordable.
scaffolds should provide an environment similar to the Various biomaterials such as ceramics, metals, and
native tissue or organ to enable the maturation of cells synthetic polymers have been used to develop tissue-
into functional tissue or organ . Therefore, the chemical engineered scaffolds for bone tissue regeneration [22-24] .
[11]
composition and physical structure should be carefully Regardless of their benefits, these biomaterials do not mimic
determined depending on the target tissue. Some of the the properties of natural bone tissue. Most metals are not
important characteristics that scaffolds should have for biodegradable, ceramics are very brittle, and most of the
bone tissue engineering applications include mechanical synthetic polymers are non-osteoconductive [25-27] . In order
properties matching those of the host tissue, fully to address these problems, blends of synthetic polymers and
interconnected porous structure, and surface properties in ceramics have been extensively investigated, benefitting
favor of cell adhesion, proliferation, and differentiation . from the favorable properties of each material. Since the
[12]
Tissue-engineered scaffolds can be fabricated using main components of bone are composed of ceramic-based
various techniques. Recently, there has been extensive materials, ceramics have been used in various regenerative
research on three-dimensional (3D) bioprinting (3DBP), applications . Moreover, the modifiability of synthetic
[23]
[28]
which enables the fabrication of complex 3D structures polymers offers a wide variety of applications (Table 1) .
mimicking the native extracellular matrix structure. Liu et al. fabricated a composite scaffold composed of
The most commonly used 3DBP techniques are inkjet, poly(e-caprolactone) (PCL) and strontium-containing
laser, and extrusion [13-18] . In inkjet printing, the solution hydroxyapatite (SrHA) using a 3D printing method for
[29]
is dispensed in the form of droplets through thermal, bone tissue regeneration . The incorporation of SrHA not

AQ2 Table 1. Previous works on polymer/bioceramic-based composite scaffolds for bone tissue regeneration

Materials Mechanical properties Defect model Degree of bone formation Ref.
PCL/SrHA Increased with the addition Rat skull defect The repair performance of the PCL/SrHA scaffold was [29]
of SrHA to PCL better than the control group
PCL/nHA Compressive modulus: Rabbit calvarial defect Percentage of defect reduction: 11.2% [30]
109.6 ± 2.0 MPa
Bioglass/mMCS/ Compressive modulus: Rabbit femoral defect Percentage of new bone area: 80% [31]
GA/PCL 12.1 ± 2.1 MPa
PCL/silica Compressive modulus: Rat calvarial defect Percentage of new bone area: 19% [32]
26.0 ± 2.2 MPa
dECM-coated CS/PCL N/A Rat calvarial defect BT/TV value of 37.75% [33]
Mg-P/KR-34839 N/A Rat calvarial defect Newly formed bone increased by 2.3-fold [34]
Abbreviations: BT/TV, bone volume per tissue volume; CS, calcium silicate; dECM, decellularized extracellular matrix; GA, gliadin; Mg-P,
Magnesium phosphate; mMCS, mesoporous bioglass fibers of magnesium calcium silicate; nHA, nano-hydroxyapatite; PCL, polycaprolactone;
SrHA, strontium- containing hydroxyapatite.

Volume 9 Issue 1 (2023)olume 9 Issue 1 (2023)
V 200 https://doi.org/10.18063/ijb.v9i1.636