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International Journal of Bioprinting 3D-printed scaffolds for osteochondral defects

Figure 4. 3D-printed biphasic scaffolds for osteochondral tissue engineering. (A) Schematic diagram of the preparation of 3D-printed biphasic scaffold and
its applications. (B) Microscopic morphology of 3D-printed biphasic scaffolds. (C) The viability of cellswithin the scaffolds on the first day after printing
24h. (D) Gross observation of the repaired joints in different groups. (E) Micro-CT images at week 12 after implantation (Reproduced from ref. with
[87]
permission from The Royal Society of Chemistry).
separate regions. Therefore, multiphasic and continuous a single structure [95-98] . It is noted that there is no clear
gradient scaffolds with gradient physical and chemical boundary between layers of the scaffolds .
[98]
properties are necessary for a smooth transition between
different layers of the osteochondral unit. The multilayered Gradient scaffolds consistently outperform monophasic
osteochondral scaffold has at least four different layers. and biphasic ones in osteochondral defect repair [99,100] . The
Increasing the number of phases from three to four gradient can be described in terms of variations in the
or more usually means dividing the AC section into chemical composition and structural characteristics of
different zones. For example, Mancini et al. proposed the basic units, further including several basic forms of
[93]
an osteochondral scaffold consisting of four different arrangement, distribution, size, and orientation [101] . The
layers, with the aim of better simulating the properties of combined incorporation of different patterns of chemical
the different regions of AC. This multiphasic scaffold has and structural gradients in a monolithic osteochondral
a different collagen arrangement from top to bottom: the scaffold have been explored in orthopedic research as well.
PCL scaffold is based on a 0°, 90° cross-alignment pattern For example, with regard to the hydrogel-based scaffolds,
with decreasing porosity until the texture is dense, with the sequential addition of different solutions into a cylindrical
CCZ-like structure acting as the interface zone; the third container layer-by-layer before the complete gelation
layer is that PCL extending along the hydrogel containing allows for the formation of a gradient interface. Utilizing
mesenchymal stromal cells with a 70% porosity; the PCL is the silk protein-based composites coupled with biosilica
removed from the fourth layer and the hydrogel is retained, selective peptide-R5, Guo et al. fabricated a bioinspired
but the MSCs are replaced by articular cartilage progenitor gradient protein/biosilica analog by layering three regions
cells (ACPCs) . Therefore, it is easy to see how complex with high, medium, and low concentrations of the R5
[94]
this construction is, and finer 3D printing technology is peptide along the longitudinal direction [102] . This gradient
required to make it easy to achieve. As shown in Figure 5C, silicified silk/R5 system showed continuous transitions in
multiphasic scaffolds with discrete gradients are prepared composition, structure, and mechanical properties and
by stitching, gluing and press-fitting different phases into could promote the osteogenic differentiation of MSCs
in vitro in a gradient manner [102] . Multiphasic gradient

Volume 9 Issue 4 (2023) 138 https://doi.org/10.18063/ijb.724