Abstract
Cell-laden scaffolds are widely investigated in tissue engineering because they can provide homogenous cell distribution after long culture periods, and deposit multiple types of cells into a designed region. However, producing a bioceramic 3D cell-laden scaffold is difficult because of the low processability of cell-loaded bioceramics. Therefore, designing a 3D bioceramic cell-laden scaffold is important for ceramic-based tissue regeneration. Here, we propose a new strategy to fabricate an alpha-tricalcium-phosphate (α-TCP)/collagen cell-laden scaffold, using preosteoblasts (MC3T3-E1), in which the volume fraction of the ceramic exceeded 70% and was fabricated using a two-step printing process. To fabricate a multi-layered cell-laden scaffold, we manipulated processing parameters, such as the diameter of the printing nozzle, pneumatic pressure, and volume fraction of α-TCP, to attain a stable processing region. A cell-laden pure collagen scaffold and an α-TCP/collagen scaffold loaded with cells via a simple dipping method were used as controls. Their pore geometry was similar to that of the experimental scaffold. Physical properties and bioactivities showed that the designed scaffold demonstrated significantly higher cellular activities, including metabolic activity and mineralization, compared with those of the controls. Our results indicate that the proposed cell-laden ceramic scaffold can potentially be used for bone regeneration.
Highlights
Biomedical scaffolds have improved with the development of tissue engineering technology
tricalcium phosphate (TCP) consists of two main crystal structures, α-TCP and β-TCP. α-TCP is more soluble compared with β-TCP and α-TCP can have a cementic reaction, which hardens the bioceramic to form a calcium-deficient hydroxyl apatite (CDHA) in an aqueous condition, such as a culturing condition in minimum essential media alpha (α-MEM)16. when used for bone tissue regeneration, α-TCP shows a more rapid bone formation in vivo relative to that of β-TCP, the two TCPs have a similar chemical structure[19, 20]
We compared the results with two controls: (1) a cell-laden collagen scaffold (CLCS), which was fabricated with cell-laden collagen cross-linked with tannic acid (TA) solution, and (2) an α-TCP/collagen scaffold, which was dipped into cell-laden collagen solution
Summary
The fabrication schematics for the two cell-loaded α-TCP/collagen scaffolds (TC-CDIP and TC-CPRINT) are described in Fig. 1b and c, respectively. We obtained optimal conditions for the printing of cell-laden collagen solution using the nozzle size of 150 μm, pneumatic pressure of 180 kPa, and non-crosslinked collagen bioink. The CLCS and TC-CPRINT scaffolds were porous scaffolds with homogeneous pore size, while TC-CDIP had a non-homogenous pore structure, caused by the blockage of the cell-laden collagen solution during the dipping process. The results of in vitro bioactivity assay showed synergism between the homogenously printed cells and the calcium and phosphorus ions released from the CDHA scaffold; this can directly affect osteogenic differentiation in the TC-CPRINT scaffold, indicating that the TC-CPRINT scaffold may be an effective bioactive platform for the regeneration of bone tissue
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