Journal
BIOMATERIALS
Volume 35, Issue 31, Pages 8810-8819Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.biomaterials.2014.07.002
Keywords
Bioprinting; Tissue engineering; Bioartificial bone; Osteoblasts; Polyphosphate; SaOS-2 cells
Funding
- ERC [268476 BIOSILICA]
- Deutsche Forschungsgemeinschaft [Schr 277/10-3]
- European Commission [604036, 286059, 268476, 311848]
- International Human Frontier Science Program
- BiomaTiCS [9737928]
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Sodium alginate hydrogel, stabilized with gelatin, is a suitable, biologically inert matrix that can be used for encapsulating and 3D bioprinting of bone-related SaOS-2 cells. However, the cells, embedded in this matrix, remain in a non-proliferating state. Here we show that addition of an overlay onto the bioprinted alginate/gelatine/SaOS-2 cell scaffold, consisting of agarose and the calcium salt of polyphosphate [polyP center dot Ca2+-complex], resulted in a marked increase in cell proliferation. In the presence of 100 mu M polyP center dot Ca2+-complex, the cells proliferate with a generation time of approximately 47-55 h. In addition, the hardness of the alginate/gelatin hydrogel substantially increases in the presence of the polymer. The reduced Young's modulus for the alginate/gelatin hydrogel is approximately 13-14 kPa, and this value drops to approximately 0.5 kPa after incubation of the cell containing scaffolds for 5 d. In the presence of 100 mu M polyP center dot Ca2+-complex, the reduced Young's modulus increases to about 22 kPa. The hardness of the polyP center dot Ca2+-complex containing hydrogel remains essentially constant if cells are absent in the matrix, but it drops to 3.2 kPa after a 5 d incubation period in the presence of SaOS-2 cells, indicating that polyP center dot Ca2+-complex becomes metabolized, degraded, by the cells. The alginate/gelatine-agarose system with polyP center dot Ca2+-complex cause a significant increase in the mineralization of the cells. SEM analyses revealed that the morphology of the mineral nodules formed on the surface of the cells embedded in the alginate/gelatin hydrogel do not significantly differ from the nodules on cells growing in monolayer cultures. The newly developed technique, using cells encapsulated into an alginate/gelatin hydrogel and a secondary layer containing the morphogenetically active, growth promoting polymer polyP center dot Ca(2+)complex opens new possibilities for the application of 3D bioprinting in bone tissue engineering. (C) 2014 Elsevier Ltd. All rights reserved.
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