Abstract
Two-photon polymerization (2PP) is applied for the fabrication of 3-D Zr-Si scaffolds for bone tissue engineering. Zr-Si scaffolds with 150, 200, and 250 μm pore sizes are seeded with human bone marrow stem cells (hBMSCs) and human adipose tissue derived stem cells (hASCs) and cultured in osteoinductive and control media for three weeks. Osteogenic differentiation of hASCs and hBMSCs and formation of bone matrix is comparatively analyzed via alkaline phosphatase activity (ALP), calcium quantification, osteocalcin staining and scanning electron microscopy (SEM). It is observed that the 150 μm pore size Zr-Si scaffolds support the strongest matrix mineralization, as confirmed by calcium deposition. Analysis of ALP activity, osteocalcin staining and SEM observations of matrix mineralization reveal that mesenchymal stem cells cultured on 3-D scaffolds without osteogenic stimulation spontaneously differentiate towards osteogenic lineage. Nanoindentation measurements show that aging of the 2PP-produced Zr-Si scaffolds in aqueous or alcohol media results in an increase in the scaffold Young’s modulus and hardness. Moreover, accelerated formation of bone matrix by hASCs is noted, when cultured on the scaffolds with lower Young’s moduli and hardness values (non aged scaffolds) compared to the cells cultured on scaffolds with higher Young’s modulus and hardness values (aged scaffolds). Presented results support the potential application of Zr-Si scaffolds for autologous bone tissue engineering.
Highlights
MethodsSynthesis of Zr-Si-based organic inorganic polymer ceramic compositesZr-Si inorganic-organic hybrids were prepared according to a procedure that was previously described [8,11]
Tissue engineering (TE) scaffolds must provide a cell environment similar to that of native tissues
This study has demonstrated the potential of application of 3-D Zr-Si polymer ceramic scaffolds for autologous bone tissue engineering
Summary
Synthesis of Zr-Si-based organic inorganic polymer ceramic compositesZr-Si inorganic-organic hybrids were prepared according to a procedure that was previously described [8,11]. In a separate container, zirconium (IV) n-propoxide (ZPO, Assay 70% in propanol, Sigma-Aldrich) was mixed with the chelating agent methacrylic acid (MAA, C4H6O2, Assay 98%, Aldrich); this approach is necessary to stabilize the zirconium (Zr) precursor. Both blends were mixed for 40 min before being combined together. The resulting liquid sol-gel composite photo-active resin was filtered through a 5 μm syringe filter to remove any inclusions that could affect laser polymerization. Substrates for scaffold fabrication were prepared by drop casting of 1 mL of liquid material onto 22×32 mm glass substrates, followed by slow evaporation of the organic solvent over 24 h at room temperature and subsequent baking at 100°C for 2 h. 300 μm thick photopolymer layers on a glass substrate were produced using this method
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