P041 - 3D Bioprinted GelMA-Gelatin-Hydroxyapatite Osteoblast Composite Hydrogels for Bone Tissue Engineering
- R. Danilkowicz (Durham, US)
- R. Danilkowicz (Durham, US)
- N. Allen (Durham, US)
- B. Abar (Durham, US)
- L. Johnson (Durham, US)
- S. Adams (Morrisville, US)
Abstract
Purpose
The purpose of this study was to investigate the suitability of an extrusion-based 3D bioink composed of gelatin methacryloyl (GelMA), gelatin, hydroxyapatite (HA), and osteoblasts for bone tissue engineering.
Methods and Materials
A mouse calvarial osteoblast-laden GelMA-gelatin bioink consisting of various concentrations of HA was 3D-bioprinted into porous hydrogel constructs. The constructs were cross-linked via photopolymerization and cultured in osteogenic medium. After 1, 14, and 28 days, the constructs were analyzed. The water weight percent differences of the hydrogels were characterized. An ALP assay and histological analysis were performed. Cell survivability and proliferation in the composite hydrogels was determined. Real-time polymerase chain reaction was performed to measure expression levels of osteogenic genes, BMP-7, and osteocalcin relative to a housekeeping gene (GAPDH).
Results
The addition of 5, 10, and 20 mg/ml of HA reduced hydrogel swelling from baseline GelMA-Gelatin hydrogels (p ≤ 0.01). HA decreased hydrogel breakdown in a concentration dependent manner (p ≤ 0.001). Alamar Blue assay demonstrated significantly increased cell proliferation. There was no difference in metabolic activity among the groups (p ≤ 0.01). The addition of 5mg/ml and 20mg/ml of HA significantly increased ALP expression at 7 and 28 days (p ≤ 0.05). Live/dead staining showed the majority of osteoblasts survived in all groups at 1, 14, and 28 days. The addition of 20mg/ml of HA (GG20HA) demonstrated greater BMP7 and BGLAP gene expression at both 14 and 28 days over hydrogels without HA (p ≤ 0.05).
Conclusion
The addition of HA to GelMA-gelatin hydrogels significantly decreased hydrogel swelling, improved the ability to resist enzymatic degradation, increased osteoblastic differentiation and mineralization, and increased osteogenic gene expression while maintaining equal cell viability and proliferation to non-HA hydrogels. These findings support a lower threshold of 20 mg/ml of HA as an optimal concentration to support gene expression associated with osteoblast cell differentiation and maturation.