Engineering bone tissue via 3D bioplotting of human Stem Cells and Growth Factor-releasing nanocarriers

Bone tissue engineering represent a promising approach to treatments of bone defects caused by traumatic events, degenerative diseases or surgery. In this study a multifunctional system merging nanotechnologies, advanced bio-fabrication and stem cells biology has been developed to promote osteogenesis and study the impact on regenerative medicine for bone tissue defects. We fabricated PLGA nanocarriers loaded with the osteoinductive growth factor BMP-2, using microfluidic assisted nanoprecipitation. This technology granted an optimal control over main aspects of nanocarriers. These nanocarriers were incorporated into a bioink of Gelatin Methacrylate (GelMA), a biomaterial known for its biocompatible and biodegradable characteristics, with mechanical properties editable at will and capabilities to underpin cells adhesion, growth and differentiation. Using an innovative approach of 3D bio printing, we built a tri-dimensional scaffold hosting Tendon Stem/Progenitor Cells (TSPCs) and the nanocarriers. The cells were cultured under perfusion for 21 days. We analysed cell viability with Live/Dead assay, revealing a limited mortality rate along the first days and a progressive cells proliferation and viability at 14 and 21 days. Furthermore, we explored the results of osteogenic induction by analysing gene expression with qPCR of specific osteogenic markers like OPN and OCN. Then we analysed the presence of calcium phosphate, mineral marker of osteogenic induction, in the ECM of the cells by running an Alizarin Red S staining protocol. The overall results obtained are encouraging, proving that the combination of nanotechnologies, bioinks and 3D bioprinting can address osteogenesis. Future studies will focus on in vivo validation and further optimisation of scaffold composition to facilitate clinical translation.