Electrostatic attachment of exosome onto a 3D-fabricated calcium silicate/polycaprolactone for enhanced bone regeneration.

Exosomes have garnered attention for use in bone regeneration, but their low activity, rapid degradation, and inaccurate delivery have been obstacles to their use in clinical applications. As such, there exists a need for an exosome-integrated delivery platform. Calcium silicate (Ca-Si) is considered one of the most promising bioceramics for bone regeneration because of its remarkable ability to promote hydroxyapatite formation, osteoblast proliferation, and differentiation. However, Ca-Si has limitations, such as a high degradation rate leading to high pH values. Here, we propose a bone regeneration platform: three-dimensional-fabricated Ca-Si scaffolds immersed in polycaprolactone (PCL) coated with exosomes. This setup enhanced porosity, mechanical strength, and natural hydroxyapatite formation. Ca-Si incorporation increased the quantity of attached exosomes on the scaffold and enabled more sustainable control of their release compared to bare PCL. The exosome-coated scaffold exhibited excellent cell attachment and osteogenic differentiation, significantly increasing biocompatibility and the recruitment of stem cells when transplanted into the subcutaneous tissue of mice. The bone regenerating efficacy of the exosome-attached scaffold was confirmed using a mouse calvarial bone defect animal model. These findings suggest a potential application of exosome-coated Ca-Si/PCL scaffolds as an osteogenic platform for critical bone defects.