Immunomodulation and bone repair of 3D-printed SrBG/PCL scaffolds with PDA coating

Abstract

3D-printed polycaprolactone (PCL) scaffolds are widely used for bone tissue engineering but suffer from deficiencies, such as difficulty in cell adhesion, lack of osteogenic activity, and poor immunomodulatory capacity. Enhancing the biological responsiveness of PCL scaffolds remains a key focus in bone tissue engineering. In this study, the following three types of scaffolds were prepared: (i) PCL, (ii) strontium (Sr)-doped bioactive glass (SrBG)/PCL, and (iii) polydopamine (PDA)/SrBG/PCL. The scaffolds were assayed in vitro for their effect on the expression of osteoinductive differentiation markers (ALP, RUNX2, and COL1), and their influence on macrophage (MP) (CD206, ARG, TNF-α, IL1β, IL-10, and IL-12) behavior was evaluated. Their effect on bone defect repair was assessed in vivo using micro-computed tomography (micro- CT), hematoxylin and eosin (HE) staining, Masson staining, and immunofluorescence staining (iNOS, CD163, BMP-2, and VEGF). The results demonstrated that PDA/SrBG/ PCL scaffolds significantly promoted the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), inhibited the differentiation of MPs to the M1 phenotype, and promoted the differentiation of MPs to the M2 phenotype, resulting in better pro-osteogenic, immunomodulatory, and angiogenic effects in vivo. This observation may be associated with the release of Sr²+ from SrBG, and surface modification with PDA further enhanced the immunomodulation and bone repair ability of the scaffold. The study demonstrated that the PDA/SrBG/PCL scaffolds exhibit excellent bone repair capabilities and hold strong potential for applications in bone tissue engineering.

Keywords

3D printing / Bone repair / Immunomodulation / Polycaprolactone / Polydopamine / Strontium-doped bioglass