Calcium phosphate (CaP) coating enhances osteointegration of melt electrowritten scaffold by regulating macrophage polarization Yubo Shi, Weidong Tao, Wenjing Yang, Lei Wang, Zhennan Qiu, Xiaoli Qu, Jingyi Dang, Jiankang He, and Hongbin Fan investigated the impact of CaP coating on the physiochemical properties of highly ordered polycaprolactone (PCL) scaffolds fabricated using melt electrowritten (MEW) technology. The study also examined the influence of these scaffolds on macrophage polarization and their immunomodulation on osteogenesis. The results showed that the CaP-coated PCL scaffold had a rougher surface and higher hydrophilicity compared to the uncoated PCL scaffold. The surface morphology of the coating and the release of Ca²+ from the CaP coating were crucial in regulating the transition of macrophages from M1 to M2 phenotypes. These factors might activate the PI3K/AKT and cAMP-PKA pathways, facilitating M2 polarization. The osteoimmune microenvironment induced by CaP-coated PCL scaffolds enhanced the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) in vitro and promoted bone regeneration in vivo. The CaP coating can be used to control macrophage phenotypic switching, creating a beneficial immunomodulatory microenvironment that promotes bone regeneration. The study focused on the effects of CaP coating on the physicochemical properties of MEW PCL scaffolds. The scaffolds were characterized by analyzing surface wettability, roughness, and compositions. The modulatory role and underlying mechanism of CaP-coated scaffolds on macrophage polarization and immune microenvironment for osteogenic differentiation were evaluated. Finally, CaP-coated MEW PCL scaffolds were implanted to examine the effects of an immune response and bone regeneration. The PCL scaffolds were fabricated using MEW. PCL pellets were heated to 90°C until they melted into a homogeneous fluid. The fluid was then used to print the scaffolds using a 26 G nozzle at a printing speed of 40 mm/s and a voltage of -7 kV. The CaP coating procedure involved immersing the scaffolds in a 2 M NaOH solution for 5 min, washing with Milli Q water five times, and then immersing in 1.5 times simulated body fluid (1.5×SBF) for 48 h at 37°C. The scaffolds were then washed with distilled water and vacuum dried. The surface morphology and element composition were examined by scanning electron microscopy (SEM) and electron dispersive X-ray diffraction (EDS). The surface wettability was measured using an automatic contact angle system, while atomic force microscopy (AFM) was used to examine the surface roughCalcium phosphate (CaP) coating enhances osteointegration of melt electrowritten scaffold by regulating macrophage polarization Yubo Shi, Weidong Tao, Wenjing Yang, Lei Wang, Zhennan Qiu, Xiaoli Qu, Jingyi Dang, Jiankang He, and Hongbin Fan investigated the impact of CaP coating on the physiochemical properties of highly ordered polycaprolactone (PCL) scaffolds fabricated using melt electrowritten (MEW) technology. The study also examined the influence of these scaffolds on macrophage polarization and their immunomodulation on osteogenesis. The results showed that the CaP-coated PCL scaffold had a rougher surface and higher hydrophilicity compared to the uncoated PCL scaffold. The surface morphology of the coating and the release of Ca²+ from the CaP coating were crucial in regulating the transition of macrophages from M1 to M2 phenotypes. These factors might activate the PI3K/AKT and cAMP-PKA pathways, facilitating M2 polarization. The osteoimmune microenvironment induced by CaP-coated PCL scaffolds enhanced the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) in vitro and promoted bone regeneration in vivo. The CaP coating can be used to control macrophage phenotypic switching, creating a beneficial immunomodulatory microenvironment that promotes bone regeneration. The study focused on the effects of CaP coating on the physicochemical properties of MEW PCL scaffolds. The scaffolds were characterized by analyzing surface wettability, roughness, and compositions. The modulatory role and underlying mechanism of CaP-coated scaffolds on macrophage polarization and immune microenvironment for osteogenic differentiation were evaluated. Finally, CaP-coated MEW PCL scaffolds were implanted to examine the effects of an immune response and bone regeneration. The PCL scaffolds were fabricated using MEW. PCL pellets were heated to 90°C until they melted into a homogeneous fluid. The fluid was then used to print the scaffolds using a 26 G nozzle at a printing speed of 40 mm/s and a voltage of -7 kV. The CaP coating procedure involved immersing the scaffolds in a 2 M NaOH solution for 5 min, washing with Milli Q water five times, and then immersing in 1.5 times simulated body fluid (1.5×SBF) for 48 h at 37°C. The scaffolds were then washed with distilled water and vacuum dried. The surface morphology and element composition were examined by scanning electron microscopy (SEM) and electron dispersive X-ray diffraction (EDS). The surface wettability was measured using an automatic contact angle system, while atomic force microscopy (AFM) was used to examine the surface rough