Synergistic Effects of Novel Superparamagnetic/Upconversion HA Material and Ti/Magnet Implant on Biological Performance and Long‐Term In Vivo Tracking

To solve the clinical challenges presented by the long‐term tracking of implanted hydroxyapatite (HA) bone repair material and to investigate the synergistic effects of superparamagnetic HA and a static magnetic field (SMF) on the promotion of osteogenesis, herein a new type of superparamagnetic/upconversion‐generating HA material (HYH‐Fe) is developed via a two‐step doping method, as well as a specially‐designed titanium implant with a built‐in magnet to provide a local static magnetic field in vivo. The results show that the prepared HYH‐Fe material maintains the crystal structure of HA and exhibits good cytocompatibility. The combined use of the superparamagnetic HYH‐Fe material and SMF can effectively and synergistically promote osteogenesis/osteointegration surrounding the Ti implants. In addition, the HYH‐Fe material exhibits distinct advantages in terms of both long‐term fluorescence tracking and microcomputed tomography (micro‐CT) tracking. The new material and tracking strategy in this study provide scientific feasibility and will have important clinical value for long‐term tracking and evaluation of implanted materials and the bone repair effect. The two‐step doping of Yb/Ho and Fe ions endows the hydroxyapatite (HA) material (HYH‐Fe) with both superparamagnetism and upconversion fluorescence. The HYH‐Fe material can effectively promote osteogenesis and osteointegration under the synergistic effect of a Ti/magnet implant, and provides long‐term and distinct in vivo tracking characteristics of microcomputed tomography (micro‐CT) imaging and laser scanning confocal microscope (LSCM) fluorescent imaging.