FIGURE 1.

Hydroxyapatite particle characterization, labelling and the study design. (A) Shows the speculated mechanism of ¹⁴C-ZA and HA binding, which makes the evaluation of in vivo HA biodistribution possible. (B) Shows the shape and size distribution of nano- and micro-sized HA particles used in this study. (C) Schematic showing the process of ¹⁴C labelling for nHA, mHA and n/mHA and its binding rate. Panel C was made on BioRender.com. (D) Shows a schematic diagram of the timeline and the evaluation techniques used in the evaluation of in vivo HA particles biodistribution. Briefly, the HA particles (nHA, mHA and n/mHA) were fabricated into uniform pellets, which were implanted in the tibia defect and covered by a collagen membrane. At each time point (D1, D7 and D28), the tibia was scanned by micro-CT to detect the local distribution of implanted HA particles and collected samples (proximal tibia and vital organs) were further analyzed for the detection of radioactivity which indirectly indicated the biodistribution of ¹⁴C-ZA labelled HA particles. This figure was made on BioRender.com.