Sustained zinc release in cooperation with CaP scaffold promoted bone regeneration via directing stem cell fate and triggering a pro-healing immune stimuli.

Metal ions have been identified as important bone metabolism regulators and widely used in the field of bone tissue engineering, however their exact role during bone regeneration remains unclear. Herein, the aim of study was to comprehensively explore the interactions between osteoinductive and osteo-immunomodulatory properties of these metal ions. In particular, the osteoinductive role of zinc ions (Zn2+), as well as its interactions with local immune microenvironment during bone healing process, was investigated in this study using a sustained Zn2+ delivery system incorporating Zn2+ into ß-tricalcium phosphate/poly(L-lactic acid) (TCP/PLLA) scaffolds. The presence of Zn2+ largely enhanced osteogenic differentiation of periosteum-derived progenitor cells (PDPCs), which was coincident with increased transition from M1 to M2 macrophages (M[Formula: see text]s). We further confirmed that induction of M2 polarization by Zn2+ was realized via PI3K/Akt/mTOR pathway, whereas marker molecules on this pathway were strictly regulated by the addition of Zn2+. Synergically, this favorable immunomodulatory effect of Zn2+ further improved the osteogenic differentiation of PDPCs induced by Zn2+ in vitro. Consistently, the spontaneous osteogenesis and pro-healing osteoimmunomodulation of the scaffolds were thoroughly identified in vivo using a rat air pouch model and a calvarial critical-size defect model. Taken together, Zn2+-releasing bioactive ceramics could be ideal scaffolds in bone tissue engineering due to their reciprocal interactions between osteoinductive and immunomodulatory characteristics. Clarification of this synergic role of Zn2+ during osteogenesis could pave the way to develop more sophisticated metal-ion based orthopedic therapeutic strategies.

Effects of incorporation of nano-fluorapatite or nano-fluorohydroxyapatite on a resin-modified glass ionomer cement.

This study aimed to investigate the fluoride release properties and the effect on bond strength of two experimental adhesive cements. Synthesized particles of nano-fluorapatite (nano-FA) or nano-fluorohydroxyapatite (nano-FHA) were incorporated into a resin-modified glass ionomer cement (Fuji Ortho LC) and characterized using X-ray diffraction and scanning electron microscopy. Blocks with six different concentrations of nano-FA or nano-FHA were manufactured and their fluoride release properties evaluated by ultraviolet spectrophotometry. The unaltered glass ionomer cement Fuji Ortho LC (GC, control) and the two experimental cements with the highest fluoride release capacities (nano-FA+Fuji Ortho LC (GFA) and nano-FHA+Fuji Ortho LC (GFHA)) were used to bond composite blocks and orthodontic brackets to human enamel. After 24 h water storage all specimens were debonded, measuring the micro-tensile bond strength (µTBS) and the shear bond strength (SBS), respectively. The optimal concentration of added nano-FA and nano-FHA for maximum fluoride release was 25 wt.%, which nearly tripled fluoride release after 70 days compared with the control group. GC exhibited a significantly higher SBS than GFHA/GFA, with GFHA and GFA not differing significantly (P>0.05). The µTBS of GC and GFA were significantly higher than that of GFHA (P≤0.05). The results seem to indicate that the fluoride release properties of Fuji Ortho LC are improved by incorporating nano-FA or nano-FHA, simultaneously maintaining a clinically sufficient bond strength when nano-FA was added.