The osteogenic capacity of biomimetic hierarchical micropore/nanorod-patterned Sr-HA coatings with different interrod spacings

Advanced titanium based bone implant with fast established, rigid and stable osseointegration is stringently needed in clinic. Here the hierarchical micropore/nanorod-patterned strontium doped hydroxyapatite (Ca₉Sr₁(PO₄)₆(OH)₂, Sr₁-HA) coatings (MNRs) with different interrod spacings varying from about 300 to 33 nm were developed. MNRs showed dramatically differential biological performance closely related to the interrod spacing. Compared to micropore/nanogranule-patterned Sr₁-HA coating (MNG), MNRs with an interrod spacing of larger than 137 nm resulted in inhibited in vitro mesenchymal stem cell functions and in vivo osseointegration, while those of smaller than 96 nm gave rise to dramatically enhanced the biological effect, especially those of mean 67 nm displayed the best effect. The differential biological effect of MNRs was related to their modulation on the focal adhesion mediated mechanotransduction. These results suggest that MNRs with a mean interrod spacing of 67 nm may give rise to an advanced implant of improved clinical performance.