The effects of plasma electrolytically oxidized layers containing Sr and Ca on the osteogenic behavior of selective laser melted Ti6Al4V porous implants

Incorporation of inorganic elements onto titanium-based implant surfaces by one-step plasma electrolytic oxidation: an efficient method to enhance osteogenesis

“…195 Cells on the Ca and P-containing PEO coatings were in the favorable stage of osteogenesis, as the ALP activity, expression of Runx-2, OSX, COL I, OPN, OCN, and the ECM mineralization have been reported to be up-regulated. 32,33,37,40,125 The incorporation of Sr, Si, F, Co, Mn, Fe, Li, and Zr leads to a similar result, 23,43,64,66,[101][102][103][104]108,110,113,[116][117][118]121,122,127,129 while the intermediate amount of Sr, F, and Fe in the coatings, namely, 11 wt% of Sr, 6 wt% of F, and 2.7 at% of Fe show the optimum effect on osteogenic activity. 110,144,163 Dose-dependent effect of Mg on osteogenesis is consistent with that on cell adhesion and extension.…”

“…34 The concentration of the released adding elements is usually increasing steadily with the prolonged immersion time, and demonstrates a controlled ion release profile. 23,36,43,64,66,107,109,110,117,129,144,163 Besides, the amounts of released ions are proportional to the content of incorporated elements in the PEO coatings, showing release curves of first fast then slow. 23,64,66,107,110,117,129,144,152,163 However, the final concentration of released ions requires careful restriction to prevent cytotoxicity.…”

“…23,36,43,64,66,107,109,110,117,129,144,163 Besides, the amounts of released ions are proportional to the content of incorporated elements in the PEO coatings, showing release curves of first fast then slow. 23,64,66,107,110,117,129,144,152,163 However, the final concentration of released ions requires careful restriction to prevent cytotoxicity. The morphology of coatings after PEO features a rough surface with numerous highly interconnected micropores, which are distributed homogeneously and ranging at micro levels, 164 and it is often described as "craterlike" and "volcano-like" in the literature.…”

“…118 Overall, the incorporation of various elements except Zr at appropriate contents did not hinder and even promoted cell adhesion and extension. The PEO surfaces containing Ca and P, 22,[32][33][34]37,40,125,130 Sr, 64,101,113,129,163 Si, 102,104,114,116,164 F, 108,113,144,163 Fe, 110 and Li 66 have shown better or similar cell proliferation as well as cell viability and no signs of cytotoxicity compared to untreated groups at the idiographic concentrations of electrolytes, element composition, and ion release rates tested in corresponding works, which is mainly due to both ion release and surface physicochemical properties. Co-, Mg-, Mn-, Ag-, and Cu-incorporated coatings have no cytotoxicity at relatively low contents (Co: ≤7.2 ± 0.2 wt%; Mg: ≤15.1 ± 0.6 wt%; Mn: ≤7.9 ± 0.5 wt%; Ag: ≤0.58 ± 0.19 wt%) and all the Zn-incorporated coatings show good cell compatibility without being reported toxic.…”

“…33,106,126–128 Furthermore, implants with porous structures manufactured by 3D printing have also been mentioned, subsequently being added elements on their surfaces via the plasma electrolytic oxidation process. 40,129…”