Effects of a micro/nano rough strontium-loaded surface on osseointegration

Abstract

We developed a hierarchical hybrid micro/nanorough strontium-loaded Ti (MNT-Sr) surface fabricated through hydrofluoric acid etching followed by magnetron sputtering and evaluated the effects of this surface on osseointegration. Samples with a smooth Ti (ST) surface, micro Ti (MT) surface treated with hydrofluoric acid etching, and strontium-loaded nano Ti (NT-Sr) surface treated with SrTiO 3 target deposited via magnetron sputtering technique were investigated in parallel for comparison. The results showed that MNT-Sr surfaces were prepared successfully and with high interface bonding strength. Moreover, slow Sr release could be detected when the MNT-Sr and NT-Sr samples were immersed in phosphate-buffered saline. In in vitro experiments, the MNT-Sr surface significantly improved the proliferation and differentiation of osteoblasts compared with the other three groups. Twelve weeks after the four different surface implants were inserted into the distal femurs of 40 rats, the bone–implant contact in the ST, MT, NT-Sr, and MNT-Sr groups were 39.70%±6.00%, 57.60%±7.79%, 46.10%±5.51%, and 70.38%±8.61%, respectively. In terms of the mineral apposition ratio, the MNT-Sr group increased by 129%, 58%, and 25% compared with the values of the ST, MT, and NT-Sr groups, respectively. Moreover, the maximal pullout force in the MNT-Sr group was 1.12-, 0.31-, and 0.69-fold higher than the values of the ST, MT, and NT-Sr groups, respectively. These results suggested that the MNT-Sr surface has a synergistic effect of hierarchical micro/nano-topography and strontium for enhanced osseointegration, and it may be a promising option for clinical use. Compared with the MT surface, the NT-Sr surface significantly improved the differentiation of osteoblasts in vitro. In the in vivo animal experiment, the MT surface significantly enhanced the bone-implant contact and maximal pullout force than the NT-Sr surface.

Effect of titanium implants with strontium incorporation on bone apposition in animal models: A systematic review and meta-analysis

“…39 36 female OVX rats HA-SLA electrochemical deposition 4, 8, 12 w Histomorphometry BIC BA Li et al . 35 40 female rats Smooth-Ti magnetron sputtering 12 w pull-out test Micro-CT Histomorphometry BIC BV/TV, Tb.N, Tb.Th, Tb.Sp, maximal push-out force Offermanns et al . 40 30 female rats Smooth-Ti magnetron sputtering process 4 w Histomorphometry BIC BA Andersen et al .…”

“…In addition, the surface topography changed by strontium incorporation process also contributed to bone-implant integration. Three of included studies revealed that micro/nanoscale topography enhanced new bone apposition and osseointegration of Sr-modified implants or had a synergistic effect with released Sr ions 28 , 29 , 35 . Hence, in-depth investigations are required to isolate the pure and independent effect of strontium or surface topography on improving bone-implant integration.…”

<p>The Fabrication and Function of Strontium-modified Hierarchical Micro/Nano Titanium Implant</p>

“…The cell behavior on AH-Ti may be ascribed to two reasons including the release of Na ions which can compromise the cell condition, 38 and the microstructure which has been proved to decrease the cell spread area. 37 The same inferior cell behavior on AH-Ti/ Sr150 was attributed to the excess amount of Sr, while the Sr amount on AH-Ti/Sr30 and AH-Ti/Sr90 was within the noncytotoxic level. 39 In addition, the AH-Ti/Sr groups (AH-Ti/Sr30, AH-Ti/Sr90, AH-Ti/Sr150) exhibited more stress fibers and actin microfilaments than control groups (AH-Ti, Ti), indicating the function of nanolayer formed by magnetron sputtering endowed the surface with numerous nanoscale cell attachment sites.…”

“…The OD increased after the deposition of SrTiO 3 , indicating a better cell viability which was attributed to the release of strontium and the alternation of surface structure. 37 Whatis more, the AH-Ti/Sr90 group showed the highest optical density, while it was decreased in the AH-Ti/Sr150 group. Both the cell proliferation in four and seven days showed the same trend.…”

“…This phenomenon was attributed to the narrowed aperture and the accumulation of SrTiO 3 nanocoating on the sponge-like surface, which was confirmed by previous studies that the smaller the aperture, the more hydrophobic it would be. 36,37 Focused ion beam and field-emission scanning electron microscopy were conducted to show the cross sectional images of specimens (Figure 4). The cross section of AH-Ti showed numerous needles like structure with many gaps which was blunt in AH-Ti/Sr30 because of the covering of thin SrTiO 3 coating.…”