The influence of Sr doses on the in vitro biocompatibility and in vivo degradability of single-phase Sr-incorporated HAP cement

State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
Journal of Biomedical Materials Research Part A (Impact Factor: 3.37). 09/2008; 86(4):947-58. DOI: 10.1002/jbm.a.31687
Source: PubMed


In previous studies, we developed a new type of Sr-incorporated hydroxyapatite cement (Sr-HAC), which was shown to have many excellent physiochemical properties, by an ionic cement route (Guo et al., Biomaterials 2005;26:4073-4083). As a further study, the main aims of this article were to examine the Sr-HAC's in vitro biocompatibility, including acute toxicity, hemolytic reaction, pyrogen reaction, and cytoxicity, to evaluate its in vivo degradability during intramuscular and femur implantation, and also to investigate the influence of Sr doses on these properties. The in vitro results show that all of the Sr-HAC samples exhibit satisfactory biocompatibility, and the Sr/(Sr+Ca) molar ratio has an important effect on these properties. For example, the Sr-HAC with a Sr/(Sr+Ca) molar ratio of 5% (5% Sr-HAC) has higher biocompatibility than both the one with a Sr/(Sr+Ca) molar ratio of 10% (10% Sr-HAC) and the Sr-free one. The in vivo results of both the rabbit intramuscular and femur implantation experiments show that the Sr-HAC samples exhibit a much faster degradation rate than the Sr-free one, and that this also depends on the Sr/(Sr+Ca) molar ratio. Specifically, the mean degradation rate of the 10% Sr-HAC increases by an amplitude of 73.9 wt % compared with that of the Sr-free HAC. In addition, the optical transmission photographs show that the Sr doses play an important role on the interface between the implants and the new bone. The energy dispersion X-ray spectrum analysis indicates that there exists a gradient distribution of Sr element in the tight and bioactive interface between the implants and new bone, indicating that the Sr element takes a share in the mineralization of the new bone together with Ca element.

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    • "Another calcium phosphate cement containing strontium and acrylate was developed by Lu, Cheung, and co-workers, which also exhibited direct contact between bone and strontium-containing cement [29,30]. Guo Dagang and co-workers [31,32] demonstrated biocompatibility and degradability of their strontium-containing hydroxyapatite in rabbit muscle and cancellous bone. "
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    ABSTRACT: Calcium phosphate cements are used frequently in orthopedic and dental surgeries. Strontium-containing drugs serve as systemic osteoblast-activating medication in various clinical settings promoting mechanical stability of the osteoporotic bone. Strontium-containing calcium phosphate cement (SPC) and calcium phosphate cement (CPC) were compared regarding their local and systemic effects on bone tissue in a standard animal model for osteoporotic bone. A bone defect was created in the distal femoral metaphysis of 60 ovariectomized Sprague-Dawley rats. CPC and SPC were used to fill the defects in 30 rats in each group. Local effects were assessed by histomorphometry at the implant site. Systemic effects were assessed by bone mineral density (BMD) measurements at the contralateral femur and the spine. Faster osseointegration and more new bone formation were found for SPC as compared to CPC implant sites. SPC implants exhibited more cracks than CPC implants, allowing more bone formation within the implant. Contralateral femur BMD and spine BMD did not differ significantly between the groups. The addition of strontium to calcium phosphate stimulates bone formation in and around the implant. Systemic release of strontium from the SPC implants did not lead to sufficiently high serum strontium levels to induce significant systemic effects on bone mass in this rat model.
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    • "Indeed, because of the bone formation stimulation effect of Sr, oral administration of Sr salts is used in the treatment of osteoporotic patients to increase bone mass and reduce the incidence of fractures [15] [16] [17]. Additionally, a hydroxyapatite bioactive cement incorporating Sr(Sr-HA) has recently been investigated for bone repair [18] [19] [20]. It was shown that the solubility and mineralization ability of Sr-HA exhibited Sr dose-dependent behavior. "
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