An in vivo study on the metabolism and osteogenic activity of bioabsorbable Mg–1Sr alloy

Abstract

An in vivo study on the metabolism and osteogenic activity of bioabsorbable Mg-1Sr alloyIn: Acta Biomaterialia (2015) Elsevier DOI: 10.1016DOI: 10. /j.actbio.2015 An in vivo study on the metabolism and osteogenic activity of bioabsorbable Mg-1Sr alloy AbstractPrevious studies indicated that local delivery of strontium effectively increased bone quality and formation around osseointegrating implants. Therefore, implant materials with long-lasting and controllable strontium release are avidly pursued. The central objective of the present study was to investigate the in vivo biocompatibility, metabolism and osteogenic activity of the bioabsorbable Mg-1Sr (wt.%, nominal composition) alloy for bone regeneration. The general corrosion rate of the alloy implant as a femoral fracture fixation device was 0.55 ± 0.03 mm y −1 (mean value ± standard deviation) in New Zealand White rabbits which meet the bone implantation requirements and can be adjusted by material processing methods. All rabbits survived and the histological evaluation showed no abnormal physiology or diseases 16 weeks post-implantation. The degradation process of the alloy did not significantly alter 16 primary indexes of hematology, cardiac damage, inflammation, hepatic functions and metabolic process. Significant increases in peri-implant bone volume and direct bone-toimplant contact (48.3% ± 15.3% and 15.9% ± 5.6%, respectively) as well as the expressions of four osteogenesis related genes (runt-related transcription factor 2, alkaline phosphatase, osteocalcin, and collagen, type I, alpha 1) were observed after 16 weeks implantation for the Mg-1Sr group when compared to the pure Mg group. The sound osteogenic properties of the Mg-1Sr alloy by longlasting and controllable Sr release suggesting a very attractive clinical potential. Statement of significanceSr (strontium) has exhibited pronounced effects to reduce the bone fracture risk in osteoporotic patients. Nonetheless, long-lasting local Sr release is hardly achieved by traditional methods like surface treatment. Therefore, a more efficient Sr local delivery platform is in high clinical demand. The stable and adjustable degradation process of Mg alloy makes it an ideal Sr delivery platform. We combine the well-known osteogenic properties of strontium with magnesium to manufacture bioabsorbable Mg-1Sr alloy with stable Sr release based on our previous studies. The in vitro and in vivo results both showed the alloy's suitable degradation rate and biocompatibility, and the sound osteogenic properties and stimulation effect on bone formation suggest its very attractive clinical potential.

Degradation behaviors and cytocompatibility of Mg/β‐tricalcium phosphate composites produced by spark plasma sintering

“…Mg also has similar elastic modulus to human cortical bone, which can reduce stress shielding caused by a mismatch of the elastic moduli between metallic implants and human cortical bone . Furthermore, Mg shows good biocompatibility and stimulatory effects on bone growth . Nevertheless, the rapid degradation rate of Mg and associated early deterioration of mechanical properties are still problematic for orthopedic implant and device applications …”

Biodegradable Mg-Cu alloys with enhanced osteogenesis, angiogenesis, and long-lasting antibacterial effects

“…The products arising from natural degradation of magnesium influences proliferation and apoptosis of osteoblasts and osteoclasts8 and a high magnesium ion concentration has been observed to introduce bone cell activation910. Some magnesium alloys such as Mg-Sr alloys containing trace metallic elements such as strontium may also stimulate new bone formation and increase new bone quality1112. In addition to promoting osteogenesis, magnesium alloys can inhibit bacteria-induced infection after implantation into bones13 thereby effectively decreasing morbidity and mortality.…”

Corrosion behavior and mechanical degradation of as‐extruded Mg–Gd–Zn–Zr alloys for orthopedic application

“…The film gradually transforms into soluble MgCl 2 which can be observed from Figure a, thus accelerating hydrogen evolution (Cao, Song, & Atrens, ; Thomas, Medhekar, Frankel, & Birbilis, ). During in vivo degradation process, Mg(OH) 2 is one of the most common degradation products, along with MgO and hydroxyapatite (HA; Bornapour, Muja, Shum‐Tim, Cerruti, & Pekguleryuz, ; Li, Gu, Lou, & Zheng, ; Shi et al, ; Tie et al, ; Wang et al, ; Yu, Lu, & Sun, ). The modified layer, composed of these corrosion byproducts, can slows down the degradation of the Mg implants in vivo (Bornapour et al, ; Wang, Liu, et al, ; Yu et al, ).…”