Synthesis and characterization of Mg‐Ca‐Sr alloys for biodegradable orthopedic implant applications

Abstract

Magnesium has recently received an increased amount of interest due to its potential use in biodegradable implant applications. The rapid degradation of conventional Mg is, however, a major limitation that needs to be addressed in the design of these materials, along with consideration of toxicity in selection of alloying elements. In this study, five alloys in the Mg-xCa-ySr system (x = 0.5-7.0 wt %; y = 0.5-3.5 wt %) were prepared and characterized for their suitability as degradable orthopedic implant materials. The alloys were characterized using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, degradation measurements in Hanks' solution at 37°C, compression testing, and in vitro cytotoxicity testing with a mouse osteoblastic cell line. The results indicate that the Mg-1.0Ca-0.5Sr alloy is the most promising alloy for orthopedic implant applications since it showed the lowest degradation rate in Hanks' solution (0.01 mL cm(-2) h(-1)) along with no significant toxicity to MC3T3-E1 osteoblasts and a compressive strength of 274 ± 4 MPa.

Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration

“…37 In our study, only Ca or Zr containing alloys (Mg-5Zr and Mg-5Zr-Ca) were more unstable, and upon degradation in vivo, they showed an abundance of residual alloy material at the implant site (Figures 3 and 4). This has not been reported earlier because the stability of Ca-containing Mg alloys has been studied only in the absence of Zr, [38][39][40][41] and Mg alloys containing only Zr have not been reported so far. The elemental constitution of the alloying metals also affects the properties of newly induced bone, as several charged groups (O, OH − , etc) on the alloy surface contribute to the overall electronegativity of the implant material.…”

An Assessment of Novel Biodegradable Magnesium Alloys for Endovascular Biomaterial Applications

“…This is a favorable quality for these experimental degradable magnesium alloys, because it has been reported that degradable polymer's such as polylactide materials have resulted in cellular cytotoxicity because of the dramatic changes in pH caused by degrading polymers [26]. Although the use of polymeric materials for endovascular applications is a growing field, the concerns of cytotoxicity is not as great of a concern when using biodegradable alloys, as research has shown that cytotoxicity effects are minimal [27,28]. However, it should also be noted that the lack of cell growth on the degradable alloys may make it difficult to achieve endothelialization on the surface of the device.…”

“…An example of such would be a magnesium stent with excessive amounts of nickel, which is known to be harmful to cells; nickel leaching within the body would produce toxic biological effects. Recent studies have further validated nickel's toxicity on human lung epithelial A594 cells [27].…”

“…Magnesium alloys possess very selective mechanical properties which result in materials that are light, biodegradable and biocompatible [25][26][27][28][29][30]. An important aspect of these materials is their mechanical properties which are specifically important for different biomedical applications: such as cardiovascular stents or orthopedic devices.…”

“…The high tensile yield strength and Young's modulus of magnesium based alloys yield to more favorable qualities for materials that are used for orthopedic and cardiovascular applications [27][28][29]. Poly(glycolide-co-caprolactone)(PGACL) [27][28][29].…”