Bioactive coating on a new Mg-2Zn-0.5Nd alloy: modulation of degradation rate and cellular response

Abstract

ABSTRACTPure magnesium implants have a problem of faster degradation which leads to the collapse of the implant before the recovery of physiological organ. A new magnesium alloy viz Mg-2Zn-0.5Nd (ZN20) is designed using a well-known alloying method to decrease the degradation rate of pure magnesium metal and its implants so as to match the tissue recovery rate. MTT assay of the ZN20 alloy via a direct contact method for 2, 4 and 6 days using MC3T3-E1 cells showed cytotoxicity. Whereas, the MTT assay results of this alloy via ion-extract method showed non-cytotoxic behaviour. The degradation rate of ZN20 alloy in SBF was ~2.5% in 16 days which is comparable to the rate of regeneration and recovery of physiological tissue. The pH of the outer solution after degradation of ZN20 alloy for 3 days was around 9.31 ± 0.05 which was higher than the initial pH of SBF used (pH 7.4). The reason for the cytotoxic behaviour of this alloy could be the increase in pH of immersion solution with the degradation of the alloy. Interestingly, the scanning electron microscope images followed by EDX spectrum of ZN20 alloy showed deposition of white crystalline mineralisation product (apatite) after 3, 7, 11 and 16 days of incubation in SBF at 37°C. The FT-IR spectrum and X-ray chromatogram of the white substance confirmed the deposition of apatite (calcium phosphate) on their surfaces. These results concluded the bioactivity of ZN20 alloy and thus could be used as an implant material for regeneration of bones/tissues.