In vitro and in vivo anti-corrosion properties and bio-compatibility of 5β-TCP/Mg-3Zn scaffold coated with dopamine-gelatin composite

Abstract

Mg alloy is an excellent biomaterial due to its ideal mechanical properties, bio-degradability and bio-compatibility. However, high local pH, subcutaneous gas pockets and compromised mechanical integrity caused by high degradation rate restrict its clinical application. The purpose of this study is to improve the anti-corrosion properties of 5β-TCP/Mg-3Zn scaffold using poly-dopamine/gelatin (PDA/G) composite coatings through an easy, convenient and cheap dipping method. We found that dopamine (C8H11NO2) slowed down corrosion by forming thin, surface-adherent PDA films on the scaffold surface. Gelatin formed a dense organic membrane cover on the rough surface which results from the processing of PDA membrane to seal the macrocracks and protect it from corrosion. As compared to bare 5β-TCP/Mg-3Zn alloy, electrochemical tests showed that the corrosion current density (icorr) decreased from 5.24 × 10−3 A/cm2 to 1.41 × 10−3 A/cm2, indicating improved anti-corrosion properties. The soaking results indicated that pH values of immersion solution, as well as the volumes of released hydrogen, were 9.83 and 9.25, 20 mL and 15 mL for bare and coated alloy, respectively, indicating that the composite coating enhanced the anti-corrosion property of Mg alloy. The in vitro cytotoxicity test showed that 10%, 50% and 100% concentration of the immersion solution were safe for cellular applications. The in vivo test showed that serum magnesium concentration for PDA/G was lower than that of the bare sample. In addition, the materials and coatings were nontoxic to muscle and other vital organs, including heart, liver, kidney, and muscle. Moreover, the PDA/G composite coating showed a better anti-corrosion property in vivo than the bare sample and displayed a longer service time. These results suggest that coating of 5β-TCP/Mg-3Zn scaffold with PDA/G slowed down the corrosion rate of Mg alloy.