Different effects of single protein vs. protein mixtures on magnesium degradation under cell culture conditions.

Bovine serum albumin (BSA) or fetal bovine serum (FBS), as the protein component, is usually added into solution to study the influence of proteins on Mg degradation. However, the specific character of proteins used and the interaction between organic molecules in FBS do not draw enough attention. This study investigated the influence of BSA, fibrinogen (Fib) and FBS on Mg degradation in Hanks' balanced salt solution without (HBSS) or with calcium (HBSSCa) and Dulbecco's modified eagle medium Glutamax-I (DMEM). The results reveal that the effect of BSA, Fib and FBS on the degradation rate of Mg is time- and media-dependent, as a result of the overlap of protein adsorption, binding/chelating to ions and interaction between organic molecules. The binding/chelating of proteins and/or the possible effect of proteins on the kinetics of products formation lead to the formation of different degradation precipitates on Mg surface in HBSS. The interaction between proteins and Ca2+/PO43- accelerates the formation of Ca-P salts in HBSSCa and DMEM, thereby impeding the degradation of Mg. Moreover, the interplay between organic molecules and the specific character of proteins are highlighted by the cooperative (in media + FBS) or competitive (in DMEM + BSA + Fib) effect of proteins in the presence of more kinds of proteins and the different effect of BSA and Fib on the degradation of Mg. Therefore, the addition of proteins to testing medium is necessary for in vitro tests and DMEM + 10% FBS is recommended as the in vitro testing medium to present an in vivo-like degradation for Mg. STATEMENT OF SIGNIFICANCE: The present study emphasizes the difference between proteins, and the difference between single protein and protein mixture in view of the effect on Mg degradation. The results highlight the importance of the interaction between proteins in media, which can increase or decrease the degradation of Mg compared to the single protein. It can aid other researchers to understand the effect of proteins on Mg degradation and to pay more attention to the interaction of organic molecules on Mg degradation when more kinds of organic molecules are used in medium, especially for FBS. The submitted work could be of significant importance to other researchers working in the related fields, thus appealing to the readers of Acta Biomaterialia.

Magnesium degradation under physiological conditions - Best practice.

This review focusses on the application of physiological conditions for the mechanistic understanding of magnesium degradation. Despite the undisputed relevance of simplified laboratory setups for alloy screening purposes, realistic and predictive in vitro setups are needed. Due to the complexity of these systems, the review gives an overview about technical measures, defines some caveats and can be used as a guideline for the establishment of harmonized laboratory approaches.

Controllable degradation of medical magnesium by electrodeposited composite films of mussel adhesive protein (Mefp-1) and chitosan.

To control the degradation rate of medical magnesium in body fluid environment, biocompatible films composed of Mussel Adhesive Protein (Mefp-1) and chitosan were electrodeposited on magnesium surface in cathodic constant current mode. The compositions and structures of the films were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and infrared reflection absorption spectroscopy (IRAS). And the corrosion protection performance was investigated using electrochemical measurements and immersion tests in simulated body fluid (Hanks' solution). The results revealed that Mefp-1 and chitosan successfully adhered on the magnesium surface and formed a protective film. Compared with either single Mefp-1 or single chitosan film, the composite film of chitosan/Mefp-1/chitosan (CPC (chitosan/Mefp-1/chitosan)) exhibited lower corrosion current density, higher polarization resistance and more homogenous corrosion morphology and thus was able to effectively control the degradation rate of magnesium in simulated body environment. In addition, the active attachment and spreading of MC3T3-E1 cells on the CPC film coated magnesium indicated that the CPC film was significantly able to improve the biocompatibility of the medical magnesium.