Cytotoxicity Of Biodegradation Magnesium Alloy Stent On Nerve Cells

Background:Magnesium alloy is widely used in medical implants in vivo, especially in bones and cardiovascular vessels. Whether or not magnesium stents can be used as cerebrovascular stents is still a matter of debate. Currently, permanent metallic implant shave been used in cerebral vascular intervention. If the stents cannot be removed, specific drawbacks will limit their more widespread use. These limitations include permanent physical irritation and long-term endothelial dysfunction, and as a result, the vessels are prone to new thrombogenicity and induction of long-term in-stent restenosis. Permanent implants also have problems, including permissive or disadvantageous characteristics for later surgical revascularization and chronic inflammatory local reactions. Patients with a metallic implants are not able to finish an MRI test, which can impeded the correct diagnosis. Magnesium has a prominent advantage with respect to degradation; and can effectively overcome the problem of restenosis in stents and permanent injury in vessels. During the degradation period, metal ions, such as Mg2+and Al3+, are released from corrodible alloys to the surrounding tissues, thus resulting a pH change. Whether or not these variations will cause biological responses in the nervous system is uncertain. The influence of the degradation products is the key to the use of magnesium alloys. The current research focused on the in vitro influence of the magnesium alloy, AZ31, on nerve cells (SY5Y) during degradation.Objective To estimate the biology safety of AZ31 regenerative magnesium alloy in vitro.Methods Indirect way:The different concentrations of Mg and Al were set in F12 medium for cultivating the SY5Y cells. The concentrations are showed in Table-1 and Table-2. The death rate of SY5Y cells was tested by MTT. The extracts of the AZ31 magnesium alloy were collected and indirectly tested with concentrations of Mg and Al. Whether or not these results were safe for SY5Y cells depends on the safety range of the ion concentrations tested by MTT.Direct testing, the SY5Y cells were cultured in extracts of the alloy, and F12 medium was used as a blank. The pH values of AZ31 extracts were adjusted and used to culture the SY5Y cells. An inverted microscope was used for assessment of cell growth, and MTT was used to calculate the death rate of the cells.Results The concentration of Al in the extracts was too low to influence the growth of the cells. Over a 3-month period, the variable concentration of Mg was a main factor. The pH value-adjusted groups reduced the death rate of SY5Y cells.MTT showed that the death rate of cells was related to the concentration of Mg and the pH value(P<0.01).Conclusion1. Al in the extracts is safe to nerve cells.2. Mg was a main factor in the extracts of AZ31 magnesium alloy which induced the death of SY5Y cells. Cell toxicity would reach toxicity Level.2 when the Mg concentration was at a higher level.3. The change of pH value induces the cytotoxicity on nerve cells in vitro.4. The AZ31 alloy was cytotoxic based on in vitro testing, but the in vivo environment and blood circulation system are able to lower the concentration and adjust the pH value. The safety of the AZ31 alloy on the nervous system needs more information about the reaction in vivo.