A Feasibility Study On The Biodegradable Magnesium Alloys As Material For Gastroenterostomy Applications

ObjectiveResearching the degradation characteristics in vitro and in vivo and biocompatibility ofthe magnesium alloys, preliminary understanding the safety and feasibility of the material asgastrointestinal anastomosis, and to provide a scientific basis for the magnesium alloys as thestapling material.MethodsThree magnesium alloys--AZ31B, AZ80, AZ91D were separately immersed into theartificial intestinal fluid for4weeks, the corrosion of the magnesium alloy and calculatingthe rate of degradation was observed, the magnesium alloy of a higher corrosion resistancewas selected to the next experiment.The AZ91D magnesium alloys were respectively immersed into Ringer solution andartificial intestinal fluid, the PH of the solution and the degradation of the magnesium alloywas observed，calculating the rate of degradation and the surface corrosion of the magnesiumalloy was observed.The AZ91D magnesium alloys were implanted in muscle of the rabbits on either side ofthe backbone, the general condition of rabbits were observed, the inflammatory changes ofmuscle tissue around the implants were observed by microscope after HE staining, thebiocompatibility of magnesium alloy in vivo was evaluate.The leaching liquor of AZ91D magnesium alloys were injected in the peritoneal of themice, calculating the Micronucleus rate and evaluating the mutate of cells, the mutagenicitywhich leaching liquor of AZ91D magnesium alloys to experimental animals were observed.The leaching liquor of AZ91D magnesium alloys were injected in the ear vein of rabbits,the rabbits temperature changes was recorded every30minutes after injected15minutes and6times in a row. Its pyrogen reaction was observed. ResultsThe degradation experiments in vitro: the average degradation rate （unit: mg/cm2·day）which the AZ31B, AZ80, AZ91D magnesium alloys in the artificial intestinal fluid in fourweeks as follows:0.36,0.39,0.34. The average degradation rate by turn at the1st, the2nd,the3rd, the4th week as follows, V_AZ31B:0.37,0.37,0.36,0.36; V_AZ80:0.40,0.40,0.38,0.39;V_AZ91D:0.35,0.34,0.33,0.33. The characteristics of test piece corrosion rate in each groupshowed a gradually decreasing trend. At the same stage of soaking, the magnesium alloysweightlessness and the corrosion rate were V_AZ80＞V_AZ31B>V_AZ91D; the slowest degradationrate was the AZ91D magnesium alloy.Further experiments showed that: the average degradation rate of the AZ91D magnesiumalloy in artificial intestinal juice was0.33mg/cm2·day; the average degradation rate inRinger’s solution was about4.33mg/cm2·day, The corrosion rate in Ringer’s solution was13.12times compared with the corrosion rate in artificial intestinal fluid. As the immersiontime went on, the PH value of magnesium alloys in soaking solution showed a graduallyincreasing trend at the same time.Implantation experiments in vivo: not a single case of experimental animals was deathand there were no obvious abnormalities about their eating, excretion, mental state during theexperiment. The surgical wounds were partly redness initially and slowly swelling down at7days. The phenomenon of suppuration was not be seen and the subcutaneous emphysemafailed to form during the experiment. Implantation no significant adhesions between themagnesium alloys and the surrounding tissue at the first and second weeks, the visible part ofthe swelling and a little exudate, HE staining mainly see small lymphocytes and neutrophils,macrophages occasional, inflammation degree <Ⅲ grades, the magnesium alloys with a thinlayer of fibrous connective tissue wrapped around the experimental animal muscle can beseen after implanted at the third and fourth weeks, HE staining indicate fibrous connectivetissue capsule, see very little lymphocytes. did not see a neutral grain and macrophages,inflammation degree <Ⅱgrades.Micronucleus test results: the leaching liquor of AZ91D group micronucleus rate（‰）of2.12±0.264,compared with the physiological saline group of1.95±0.327. There were no significant difference between them. The cyclophosphamide group micronucleus rate of17.52±0.460, there was a significant difference compared with The leaching liquor groupand the saline group.Pyrogen test results: three rabbits injected by the leaching solution of the AZ91Dmagnesium alloys and one rabbit of the temperature test was2times decreased in6times,the decreased value is less than0.3°C, the remaining measured values elevated temperaturewere <0.5°C below, The elevated total degree of the temperature was0.8°C <1.4°C, Withinthe normal range.Conclusion1. The AZ91D magnesium alloy material has good biocompatibility, no mutagenicityand no pyrogen reaction.2. The AZ91D magnesium alloy is poor corrosion resistance in the solution of low pHand high CL^-.