Design And Experimental Study Of Magnesium Alloy Applied To Degradable Temporary Pacing Electrodes

Background and AimAfter cardiopulmonary bypass assisted cardiac vascular surgery,some patients have poor cardiac rebound.Installing a temporary pacemaker will help them survive the perioperative period.When the patient's circulatory function is stable,the pacemaker is closed,the temporary pacemaker electrode is removed.However,serious complications may be combined during the electrode removal process,and the electrode roots left in the body also cause rare complications.The purpose of this study is to design a degradable temporary pacing electrode(DTPE),related experimental research is conducted on the application of degradable biomedical magnesium alloys to the conductive parts of DTPE.The degradable biomedical magnesium alloys is developed by the National Engineering Research Center of Light Alloy Precision Molding,College of Materials Science and Engineering,Shanghai Jiao Tong University,and is named JDBM.MethodThis study is divided into the following three parts:?.Correlative study on pacing performance of four different diameter JDBM-3SD rats were anesthetized by gas inhalation,tracheal puncture was performed with an intravenous indwelling needle,and small animal ventilator was mechanically ventilated to maintain anesthesia and breathing.The left thoracotomy was used to expose the heart.After esmolol left ventricular injection,Medtronic 5348 single ventricular temporary pacemaker was used to test the pacing function and related parameters of isometric various JDBM-3 and clinical Covidien 8886 2592-43 temporary cardiac pacing electrodes.Digital multimeters were used to measure the resistances of various diameter of equal lengths JDBM-3 and Covidien 8886 2592-43,and Graphpad Prism software was used to statistically analyze the resistance of each group.?.Correlative study on cytotoxicity of four different diameter JDBM-3 in vitroTissue block attachment method was used to isolate and culture human pericardial interstitial cells.The cardiac interstitial cells of SD rats were isolated and cultured by type II collagenase digestion overnight and differential adherence method.HPICs and RCICs were identified by immunofluorescence method.Vimentin was used for positive identification.Endothelial cell marker CD-31 and myocyte marker ?-SMA were used for negative identification.According to the method in GB / T 16886.12-2017,the extract solution was prepared for each group of materials.According to the GB / T 16886.5-2017 scale,HPICs and RCICs were applied to the cytotoxicity of four models of JDBM-3 and other material extracts,and qualitative classification was performed using morphological methods;L929 mouse fibroblasts were used to quantitatively grade the cytotoxicity of extracts of four types of JDBM-3 and other materials with the CCK-8 method.Graphpad Prism software was used for statistical analysis of experimental data.?.Correlative study of four different diameter JDBM-3 implanted into the chest wall of SD ratsAccording to the weight from small to large,each group is 4 groups,a total of 15 groups(3 groups are reserved),and SD rats are subjected to gastroinhalation anesthesia for electrode chest wall implantation.A model of JDBM-3 and Covidien 8886 2592-43 were implanted in the left and right pectoralis major muscle space.Observe the postoperative incision healing and the overall condition of the rats;chest X-ray examinations were performed 2 weeks after the operation;samples were taken every 4 weeks after operation,and the micrometer was used to measure the diameter of JDBM-3 to explore its degradation rate;Graphpad Prism software was used for statistical analysis of experimental data.at 2,4,and 8 weeks after operation samples were taken and observed under the scanning electron microscope to explore the degradation pattern of JDBM in the chest wall.Materials were taken at 2,12,and 24 weeks after operation.After paraffin-embedded and ultra-thin sections were applied,HE staining,Cason staining,and SP immunohistochemistry were used.The scale in the GB / T 16886.6-2015 medium was used to compare the inflammatory response of different JDBM-3 and Covidien 8886 2592-43 to surrounding tissues to determine the degree of foreign body stimulation of different JDBM-3 on tissues.Comprehensive evaluation of degradation,inflammatory response and other factors,the optimal JDBM-3 diameter range that meets the requirements of clinical applications is selected.Result?.Various types of JDBM-3 electrodes may be applied to temporary pacing electrodesThrough SD rat in vivo heart model experiments,all types of JDBM-3 and Covidien 8886 2592-43 can pace the SD rat in vivo heart normally.A digital multimeter was used to measure the resistances of various types of JDBM-3 and Covidien 8886 2592-43.According to the level of ? = 0.05,the difference in the average resistance of each group was statistically significant.It is speculated that the conductivity of various types of JDBM-3 electrodes may be better than some temporary pacing electrodes that have been used clinically,further confirming that JDBM-3 may be applied to temporary pacing electrodes.?.All types of JDBM-3 have low cytotoxicity and good biocompatibility,and can be used as temporary pacing electrodes.The morphological methods were used to classify the extracts from each group of materials,and it was found that all types of JDBM-3 extracts were cytotoxic.According to the quantitative classification by CCK-8 method,it was found that the cytotoxicity of each type of JDBM-3 extract was small,and there was no statistical difference with the negative control group,which was better than some temporary pacing electrodes that had been used clinically.We believe that all types of JDBM-3 are biocompatible and can be used as temporary pacing electrodes.?.Situation of SD rats after chest wall electrode implantation and chest X-ray performanceNone of the rats who underwent electrode chest implantation surgery experienced anesthesia reactions or intraoperative accidents.After the anesthesia was awake,their activities,eating,excretion,mentality,and sleep were normal,and no poor incision healing occurred.No abnormal death occurred in each group until the end of the observation period.Two weeks after the operation the chest X-ray showed that all types of JDBM-3 is not found.?.Degree of foreign body stimulation of various types of JDBM-3 on rat chest wallAccording to the scale in GB / T16886.6-2015,biological evaluation of different JDBM-3 was performed to determine the degree of foreign body stimulation of chest wall tissue by different JDBM-3.With the prolonged implantation time in the body,compared with the same length of Covidien 8886 2592-43,the foreign body stimulation degree of various types of JDBM-3 on chest wall tissues is gradually reduced to no stimulation.Microscopic observation revealed that all types of JDBM-3 caused a severe inflammatory response in the acute phase.With the prolonged implantation time,the inflammatory response decreased.Covidien 8886 2592-43 caused a milder inflammatory reactions in the acute phase,but caused gradual aggravating inflammatory reactions in the later period.?.Degradation of JDBM-3 in rat chest wallScanning electron microscopy observations of JDBM-3 materials taken before and after implantation revealed that the surface of JDBM-3 before the implantation had grain-like scattered rough protrusions;as the implantation time prolonged,fine crack-like smooth membrane structures gradually appeared.Macroscopic observation of different types of JDBM-3 implantation revealed that no emphysema was formed around JDBM-3 at an early stage.Each type of JDBM-3 has a fast degradation rate in the early stage.As the implantation time prolongs,the degradation rate slowly decreases.The metal luster on the electrode surface gradually disappears,the diameter gradually decreases,and the length gradually becomes shorter.During the observation period,intermittent complete degradation is found.There is a statistical difference in the degradation trends of each type of JDBM-3.ConclusionEach type of JDBM-3 has good electrical conductivity and biocompatibility,and has the potential to become the metal conductive material of temporary pacing electrode,and its diameter is preferably in the range of 150 to 200 ?m.