ASTM F2129规定的医疗器械腐蚀试验

The human body 和 its immune 和 inflammatory mechanisms can create an aggressive environment for metallic implants resulting in implant rejection 和 failure (Gilbert, 腐蚀, 2017;73(12):1478-1495). In vitro testing of small implants is typically performed per ASTM F2129 to mitigate these risks. While this testing helps determine implant susceptibility to corrosion, 它没有考虑到细胞的影响, 蛋白质, 和 other biological effects that implants will experience in vivo.

尽管有其局限性, ASTM F2129 has undergone several revisions since its original publication in 2001 to better assist medical device manufacturers in assessing their small implants’ resistance to pitting 和 crevice corrosion. The st和ard provides a test method for conducting cyclic (forward 和 reverse) potentiodynamic polarization measurements on whole devices in their final form 和 finish.

在下面的部分中，我们将描述 测试方法, 装置, 结果 和 验收标准 用于小型种植体体外腐蚀试验.  

试验装置  

A typical multiport electrochemical test cell is used for testing. It has inflow/outflow ports for the nitrogen 气体 和 heated water circulation, 供参考的端口, 石墨计数器和工作/样品电极, 还有一个盐水浴的内室.  

附加组件包括恒电位器, 电脑, 酸度计, 氮罐, 水泵, 导电环氧树脂与紫外线灯和掩膜固化, 和不锈钢丝样品连接. Reagents such as phosphate buffered saline are used for the bath, 和 isopropyl alcohol 和 type II reagent grade water for sample rinsing. Optical 和 electron scanning microscopes are used for pre-和 post-test inspections.   

测试方法 

Table 1 provides a brief terminology summary; for further details consult the ASTM F2129 st和ard.

Briefly, the implant is held in saline at 37±1°C with a starting pH at 7.4±0.2在右边显示的设置. A potential is introduced between the implant 和 a reference electrode 和 ramped up to the above physiological potentials. A breakdown will typically will result in a rapid increase in current density, 从电位vs的输出图可以看出. 对数电流密度. The total surface area of the sample exposed to the solution needs to be calculated or estimated so that the current density generated by the sample can be determined.

Samples are prepared for testing 和 thoroughly inspected. Any preconditioning should be performed as it can impact the behavior of the implants. Conductive epoxy is used as the interface to the sample (specimen holders vary depending on the device type), 通过导线连接到恒电位器上, 并检查电阻，以确保良好的连接. 试验细胞中充满生理盐水(至少500ml), 通常1 l), 加热到目标温度, 启动150ml /min的氮气流量. Nitrogen 气体 flow is used to deaerate the solution 和 lower dissolved oxygen concentration to decrease the potential at which oxidation 和 reduction currents are equal. 

温度, pH, 和 nitrogen 气体 flow time (30 min minimum) 记录, then the device is rinsed 和 inserted in the test cell with the wire. 在参比电极夹中加入生理盐水, 和 the electrode is inserted at 5mm or less from the sample, 但没有接触到样品. 氮气吹扫在整个试验过程中持续进行. 开路试验开始，E_r 1小时后的记录. Then, the cyclic polarization test is initiated at a 1 mV/s scan rate by setting E_i 和E_f E_r. The cyclic polarization is closely monitored; if a current density increase larger than two decades occurs, 电压反转. 

When the test is completed, the 最终温度, pH, E_r, E_bEf和E_p 记录. 样品从测试中取出并冲洗, 电线夹在样品上方1英寸处, 和 the sample is stored for further post-test inspection. While the st和ard does not indicate how many samples should be tested, 每次表面处理我们通常会看到3-8个样品.   

测试结果

Test conditions 记录 for each sample: nitrogen flow time, 初始温度, 初始pH值, 最终温度, 和最终pH值. Sample test 结果 are typically provided in tabular 和 graphical formats. Pre- 和 post-test observations 和 inspection 结果 are also provided. 

The graph above shows 结果 from a corrosion test of 8 samples of a nitinol device plotted as potential (mV) vs. 日志电流(A). Results show consistency between the 8 samples; the purple data set with the increase in current density is an example of a breakdown potential.

验收标准 

ASTM F2129 does not define 验收标准 but identifies E_b as the critical data point above which pits nucleate 和 grow. 因此，E越高_b 是不是金属越耐点蚀. 也建议E_b values are compared to those of predicate devices that have demonstrated good corrosion resistance in vivo as a reference. Device manufacturers define the 验收标准 for their implants. 根据我们的经验，可接受的_b values are most commonly set above 300 mV, 和 they are often set at much higher threshold values. 

咨询

我们经常表演 腐蚀测试 on medical devices to characterize their corrosion potential. 如果您想了解更多关于我们的 医疗器械腐蚀试验 services, or for assistance with your device’s corrosion 和/or fatigue testing, im体育APP的专职专家 讨论我们能帮上什么忙.

im体育APP offers the broadest scope of medical device testing, 因此，如果您正在寻找服务，如 包测试, 微生物分析, 加速老化-保质期测试, or EMC/EMI testing, contact us to connect with the right lab.