Sterilization Options for Microdialysis Probes

Posted on 09/17/2019 by Candace Rohde-Johnson


Membranes on our microdialysis and ultrafiltration probes are protected with a coating of glycerol to help keep the microscopic pores open. It is critical that this glycerol stays in place until the probe is ready to use, and essential to keep the probes wet once the glycerol has been removed. It is this feature that causes most of the issues related to probe sterilization. Certain approaches will either remove the glycerol or will adversely impact the probe performance.

Steam sterilization/Autoclave-
Do not use this method. Not only will the high temperatures and steam affect the membrane, but it will also compromise the materials and adhesives used to build the probe.

Cold sterilization-
This method is possible, but keep in mind that these probes will be implanted in living tissues to understand more about the organ system. An outside agent, such as that used to cold sterilize the probe, could interfere with test results and is not recommended. Additionally, the CDC generally recommends against cold sterilization since “sterilization with a liquid chemical sterilant may not convey the same sterility assurance as other sterilization methods.” Cold sterilants also require between 3-12 hours for effectiveness. If other options are available, then use them.

EtO or sterilization with Ethylene Oxide-
This option is available in most research institutes and is a reasonable option to sterilize your probes. However, the EtO process does impact the glycerol coating. When using this method, it is extremely important to sterilize the probes only as needed, and to use them as soon as possible after outgassing, ideally within one day. Also, the probe packaging is not suitable for use in these sterilization devices. Make sure to move the probe to an appropriate package, and with brain probes, be sure to take extra precautions to protect the tip from damage (see the manual for more details).

Hydrogen Peroxide Vapor -
Sometimes referred to as Sterrad or gas plasma sterilization- this option is not available to all research facilities; however it is an ideal method for BASi probes. It does not have any adverse effects on the glycerol, the membrane of the probe construction. Do keep in mind that this method is not used for human medical devices at this time, but it is regularly used for many applications instead of EtO since the processing time is shorter and because there is a perceived safety of using hydrogen peroxide instead of a chemical agent that has to be outgassed. Unlike EtO, there is no time limit to use the probe after it’s been processed. Like EtO, the probe will need to be moved to an appropriate package for the system.

this method is the gold standard. It is safe, it is effective, it leaves no residues, and it requires no extremes of temperature or humidity. So what’s the downside? It’s very expensive.  There are limited suppliers for this option and they typically service large medical device companies who may sterilize by the truckload. That means that the fee for a single round of sterilization will cost upwards of $2000. If you are interested in this method, we can point you in the right direction. Occasionally, we get lucky and can access it for a reasonable fee, and on your timeline, but this option is sporadic, and not under our direct control. Let us know if you’d like to learn more about this option.

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