Hydrophilic Coatings Particulate

Posted by Josh Simon on Fri, May 11, 2012 @ 02:54

As promised to one reader, I am putting a little bit more information here on particulates and particulate testing with regards to hydrophilic coatings.

The first thing I want to do is point you to some great information on general theory and the regulatory status of particulates for medical devices.  There is an excellent article by Susan Reynolds and Ryan Lunceford on the basics of particulate testing.  It talks about the prevalent use of USP 788, as I have done in my previous article on medical device particulates here, including some specifics on the differences between laser counting versus microscopic counting of particles.

The article is a few years old, and at that time, the AAMI was not yet finished writing its report on setting medical device particulate limits.  However, now that report is out, and you can find it here.  Personally, I found it a little vague.  It does not give any sort of concrete limits to follow, and is not any sort of draft guidance.  It is good for figuring out how to think about this when going about your own particulate tests, however.

One item touched on by both the AAMI report and the article is composition.  Specifically for hydrophilic coatings and/or lubricious coatings, these particles have characteristic identities.  Like anything else, a major consituent of particulate could be clean room dust, which originates from human skin or clothing, or other particles tracked in from the outside.  However, after abrasion, it can also be due to coating wear particulate.  In fact, one method of testing durability for a hydrophilic coating is to run it through a tortuous path test and then measure the amount of particulate in the path after multiple cycles.  For increasing number of cycles, you can track the increase in particle count.

Again, this is just an idea and not a standard.  There are no suggested limits for a test like this right now.  Everything in this field is at this point "unregulated", and we are all concerned about what the FDA will eventually do to throw a wrench in the innovation in the name of hypersensitivity. 


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Tags: lubricious coating, Hydrophilic Coating, medical device coatings, hydrophilic coatings, lubricious coatings, particulate testing

Medical Device Coating Particulate

Posted by Josh Simon on Tue, May 24, 2011 @ 07:27

At the time of this writing, there is no official FDA Guidance Document detailing allowable particulate from medical devices.  You can imagine that this would be an issue especially in blood-contacting applications.  Particulate escaping into the vasculature can ultimately accumulate in the brain, occluding small vessels and leading to ischemic stroke.  At the very least, insoluble particulates will accumulate in the lymph nodes where they may just hang out forever, participating in a life-long chronic immune response in much the same way those ink particles in your tatoo are doing.

Word reaching my ears from the street is that the FDA is concerned about particulate in medical devices and is asking companies who are developing catheters and other blood contacting devices to run particulate tests.  Since there is no official medical device particulate test, it looks like they are requesting USP 788.

USP 788 is actually a test for particulates in injectible formulations.  It involves streaming a liquid exudate from a device through a sensor that can count the particles, usually with a laser.  Some of the newer equipment used for this can even "see" clear particles and count them.  For medical devices, it looks like the FDA is specifically asking for "Text 1B" in the USP 788 document, which is a test for particulates in a container with a nominal volume of 100 mL.  The allowable limits are also given in the document.

ParticleCounterFor those that sell or use hydrophilic coatings, this is something to look out for.  I dare say you should even design this requirement in ahead of time, even though it is not official yet.  I believe that in the future there will be a medical device coating requirement on particulates.

Tags: medical device coating, coating particulate, USP 788, particulate testing, FDA