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Cytotoxicity at the end of life-time

#1
We have recently changed the supplier of our polypropylene and are preparing the bioloical evaluation for the new one.
Material characterization and cytotoxicity tests were passed. And now we are planning to perform cytotoxicity at the end of life time, which is one year.
Does anyone know a rationale how to shorten the sterlization cycles (365 cycles) to perform a cytotoxicity on the material afterwards?
 
#2
Lenka,

if your material characterization / cytotoxicity data is equivalent on both the legacy and new supplier for the very same specified material, then you can use this data as basis for a rationale to not repeat end-of-life cytotoxicity testing at all - or perform reduced confirmatory cytotoxicity testing, say after 50 sterilization cycles, to further substantiate your rationale.

Alternatively, if you can think of introducing an acceleration factor, typically based on temperature elevations and usage of the Arrhenius equation, into your sterilization cycle, then you might be able to reduce the number of cycles to run. I guess you are using steam sterilization? If yes, temperature elevations may be out of scope, however, as you get too close to temperatures where you introduce material effects, which are not related to aging.

HTH,

Gerhard
 
#3
Lenka,

if your material characterization / cytotoxicity data is equivalent on both the legacy and new supplier for the very same specified material, then you can use this data as basis for a rationale to not repeat end-of-life cytotoxicity testing at all - or perform reduced confirmatory cytotoxicity testing, say after 50 sterilization cycles, to further substantiate your rationale.

Alternatively, if you can think of introducing an acceleration factor, typically based on temperature elevations and usage of the Arrhenius equation, into your sterilization cycle, then you might be able to reduce the number of cycles to run. I guess you are using steam sterilization? If yes, temperature elevations may be out of scope, however, as you get too close to temperatures where you introduce material effects, which are not related to aging.

HTH,

Gerhard

Hi Gerhard,

thanks a lot. Unfortunately we do not have any reliable end-of-life cytotoxicity testing for the currently used material either.
But the material is used in our product for over 15 years and equivalancy can be shown on the baseline level. Would you find reduced cytotoxicity testing after 50 cycles to be sufficient on that data base?

Thanks, Lenka
 
#4
Lenka,

some food of thought:
  1. Is your existing testing and post-market experience with the number of allowed reprocessing cycles substantiating the life-time of your device with material sourced from your legacy supplier?
  2. Are your _beginning of life_ material characterization / cytotoxicity data equivalent for both the legacy and new supplier?
  3. Do both suppliers fufill the same comprehensive material specification in terms of composition and physical properties? (whereby "comprehensive" means e.g. you do not allow any unknowns in the composition, such as unknown (colour) additives, process enhancers etc.)
If all YES, then in my opinion you can use your 15-years experience as baseline, together with evidence from (2) and (3) above, to conclude that your device with material sourced from your new supplier is biocompatible over its life time - without any additional testing after reprocessing. Confirmatory testing after a limited number of resterilization cycles (and that's why I proposed 50 cycles) may further substantiate this conclusion, but may also be omitted - but this depends on your biological risk management process and to what extend you can show equivalency for item (2) and (3) in the list above.

HTH,

Gerhard
 

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