Non-destructive CCI Testing of assembled auto-injectors

Until now, container closure integrity testing of auto-injectors has been performed by destructive random testing. The assemblies to be tested are disassembled and the syringe inside is inspected and tested for leaks using conventional methods. At WILCO, together with a customer, we have developed a method for non-destructive leak testing of autoinjectors with different fill levels and headspace volumes.

The challenge in leak testing of assembled pre-filled syringes

In order to verify the stability of the aseptically filled pre-filled syringe (PFS) or cartridge in assembled medical devices, leak tests are performed frequently. The leak test has to be performed on the complete assembled device. Potential leakages can compromise the entire product development.

Probabilistic test methods e.g. Dye Ingress, require a disassembly of the medical device. This disassembling process adds to the dangers of introducing risks due to operator failure.

For some device types, a controlled and non-destructive disassembly is not applicable and requires additional steps, excessive effort or even the activation of the device to gain access to the primary container.

This step requires even more time and adds the risk of introducing defects that may even lead to false results and false rejects respectively.

Our approach for non-destructive leak detection for autoinjectors

  • Our customers approach us typically in phase 3 of development. At this point, we need to understand the behavior of the auto-injector components under the influence of the vacuum decay’s testing pressure of 5 mbar absolute. When the syringe or cartridge is exposed to this vacuum level, the headspace will expand, moving the stopper outwards towards the non-sterile area. This movement creates an additional vacuum level within the barrel.
  • The headspace expansion under the vacuum level will depend on the headspace volume available in the auto-injector arrangement. With a leak in the headspace, it may be possible that the differential pressure generated between the headspace and the volume around the primary container syringe is not sufficient for detection. Therefore, the influence of the headspace volume on the vacuum decay technology (LFC method®) is also analyzed.

Our CCIT solution for the inspection of assembled auto-injectors

The engineering and method development studies result typically in the vacuum decay technology (LFC method®) that can test complex auto-injector products with given preconditions - minor expansion of headspace. The sensitivity of both headspace and product leak is qualified with the mass spectrometry method as a cross-reference.

«Disassembly of our auto-injector design is very challenging. Therefore, we are looking into non-destructive approaches as well.»

Amisha Nair / Dermira

Benefits of our non-destructive leak inspection solution of assembled auto-injectors

  • Disassembly of the device is not necessary for leak testing
  • Significant time reduction with non-destructive auto-injector leak detection
  • Operator independent results
  • Semi-automated inspection with quantitative data record