VALIDATION OF THE EQUIPMENT
The main changes in equipment compared with classical filling technologies are the needle piercing of the stopper and the
laser resealing of the piercing trace.
Regarding the validation of the needle, the three main aspects assessed were the venting of the overpressure created inside
the vial during filling, the level of particle generation during piercing, and the ability of the needle to support thousands
Venting of the overpressure was validated by using a manometer connected to the inside of the vial. It showed that the pressure
increased during filling in the range of 0.1–0.2 bar according to filling speed and vial size, then returned back to normal
atmospheric pressure within 0.2 to 0.4 seconds. This measure correlates well with the observation that a short delay is necessary
before needle withdrawal to avoid drop generation due to filling tube expansion, especially if silicone tubing is used.
Results of the particulate analysis showed that the needle generates very limited amount of particles during the piercing
process. This result was obtained because of the noncoring pencil point design of the needle.
Moreover, the evolution of the particle generation inside the vial along a 5000-vial filling campaign using the same needle,
did not show any increasing trend that could have been induced by the needle wear. Being observed with a microscope, the needle
did not show any difference in shape, cutting edge or surface quality.
The laser needs to be validated on several aspects. First, the absorption coefficient of the stopper material must be characterized;
second, the impact on material should be assessed; third, the effectiveness of the resealing should be validated and last,
the absence of effect of the laser on the product should be verified.
The TPE characteristics should ensure absorption of the laser beam energy by the stopper in such a way that the needle trace
is resealed to a sufficient depth without burning the surface of the stopper. Simultaneously, almost all the laser beam energy
must be absorbed in the stopper thickness to avoid the laser beam passing through the stopper and hitting the filled product.
The right absorption rate is obtained because of a colorant master batch mixed with the stopper material. The range of colorant
percentage in stopper composition is precisely defined to obtain absorption of at least 97% of the laser energy over the thickness
of the stopper, according to a Beer-Lambert curve.
The potential effect of the laser shot on the stopper material was assessed by near-infrared spectrometry of the stopper surface
before and after a laser shot. The profiles are identical between the two records, showing that there is no detectable change
of stopper composition.
The laser power to be selected for an effective laser resealing was validated with physical challenge tests on the closure
integrity of the resealed stoppers: dye test on vials resealed at different laser powers and bubble test looking for leakage
from over-pressurized vials. It was shown that the stoppers that were not resealed only exhibit a small percentage of failure
at the dye test while stoppers resealed with enough energy do not fail. Another way to assess the effectiveness of the resealing
is to cut the resealed stopper perpendicularly to the trace. The resealing depth ranged from 0.4 mm to 1.0 mm when using a
6 mm diameter 12W laser beam. To assess the resistance of the weld, overpressure was produced inside the vials through their
bottom side and leakage was assessed by bubble generation at the piercing trace. Resealed vials started leaking from 140 kPa
to 200 kPa whereas a range from 30 kPa to 150 kPa was observed for the nonresealed vials.
To ensure that the product was securely stored when laser resealed, the effect of a laser shot on the temperature was measured
at different location of a 2-mL vial and results are illustrated in Table IV.
Table IV: Temperature change recorded at various position of the vial when a 4 mm laser shot is applied.
The results, achieved using a 4 mm diameter laser and reproduced with a 6 mm diameter laser, showed that the product was fully
secured inside the vial because no temperature change could be detected following laser resealing of the stopper.
ROBUSTNESS OF THE CONCEPT
To challenge the new concept, media fills had to be run. The first media fills were performed with equipment in an assembly
workshop. These conditions were challenging for several reasons including:
- The sanitization by wiping was performed with doors opened in an unclassified environment.
- The vials were loaded under laminar airflow protection but surrounded by the unclassified environment.
- Tryptic Soy Broth (TSB) bulk was connected through the Gamma-SART connector from an unclassified environment to the ISO5 environment
- The bottom of the line enclosure was directly opened to the unclassified environment.
Despite these adverse conditions, none of the 26,313 TSB filled vials were contaminated during media fill. Contamination was
assessed after vials were incubated for 14 d, during 7 of which they were stored upside-down. Since installation of that equipment
in an ISO8 clean room, more than 88,000 additional vials have been filled with TSB without any contamination.