Whereas vials can easily sit on a track and be directed along their sides with relatively simple belts and conveyors, syringes
require direct handling (see Figure 2). Syringes are unstable because of their high center of gravity and therefore require
specialized transport systems to reduce the risk of breaking or scratching. The finger flange of the syringe can be the most
vulnerable, so the handling system must allow space between each unit.
Figure 2: Automated filling lines provide the necessary direct and individual handling of syringes (photo courtesy of Baxter
Syringes can be transported using pucks constructed of thermoresistant plastic or stainless steel. The pucks hold the syringes
upright as they move them through heat tunnels. Specially designed trays transport the syringes into autoclaves. Traditional
lines are designed to hold syringes by the flange, but some experts believe this system poses a risk to breakage.
"We are seeing more systems that have either pucks or systems that hold the syringe throughout the transport systems using
vacuums on the starwheel. This allows the syringes to be elevated as needed without being supported on the bottom or by the
finger flange" says Isberg.
Syringes may be supplied in bulk (e.g, for plastic syringes), rondo trays (e.g., for flanged syringes), or in nested tubs. Bulk plastic syringes are first sorted before being arranged in a line and must
be presterilized by autoclaving. Current state of the art includes automatic handling units for transferring the syringes
into the filling line transport system.
Syringes packed in nested tubs have gained much interest. The tubs are packaged sterilized in bags and contain presterilized
units. There are still challenges in their handling with isolators, however. First, the tubs must be removed from the outer
bag without compromising sterility. In addition, the outside of the tub must be disinfected before it is transferred into
a barrier system, the tubs are continuously transferred into and out of the barrier system, the Tyvek lid of each tub must
be removed, and the "nest" and tub must be separated (see Figure 3).
Figure 3: This load-lock system for nested tubs is an integrated three-isolator design with optimized mouseholes, pressure
cascades to protect the air in the main chamber, sliding partitions within each chamber, biodecontamination within the main
chamber, and shared air handling (photo courtesy of Robert Bosch Packaging Technology).
Isolator manufacturers are working toward new designs that will accommodate this process. Isberg points out that nested tubs
have had "major implications" on barrier design, including: large custom mouseholes at the inlet at outlet points, pressure
and air separation must be maintained, barriers must be compatible with tub disinfection systems, barrier footprints are wider
because of the tub transport system, and removal of the Tyvek sheet lids from the barrier chamber. One new robotic system
has been designed to remove these sheets from the tub in an ISO 5 environment, eliminating the risk of contamination and particle
generation during delidding.
Moving away from traditional cleanrooms and toward barrier systems requires a greater reliance on automated systems and robotics.
Already there is very little human intervention in the process, but more automation could provide greater consistency.
Automation strategies for prefilled syringes include automated loading of lyophilizers, autoclaves, and dry-heat sterilization
tunnels as well as robot transfer systems (2).
"Full automation of all syringe processing steps will soon be a reality," predicts Isberg. "Barrier systems must adapt to
accommodate new ways to process syringes, including the use of robotics."
Robotic handing units are commercially available and several have already been installed in pharmaceutical companies. Still,
there has been some hesitation in the industry about adopting these units into the processing lines.