RTS
stoppers
Ready-to-Sterilize (RTS) stoppers are expected to enter aseptic manufacturing immediately after sterilization through Rapid Transfer Port (RTP) systems. This requires every sterilization cycle to deliver stoppers in the same microbiological and physical condition, ensuring repeatable process performance from batch to batch.
For this reason, sterilization defines more than microbiological safety. It also determines the physical condition in which the stopper enters the filling process, influencing production readiness from the very beginning.
Residual humidity, final load temperature and cycle duration are therefore not simply process parameters. Together with sterility, they define whether an RTS stopper is ready to become part of a predictable and repeatable aseptic manufacturing process.
THE AUTOCLAVE DEFINES THE PHYSICAL CONDITION OF THE STOPPER.
Physical Condition is not defined by a single process parameter. It is the measurable combination of microbiological, moisture and thermal conditions in which an RTS stopper leaves sterilization and enters aseptic manufacturing.
Achieving this condition requires sterility, drying and cooling to be governed as one continuous process rather than independent process phases.
We don't simply sterilize RTS stoppers. We engineer the Physical Condition required for the next manufacturing process.
Microbiological condition
Validated steam sterilization establishes the sterility required for aseptic manufacturing.
Moisture condition
Residual humidity defines the amount of moisture remaining within the stopper after sterilization and drying. For moisture-sensitive products, this becomes part of the process conditions entering filling.
Thermal condition
Final load temperature determines when sterilized stoppers can be transferred through RTP systems and introduced into production.
Manufacturing consistency
Only when sterility, drying and cooling are governed together does every batch leave the autoclave in the same repeatable Physical Condition.

ENGINEERING THE PHYSICAL CONDITION
Physical Condition is not verified after sterilization.
It is engineered during the process and demonstrated through measurable industrial results.
IMMEDIATE RTP READINESS
Through the integration of sterilization, drying and cooling, we consistently deliver RTS stoppers at a final load temperature of ≤50 °C, enabling immediate RTP transfer without additional cooling or waiting time before filling.
INDUSTRIAL CYCLE PERFORMANCE
By optimizing the complete sterilization process, we achieve full process readiness in approximately 5–6 hours, combining industrial productivity with the repeatability required for aseptic manufacturing.
emerge sterile, dry and ready for immediate use.
How is RTS stopper sterilization different from bulk stopper processing?
RTS stopper sterilization begins with components already prepared for sterilization and focuses on delivering validated sterility together with the physical condition required for aseptic manufacturing. Bulk stopper processing additionally integrates washing, particle removal and endotoxin removal before sterilization.
Furthermore, RTS caps are packaged in Tyvek bags and therefore the sterilization process acts on a static and more challenging product compared to the bulk process, where the caps are processed without disposable packaging and moved continuously.
Why is a final load temperature below 50 °C important?
Maintaining a controlled unloading temperature allows RTS stoppers to be transferred immediately through RTP systems without additional cooling, reducing waiting time before filling.
Why is a 5–6 hour cycle significant?
A complete cycle includes sterilization, drying and cooling. Optimizing all three phases reduces manufacturing time while maintaining the physical condition required for repeatable aseptic processing. The reduction in cycle duration directly implies an increase in productivity in the department, ensuring the possibility of carrying out other sterilization cycles (for example a machine parts cycle) during production shifts.
Why isn't sterility alone sufficient for RTS stoppers?
Sterility confirms microbiological safety. Residual humidity, final load temperature and cycle repeatability determine the physical condition in which the stopper enters aseptic manufacturing and its readiness for predictable production.
Why is residual humidity important?
Residual humidity is part of the physical condition created during sterilization. Controlling residual moisture supports repeatable manufacturing conditions and helps reduce variability, particularly for moisture-sensitive pharmaceutical products.
How is residual humidity measured?
Fedegari uses the GRAV gravimetric method, measuring stopper weight loss after controlled heating to constant weight to determine residual humidity objectively.
HIGH TEMPERATURE FOR POROUS LOADS
Manufacturing components such as stoppers, filters, garments and silicone tubing requires more than achieving sterility. Manufacturers must be able to consistently demonstrate that every critical surface has been effectively sterilized, batch after batch, providing objective evidence for process validation and regulatory confidence.
INSULIN PROCESSING
Insulin production increasingly relies on high-throughput syringes and cartridge filling lines, with cartridges serving reusable and disposable delivery pens. At these output levels, filling capacity alone does not determine production performance.
Closures and reusable filling-line parts must be washed, sterilized, handled and delivered to the filling area at the required pace and under controlled aseptic conditions. If these upstream activities are managed as separate, disconnected operations, they can become a bottleneck while increasing equipment, transfers, manual handling and operating costs.
VACCINES
Vaccine manufacturing places exceptional demands on fill-finish operations, where product sterility depends on the controlled preparation and transfer of every component entering the aseptic filling area.
Sterile vials, stoppers and product-contact machine parts must be available in step with the filling line and introduced without contamination or particle exposure. Multiple preparation systems, intermediate containers and manual transfers increase process complexity, footprint and critical interfaces. Dependence on ready-to-use components can also limit sourcing and campaign flexibility.
ALBUMIN PASTEURIZATION
Albumin is a heat-sensitive biological product. Once prepared, purified, formulated and stabilized, it is sterile-filtered and aseptically filled into final glass vials or bottles. Because it is not subjected to conventional terminal sterilization at 121°C, the filled and sealed containers undergo validated pasteurization at 60°C for at least 10 hours to support viral inactivation while preserving protein stability and product quality.
Albumin pasteurization is traditionally performed in water-bath systems. Although effective for heat transfer, this established approach requires very large quantities of process water, increasing utility consumption, wastewater generation and operating costs across a long and production-critical treatment
RADIOPHARMA
Radiopharmaceutical production combines pharmaceutical contamination control with the radiological protection of operators and the surrounding environment. The exact route varies with the radionuclide, formulation, product stability, container and intended diagnostic or therapeutic use. Some products are sterilizing-filtered and aseptically filled; others can be filled, closed and terminally sterilized. At the same time, reusable product-contact parts require controlled preparation, while radioactive wastewater cannot automatically enter the conventional drain.
HIGH-VISCOSITY PRODUCTS
Hyaluronic acid pre-filled syringes combine a thermally sensitive formulation with a pressure-sensitive container-closure system. Product performance depends on the molecular weight and rheological behaviour of the formulation, while moist heat progressively reduces viscosity as exposure continues. At the same time, heating increases the internal pressure of the filled syringe through liquid expansion and vapour pressure, potentially causing plunger movement, leakage or loss of container integrity.
STERILE POWDER MANUFACTURING
Sterile powder manufacturing presents one of the most demanding combinations of aseptic processing and high-containment production. Reusable containers, machine parts and thermosensitive materials must each follow dedicated preparation pathways before entering the filling environment, while uninterrupted production campaigns require a sufficient number of sterile containers to be available before filling can even begin. The challenge therefore extends well beyond aseptic filling itself: manufacturers must coordinate washing, depyrogenation, sterilization, material bio-decontamination, protected transfers and containment into a single validated manufacturing workflow that preserves both product sterility and operator safety.
CAR-T CELL THERAPY
CAR-T therapies transform a patient’s own immune cells into a personalized treatment, but every individual batch must move through a complex, time-sensitive manufacturing journey.
Cell variability, manual operations, aseptic connections and fragmented equipment interfaces make execution difficult to standardize. At the same time, patient identity, material genealogy and process data must remain connected from leukapheresis to infusion.
HIGH-POTENT ASEPTIC MANUFACTURING
High-potent sterile manufacturing is one of the fastest-growing pharmaceutical sectors, driven by oncology biologics, antibody-drug conjugates (ADCs), peptides and other highly active compounds. While aseptic filling remains essential, manufacturers must simultaneously protect product sterility, operators and the surrounding environment. As occupational exposure limits decrease to the ng/m³ range, every reusable machine component leaving the filling isolator becomes a potential contamination source.
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