A new system for the rapid transfer of sterile liquid through a containment wall

Sterile liquids are frequently transferred during the processing of sterile liquid drugs such as injectables or ophthalmic drops. Several types of transfer can be performed, each requiring a validated method to ensure the desired sterility-assurance levels are achieved.

The transfer between two containers is usually achieved through a valve-to-valve connection followed by steam sterilization of the space located between the two valves. This well-established procedure, mostly in the context of large stainless steel equipment, takes at least 2 hours, including the cooling-down period. It also requires the availability of clean steam, the evacuation of condensates and a recording system for several parameters, including temperature, relative humidity (RH) and pressure. These parameters are sensed, recorded and then assessed to ensure the connection adheres to particular quality assurance (QA) specifications.

This technique is clearly not very attractive for applications that require more frequent connections to multiple, smaller containers in environments where disposable equipment is used, such as blood banks, because of the time lag, cost and quality assurance/quality control (QA/QC) implications.

In the early 1980s, the flaming technique of the tubing ends commonly used under laminar flow conditions were replaced with hot plate welding (also called tube fusing). This technique is suitable for small diameter thermoplastic tubes made of PVC, thermoplastic elastomer or other polymers.

Presterilized disposable systems for connecting two tubes together have been introduced by Pall Kleenpak, BioQuate DAC and Millipore Lynx S2S,^1–3 which the manufacturers claim can be used in low classification and even unclassified environments, and application is connection inside a room, but not through a wall.

A new situation for aseptic transfer arose with the additional protection required between barrier and isolators around critical aseptic processes.

In such cases, it is preferable to leave the container outside of this protected environment, but obviously a connection mechanism is required for the sterile liquid to cross the wall. It is actually quite difficult to introduce the container to the protected environment because the outside of the container cannot be thoroughly sterilized.

The first transfer system devised to overcome this problem was also for large, infrequent liquid transfers and incorporated the rapid transfer port (RTP) container from La Calhène (France). It consists of introducing folded steam-sterilized tubing in the barrier/isolator that can be unfolded from the inside of a stainless steel transfer container.

It is possible to sterilize the preassembled system, for example, the RTP container with the empty tank, but in many cases, valve-to-valve steam sterilization was still necessary.

As flexible pouches are increasingly being used for aseptic liquid storage, Stedim (Aubagne, France) introduced the rapid aseptic fluid transfer (RAFT) that connects pouches together through a Biosafe port. The stainless steel container is replaced by a plastic bag equipped with a disposable flange that is docked to an RTP port. The disposable part is attached to the flexible pouch and these are gamma sterilized together as a closed system. Unfortunately, the docking system cannot be reused as a reclosing/reopening process is not feasible, unless multiple flanges are attached to the bag.

This article describes a new approach for aseptic fluid transfer: the Sartorius aseptic rapid transfer (SART) connection technology. This system consists of a SART port and a disposable Gammasart aseptic transfer device (ATD) connector to address both the quality of the aseptic connection and to simplify passage (of liquid) through a wall. This article aims to show that SART meets the stringent product qualification requirements set by the Pharmacopoeias by discussing the product-qualification results.

Principle of the technology

SART technology was developed for the aseptic transfer of liquid through a barrier or separating wall. The system has the following features:

• Reduced port size (because wall space is restricted in many isolators).

• An approved RTP system made of the four 'V-shaped profiles' (two of them being seals) which match at the tip. The contact surfaces are minimized to allow accurate matching of the shaped profiles.

• No rotation (or twist) of the tube of the incoming liquid during docking in the port. The risk of rotating the tubing is that a leak is created, which could lead to contamination.

• A mechanical interlock system to prevent accidental opening of the port in the absence of a connector.

• A disposable connector attached to the external container tubing. This is also small to accommodate small containers.

• The inner tubing is made of rigid plastic to prevent pinholes and provide sterility protection.

• All connectors are individually tested.

• A leak test limit that meets high standards comparable to those in place for closure integrity of the attached container. The connectors are tested during the manufacturing process.

• A maximum of five reclosing and reopening cycles to cope with the partial emptying of a given container and to provide flexibility in case of interrupted operation.

• Compatibility with rigid liquid containers (e.g., stainless steel, glass, plastic) and flexible containers, such as pouches.

• A simple and low-cost solution for multiple applications or when a small volume of liquid is to be transferred.

The Gammasart ATD connector consists of two parts: the connector body containing the rigid tubing and the connector cover (Figure 1). To open the docked connector, the cover is locked into the SART port and is removed by unscrewing it, leading to the release of the tubing in the aseptic area.

Figure 1

Both the connector body and the connector cover are made of polybutylene terephtalate (PBT) and molded in a classified environment. A seal made of the thermoplastic elastomer Santoprene (Advanced Elastomer Systems, Akro; OH, USA) is overmolded on the connector cover. This seal ensures the quality of the closure integrity of the system.

The principle of the SART connection is based on the alpha-beta concept of the four V-shaped profiles, all in contact at the tip. This alpha-beta concept was initially developed for the nuclear industry in the 1960s and was approved by pharmaceutical authorities with the introduction by La Calhène in the 1970s. As illustrated in Figure 2, the four V-shaped profiles of this system come from the connector body, the connector cover, the internal part of the port and the seal of the port. Two of them are rigid (the connector body made of PBT and the internal port made of stainless steel) and two are flexible (the connector cover seal is made of Santoprene and the external port seal is made of silicone).

Figure 2

The connector device has to be sterilized by gamma irradiation at minimum of 25 kGray to ensure sterility, but the device was validated at 45 kGray to ensure that the entire irradiation range was validated. If the connector is assembled on a nonirradiated container, such as a stainless steel vessel, this irradiation should happen alone. When using containers that have to be irradiated, such as plastic pouches, the sterilization of the connector is performed when assembled and not prior to assembly. When a connection is required on a stainless steel vessel, the connector can be autoclaved. A cycle of high and low pressure is required to push water vapour inside the connector and to dry it. Preliminary tests performed with 10⁶ biological indicators located in the assembled connector have shown total kill.

The connection process consists of the following steps (Figure 3):

• The Gammasart ATD disposable connector is introduced in the port and secured with two clamping devices on the external port (Figure 3(a)).

• The internal port has a clamping system to hold the connector cover firmly inside. The objective is to entrap all of the connector cover's exposed outer parts inside the port (Figure 3(b)). The internal port is sanitized inside this clean environment with the rest of the main equipment, for example, with the vapourized hydrogen peroxide cycle.

• The port is opened by rotating the internal port (Figure 3(c)).

• The tubing (e.g., silicone) is placed in the contained area on the connector's sterile tubing (Figure 3(d)).

The connector can be closed and reused up to five times in one week. This is useful for multiple transfers (e.g., a single bag containing five volumes of one formulation component to be transferred in five different batches) or, more frequently, in the exceptional cases of major operation troubles. For example, a major breakdown on a liquid filling line would lead to the risk of destruction of connected bulk material. The Gammasart ATD connector allows the bulk to be safely removed from the line, stored and reused within the next few days. The functionality has been obtained by having a slight additional screwing of 9° compared with the initial position, generating a recompression of the seal to maintain good closure integrity. To avoid the leakage when a joint is opened and closed after a long compression period, we need to close the connector tighter and therefore, an additional rotation of 9° compared with the storage position is required.

Figure 3

Application of Gammasart ATD

The connector can be used across two different containment areas. The most common example in the pharmaceutical industry is the transfer of formulated bulk to the aseptic filling line. This could be the transfer from a clean room to a protected environment, such as an isolator restricted access barrier system (RABS), or from a corridor to the class A/ISO 5 clean room.

Transfer during formulation is also possible. This can be achieved in two ways:

• Transferring the different components to the formulation container.

• Transferring the formulated bulk to the different storage units.

In the latter example, Gammasart ATD is used in the reversed direction. The flow moves from inside the contained area to the sterile container.

This connector is resistant to gamma irradiation and steam sterilization. Both sterilization procedures can even be combined. There are, therefore, two sterilization scenarios:

• For containers that are sterilized by gamma irradiation, such as flexible pouches, the connector should be preassembled and the full assembly should be irradiated.

• For containers that are only steam-sterilized, such as stainless steel containers, the pre-irradiated connector should be assembled before sterilization.

Qualification of the Gammasart ATD connector

The connector was validated after undergoing a 45 kGray irradiation and a cycle of steam sterilization (Table 1). The following tests were performed:

Table 1 Test results for validation plan.

• Leak test. This test is critical to ensure that the seal effectively preserves the sterile environment of the Gammasart ATD connector and that there is no risk of viable particle penetration inside the connector during storage. The leak was fixed at 0.9 cc/min at 350 mbar or 35000 Pa, corresponding to the closure integrity of the attached container.

• Leak test after multiple opening/closure cycle. This test was performed to validate that a connector can be opened and reclosed up to five times within one week. The relatively short period of time results from the fact that the connector seal is overcompressed at the first reclosure to obtain new closure integrity. Nevertheless, because overcompression can be obtained only once, the closure integrity cannot be maintained for long periods of time after this, especially after subsequent openings.

• Ageing conditions. The connector was tested at various ageing times to assess if the specifications, such as closure integrity, are maintained. The various ageing periods are:

• One month's ageing at room temperature.

• Accelerated ageing for 74 days at 60 °C, corresponding to about 2 years of ageing in normal conditions.

• One year of ageing at room temperature.

• Low temperature. The connectors were stored at -20 °C and -60 °C for 15 days before use. After being unfrozen, the connectors behaved similarly to the ones that were frozen.

• Fitting and traction test. This involved testing the ease of installing the tubing once the connector is open and verifying its resistance to rapid flow.

• Burst pressure test. The resistance of the connector to high pressure was tested to ensure that there is no risk of accidental unscrewing by the operator if the pressure increases inside the container attached to the connector (e.g., the liquid transfer inside a container with a defective vent filter). The test has been conducted at 6.5 bars for 30 s. About half of the connectors showed a seal deformation, but none of them disassembled.

Particle test. Because the Pharmacopoeia allows the presence of a limited amount of particles from the container and filling process, the presence of particles was recorded in various volumes collected over time. The objective was not to exceed 600 part cles bigger than 10 μm and 60 particles bigger than 25 μm per 50 mL volume. These data correspond to 10% of the pharmacopoeia limits for a single injection, whatever the volume.

• USP cytotoxicity and bio compatibility. These tests confirmed that the TBT material meets the most stringent safety criteria (USP class VI) because no sign of toxicity was recorded on the cell or when administered to animals by three different methods.

• Extractable profiles. Connector bodies were placed in a worst-case situation; that is, immersed in water for injection for 24 h at 80 °C or in ethanol for 24 h at 50 °C. Analyses showed a very low release of material; that is, always less than the 50 μg/connector and usually less than a few micrograms per connector. To extrapolate these data to the release from the internal tubing surface, the data must be approximately divided by a factor of ten.

• Endotoxin detection. Preliminary tests showed an undetectable level of endotoxin inside the connector tubing where the liquid passes through. This test will be repeated once the final packaging is available.

• Media transfer simulation. Media fill simulations using closed vial technology were used to validate the quality of the connection. Three lots of ;6300 vials have been filled in the assembly workshop; that is, a nonclassified area. Two connectors were used for each lot to create a circulation loop. The presence of colony-forming units was also recorded by collecting seven samples of one cubic metre of air inside the RABS. No contaminant was discovered in the vials or in the environment on the recorded samples (Table 2).

Table 2 Media fill results.

Conclusions

The SART connection technology performs aseptic transfers between different containment areas.

The Gammasart ATD connector has several advantages. The major one is the robustness of the connection system to prevent contamination of the area with the highest sterility assurance level. This is achieved by using the very precise alpha-beta system, which has been extensively used for several connection models, such as the RTP container or beta-bag, to bring autoclaved material inside the protected environment.

The second key advantage is ease of use. The set-up time is less than 1 min and the container is kept outside the critical area. The system also has security features, such as interlock, which prevents operator mistakes and, therefore, the risk of contaminating the transferred product.

The third advantage is the possibility of reversing the connection if problems arise during the process. Most systems do not allow the connection to be reversed to save the transferred product so there is a risk of losing the product.

Finally, the solution is inexpensive and flexible, allowing the users to adapt it to several situations.

The connector's qualification plan confirms that the materials used and the design of the port and the connector device meet the most stringent criteria. Therefore, the SART connection system is suitable for multiple transfer applications in the pharmaceutical industry.

Acknowledgments

The authors would like to thank Thomas Paust, Paul Priebe and Patrick Balériaux for their recommendations on this article. Aseptic Technologies benefits from grants from the Walloon Region and from the Agence Wallone à l'Exportation (AWEX).

Benoît Verjans is commercial director at Aseptic Technologies (Belgium).

Jacques Thillyis technology director at Aseptic Technologies (Belgium).

Christian Vandecasserie is a consultant at Aseptic Technologies (Belgium).

Hartmut Hennig is head of new technologies in the departments of QA/R&D at Sartorius (Germany).

Patrick Evrard is manager at TS Biotech Devices at GSK Biologicals (Belgium).

References

1. Pall Corporation www.pall.com

2. Bioquate Incorporated www.bioquate.com

3. Millipore Corporation www.millipore.com