Jacques Thilly

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,

  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.  

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.  

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). 

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 10

  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.  

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.			

 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. 

Articles

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.

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

Aseptic filling has been well-established for several decades, but regulatory requirements have become more and more restrictive over time. For example, authorities have requested increased environmental safety in the filling area, with very strict requirements regarding eliminating potential contamination agents and reducing particles, in addition to revising product formulations to eliminate preservatives. These recommendations have led to two major improvements: better air quality control to reduce contamination risk and new container designs. 

Containment technologies reduce the risks associated with the human presence in Class 100 clean rooms. The isolator appears to be the best solution in terms of quality, although it is the most complex for pharmaceutical manufacturing, especially for conducting multiple and difficult validation experiments; performing controlled vapour-phase hydrogen peroxide sterilization; maintaining delicate pressure balances; and controlling the complex airflow patterns generated in the closed environment. 

Faced with the complexity of using isolators, manufacturers have developed open barriers, particularly the restricted access barrier system (RABS), which consists of a barrier system with hard walls (allowing access only through gloves), but which is in fact an open system. The RABS is based on the principle of a regular air flow pushing all possible sources of contamination to the bottom and then outside the barrier without any air recirculation. The sterility assurance level inside a RABS appears to be similar to that of an isolator.  

Since the classical ampoule was introduced, several new container designs have been configured such as the vial, the cartridge, and more recently, the prefilled syringe. All these containers have been developed in response to one key concern: ease of use throughout the supply chain. The vial, for example, is a more-solid container with a reduced risk of generating glass particles, and the prefilled syringe eliminates handling during drug administration. Nevertheless, because all these containers remain open during aseptic filling, they do not succeed in significantly reducing the risk of contamination from the environment. 

This article presents a new concept: closed-vial technology, which is based on a vial that is supplied closed and sterile and therefore ready-to-fill. This sterile vial, which functions like a mini-isolator, is filled in a Class 100 environment inside a RABS. 

The principle of the closed-vial concept can be summarized as follows: 					

The body of the closed plastic vial is made of cycloolefin copolymer (COC), a plastic material that can be molded into shapes that are not feasible with glass and that allows for tighter seals between parts of the vial, thus improving closure integrity.

Closed vials are clean and do not require washing before filling. The vial body and the stopper are molded and assembled in a Class 100 environment, leading to extremely low particle levels inside the container.

The vial is sterile. After assembly, the closed vial is sterilized in a gamma-irradiation unit to secure the absence of vial contamination, eliminating the vial washing and depyrogenization step in the filling line.

In the filling process, a needle penetrates the closed vial through the stopper. After the liquid is delivered, the needle's path is resealed with a laser beam to restore closure integrity. Stopper integrity can be achieved because the stopper is made of a thermoplastic elastomer, which can remelt and fuse when the temperature is increased. 

The closed vial consists of five major elements (Figure 1); the vial body, which can hold 0.5–100 mL of liquid (Figure 2); the stopper, which is pierced by the needle and then resealed with a laser; the top ring, which provides a tight seal between the vial body and the stopper; the bottom ring, which facilitates mechanical processing; and the flip-top plastic cap, which protects the piercing area.  

 Figure 1. The five vial elements are (from bottom to top): the bottom ring for mechanical stability and processing; the vial body containing the liquid; the stopper that can be resealed with a laser; the top ring, which ensures closure integrity between the vial body and stopper; and the flip-top cap to protect the piercing area.			

The closed vial body is made of COC, a plastic that has already been used to contain parenteral drugs (e.g., the COC prefilled syringe) and that provides excellent resistance, minimized transmission rates for water and various gases, and excellent optical performance. COC is hydrophobic and therefore does not require additional siliconization to allow easy liquid collection.  

Figure 2.  Closed vials are available in sizes ranging from 2â100 mL, all with the same cap size.			

COC can be molded to achieve several desired properties in the vial body. In particular, right-angle snap fits have been designed to ensure that the vial's parts fit tightly together, and a confidence ring has been placed around the top of the vial body to create a concentrated pressure contact point between the stopper and the vial body. These two elements ensure excellent closure integrity for the assembled vial. 

The stopper is made of a thermoplastic elastomer that can absorb laser energy to melt and fuse without burning. After it has cooled down, the mechanical properties of the melted material are identical to those of the initial material (which was also melted during the molding process). The stopper shape has been designed to minimize dead volume (no recess area exists) and to provide a large piercing area for the practitioner, facilitating liquid collection and minimizing the risk of injury when the needle is inserted. The stopper is also highly flexible, allowing it to maintain close contact with the needle during the filling process. Both the vial body and stopper materials meet USP Class VI criteria to ensure patient safety. 

The vial's top ring ensure a tight seal between the vial body and the stopper by leveraging the property of right-angle snap fits described above. These snap fits provide strong closure integrity without requiring significant downward pressure during assembly, which would weaken closure integrity. 

The bottom ring helps stabilize the vial during line loading, but its key role is to allow the vial to be held tightly with clamps during the needle withdrawal step at the end of the filling process. Without such a tight hold, it would be very difficult to withdraw the needle without lifting the vial. 

Finally, the sterilized cap protects the piercing area until the flip-top cap is opened. This protection is obtained by a circular rib that tightly covers the stopper's surface. The cap is installed inside a barrier isolator to maintain aseptic Class 100 condition below it (Figure 3).  

Figure 3. The sterile, ready-to-fill vial is delivered uncapped (left). After filling, the vial is capped (middle) inside an isolator. To use the vial, the central part of the flip-top cap is removed (right), exposing the large puncture area that has been kept sterile by the circular rib.			

The method of manufacturing closed vials is also new. Closed vials are molded and assembled in a Class 100 environment to minimize the number of particles present inside the vial after production. The manufacturing principle consists of the following five steps. 

 Two molding machines are installed in a Class 100 environment; material is injected directly from plasticating screws located outside. After molding, the vial body and the stopper are picked up by robotic arms, which are used to manufacture microelectronic parts and therefore are designed to maintain Class 10 environment conditions. 

The two robotic arms are placed across from each other. A stopper is inserted into the vial with light pressure and a slow, precise motion. The assembled vial is then transferred to an adjacent Class 10000 clean room for further processing. The fact that 32 vial bodies and 32 stoppers are molded and assembled at the same time allows the use of slow machine movements during their manufacture to minimize particle generation while achieving satisfactory output levels. 

 The top and bottom rings are applied by simple pressure. 

 The vials are placed in corrugated polypropylene boxes and double-wrapped in polyethylene bags. 

 A complete pallet of vials is transferred to a gamma sterilization unit and a minimum of 25 kGy are delivered. 

The setup of the closed-vial filling line is illustrated in Figure 4. The filling process consists of five steps: the opening of the polypropylene boxes that contain the vials; sterilization by a miniature electronic beam directed at the top surface of the vial; vial filling by inserting a needle through the stopper; resealing the stopper with a laser; and capping. The two first steps are conducted under a classic laminar airflow, and the last three are performed in a RABS.  

Figure 4. An overview of a production line for closed vials. First, under soft-wall laminar airflow, boxes of vials are opened mechanically on the loading table, and the vials top surface are sterilized by an electron beam. Then, in the RABS, the vials' linear movement is converted to a parallel movement by a floating pulley. The vial filling and the laser resealing are performed on the transport bars, and then the vials are capped.			

The filling line can be set up in one of two formats. The clinical format (Figure 5) has a filling capacity of 1500–3000 vials/h, with one or two vials processed at a time. In this setup, filling operations are performed on a wheel that stops at each step (Figure 6). The commercial production setup, in turn, has a filling capacity of 10000–40000 vials/h, depending on the number of vials processed in parallel (6, 12, 18, or 24 vials).  

Figure 5. Overview of a clinical machine with the loading and electronic beam steps conducted under a soft-wall laminar airflow (on the left) and the filling steps (filling, laser resealing and capping) conducted in a restricted access barrier system (RABS, on the right).			

To load the line, a mechanical system allows the vial boxes to be opened without the operator's hands coming close to or above the vials. This line-loading operation is performed under laminar airflow with soft walls to allow access if necessary.  

Figure 6. Overview of the filling area in a clinical line. Inside the RABS, a wheel moves the vials to each filling step: the filling with the needle piercing the stopper (top right); the resealing of the stopper with a laser (top left); and capping (bottom left) before the vials exit the RABS.			

Then, just before the vials are transferred to the RABS, a miniature electronic beam sterilizes the critical top surface of the vials. This miniature electronic beam is very small (it is a 60 cm cube weighing 120 kg, including lead protection) and delivers a dose of 25 kGy. The radiation penetrates the stopper to a depth of 30 mm, eliminating the shadow risk. 

The next three filling steps are conducted within the RABS. First, a needle pierces the stopper to dispense the liquid drug. The needle has been designed to minimize particle generation (a noncoring pencil point is used), to inject the liquid smoothly (at a 30° angle through holes in the needle wall), and to allow excess pressure to vent (grooves allow gas to flow out of the vial). 

Next, a laser reseals the pierced stopper. A laser beam with a flat-top energy curve is applied to reseal an area significantly larger than the piercing path. The use of a flat-top energy curve allows equal energy distribution to avoid the risk of burning the middle and not resealing the sides. The stopper surface temperature increases to 160°C during a very short period, but the inner face of the stopper only reaches 38°C for a few seconds, so the product is not affected by the temperature increase. 

The last step is capping, which is also done in the RABS to entrap aseptic conditions at the stopper surface. The circular rib ensures closure integrity. 

The closed-vial technology provides four major advantages: 					

Better sterility assurance combined with a lower level of particle contamination for patients. The closed vial is never exposed to air and therefore has properties that are similar to those of an isolator that is only disturbed during needle penetration. The quality of the vial manufacturing and the filling process, ensure very low levels of particle generation and glass-free manufacture of the vials.

Less investment is required by pharmaceutical manufacturers. The closed-vial filling line, which is simpler than a classical filling line because several steps (e.g., washing, passing vials through a hot-air tunnel, and stoppering) are eliminated, is also significantly cheaper compared with a similar-capacity process conducted under an isolator. In addition, other production costs can be eliminated (e.g., the water-for-injection [WFI] loop for vial washing) or reduced (e.g., clean room space to install the line can be reduced by more than half compared with classical glass-vial filling lines). Eliminating WFI production, including the associated validation and monitoring costs, is the major driver for cost reduction. Other sources of cost reduction include reducing energy consumption, employing fewer workers, increasing productivity, and reducing dead volume in the vial.

Operator safety is improved throughout the supply chain. Closed vials are filled in a confined environment (a RABS), eliminating the risk of spillage outside the RABS that could expose operators to potent or cytotoxic drugs. In addition, the mechanical resistance of the plastic vial minimizes, and practically eliminates, the risk of breakage during filling, labelling and packaging, and throughout the entire the supply chain to the healthcare practictioner's office.

Because of its advantages, closed-vial technology is likely to become a standard for pharmaceutical aseptic filling processes. 

The technology not only improves quality for the patient, but also significantly reduces the complexity and cost of filling operations for manufacturers. 

The closed vial has been developed to improve aseptic filling quality and to reduce process complexity. A ready-to-fill closed vial consists of a sterile vial provided with the stopper secured in place. The vial is filled by inserting a non-coring needle through the stopper, which is then resealed by laser.