How to optimise silicone tubing in single-use systems

AXIEO Specialties

By Csilla Kollar*, Jennifer Gemo^ and Lise Tan-Sien-Hee°
Friday, 28 October, 2016


How to optimise silicone tubing in single-use systems

Pharmaceutical and biopharmaceutical companies and contract manufacturers are increasingly adopting single-use systems to replace expensive stainless steel vessels and piping for high-purity fluid transfer in processing operations such as sampling and batch and vial filling. Stainless steel, while strong and durable, requires aggressive cleaning, poses the risk of contamination and makes it cumbersome and inefficient to switch from one drug to another.

Single-use systems consist of multiple components connected with heat seals, overmoulds or mechanical fasteners. They often include a bag, a supporting frame and a mixing attachment. Ports or openings in the bag allow fluid input and output via tubing assembly systems, sometimes in conjunction with a pump.

Silicones offer critical advantages for tubing assemblies: they bring a long history of safety, purity from their low level of extractables and particulates, and biocompatibility in healthcare applications, documented with exhaustive testing. Silicone elastomer tubing can be used in a wide temperature range (from -80 to +215°C) because of silicone’s low glass transition temperature and thermal stability. Consequently, silicones are typically more suitable for autoclave sterilisation and also for low-temperature storage applications than most thermoplastic tubing. Flexibility, resilience, kink and pressure resistance are also major benefits of silicone elastomer tubing for pharma and biopharma processing.

Critical performance challenges for any tubing assembly include maintaining system integrity under pressure, after gamma irradiation and autoclaving, and minimising extractables and particulates. Optimising the assembly calls for a detailed understanding of silicone properties and performance. For example, preventing or minimising leakage caused by pressure at assembly connection points requires expertise in multiple areas, from understanding the performance of the polymeric material design parameters to testing and analysis.

Many pharma and biopharma companies, contract manufacturers and integrators, particularly those accustomed to using stainless steel equipment, may lack this detailed understanding. The best way to obtain such understanding is by partnering with your silicone supplier. Typically, a leading silicone manufacturer will be able to offer extensive material and application testing capabilities, global resources and specialised facilities to support its customers. Collaboration with the silicone manufacturer can benefit integrators and end users in multiple ways.

Partnering with the silicone supplier

Regulatory compliance

Global regulatory requirements are increasingly focused on the biocompatibility of materials that contact drug products or could potentially leach into them. End users and integrators need to know whether the single-use components contain any undesirable materials such as genetically modified organisms (GMOs), animal-derived ingredients, natural rubber, latex, organic impurities or phthalates. Dow Corning is a vertically integrated supplier that retains control over each process — from synthesising the silicone polymer and formulating the silicone elastomer to extruding and fabricating the components and delivering the tubing or subassembly. This company can help strengthen compliance with regulatory requirements. Its vertically integrated supply chain enables change control, reliability of supply, traceability and consistent quality.

Further, suppliers such as Dow Corning have the expertise and capabilities to test the effects of gamma irradiation and other sterilisation techniques on the level of extractables in silicone tubing and subassemblies. Although the silicone elastomers used for these applications typically should not contain plasticisers, stabilisers, ultraviolet (UV) absorbers or antioxidants, test results can provide valuable information to determine a product’s suitability for your application.

Performance optimisation

Silicone tubing and subassemblies are subjected to sterilisation before use, and to various temperatures and pressures during fluid transfer operations. Silicone manufacturers with extensive testing capabilities can conduct performance analyses of materials and components to evaluate the stability of key mechanical properties, such as tensile strength, modulus and elongation. They can test for pressure-induced changes in the diameter of silicone elastomer tubing following sterilisation and recommend the most suitable tubing type for the specific application.

Another valuable test that a silicone supplier can conduct is assessing the potential for subassembly leakage at connection points and bursting under high pressure. The testing results can then be related to factors such as wall thickness, inside diameter, formulation and type of connection. Material variables including durometer (Shore A hardness), crosslink density and reinforcing fillers can be adjusted by the supplier to meet specific pressure resistance needs. Similarly, tubing and subassemblies provided by the silicone manufacturer, changes in the tubing diameter, wall thickness, connection type and other parameters can be made to optimise performance.

Processing efficiency

The need to reduce project costs and time continues to be a primary driver for implementing single-use systems. Pharmaceutical companies that make the switch to single-use assemblies are looking for improved processing efficiency and productivity, including flexible capacity, fast changeovers and rapid production.

For example, silicone tubing can be altered, adjusted and customised more easily and quickly than stainless steel piping. This is particularly beneficial for contract manufacturing organisations (CMOs) as it allows them to change their processes more readily and safely compared to traditional methods.

To achieve these benefits, the end user requires the right tubing or subassemblies. When companies work with a supplier that can document the performance of the subassembly and its tubing under various test conditions, they can have greater confidence that the product will perform correctly and adhere to the users’ requirements. These tests include evaluation for leakage or bursting, pull-apart strength for assemblies, and pump life and filling accuracy for pump tubing, as well as measurement of extractables, particulates, bioburden and endotoxin for cleanliness.

Providing the solutions

When evaluating possible partners, a company that is vertically integrated can help ensure reliability of supply, traceability and quality control. Vertical integration begins with silicone production and proceeds through basic processing, polymerisation, finishing, testing and packaging.

You can count on consistent quality when your partner produces its materials for the global healthcare sector at a US Food and Drug Administration (FDA) registered clean manufacturing site subject to regular agency inspections, as well as when your partner’s facility adheres to the principles of current good manufacturing practices (cGMPs) as defined by FDA guidelines and is ISO 9001 compliant, thereby meeting stringent international quality standards set by the International Organization for Standardization.

Capabilities the company should provide include comprehensive testing throughout the manufacturing process, from incoming raw materials to final lots, such as chemical and material analysis/characterisation, regulatory compliance and application performance testing.

Conclusion

Single-use systems that use silicone tubing are quickly gaining in popularity for pharmaceutical and biopharmaceutical processing because of their financial and operational advantages over traditional processing with stainless steel. However, to gain the greatest benefits from single-use systems, integrators and manufacturers need to be sure that the silicone material and components they select will deliver consistent performance, high quality and regulatory compliance.

Because an understanding of silicone technology is often outside the core competency of most pharmaceutical manufacturers and integrators, it would be beneficial to work with a recognised supplier that offers extensive knowledge, capabilities and a track record of excellence in the healthcare field. With more than 70 years of experience in silicone technology and manufacturing, Dow Corning is a leading supplier of silicone materials, tubing and subassemblies for pharmaceutical processing, whose extensive knowledge and technical and regulatory resource can guide you as you adopt single-use systems featuring silicone components.

*Csilla Kollar is an Application Engineering and Technical Service Specialist at Dow Corning.

^Jennifer Gemo is Global Segment Leader for Bio-Pharma Processing at Dow Corning.

°Lise Tan-Sien-Hee is an Application Engineering and Technical Service Specialist at Dow Corning.

Image courtesy of Nicholas Lundgaard under CC BY-SA 2.0

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