Thomas Paust is global director of marketing at Sartorius Stedim Biotech GmbH in Goettingen, Germany.

Thomas Paust

For the past decade, the development and approval of biological drugs has increased rapidly. This increase highlights the significance of aseptic processing because biologics commonly cannot be heat sterilized. Because aseptic processing receives greater regulatory scrutiny than heat sterilization does, the industry developed, in addition to risk-management and risk-analysis activities, new processing equipment and technologies to overcome potential weaknesses (1). These technologies' main purpose was the avoidance of human intervention, which is one of the most substantial risks in aseptic processing. The technologies included environmental-containment solutions such as isolators and restricted-access barrier systems, and new filling strategies such as blow–fill–seal. Disposable solutions have changed, and their applications have broadened, during the past several years. 

The most far-reaching changes in the technology's early days affected processing equipment, which gradually was converted into single-use equipment (2). The benefits of single-use equipment not only enable a potentially higher sterility-assurance level within process steps than was possible before, but also enable production-utilization enhancements, cost savings, and end-user protection. Single-use equipment does not require setup times of 8–10 h or copious amounts of water for cleaning purposes (3). Furthermore, it protects end users from contact with potentially hazardous fluids. This article will focus on recent advances in single-use technologies. 

The first disposable process parts to be used were tubing sets. They were followed by filtration devices called capsule filters. Capsule filters were only available in small effective-filtration-area units, commonly between 0.5 and 2 ft

. The introduction of single-use components for mixing and fluid containment required larger filter capsules, and end users requested small-scale pleated devices for scaling studies. These two factors led the filter-capsule range to be expanded to an area of 0.1 to 30 ft

 (4–6). Current filter capsules are gamma-sterilizable and commonly connected to tubing sets or bag assemblies (see Figure 1).  

Figure 1 (IMAGES ARE COURTESY OF THE AUTHORS) 

Single-use technology for mixing and holding tanks also emerged (e.g., single-use bag devices). Single-use bags are available in volumes of 20 to 3000 L and can replace glass vessels, carboys, and stainless-steel tanks. Before single-use bags could be introduced into the production process, they needed to demonstrate mechanical stability, chemical resistance, a barrier to oxygen transfer, and low leachable levels, even when the bags were gamma sterilized at 50 kGy. New polymeric films laminated onto each other made these characteristics possible and have become common (see Figure 2).  

Single-use bags are used most often in an assembly format, either with or without a filter, as part of a multibag system. The entire assembly is gamma irradiated in the packaging and is ready to use. 

Single-use systems, though, are not restricted to bags and filters. Various equipment components are available that can be combined into a single-use system or process step. Such equipment components include the following:  

Mixing systems of various designs and volumes

Sensors (e.g., for dissolved oxygen, pH, and conductivity)

Sterile fluid-transfer connectors and tubing

Bioreactors of different designs, volumes, and agitation technologies) 

Aseptic-transfer systems for fluids and solids 

Membrane-chromatography (e.g., ion exchange) columns (7, 8)

Viral-clearance and ultraviolet-inactivation filters.

At first, single-use components were designed to be connected to a traditional unit operation. The newest advance in technology combines single-use components into a single-use unit operation. One day, these unit operations likely will be connected together to form a single-use process (see Figure 3).  

Single-use unit operations currently are available for buffer and media preparations, ultra- and diafiltration, virus filtration, and bioreactors. Other process steps will follow soon, and low-volume streams inevitably will be processed within single-use designs in the near future. Large volumes probably will still need to be processed in hybrid solutions, which connect reusable and single-use process steps.  

New disposable sensor technologies will ensure that process analytical technology needs are not neglected. Radio-frequency identification tags will enable the end user to connect systems safely and track systems during inventory-management or transfer activities. 

Limitations such as mechanical instability at large volumes and cost factors within affinity chromatography will restrict the development of single-use processes (see Figure 4). Despite these limitations, the advantages of reduced setup times, the elimination of cleaning activities, and end-user protection justify converting even a small number of process steps to single-use technologies. Eliminating end-user intervention with presterilized, interconnected unit operations potentially can enhance safety within aseptic processing. Single-use technology inevitably will be an essential component within biopharmaceutical processes, even if the majority of components in a process is not single-use.  

The validation requirements for a single-use aseptic process are the same as those for a traditional stainless-steel process. Because single-use systems are preassembled and presterilized by the vendor, the validation work requires a high level of vendor involvement. The end user works closely with the vendor to determine the specific validation and qualification parameters and activities needed to ensure the expected product performance for a given application. The vendor, therefore, must have an in-depth understanding of current regulatory requirements and good manufacturing practices. Moreover, the vendor must be able to adjust to the end user's needs. Every application and process stage has different specifications and critical aspects. These differences must be taken into consideration to avoid working too much or too little to satisfy validation requirements. 

Most single-use systems are gamma-irradiated at 25–50 kGy. The irradiation sterilization makes short- and long-term stability studies necessary to evaluate potential polymeric degradation, which could raise leachable levels or lower mechanical resistance. Irradiation commonly reduces the shelf life of polymeric devices, and personnel must determine the radiation limit that a given device can withstand. Qualification tests, defined by the vendor, are performed before any single-use unit or system is distributed to the industry. These qualification tests are manifold and are designed to meet regulatory requirements (see Table I). The end user can rely on the results of the vendor's qualification tests, but should consider process-specific validation requirements.  

Table I: Common qualification tests performed by single-use equipment vendors. 

Process-validation studies would, for example, use a model solvent and simulate the process parameters within the end user's specifications. Leachable testing cannot always be performed with the product because the product would mask potential peaks. For this reason, model solvents that are similar to the solvent used within the product stream often are chosen. The possible influence of the environmental conditions within the end user's processes should be tested, however, to ensure that the disposable device performs to specifications. Process-validation steps vary according to disposable devices' purposes. Sterilizing-grade filters must undergo a product bacteria-challenge test under end users' process conditions. The influence of the process conditions and fluid on the challenge organisms or separation mechanisms should be determined. Product hold bags or mixing bags do not have to undergo bacteria-challenge tests, but possibly bacteria-ingress tests. Both filter and bag systems must be tested for leachables and extractables. As mentioned previously, the end user should request the vendor's assistance. 

Many single-use devices already are available, most commonly as individual entities. More and more filter–bag and bioreactor–filter systems have been introduced, and single-use unit operations recently have become available. Components' rapidly developing connectivity will enhance the development of integrated systems and, potentially, totally disposable processes. Some limitations, especially in the filling area still must be overcome (e.g., fill precision). The last step in aseptic processing has not reached the level of disposability that one finds in the intermediate steps.  

Single-use components have many benefits within aseptic processes. For example, cleaning deficiencies are a common regulatory observation that would be eliminated by single-use equipment. The equipment also greatly reduces the risk of cross contamination. Moreover, disposable, aseptic connectivity will reduce end-user manipulation within the process and therefore improve safety. Some in the industry have wondered whether the benefits of single-use systems are outweighed by their environmental impact. Further studies and thorough evaluations, however, might show that the environmental impact of cleaning and sterilizing stainless-steel equipment is greater than that of single-use systems. This topic will likely be addressed in the near future. 

 is vice-president of marketing FT/FRT, and 

 is global director of marketing IS, both at Sartorius Stedim North America, 5 Orville Dr., Bohemia, NY 11716, tel. 631.254.4249, 

. Jornitz also is chair of the Parenteral Drug Association.  

*To whom all correspondence should be addressed. 

Concerning Medicinal Products for Human and Veterinary Use,

 Vol. 4, Annex 1, p. 12 (European Union, Brussels, 2008). 

 2. P.M. Priebe, PDA SciTech Conference (Orlando, FL, 2004). 

 5. PDA, "Liquid Sterilizing Filtration," Technical Report 26 (Parenteral Drug Association, Bethesda, MD, 2008). 

Articles

The authors describe the origins of single-use components and explain their application to aseptic processes. They also show how disposable devices have changed over time and offer a glimpse of the future.

The Evolution of Single-Use Technologies in Aseptic Processing

 Patent expirations, stiff competition, plant utilization, product safety, and supply assurance are some of the challenges facing the biopharmaceutical industry. The manufacturing landscape has changed dramatically during the past several years—and it's still evolving.    

 Figure 1: Single-use cell culture system. (ALL FIGURES ARE COURTESY OF THE AUTHORS) 

Novel approaches for treating specific diseases such as cancer are very promising. However, the days of biotechnology innovations being measured purely on gaining blockuster status (i.e., reaching more than $1 billion in revenues) are largely gone. The capacity constraints predicted in the late 1990s, combined with insufficient development pipelines and tougher regulations, caused a major market consolidation, evidenced by acquisitions, alliances, and outsourcing.  

Similar to what the semiconductor industry already experienced, drug manufacturers face a changing environment that requires innovation and efficiency. They must manufacture products economically and efficiently while also improving quality and safety. Understanding cost drivers within the manufacturing and development processes is key to assessing the impact of new business models and technologies.  

The costs associated with constructing and operating manufacturing capacities as applied to clinical phases and large-scale manufacturing call for challenging current paradigms. Single-use technologies represent one option to achieve operational excellence without compromising quality.  

Single-use technologies are being used more in biopharmaceutical manufacturing and that use is expected to increase substantially in the coming years. With the further penetration of disposables into larger volumes and more critical areas of the biomanufacturing process, however, companies involved in biopharmaceutical development and the production of new molecules must closely examine the advantages, limitations, and facility implications of single-use manufacturing scenarios.  

The challenge is to design and implement application-specific, integrated-process solutions that follow the same principles as conventional process designs regarding quality, engineering, automation, and control. Single-use technologies are not an "one-size-fits-all" solution. They must be intelligently integrated into process designs.  

Process analytical technologies (PAT) and quality by design (QbD) are major initiatives in the industry that will influence the future technology penetration significantly. It's important to examine additional improvement opportunities offered by the increased implementation of single-use solutions to exploit advantages. Production facilities, traditionally, were built to house stainless steel-based production scenarios. Does this mean that new facilities are required to be built the same way? What about cleanroom classifications to operate individual process units? Single-use solutions are presterilized, closed systems that can reduce, if not eliminate the need for extensive cleaning and steaming utilities. Aseptic-processing requirements that benefit from single-use solutions through the reduction of cross-contamination successfully support the shift to multipurpose manufacturing designs and concepts. One might think that disposing such solutions adversely affects carbon-footprint evaluation. However, there is no standardized approach to such calculations and studies published in the past two years demonstrate that the opposite is true. The authors contend that understanding the advantages provided by single-use technologies, mitigating the limitations, and exploring new opportunities is the most-appropriate approach for operational excellence.  

The "single-use" concept came loaded with huge expectations of finding new solutions to address the needs of the changing biopharmaceutical industry. Suppliers of single-use equipment have had difficulty living up to these expectations thus far, partly because the expectations were not properly defined and partly due to intellectual property (IP) and supply-chain issues. 

In a hard-piped manufacturing process, the bioprocessing flow path is only qualified once. With single-use technology, a new flow path might be supplied various times, especially in multipurpose scenarios, and the qualification of the new flow's components is often in the hands of the supplier. The supplier is urged to provide disposable flow paths using the same components and properties for years to come.  

Figure 3: Water-consumption percentage differences: Stainless steel versus single-use equipment (Data from Ref. 9).  

To meet this request, however, the supplier must own all of the critical pieces of a particular assembly. For this reason, many suppliers are aligning with, or acquiring, component suppliers and IP owners. Unfortunately, a lack of standards and competition in this arena has promoted a vast array of equipment items, assemblies, and validation-procedure differences. These varieties, marketing-driven product and validation claims cause more insecurities and questions, than solid standardized solutions. 

Promising new development, in the form of single-use unit operations, is moving away from isolated technical solutions and toward new, highly-integrated concepts. End-users of disposable bags for media initiated this trend in an effort to move from a fixed process to a single-use process that includes mixing, filtration, temperature, recipe, and level control.  

The integration of disposable sensors helped develop fully-disposable, cell-culture systems and opened the door for single-use applications for most of the unit operations within a manufacturing process. New approaches are supplying single-use technology platforms along the typical manufacturing process. 

The application know-how determines the design of those platforms, but standardization of components such as tubing and connectors, ensures interconnectivity at the same time. These concepts allow a clean and streamlined process with a unified automation, control, and validation concept and, finally, a high level of operational excellence and security.  

The single-use approach demands the highest level of technology integration possible. However, the economic and operational advantages of the disposable option apply mostly to Green Field Facilities (i.e., facilities planned from scratch) with high-value, low-volume products and might not be an option for existing manufacturing processes. This restriction to new facility design is a purely economical one as most of the capital investments within existing processes are made and the equipment is written off. Nevertheless, the flexibility of single-use manufacturing philosophy is attractive for expansion projects within existing facilities. In addition, so-called "hybrid" systems merge the best out of both worlds by integrating single-use unit operations such as buffer and media-hold steps, into existing production facilities.  

Single-use equipment and its support of QbD

QbD has found success within pharmaceutical processes and gained momentum in the production of biologics (2). Knowing the quality attributes and properties of a product creates the opportunity to design quality into the process with process analytical technology (PAT) tools. The very well-known saying, "to design quality into a process instead of testing it in" and Janet Woodcock's statement, "a maximally efficient, agile, flexible pharmaceutical-manufacturing sector that reliably produces high-quality drug products without extensive regulatory oversight" (10) are very much supported by single-use technologies, especially interconnected unit operations.   

Once the critical quality attributes are known, process-development activities can include small-scale, single-use process steps to evaluate the reliability of the equipment and its potential effect on the product. Furthermore, single-use sensor technologies can be deployed to allow for process controls, creating a dependable and robust output. Such small-scale systems, however, must be scalable to avoid surprises in process scale.  

It is, therefore, important for single-use vendors to supply a scaling-basis system supported by various single-use sensor technologies and appropriate qualification documentation. The benefits of single-use unit operations include less human intervention and fewer possible set-up failures. The process step is assembled and ready-to-use coming as soon as it comes out of the package. The assembly is fitted into the supporting hardware systems, which is simpler than disassembling a process step, cleaning the components, assemblying the components, and sterilizing the system before moving to point-of-use (POU).  

Single-use process steps are unfolded at POU and interconnected aseptically by validated-connection systems. Any designs within a hardware system might be complex to disassemble, clean, and then reassemble. An interconnected single-use operation is less complex because the end-user does not have to assemble multiple components. Such design benefits and ever-advancing, single-use sensor technologies create opportunities to support QbD initiatives with PAT.  

A PAT approach must take into account any out-of-specification situation within a process step. Sensor technologies in single-use format include pressure, pH, conductivity, dissolved oxygen, and temperature sensors (7). However, more needs to be done within the sensor-technology field. The qualification documentation, which commonly goes together with any single-use components or assemblies, can be used to determine any obstacles to critical quality attributes and potential influences on product quality. Vendors of single-use technologies have a thorough understanding of their raw material, finished goods, and assemblies. Furthermore, they support validation requirements with their service organization. End-user process-development resources should exploit service support opportunities by vendors to establish appropriate qualification and validation activities. 

Biopharmaceutical manufacturing typically involves numerous process steps. The sequence, number, or size os steps differs by application and individual bioprocesses (8). To reduce the time and engineering effort required during the design and construction of production facilities, process platforms are increasingly used to define cost-effective solutions.  

Process platforms are well-defined sequences of processes or process steps, which enable progress in biopharmaceutical development and production as they expedite time-to-market. Significant benefits associated with process platforms include efficient-engineering workflows and more precise cost determinations and cost allocations, particularly in the early design phases. Furthermore, projects can be implemented faster and investment decisions can be postponed until the drug candidate shows positive results.The use of process platforms also offers potential for process optimization, implementation support of QbD initiatives, accelerated production start-ups, and improved supply security. 

The prerequisite is closed, preconfigured, single-use unit operations. These units serve as process platforms while supporting  bioprocess and user safety. By maintaining flexibility and allowing different configurations, process complexity is significantly reduced, which is often considered a key success factor by the end user.  

Several suppliers have already launched their first configurable disposable solutions or systems (CDS). These solutions address the different volume needs, within the development cycle to production-capacity needs for buffer or media preparation, from 50 to 1000 L. The integration of monitoring and control features for pH, pump-speed, and fluid-level control is an additional milestone in the development and implementation of process-relevant, single-use equipment. The integrated controls allow end users to perform other tasks during, for example, buffer-preparation operations.  

Whether a production facility is a retrofit or green field, the process and workflows must always be defined to assist in developing the facility layout. Logistics for material handling, segregation of critical steps, space requirements for work-in-progress and storage, plus provision of the utilities required for process and cleaning needs at every critical process step, must be fully specified. 

Finally, support spaces required and their interactions with the process path must be clearly defined (5). Employing single-use equipment generally requires more space to accommodate movement and handling. For this reason, horizontally-positioned production operations located on one floor, with sufficient space for material and personnel transfer, are the best layout for disposable-production facilities. Although this may require more floor space than production facilities which are installed vertically, this arrangement is recommended for bag-based transport and storage of raw materials, semi-finished, and finished products. 

Vertically arranged equipment (common in many current biopharmaceutical-production facilities) tends to be more cost-effective, due to the compact-building design possible and the resulting low ground-area footprint. However, in the conventional arrangement, where both medium and buffer preparation take place on the floor above the process suites, a vertically-designed, disposable production facility is at a disadvantage because transporting medium and buffer bags must be done over one floor or the fluid transport must be accomplished between different floors and, thus, involve piping. In the latter case, the potential advantages associated of storage and transporting media and buffers in disposable bags would be negated. 

Environmental impact of single-use technologies

More often, biopharmaceutical companies are confronted with the need of utility reduction, recycling, and effective waste treatment (3). Several studies have evaluated the impact of single-use technologies applied in biomanufacturing scenarios. Single-use based facilities have the ability to reduce the overall environmental impact despite the creation of solid plastic waste, as demonstrated in a case study that compared stainless steel-based facilities to single-use-based facilities (1). A cost-of-goods model presented an even higher economic efficiency for single-use-based facilities.   

Water, water-for-injection, and pharmaceutical-grade water are some of the largest cost and environmental contributors in stainless-steel plants. Clean-in-place (CIP) and steam-in-place (SIP) are major operating procedures in stainless-steel scenarios combined with a high consumption of energy, water, and chemicals. Implementing single-use technologies in these situations can reduce water usage between 50–80%, and energy consumption up to 30%, depending on the process and application (9). 

 Because single-use systems are presterilized, mobile, and considered closed systems, they can reduce space requirements and the need for large cleanroom floor space, which is a high-energy consumer. Aseptic-transfer ports separating higher-classified production areas from lower or nonclassified utility areas can easily be applied. Corresponding heating, ventilation, and air conditioning  costs could be decreased and high-level production areas could be reduced a well due to relocation of the respective process steps into lower-classified or nonclassified areas. 

Any discussion of the environmental impart of single-use technologies needs to consider that landfill and incineration are still the common method for plastic waste treatment, with energy savings realized through cogeneration techniques for the production of heat or electricity. Recycling of single-use assemblies is limited due to multilayer films of bags and different materials of additional single-use components (e.g., sensors, filters, connectors, and tubing).  

The overall carbon footprint balance between stainless-steel and single-use facilities has been described by Sinclair et al as approximately 25% in favor of single-use facilities (9). However, a thorough analysis of example processes is still pending. For this reason, vendors are still calculating and evaluating the environmental differences between the two setups.  

The biotechnology industry—like the pharmaceutical industry—has to continuously and rapidly reinvent itself. The patent-expiration cliff, increasing competition, and decreasing development pipelines pose indisputable threats. Single-use technology can help reduce this burden. The technology has already improved specific process steps (e.g., buffer and media prep and hold) and new trends in standardized, single-use unit operations promise even more cost reductions and enhanced product safety. 

Although single-use technologies are not a silver bullet, they do open the door to new, innovative process and facility designs. Initiatives such as QbD and PAT are supported by closed, single-use systems and might accelerate their implementation. The environmental aspect also bodes well for single-use technologies. 

With single-use unit operations surfacing, a complete, single-use process might not be far-fetched for the biopharmaceutical-manufacturing industry, certainly not for development processes with lower volume needs. The future for such processes appears bright and innovative. 

 is global program manager of FlexACT,and 

 is director of sales and marketing for Europe/Asia, all at Sartorius Stedim Biotech GmbH in Goettingen, Germany. 

 is global director of sales engineering at Sartorius Stedim Systems GmbH in Melsungen, Germany, and 

 is vice-president of marketing FT/FRT, at Sartorius Stedim North America, 5 Orville Dr., Bohemia, NY 11949. 

To whom all correspondence should be addressed. 

 1.  E. Cronin and et al., "Sustainability Single Use Technologies, Environmental Impact and Waste Management," presentation, 

www.pharmamanufacturing.com/articles/2006/163.html

http://americanpharmaceuticalreview.com/ViewArticle.aspx?ContentID=48

Harmonized Tripartite Guideline on Pharmaceutical Development

 5.  C. Jimenez-Gonzalez and et al., "An Executive Guide to Pharmaceutical Manufacturing Efficiency and the Effect of Environmental Legislation," (Rockwell Automation, SSB-WP001A-EN-E  December 2009). 

The authors propose increased use of single-use technologies in biopharmaceutical manufacturing to achieve operational excellence without compromising product quality.