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Dear Readers, Welcome to the latest issue of Mi
Single-use systems (SUS) play an essential role in the biopharmaceutical industry for the storage, transport, mixing and processing of buffers, media and other process intermediates. The films used in SUS play a critical role in the protection of process fluids, the integrity of the containers and the quality of the final product.
The selection of the right film requires an integrated assessment of the transmission of water vapor and oxygen, mechanical strength, chemical compatibility, resistance to steam and sterilization, and E&L.
The objective of this article is to propose a methodology for the selection of films and to demonstrate the need for a collaborative approach between film manufacturers and SUS system manufacturers.
Single-use bioprocess containers are engineered systems, not simple systems like flexible containers. The life cycle performance of the container depends on the integral components of the system, including films, welds, ports, tubing, connectors, and other subsystems. A film can be stressed for a number of competing reasons.
It must provide the required level of barrier properties, be tough enough to withstand the stresses of material handling, support welding and fabrication, among other things.
For example, an increased level of barrier properties may make a film thinner and more susceptible to failure during handling. The film with the lowest transmission of oxygen, or the highest tensile strength may not be the best film for the application.
The right film is the one which best satisfies the requirements of the complete application.
The Oxygen Transmission Rate (OTR) is the measurement of the rate, in cm3/m2/day, that oxygen passes through a film. High levels of oxygen permeation can affect sensitive formulations and biologics. How much oxygen is required depends on the application.
In cell culture, oxygen is essential for aerobic growth, and in some applications, minimizing the oxygen permeation of the container may not be beneficial.
The permeation rates of polymers are affected by many things including, chemical functional groups, the mobility of the chains, the thickness of the film, and its crystallinity.
Temperature and other environmental conditions also play a role in the permeation of gases. Low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) films are used for applications that require a high level of flexibility, and toughness, however, they are not suited for applications that require very low oxygen barrier films.
EVOH can be used in conjunction with other polymer films to provide an improved oxygen barrier, however, other factors including humidity can also affect EVOH’s performance.
The rate of water vapour transmission (WVTR) is defined as the rate at which water vapour passes through a film, usually expressed in terms of mass of water vapour passing through a film of unit area in a given time.
Moisture loss can adversely affect the formulation stability and the performance of moisture sensitive products and therefore it is important to reduce WVTR of pharmaceutical packaging films.
The International Standards ASTM D3985 and ASTM F1249 describe methods for measurement of oxygen and water vapour transmission respectively. Results of these tests should only be compared when the relevant test conditions are the same.
The sensitivity of a fluid to oxygen and moisture is dependent on a number of factors including how long the fluid is stored, the temperature at which it is stored, and the ratio of the surface area to volume of the container.
In addition, the seals and ports of the container as well as other pathways for ingress may affect the sensitivity of a fluid to oxygen and moisture.
There are a number of reasons to prefer a multilayer film over a monolayer film. One of the reasons is that there is not a single polymer which is ideal for all the functions which may include optical, fluid and moisture barrier, oxygen barrier, low temperature flexibility, sealant layer and adhesive.
Each of these functions may be performed by different layers in a multilayer film.
There are certain risks introduced by a barrier layer which must be measured against acceptable limits.
For example a multilayer film must be assessed for delamination, chemical and processing stability as well as performance after the required sterilization cycle.
If EVOH or other barrier material is considered, assessment must be made on the effects of exposure to moisture on the barrier performance in the multilayer construct and its consequences on the system.
If a barrier film has a very low OTR, it may not be of good use if it cannot withstand the welding process or its chemical and characterisation profile doesn’t meet the requirements of the process. Therefore the idea is to achieve an optimal balance.
Ami Polymer has unique positioning with its film manufacturing unit, and understanding of barrier performance, to engineer bioprocess films aligned with the requirements of single-use system bag manufacturers.
With its advanced manufacturing capabilities and understanding of polymer performance, barrier performance, and process requirements, Ami Polymer is positioned to manufacture high performance films for the biopharma industry to meet the demands of single-use system bags.
When considering barrier film for processing fluids, different aspects must be taken into account including mechanical properties of the film, chemical aspects, moisture and oxygen transmission, and effects of sterilisation. OTR and WVTR values are helpful indicators but in themselves do not determine the suitability of a film for single use containers.
Chandan Sah General Manager – SUS Production Department
