Freeze Bulk Bags: A Case Study in Disposables Implementation - Genentech's evaluation of single-use technologies for bulk freeze-thaw, storage, and transportation. - BioPharm International


Freeze Bulk Bags: A Case Study in Disposables Implementation
Genentech's evaluation of single-use technologies for bulk freeze-thaw, storage, and transportation.

BioPharm International Supplements

Nalgene Nunc's bag management system
As with stainless steel, disposable bulk containers do have their own set of drawbacks. For example, BPCs and flexible tubing usually cannot handle more than a few psi of pressure. Temperature limits are also an important detail to consider when companies are looking for disposable systems or parts. Most disposable systems are validated for operation at standard biopharmaceutical temperatures, but some BPCs or their connectors and tubing may need additional validation for storage at low temperatures. For example, certain biotech raw materials such as media or cell lines must be stored at –80 C, so it is necessary that commercial manufacturing facilities validate all single-use technologies to ensure compliance with these and other specific temperature regulations. Although it can be argued that stainless steel vessels are better than single-use systems because they do not have temperature limits, stainless steel vessels often contain gaskets and elastomers that have different heating and cooling properties, which can cause leaks and sterility problems.

Operational and Functional Testing

Manufacturers of bulk shipping containers typically put their products through three different types of functional testing:

  • shipping and transportation
  • drop
  • handling.

Shipping and transportation testing includes packaging bioprocess containers into a variety of shipping and support containers either individually or in groups depending on the type of unit being tested. Frequently, the units are filled with water or some equal buffer substance at the nominal volume of the container before package testing. The units then undergo trials of shock and vibration tests to simulate conditions stipulated by the International Safe Transit Association.2 Next, a BPC endures individual drop testing to assess the durability of the unit without the exterior packaging. In this test, units are dropped from a height of one meter onto a hard concrete surface to simulate the worst-case scenario drop that might occur in normal shipping operations. Finally, handling tests ensure that the BPCs are operational from the beginning until the end of the manufacturing process. The units go through a cycle process several times for at least 48 h, in which they are frozen horizontally at –85 C, and then incubated at +60 C.

Mechanical Properties of Film

Along with functional testing, all BPCs must also undergo specific tests to ensure the compatibility and robustness of the films that will hold the bulk product. Among the specific properties that films are tested for and required to possess include (but are not limited to):

  • tensile properties
  • toughness
  • elasticity
  • puncture resistance
  • tear resistance
  • flex durability.

Tensile properties describe the ability of a film to stretch when stressed to its limit. A tensile test is described as the process of elongating a film sample and measuring the strength that results. The moment the film or object breaks is when elongation is recorded. This number is often recorded as the percent of film elongated compared to its original length. When a specimen has a high elongation at break, it can endure a large amount of deformation before breaking and is considered a highly flexible film.

A material's ability not to fracture when stressed is measured as a film's toughness. This describes a film's maximum absorption of energy before the film rips. Toughness is calculated by finding the area underneath a stress–strain curve, but toughness and strength do not necessarily mean the same thing. For example, a brittle film material would be one that is strong but not tough.

The elasticity of a film is measured by Young's Modulus (also known as an elastic or secant modulus). The more rigid a material is, the higher the elastic modulus is said to be. If the modulus is lower, then the film material is more flexible and easier to mold. This elastic modulus can be calculated by determining the slope of the line on a stress–strain curve from the origin of the graph to the strain is held constant at a value of 2%. This provides an estimate for the rigidity or flexibility of a material.3

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