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Development of a novel cold-chain tubing, FP-FLEX and single-use freezing bag

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Working cell banks (WCBs) are commonly applied to initiate cell culture manufacturing campaigns to produce therapeutic proteins.

Those campaigns typically begin with the inoculation of cells previously cryopreserved in vials. Although vials are typically used to establish WCBs and initiate manufacturing campaigns, they
are not optimal for the growing demands of commercial production.


Vials are small, and filling and removal of their contents are performed through an open cap. That process leads to numerous manual operations and culture vessels, resulting in contamination risks and potential campaign-to-campaign variability. Single-use bags would be ideal for WCB applications, but adoption has not been observed because currently available bags and tubing don’t hold up to the demands (e.g., they break and/or can’t be welded) when stored and transported at cryogenic (-196ºC) temperatures.


To overcome such challenges, novel thermoplastic tubing was developed to balance both the flexibility and robustness demands of cryogenic storage and tube welding characteristics necessary for sterile closed-system processing. The new FP-FLEX tubing can be frozen and maintained at cryogenic temperatures, thawed, and sterile welded to other thermoplastic tubing (such as C-Flex tubing).


Material and methods

Studies were designed and performed to assess durability and functional utility of the new FP-FLEX tubing for frozen storage and processing applications. A novel manufacturing method also was developed to enable unitised welding of FP-FLEX tubing directly to Freeze-Pak bags.


Handling and transportation testing

Testing was carried out using 500 mL bags with either FP-FLEX tubing or PVC tubing (standard). Bags were filled to 140 ml (±5 ml) with water, placed into storage cassettes and frozen in LN2 (-196ºC) with tubing attached. For the handling test bags were pulled from liquid nitrogen (LN2) storage, immediately dropped horizontally 4X from 1 ft., thawed and evaluated. Ten of 10 bags with FP-FLEX were completely intact, whereas 10 of 10 bags with PVC tubing were broken. A single drop from 2 ft resulted in similar results. For the transportation test, bags (in cassettes) were placed in LN2 shippers followed by simulated ASTM transportation testing. After testing, bags were removed, thawed, and evaluated for damage.

Welding/ Functional testing

20161231ep36To evaluate sterile welding capabilit ies of FP-FLEX tubing postthaw, tubing was frozen, thawed, and welded to C-Flex tubing. Testing included integrity, flow rate, and weld strength. Tubing was capable of welding directly to C-Flex tubing using standard sterile welders with flow rates up to 1L/min achieved successfully.


Freeze, Thaw, Weld: Making The Cold Chain Link WCBs are commonly used for seed-train manufacturing of therapeutic products. Traditional vials represent an open manufacturing process and are also limited to small volumes, which contribute to lengthened production campaigns. The new FP-FLEX tubing has been designed and shown herein to meet the critical processing requirements for WCBs, including:

  • Freezing/ storage/ transport to as low as -196ºC
  • Weldable to C-Flex postfreeze/ thaw
  • Compatible with standard tube welding and sealing devices
  • Closed-system aseptic transfer through tube-to-tube connection.

FP-FLEX tubing and Freeze-Pak Bag represent a closed-system solution, enabling frozen storage, sterile connection, and reduced scale-up time for therapeutic production.

Charter Medical have a 25 year history of developing and providing specialty single-use products to the blood transfusion, cell therapy, biotechnology and pharma markets. Their 15,000 sq ft of clean room space located in Winston-Salem, NC, USA is ISO 13485 certified and FDA registered. Focus is on designing and supplying single-use solutions for cell growth, frozen storage and biological fluid handling. Charter Medical is committed to providing quality products and services with and experienced staff dedicated to exceeding customer expectations from product development, delivery and implementation. Partnering with Shah Brothers, Charter Medical wishes to offer the latest path breaking products and customised single use solutions for the Indian market.

(This article has been authored by Dominic Clarke, Global Product Manager for Bioprocessing and Cellular Therapy. For any queries please write to [email protected])

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