Concentration and Diafiltration

Tangential flow filtration (TFF) is commonly used for concentration and diafiltration operations in a purification process.

Concentration is the unit operation where the feed volume is reduced and the species retained by the membrane increases in relative concentration.

Diafiltration is the convective elimination of permeable solutes passing to the permeate and the addition of fresh solvent to the retentate.

Membrane purification is a diafiltration operation where membrane filtration is used to separate complex protein mixtures, particularly in downstream processing of recombinant products.

Factors affecting membrane purification include:

  • Membrane pore size, selectivity, chemistry
  • Feed stream composition / purity
  • Buffer conditions: Ionic strength, pH, Composition
  • TFF operating conditions: trans-membrane pressure (TMP), cross-flow

The biotechnology industry immediately recognized the benefits of single-use products for their ability to provide significant savings in time, labor and capital. Furthermore, single-use disposables are considered to be a scalable technology, and this flexibility increases production while eliminating the need for Cleaning in Place (CIP) and product validation. Since sanitization steps are not required, the use of caustic chemicals and purified water is minimized or eliminated, also reducing the risk of cross contamination.   

Many intangible benefits are also realized, including reduced risk of cross-contamination, batch-to-batch reproducibility, and manufacturing flexibility.

The graph below demonstrates how total labor costs can be reduced by up to 50% due to reduction in prep time, and how one process run can be completed in one shift by using single-use TFF.

TangenX™ TFF Solutions

Repligen manufactures  two ultrafiltration membranes: ProStream™ and HyStream™. Both are modified Polyethersulfone (mPES) membranes validated for use in cGMP processes. The modification, achieved by the addition of a second polymer into the pre-casting membrane solution, ensures total and consistent surface modification.

Both ProStream and HyStream membranes are available in TangenX™ SIUS™ Single-use Cassettes and TangenX™ PRO  Reusable Cassettes. Standard disc formats and custom configurations may be die cut from sheet stock upon request.

TangenX membranes

TangenX™ SIUS™ Single-use TFF Cassettes

As the first purpose-built flat sheet cassettes for tangential flow filtration (TFF), TangenX™ SIUS™ cassettes deliver the performance of reusable cassettes with single-use convenience and at a fraction of the cost. 

TangenX™ SIUS™ Single-use TFF Cassettes

TangenX™ PRO Reusable TFF Cassettes 

These are flat sheet cassettes that may be cleaned and re-used multiple times while maintaining reproducible cassette performance. They are engineered with optimized channel geometry and enhanced device rigidity to ensure that hydraulic performance is maintained during processing and scale-up. 

•Equivalent performance, interchangeable with TangenX™ SIUS™ Single-use TFF Cassettes
•Scalable from bench to production scale
•Up to 30% filter cost reduction compared to other commercial reusable filters
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