Unit Operations
Ultrafiltration / Diafiltration
Used in nearly every biotherapeutic process, ultrafiltration/diafiltration (UF/DF) is a critical purification process, using tangential flow filtration (TFF), prior to final drug formulation.
What is Ultrafiltration–Diafiltration (UF/DF)?
Ultrafiltration (UF) and diafiltration (DF) are membrane-based separation techniques widely used in downstream bioprocessing to concentrate biologics and exchange them into formulation-appropriate buffers. Together, they form a critical unit operation for preparing therapeutic proteins, antibodies, viral vectors, and other large biomolecules for subsequent purification or final formulation.
Ultrafiltration (UF)
Ultrafiltration, sometimes referred to as concentration, uses a semi-permeable membrane with a specific molecular-weight cutoff (MWCO) to separate molecules based on size, shape, and, to a lesser extent, charge.
- Larger molecules are retained by the membrane (the retentate).
- Smaller molecules, such as salts, buffer components, and small impurities, pass through into the permeate.
UF is typically used to increase product concentration, reduce process volume, and remove low-molecular-weight contaminants. This step enhances downstream processing efficiency and prepares the product for buffer exchange.
Diafiltration (DF)
Diafiltration, often called buffer exchange, involves the controlled addition of fresh buffer to the retentate while ultrafiltration continues. As small molecules permeate the membrane and are replaced by clean buffer, the product is effectively washed into a new chemical environment.
DF enables:
- Desalting
- Removal of process-related impurities (e.g., imidazole, guanidine, ethanol, or residual reagents)
- Transfer into formulation or storage-stability buffers
Multiple diavolumes are typically applied to achieve the desired level of impurity clearance.
UF/DF as an Integrated Operation
UF and DF are frequently performed sequentially or in repeated cycles within downstream manufacturing. A typical workflow includes:
- UF to concentrate the biologic of interest to a workable volume.
- DF to exchange the buffer and remove unwanted small molecules.
- Optional UF to adjust the final concentration for storage, chromatography, or formulation.
As a result, UF/DF represents an essential purification and conditioning step in the development and manufacturing of biologics.
Comprehensive Solutions for Ultrafiltration Diafiltration (UF/DF) Processing
Streamline UF/DF operations from early research through GMP manufacturing with Repligen’s automated, scalable tangential flow filtration systems. Choose from a broad range of hollow fiber and flat sheet cassette filters in multiple chemistries, formats, and MWCOs to meet diverse purification needs. In-line process analytics enable real-time monitoring and control for improved consistency and product quality, while Repligen’s global field applications and engineering experts provide hands-on support to help streamline workflows, protect product integrity, and achieve optimal downstream purification performance.
KrosFlo® Tangential Flow Filtration (TFF) Systems comprise a broad range of platforms designed to address diverse ultrafiltration and diafiltration (UF/DF) requirements across research, process development and biomanufacturing. From flexible, benchtop configurations to fully automated production-scale systems, the KrosFlo portfolio enables tailored process control for concentration and buffer exchange.
Compatibility with multiple membrane formats, configurable flow paths, and support for advanced in-line analytics allow users to adapt system performance to meet evolving process needs. Together, these capabilities provide a scalable, reliable foundation for consistent UF/DF performance from early-stage research through GMP operations.
TangenX® SIUS® TFF Cassettes are purpose‑built, single‑use flat sheet filtration devices designed to deliver high‑performance ultrafiltration and diafiltration with significant reductions in labor, buffer usage, and operating costs.
Validated for GMP use and shipped pre‑sanitized, SIUS® cassettes eliminate cleaning and reconditioning steps while providing consistent, reproducible performance from process development through commercial manufacturing.
Available with ProStream® and HyStream™ membrane chemistries across a wide range of pore sizes, flow‑channel configurations, and surface areas, TangenX® SIUS® cassettes enable efficient scale‑up, compatibility with existing cassette holders, and reliable process transfer across development and production environments.
Ideal for concentration and diafiltration of shear‑sensitive modalities, Spectrum® Hollow Fiber Filter Modules are an industry standard in bioproduction with a wide range of molecular weight cut offs for ultrafiltration and microfiltration of your product.
Available in more than 1,400 configurations, these hollow fiber filters support processing volumes from milliliters to 1,000+ liters, enabling predictable scale‑up by increasing fiber count while maintaining constant path length.
Offered in a broad range of sizes, surface areas, and membrane chemistries, Spectrum filters are designed to optimize process performance and support plug‑and‑play integration, from small‑volume process development and R&D through commercial manufacturing.
Automate your UF/DF process with continuous concentration measurements and real-time process management control. Powered by process analytical technology (PAT), the PATsmart™ FlowVPX® spectrophotometer integrates seamlessly in-line and continuously analyzes your data during the filtration process, allowing you to consistently hit your targets every time.
Based on revolutionary variable pathlength technology (VPT), the FlowVPX System requires no off-line testing, baseline correction, or dilution, and alerts you to any deviations to keep your workflow running smoothly. With software features designed for GMP environments, customize your concentration and diafiltration start and end points with just a press of a button and keep your UF/DF process on track.
Explore our series of KrosFlo® Real-Time Process Management (RPM™) Systems, which combine the TFF technology of KrosFlo TFF Systems with FlowVPX process control in complete, out-of-the-box solutions and dedicated software for UF/DF processes of various scales.
Repligen eStore for UF/DF essentials and accessories
Know what you’re looking for? The Repligen eStore offers a variety of accessories, spare parts, and compatible components to support your unique UF/DF setup. Whether you need replacement modules, tubing assemblies, or connectors, the Repligen eStore makes sourcing essential items straightforward and efficient. Browse the catalog to find everything required to maintain and optimize your process.
Resources
Mixing homogeneity impact study on ultrafiltration diafiltration (UF/DF) performance
Discover the difference that good mixing can make on membrane performance during ultrafiltration diafiltration (UF/DF). Explore the impact of vessel design, mixing dynamics and methods of analysis to enhance diafiltration performance in this insightful study.
Comparability of In-line and At-line Variable Pathlength Technology for Concentration Monitoring in UF/DF Processes
Discover how the PATSmart™ FlowVPX® and SoloVPE® PLUS Systems are transforming ultrafiltration/diafiltration (UF/DF) processes through advanced Variable Pathlength Technology (VPT). This white paper assesses the performance of these platforms, highlighting their real-time monitoring capabilities, increased accuracy, and scalability for monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs).
Tangential Flow Filtration: A Complete Guide for Bioprocessing Professionals
Discover the fundamentals and best practices of tangential flow filtration (TFF) in this comprehensive guide from Repligen. Explore how TFF enables concentration, diafiltration, and buffer exchange across key modalities — including mAbs, mRNA, viral vectors, and pDNA. Learn how to select the right membrane format, optimize transmembrane pressure and crossflow flux while evaluating automated TFF systems for your process development or manufacturing needs.
