Single-use technologies (SUTs) are transforming downstream processing (DSP) in biopharmaceutical manufacturing. By replacing fixed stainless steel equipment with pre-sterilized, disposable systems, facilities gain agility, reduce contamination risks, and accelerate product changeovers. These benefits are particularly valuable in multi-product facilities, gene therapy, personalized medicine, and vaccine manufacturing.
At the heart of this transformation is real-time, in-line monitoring of analytical and physical parameters. From harvest to fill/finish, embedding pre-calibrated, gamma-sterilized sensors for parameters such as pressure, UV absorbance, conductivity, pH, temperature, turbidity, and flow enables operators to make data-driven decisions that protect yield, quality, and compliance.
The type of modality influences the strategy for downstream processing (DSP). Monoclonal antibodies (mAbs), viral vectors, mRNA vaccines, and cell therapies differ in their properties, impurity profiles, and sensitivity to processing, requiring tailored approaches. mAbs often use a platform process with Protein A chromatography, viral vectors require gentle clarification and specialized polishing to preserve infectivity, and cell therapies demand minimal mechanical stress to maintain viability.
Regardless of the modality, continuous monitoring and consistent control of analytical and physical parameters are essential.
Single-use in-line sensors enable real-time measurement of these parameters, supporting better process control and automation, minimizing off-line testing, and ensuring product quality across diverse DSP workflows.
Both the EMA and FDA accept single-use systems provided they operate under a validated, risk-based control strategy.
Key references include:
Viral safety – ICH Q5A(R2) (2024), EMA “Viral Safety of Biotechnological Products” guidance
Product specifications – ICH Q6B
Aseptic manufacturing – EU GMP Annex 1, FDA aseptic processing guidance
Process validation – FDA Process Validation Guidance (Stage 1–3), EU GMP Annex 15
Data integrity – 21 CFR Part 11, EU GMP Annex 11
Advanced SUTs combine flexibility with robust process performance. For example, gamma-sterilized in-line pH/temperature combination sensors rated for pH 1–13 allow accurate, real-time monitoring during low-pH viral inactivation.
These sensors provide evidence of control strategy effectiveness, enabling rapid responses to process deviations while meeting FDA and EMA expectations for data integrity and process monitoring.
Downstream processing purifies biologics after upstream cell culture or fermentation by isolating the target molecule and removing host cell proteins, DNA, aggregates, viruses, and other impurities. Modern single-use DSP systems use disposable components such as sterile bags, filters, tubing, and pre-packed chromatography columns to improve efficiency, minimize cleaning and validation requirements, and reduce the risk of contamination.
Building on this approach, single-use in-line sensors provide real-time continuous monitoring of critical process parameters, enabling tighter control, faster data-driven decisions, and consistent product quality throughout the DSP workflow.
Steps | Purpose | Key In-Line Measurements |
Harvest | Removes cells and debris using depth filtration or single-use centrifugation. | Pressure, turbidity, conductivity |
Capture Chromatography | Primary purification often employs Protein A for mAbs. | UV absorbance, pH, pressure, flow |
Intermediate and Polishing Chromatography | Removes process- and product-related impurities. | UV absorbance, conductivity, pH, pressure |
Viral Clearance | Inactivates or removes viruses via low pH, detergent treatment, or nanofiltration. | pH, temperature, pressure, flow, UV absorbance |
Ultrafiltration/Diafiltration (UF/DF) | Concentrates the product and performs buffer exchange. | Pressure, conductivity, temperature, UV absorbance, pH |
Formulation | Adjusts pH, concentration, and adds excipients to ensure stability and therapeutic activity. | pH, conductivity, osmolality |
Sterile Filtration | Final 0.22 µm filtration step to remove particulates and bioburden. | Pressure, flow |
Fill/Finish and Storage | Final drug substance is filled into containers and stored under appropriate conditions. | Weight/volume sensors, temperature |
Source: “Integrating Continuous and Single-Use Methods to Establish a New Downstream Processing Platform for Monoclonal Antibodies.” Continuous Processing in Pharmaceutical Manufacturing, January 2015.
Harvest is the first decisive step in downstream processing, separating cells and debris from the bioreactor to obtain a clarified, cell-free supernatant. This step is typically achieved using depth filtration or single-use centrifugation, with careful control to prevent shear damage and avoid filter clogging that can reduce yield or compromise quality.
Real-time monitoring of turbidity detects particulate breakthrough or incomplete clarification, while pressure identifies filter clogging or blockage. Conductivity confirms correct buffer composition and detects cross-contamination. Trending turbidity (NTU) and pressure slope across runs enables timely filter changes before breakthrough, protecting product integrity and process performance. These controls align with 21 CFR 211.113(b) on microbiological contamination control and EU GMP Annex 2 requirements for bioburden and impurity removal.
Capture chromatography is the primary purification stage, selectively binding the target molecule, such as monoclonal antibodies, from a complex mixture using affinity resins (e.g., Protein A) or ion-exchange media. Harsh elution conditions, such as low pH, can cause aggregation, while column overloading can impact yield and purity. In-line monitoring of UV absorbance (280 nm) confirms target molecule concentration and detects product breakthrough, pH ensures binding/elution conditions are maintained, conductivity verifies buffer accuracy, and column pressure identifies fouling or over-compression. Flow rate monitoring prevents pump-related deviations. Trending these measurements across cycles provides early detection of fouling, insight into resin performance, and evidence of process consistency. The on-line monitoring of these parameters provides documented compliance with validated profiles and aligns with the FDA’s Process Validation Guidance, as well as ICH Q8/Q9 for control strategy design.
Trending these measurements across cycles provides early detection of fouling, insight into resin performance, and evidence of process consistency. The on-line monitoring of these parameters provides documented compliance with validated profiles and aligns with the FDA’s Process Validation Guidance, as well as ICH Q8/Q9 for control strategy design.
Intermediate and polishing chromatography further enhance product purity by removing process-related and product-related impurities, including HCP, DNA, aggregates, and charge variants.
Common approaches include ion-exchange (IEX), hydrophobic interaction chromatography (HIC), and mixed-mode chromatography. Performance may be affected by suboptimal buffer conditions or column fouling that reduces resolution. Continuous monitoring of conductivity detects buffer composition errors, pH deviations can affect separation selectivity, pressure identifies column fouling, and dual-wavelength UV (260/280 nm) tracks impurity clearance and product recovery.
This data facilitates buffer adjustments and supports predictive maintenance. Monitoring these parameters over time optimizes buffer usage and helps ensure each cycle meets predefined clearance targets, thus reducing reliance on off-line analysis and improving overall process efficiency. These parameters align with risk-based process control principles of ICH Q8 and Q9. Buffer systems should be qualified and stored under controlled conditions for reproducibility.
Viral clearance safeguards patient safety by removing or inactivating adventitious and endogenous viruses. Common strategies include low-pH holds, detergent treatments, and virus-retentive nanofiltration. Risks include aggregation from prolonged low-pH exposure or product alterations from residual detergents.
Real-time monitoring of pH ensures viral inactivation conditions, temperature protects clearance efficiency, pressure detects filter blockage, and flow confirms stable filtration rates. UV absorbance can reveal product loss or breakthrough during nanofiltration. In-line pressure monitoring is critical for verifying filter integrity and avoiding log reduction value (LRV) failures. Trending these parameters across runs supports predictive maintenance, confirms compliance with pH/time specifications, and provides documented evidence for meeting validated LRV targets.
Ultrafiltration and diafiltration (UF/DF) prepare the biologic for formulation by concentrating the product and exchanging buffers via tangential flow filtration (TFF). These steps adjust volume and composition while preserving stability. Risks include shear-induced denaturation and incomplete buffer exchange.
Real-time monitoring of transmembrane pressure (TMP) identifies membrane fouling, UV absorbance tracks concentration, pH, and permeate conductivity confirm complete buffer exchange. Deviations can indicate pump malfunction, membrane degradation, or incorrect endpoint determination. Trending TMP and other parameters across runs supports membrane health tracking, predictive maintenance, and consistent cycle performance.
Formulation buffers and stabilizes the final drug substance to preserve long-term potency and efficacy. This often involves pH adjustment and addition of excipients such as sugars, surfactants, or stabilizers. Incorrect excipient levels or buffer composition can lead to instability, precipitation, or container incompatibility.
Continuous monitoring of pH ensures stability, conductivity confirms correct buffer composition, and osmolality verifies excipient levels. Incorrect osmolality can cause product instability or reduced efficacy. Trending these parameters during production provides early confirmation of process consistency and reduces the risk of deviations. Release decisions are based on verified formulation specifications and excipient quality against USP–NF or Ph. Eur. monographs. Best practice includes using pre-qualified excipient lots, verifying container compatibility, and conducting stability studies under ICH guidelines to confirm shelf-life robustness.
Sterile filtration is the final sterilization step before fill/finish, typically using a 0.22 µm filter to remove microorganisms and particulates. Key risks include product loss due to adsorption or filter failure. Real-time monitoring of pressure detects filter fouling or integrity loss, and flow confirms unobstructed processing.
Deviations may indicate imminent filter failure or a breach in sterility assurance. Thus, the data trend can help confirm filter performance and compliance with EU GMP Annex 1 and FDA aseptic processing guidance. Decision-making relies on successful integrity tests and achieving the required sterility assurance level (SAL). In-process controls, such as particulate and bioburden testing, offer early quality confirmation, supporting confident and timely batch release.
Fill/finish and storage finalize the process, with the biologic aseptically filled into vials, syringes, or bags and stored under controlled conditions to preserve sterility and stability.
Risks include fill-volume inaccuracy, closure failures, and temperature excursions. In-line weight/volume verification prevents underfill/overfill non-compliance, and temperature monitoring ensures storage conditions remain within validated limits to maintain potency and stability.
METTLER TOLEDO Pendotech offers pre-sterilized, single-use sensors and monitoring solutions that bring precision and efficiency to downstream processing (DSP).
These pre-calibrated pressure, flow, UV, conductivity, pH, temperature, and turbidity sensors capture real-time, GMP-compliant data across filtration, chromatography, UF/DF, and formulation processes without the delays of cleaning validation.
Seamlessly integrated into closed, sterile systems, these low-volume sensors accelerate tech transfer, shorten changeovers, and strengthen process control. Electronic batch record–ready data complies with 21 CFR Part 11 and Annex 11, aligning seamlessly with the FDA’s Process Validation Guidance (Stage 3). This compliance framework enables data-driven operations, ensures consistent product quality, and gives manufacturers the confidence to scale in fast-moving, multi-product environments.
This video explores the key decision between reusable and single-use sensors in biomanufacturing, focusing on how this choice affects efficiency, flexibility, and regulatory compliance. Whether in large-scale or modular setups, understanding the pros and cons of each sensor type is essential for achieving robust and efficient production.
