The biopharmaceutical industry is currently shifting from reactive, offline quality control measures to a proactive quality by design (QbD) framework, facilitated by Process Analytical Technology (PAT). By employing rapid, non-destructive spectroscopy, manufacturers can monitor processes continuously, eliminating the delays associated with traditional episodic measurements in both upstream and downstream operations. This approach enables predictive, closed-loop control and prevents the yield losses and compromised cell health often caused by delayed insights into nutrient dynamics and purification decisions. A unified strategy combining Raman spectroscopy for bulk monitoring and Absorbance-Transmission Excitation-Emission Matrix (A-TEEM) for high-specificity characterization allows for an end-to-end PAT strategy that links process dynamics directly to product quality.
Read the article over at Genetic Engineering & Biotechnology News.
In upstream processing, Raman spectroscopy facilitates automated nutrient control. It achieves this by translating in situ spectral fingerprints of key metabolites into actionable concentration data using multivariate models.
While Raman is excellent for bulk monitoring, complex biologics require higher specificity. A-TEEM (Absorbance-Transmission Excitation-Emission Matrix) integrates absorbance, transmittance, and excitation-emission fluorescence into a single rapid measurement. This generates sensitive three-dimensional molecular fingerprints suitable for detailed molecular characterization across the bioprocess lifecycle.
A-TEEM overcomes the inner filter effect (IFE) inherent in concentrated samples by using absorbance data to mathematically correct fluorescence intensities. This correction linearizes the instrument response from ppb to mg/mL, allowing for the label-free quantification of components like aromatic amino acids and vitamins. Additionally, the technique is insensitive to common non-fluorescent process components like water and simple sugars, simplifying the analysis of complex media.
Because bioprocess samples generate overlapping signals, multivariate analysis is required.
A-TEEM provides a continuous, label-free method to track degradation and aggregation, which are critical quality attributes. For example, during thermal stress studies of monoclonal antibodies (mAbs), A-TEEM detected early chemical degradation via a red shift in tryptophan emission and a decrease in intensity, signaling the unfolding process. Later, it detected new spectral features representing oxidative degradants or aggregation.
Yes, A-TEEM is effective for characterizing Adeno-Associated Virus (AAV) vectors. It can quantify the full/empty capsid ratio rapidly and without labels because the packaged DNA payload in a full capsid acts as an internal quencher. Consequently, full capsids produce a lower protein signal compared to empty capsids, providing a vital metric for viral vector efficacy.
A-TEEM can monitor biological and chemical reaction dynamics, such as T-cell expansion or protein conjugation. In T-cell cultures, spectral shifts in the NAD(P)H region correlate directly with Total Viable Cell Count. Similarly, during conjugation reactions (e.g., CRM197 with polysaccharides), progress is tracked by observing the quenching of intrinsic protein fluorescence and the emergence of a new band characteristic of the covalent bond.
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