Assessing Biotherapeutics Stability using Raman Spectroscopy

Raman Analysis of lysozyme

Raman Analysis of lysozyme (200 mg/mL) in 20 mM Citrate-PBS buffer at pH 4.0 before and after the addition of 20 % ethanol. Sample was excited with a 532 nm laser and a grating of 1800 lines/mm on the XploRA, a 200mm focal length instrument.

For close to 20 years the pharmaceutical industry has been producing biotherapeutic drugs as they offer targeted drug efficacy with minimal side-effects. Responding to the need for self-administered drugs, protein-based therapeutics have to be delivered at high concentrations. However, the tendency for proteins to aggregate in solution is increased at these high levels (>100 mg/mL). As a result, the formation of aggregates can alter protein structure which can, in turn, influence the bioavailability of the drug, can induce immunogenic reactions, and can even cause thrombolytic events. We have measured solutions of lysozyme under conditions known to effect its physical state in order to investigate the potential of Raman spectroscopy as a non-invasive and label-free tool to assess protein formulation stability. Results from this study identified specific Raman signature bands in this protein that can be used to identify individual amino acid residues that are reflect structural changes in proteins.

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