A protein’s activity arises from its structure. In bioprocessing, a protein’s secondary structure—twists like an alpha-helix or folds like a beta-pleated sheet—plays a fundamental role in the performance of a biotherapeutic. “Very small changes in the structure of a protein and peptide biotherapeutic could affect its accuracy and specificity,” says Jeff Zonderman, chief commercial officer at RedShift BioAnalytics in Burlington, MA.
Processing a protein can change its secondary structure. The denaturing of proteins in frying an egg, for example, resembles aggregation that can arise in bioprocessing. This clumping in a biotherapeutic not only impacts its efficacy, but can turn it toxic. That explains the industry’s interest in this process, which was described in “Aggregation Analysis.”
With microfluidic modulation spectroscopy (MMS), bioprocessors can analyze secondary structure. This technology can be applied to samples at high or low concentration and from discovery through manufacturing, notes Zonderman. “We use this technology to give more insight into what’s going on with a molecule: If the structure is changing, is it a lot or a little?” That information can also be used to determine how to address changes in secondary structure. So, the first step is identifying these structural changes, but it’s just as important to know how to correct them.
With no technology providing a good measurement of secondary structure in-line or at-line, bioprocessors take samples to a QC lab. There, MMS can provide automatic analysis of samples taken directly from a bioprocessing line. Fourier-transform infrared spectroscopy (FTIR) or circular dichroism could also be used.
“FTIR uses a ton of material and cannot be automated,” continues Zonderman. “Circular dichroism can be automated a bit, but you need to change the matrix or dilute it to look at secondary structure, and it is not a sensitive technique for measuring and quantitation of features like b-sheet for aggregation.”
Like most analytical challenges, scientists can consider various methods, and pick the one that provides the most benefits and the fewest obstacles in a specific application.
“No one technology is THE technology for analysis,” emphasizes Zonderman. “It’s about people building a toolbox.”
Only then, can bioprocessors analyze and adjust the secondary structure of a biotherapeutic to ensure its intended efficacy and safety. Consequently, the secondary structure of biotherapeutics is a primary concern of patients.