Multi angle light scattering as a process analytical technology tool for real-time monitoring of molar mass of protein-polysaccharide conjugate fractions

Current polysaccharide conjugate vaccine manufacturing process involves conjugation of polysaccharide with protein followed by separation/purification of the conjugate from reaction components and free polysaccharide/protein, by preparative Size-Exclusion Chromatography (SEC). Each SEC fraction is analyzed and pooled the conjugate based on its molar mass and absence of free polysaccharide. In the present work, we have evaluated in-line Multi Angle Light Scattering (MALS) as a Process Analytical Technology (PAT) tool to eliminate the need for offline analysis of individual fractions after purification. The preparatory SEC unit is coupled to a MALS detector, i.e. preparatory SEC-MALS. In SEC, the molecules are separated based on size, where polysaccharide-protein conjugate elutes first followed by free polysaccharide and then free protein. The MALS detector monitors in-line weight-average molar mass (Mw) during SEC-fractionation. Except the first fraction, the molar mass distribution data from in-line MALS enables decision on preparative SEC fractions to be pooled. We found that offline analysis of preparative fractions using analytical SEC-MALS was in good agreement with the >2000 kDa cutoff criterion. Thus in-line process analysis is effective, time-saving, and simple to implement in manufacturing processes of conjugate vaccines.