Light scattering is an excellent means for assessing the degradation of biopolymers as a result of exposure to heat, light, high or low pH, and other stimuli.
Aggregation and fragmentation
Some common forms of biodegradation are aggregation and fragmentation, both readily characterized with high information content via SEC-MALS. Simply take aliquots of a biopolymer sample before and after exposure to environmental or chemical stress and inject onto an appropriate GPC column followed by MALS and dRI detection. The analysis can provide several means of quantifying degradation, e.g. shifts in Mn, Mw and Mz, representing the number-, weight- and z-averaged molecular weights of the sample, respectively. Biodegradation may also lead to changes in molecular conformation, indicated in SEC-MALS by the ratio of rms radius Rg to molecular weight.
Another manifestation of biodegradation is the formation or dissociation of particulates. For a quick assessment of nanoparticle populations, DLS is ideal, requiring little sample and very little time for preparation an measurement. While the size of monodisperse particles can be measured accurately by DLS, size distributions tend to be more qualitative than quantitative. A more thorough analysis is provided by FFF-MALS, which separates both soluble and insoluble components with excellent resolution so they may be analyzed by downstream light scattering detectors.
While very slow processes are amenable to analysis by SEC-MALS via periodic sampling from a reaction vessel, batch MALS, batch DLS and CG-MALS offer alternative approaches to analyzing kinetics of more rapid reactions.
If there is enough time between initiating the reaction, and mixing and pipetting to a cuvette, batch MALS or batch DLS can work. The Calypso can perform this automatically with a dead time of just a few seconds.