A new paper from the group just appeared in Macromolecules ASAP.  “Tunable Encapsulation of Proteins within Charged Microgels” describes some light scattering studies by Mike Smith wherein he used the Calypso coupled to MALS and dRI detection to study the loading of cytochrome C within pNIPAm-AAc microgels. The take-home message here is that for the case of cationic protein encapsulation within anionic microgels, the increase in capacity is not a simple linear function of anion density. For example, a ~10-fold increase in protein loading is obtained by increasing the AAc content from 20 mol% to 30 mol%. Additionally, the loading is extremely sensitive to ionic strength, with very tight protein binding being observed at ~20 mM salt. Nearly quantitative release is then obtained upon raising the ionic strength to physiological levels (~140 mM), suggesting a mechanism for triggering the release in vivo. We hope to use the analytical methods presented in this paper to perform detailed, quantitative studies of protein-microgel affinity for a variety of proteins that are of interest in pharma applications.

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