Spectrophotometric Insights into Protein Encapsulation and Dilution in Polyelectrolyte Complex Micelles

In this presentation, we discuss the evolution of protein aggregation states upon their encapsulation into polyelectrolyte complex (PEC) micelles. PEC micelles are nanosized complexes comprising oppositely charged block polyelectrolytes that self-assemble in aqueous milieu and are theorized to have an incredibly low or nonexistent critical micelle concentration (CMC). The charged, hydrophilic, and polymer-dense environments of PEC micelle cores have been shown to sequester and protect enzymes and nucleic acids, and these micelles have been suggested as potential therapeutic and biomedical carriers. Yet, the local environments in PEC domains and their CMC remain poorly understood. To address these knowledge gaps and gain insight into the PEC domain environment, we encapsulated fluorescein-tagged bovine serum albumin (FBSA) in PEC micelles and utilized fluorescence spectroscopy at ultra-low concentrations to correlate spectral shifts with the oligomerization state of FBSA and the stability of PEC micelles. Thus, we demonstrate the characterization of the PEC domains using fluorescence spectroscopy, providing insight into the structure and dynamics within these domains and their CMC.