In this review, we highlight the recent progress in our understanding of the structure, properties and applications of protein–polyelectrolyte complexes in both bulk and micellar assemblies. Protein–polyelectrolyte complexes form the basis of the genetic code, enable facile protein purification, and have emerged as enterprising candidates for simulating protocellular environments and as efficient enzymatic bioreactors. Such complexes undergo self-assembly in bulk due to a combined influence of electrostatic interactions and entropy gains from counterion release. Diversifying the self-assembly by incorporation of block polyelectrolytes has further enabled fabrication of protein–polyelectrolyte complex micelles that are multifunctional carriers for therapeutic targeted delivery of proteins such as enzymes and antibodies. We discuss research efforts focused on the structure, properties and applications of protein–polyelectrolyte complexes in both bulk and micellar assemblies, along with the influences of amphoteric nature of proteins accompanying patchy distribution of charges leading to unique phenomena including multiple complexation windows and complexation on the wrong side of the isoelectric point.

Metal cation identity determines the zeolite topology. Framework topology determines the total zeolite cationic content. Potassium predominantly counterbalances Al anions; sodium and calcium are predominantly structure-directing agents.

We present structural and turbidimetric characterizations of aqueous dispersions of oppositely charged nanoparticles and polyelectrolytes that undergo complexation and flocculation to form particle-rich agglomerates over a wide range of polyelectrolyte and nanoparticle concentrations with varying polyelectrolyte sizes and persistence lengths. Compaction of nanoparticles in the polyelectrolyte-nanoparticle complexes, signified by decreasing internanoparticle spacing until they are brought in near-contact, is observed upon increasing screening of interparticle repulsion arising from adsorption of polyelectrolytes on the nanoparticle surfaces. We identify the ratio of charge borne by the polyelectrolytes and the nanoparticles as a key parameter dictating the compaction of nanoparticles into complexes as well as densification of complexes into agglomerates. Moreover, the emergence of turbidity in solution is shown to correlate with the initiation of nanoparticle compaction by polyelectrolytes but failing to describe further structural evolution of the complexes, emphasizing the need for alternate characterization techniques.

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