Ferritins, the cellular iron repositories, are self-assembled, hollow spherical nanocage proteins composed of 24 subunits. The self-assembly process in ferritin generates the electrostatic gradient to rapidly sequester Fe­(II) ions, thereby minimizing its toxicity (Fenton reaction). Although the factors that drive self-assembly and control its kinetics are little investigated, its inherent reversibility has been utilized for cellular imaging and targeted drug delivery. The current work tracks the kinetics of ferritin self-assembly by laser light scattering and investigates the factors that influence the process. The formation of partially structured subunit-monomers/dimers, at pH ≤ 1.5, serves as the starting material for the self-assembly, which upon increasing the pH exhibits biphasic behavior (a rapid assembly process coupled with subunit folding followed by a slower reassembly/reorganization process) and completes within 10 min. The ferritin self-assembly accelerated with subunit concentration and ionic strength (t 1/2 decreases in both the cases) but slowed down with the pH of the medium from 5.5 to 7.5 (t 1/2 increases). These findings would help to regulate the ferritin self-assembly to enhance the loading/unloading of drugs/nanomaterials for exploiting it as a nanocarrier and nanoreactor.

In the present study, we have investigated the effects of surfactant addition on the structure and dynamics of gellan gum hydrogels. A strong interaction is seen between gellan gum and oppositely charged cationic surfactant, hexadecyltrimethylammonium bromide (CTAB) whereas rather weak or minimal interactions are observed when either anionic surfactant, sodium dodecylsulfate (SDS), or nonionic surfactant, Triton X‐100 is added to the system. The dynamics of the hydrogels was studied, using dynamic light scattering measurements and the heterodyne method was used for data evaluation. The correlation function of parent hydrogel was fitted with a stretched exponential function, while a single plus stretched exponential function was employed to study the dynamics of hydrogel with surfactants and the corresponding relaxation times were appropriately analyzed. An interesting crossover from stretched to compressed exponential was seen when CTAB was added beyond critical micellar concentration to the system, which was not evidenced for the other two surfactants. Ensemble averaged intensity was also analyzed and the general picture that emerges is that the oppositely charged surfactant has the strongest ability to form large associations as oppose to nonionic and like‐charged surfactants. The rheological measurements were carried out to determine the elastic response of the gels over a wide range of frequencies. It was seen that the elastic modulus was dependent on both the surfactant concentration and type. Cationic surfactant increased the elastic modulus markedly as opposed to the nonionic and anionic surfactants. These results may have implications for the use of polymer surfactant systems as potential products.

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