Micellar solubilization of Lavender oil in aqueous P85/P123 systems: Investigating the associated micellar structural transitions, therapeutic properties and existence of double cloud points

Probing Interparticle Interaction and Ordering in Silica-Pluronic-Based Solutions and Emulsions by Small-Angle Scattering Techniques

Introduction of non-DLVO forces by nonionic surfactants brings about fascinating changes in the phase behavior of silica nanosuspensions. We show here that alterations in the interaction and wetting properties of negatively charged silica nanoparticles (Ludox® LS) in the presence of polyethylene oxide-polypropylene oxide-polyethylene oxide-based triblock copolymers called Pluronics lead to the formation of stable o/w Pickering emulsions and interparticle attraction-induced thermoresponsive liquid-liquid phase separations. The results make interesting comparisons with those reported for Ludox® TM nanosuspensions comprising larger silica nanoparticles. Association of these nanosystems with Pluronics occurs through their surface silanol groups. LS nanoparticles with a higher surface-to-volume ratio thus need a higher amount of Pluronics for the onset of interparticle attraction as compared to their TM counterparts. Small-angle X-ray scattering studies reveal that unlike TM nanosuspensions, LS nanosuspensions form Pickering emulsions with the ordering of both Pluronic-coated and bare nanoparticles at the oil-water interface. This could arise due to steric limitations in accommodating large Pluronic molecules between smaller LS nanoparticles, with highly curved surfaces, in closed-packed configurations. Small angle neutron scattering studies show clear signatures of the onset of thermoresponsive intermicellar attraction in these systems as a function of temperature and Pluronic concentration, induced solely by the modulation of non-DLVO steric and hydrophobic interactions, not reported hitherto in charged nanosuspensions. The results give insights into the roles of hydrophilic-lipophilic balance of surfactants and size of silica nanoparticles in determining the phase behaviors of silica-surfactant nanocomposite systems.

Direct and Reverse Pluronic Micelles: Design and Characterization of Promising Drug Delivery Nanosystems

Pluronics are a family of amphiphilic block copolymers broadly explored in the pharmaceutical field. Under certain conditions, Pluronics self-assemble in different structures including nanosized direct and reverse micelles. This review provides an overview about the main parameters affecting the micellization process of Pluronics, such as polymer length, fragments distribution within the chain, solvents, additives and loading of cargo. Furthermore, it offers a guide about the most common techniques used to characterize the structure and properties of the micelles. Finally, it presents up-to-date approaches to improve the stability and drug loading of Pluronic micelles. Special attention is paid to reverse Pluronics and reverse micelles, currently underexplored in the literature. Pluronic micelles present a bright future as drug delivery agents. A smart design and thorough characterization will improve the transfer to clinical applications.