Metallosurfactant aggregates: Structures, properties, and potentials for multifarious applications

Metallosurfactants offer important scientific and technological advances due to their novel interfacial properties. As a special class of structures formed by the integration of metal ions into amphiphilic surfactant molecules, these metal-based amphiphilic molecules possess both organometallic and surface chemistries. This review critically examines the structural transitions of metallosurfactants from micelle to vesicle upon metal coordination. The properties of a metallosurfactant can be changed by tuning the coordination between the metal ions and surfactants. The self-assembled behavior of surfactants can be controlled by selecting transition-metal ions that enhance their catalytic efficiency in environmental applications by applying a hydrogen evolution reaction or oxygen evolution reaction. We present the different scattering techniques available to examine the properties of metallosurfactants (e.g., size, shape, structure, and aggregation behavior). The utility of metallosurfactants in catalysis, the synthesis of nanoparticles, and biomedical applications (involving diagnostics and therapeutics) is also explored.

Spherical Polyelectrolyte Brushes as a Novel Platform for Paramagnetic Relaxation Enhancement and Passive Tumor Targeting

A novel platform for the development of highly efficient magnetic resonance imaging (MRI) contrast agents has been demonstrated. New contrast agents are designed and produced through electrostatic self-assembly of cationic gadolinium(III) complexes onto anionic spherical polyelectrolyte brushes (SPB). The structurally well-defined SPB are composed of polystyrene core and polyacrylic acid brush layer, where numerous binding sites and confined microenvironments are available for the embedment of the gadolinium(III) contrast agents. Both in vitro and in vivo experiments show excellent biocompatibility and relaxometric performance of these SPB-based gadolinium hybrid materials. The enhanced relaxivity value is up to 86.2 mM^-1 s^-1 per Gd, a remarkably high record value at 1.5 T magnetic field. In vivo imaging displays a prolonged blood circulation time and massive accumulation of the contrast agents at the tumor region due to the enhanced permeability and retention effect. The SPB-based gadolinium hybrid materials not only broaden the horizons of new MRI contrast agents, but also have a great potential for tumor diagnosis.