A Supramolecular Crosslinker To Give Salt‐Resistant Polyion Complex Micelles and Improved MRI Contrast Agents

Abstract

Three‐component mixtures (diblock copolymer/metal ion/oligoligand) can assemble into micellar particles owing to a combination of supramolecular polymerization and electrostatic complex formation. Such particles cover a large range of compositions, but the electrostatic forces keeping them together make them rather susceptible to disintegration by added salt. Now it is shown how the salt stability can be tuned continuously by employing both a bis‐ligand and a tris‐ligand, and varying the ratio of these in the mixture. For magnetic ions such as MnII and FeIII, the choice of the multiligand also affects the ion/water interaction and, hence, the magnetic relaxivity. As an example, MnII‐based nanoparticles with a very high longitudinal relaxivity (10.8 mm−1 s−1) were investigated that are not only biocompatible but also feature strong contrast enhancement in target organs (liver, kidney), as shown by T1‐weighted in vivo magnetic resonance imaging (MRI).

On Complex Coacervate Core Micelles: Structure-Function Perspectives

“…Exciting emerging applications of C3Ms also profit from the uniquely responsive nature of C3Ms and advances in controlled polymerization techniques, which enable the preparation of micelles with increasingly custom-tailored structure, stability, properties, and function. The incorporation of multivalent metal ions, spectroscopic probes, multiblock copolymers, stimuli-responsive (macro)molecules or nanoparticles, and unconventional water-soluble blocks extends the functionality of C3Ms to, e.g., diffusional probes [ 168 , 169 ], contrast agents and imaging probes [ 138 , 170 , 171 , 172 , 173 ], nanoreactors [ 174 ], hydrogelators [ 175 ], and crystal growth modifiers [ 176 ], and facilitates in-depth characterization at the ensemble and single-micelle level [ 177 , 178 , 179 ]. The straightforward preparation by direct dissolution from cost-effective raw materials further facilitates the translation of key concepts and innovations with high application potential into marketable technologies.…”

Dendrimer‐Based Polyion Complex Vesicles: Loops Make Loose

“…(Section 4.2, Supporting Information; sample preparation) As shown in Figure 1a, the scattered light intensity increases with increasing charge ratio and reaches a maximum around f +/− = 0.8. This point is known as the "preferred micelle composition," PMC, [32] and typically appears around unity charge ratio, where charge stoichiometry is achieved. The slight deviation of the PMC point here indicates that the partially protonated internal tertiary amines of PAMAM dendrimers may also contribute to the electrostatic assembly, which lowers the value of f +/− .…”

PEO-b-PPO star-shaped polymers enhance the structural stability of electrostatically coupled liposome/polyelectrolyte complexes

“…lipid tails) of several liposomes, while the oppositely charged polyelectrolyte leads to an additional electrostatic “gluing” of lipid head groups of various liposomes. It was demonstrated that the size of the liposome aggregates increases due to a fluffy interconnection of the liposomes at rather low concentrations of the amphiphilic polymer “glue” [48]. However, the structure of the liposome aggregates is compacted at higher concentrations of the amphiphilic polymer.…”