Revealing and tuning the core, structure, properties and function of polymer micelles with lanthanide-coordination complexes

Abstract

Controlling self-assembly processes is of great interest in various fields where multifunctional and tunable materials are designed. We here present the versatility of lanthanide-complex-based micelles (Ln-C3Ms) with tunable coordination structures and corresponding functions (e.g. luminescence and magnetic relaxation enhancement). Micelles are prepared by charge-driven self-assembly of a polycationic-neutral diblock copolymer and anionic coordination complexes formed by Ln(III) ions and the bis-ligand L2EO4, which contains two dipicolinic acid (DPA) ligand groups (L) connected by a tetra-ethylene oxide spacer (EO4). By varying the DPA/Ln ratio, micelles are obtained with similar size but with different stability, different aggregation numbers and different oligomeric and polymeric lanthanide(III) coordination structures in the core. Electron microscopy, light scattering, luminescence spectroscopy and magnetic resonance relaxation experiments provide an unprecedented detailed insight into the core structures of such micelles. Concomitantly, the self-assembly is controlled such that tunable luminescence or magnetic relaxation with Eu-C3Ms, respectively, Gd-C3Ms is achieved, showing potential for applications, e.g. as contrast agents in (pre)clinical imaging. Considering the various lanthanide(III) ions have unique electron configurations with specific physical chemical properties, yet very similar coordination chemistry, the generality of the current coordination-structure based micellar design shows great promise for development of new materials such as, e.g., hypermodal agents.

Supramolecular Virus‐Like Nanorods by Coassembly of a Triblock Polypeptide and Reversible Coordination Polymers

“…Upon mixing with the cationic blocks, the local concentration of L 2 EO 4 and metal ions in the assemblies increases by hundreds of times, which dramatically shifts the equilibria of the coordination structures to form coordination polymers . For Eu‐L 2 EO 4 at a Eu/DPA ratio of 1:3, network structures with each coordination unit carrying three negative charges are formed (Scheme d), which was fully confirmed in our recent study . These anionic coordination polymers assemble strongly with the cationic blocks from the polypeptide.…”

“…[9] For Eu-L 2 EO 4 at aEu/DPAratio of 1:3, network structures with each coordination unit carrying three negative charges are formed (Scheme 1d), [10] which was fully confirmed in our recent study. [11] These anionic coordination polymers assemble strongly with the cationic blocks from the polypeptide. We reasoned that the silk blocks, initiated by the charge complexation, could fold, and that the coassembly should eventually result in rod-like structures as shown in Scheme 1b.T hese complexes are abbreviated as Eu-L-P in which La nd Pi ndicate the L 2 EO 4 ligand andt he C 4 -S 10 -B K12 polypeptide, respectively.…”

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

“…Unlike micelles formed by common synthetic polyelectrolytes only, such coordination polyelectrolytes bring hundreds of metal ions in the micellar core, resulting in novel functional properties, for example, magnetic and fluorescent properties . Moreover, control of the coordination structures allows to manipulate the strength of the magnetic response or the fluorescence of the micelles, which gives them great potential as imaging probes . Regrettably, it was the poor stability against salt that hampered their practical application, particularly for first‐row transition metals .…”

Redox-responsive core cross-linked prodrug micelles prepared by click chemistry for pH-triggered doxorubicin delivery

“…Drugs can be loaded into these micelles which not only avoid the metabolization and rapid clearance from the body but also reduce toxicity of drug towards healthy tissues [5][6][7][8]. The drug of interest is either dissolved, entrapped, attached or encapsulated into the polymeric micelles depending on the method of preparation [9][10][11]. However, the in vivo stability of polymeric micelles, following intravenous administration still leaves a challenge due to dissociation into unimers under certain factors such as low concentration, high shearing force in the blood circulation [12].…”

“…However, the in vivo stability of polymeric micelles, following intravenous administration still leaves a challenge due to dissociation into unimers under certain factors such as low concentration, high shearing force in the blood circulation [12]. To stabilize polymeric micelles for in vivo applications, hydrophobic blocks can be cross-linked by various strategies including dimethylmaleide photo-crosslinking [13], phototriggered disulfide cross-link [14], and metal-coordination complexes [9,15], resulting in core cross-linked micelles. Nevertheless, conventional antitumor drugs are quickly distributed at administration in the body leading to fast renal clearance, short durations of action, and significant dissipation, with only a fraction reaching targeted side [16].…”