Effect of pH on Complex Coacervate Core Micelles from Fe(III)-Based Coordination Polymer

Abstract

The effect of pH on iron-containing complex coacervate core micelles [Fe(III)-C3Ms] is investigated in this paper. The Fe(III)-C3Ms are formed by mixing cationic poly(N-methyl-2-vinylpyridinium iodide)-b-poly(ethylene oxide) [P2MVP(41)-b-PEO(205)] and anionic iron coordination polymers [Fe(III)-L(2)EO(4)] at stoichiometric charge ratio. Light scattering and Cryo-TEM have been performed to study the variations of hydrodynamic radius and core structure with changing pH. The hydrodynamic radius of Fe(III)-C3Ms is determined mainly by the corona and does not change very much in a broad pH range. However, Cryo-TEM pictures and magnetic relaxation measurements indicate that the structure of the micellar cores changes upon changing the pH, with a more crystalline, elongated shape and lower relaxivity at high pH. We attribute this to the formation of mixed iron complexes in the core, involving both the bis-ligand and hydroxide ions. These complexes are stabilized toward precipitation by the diblock copolymer.

Dual T1/T2 Nanoscale Coordination Polymers as Novel Contrast Agents for MRI: A Preclinical Study for Brain Tumor

“…In our case, the in vitro phantom imaging studies are in agreement with this assumption for Fe-NCP, since the relaxivity ratio r 2 /r 1 is 2.1, indicating its potential use as DMCA. The r 1 value of Fe-NCP is comparable or even higher than those found for previously reported iron-based coordination polymers, 56,57 or molecular complexes, 58 which exhibit r 1 values up to 3.0 mM -1 s -1 .…”

Controlled mixing of lanthanide(iii) ions in coacervate core micelles

“…Cryo-TEM shows that the formed micelles have a core radius around 8 nm, so the thickness of the corona is about 12 nm, which fits with the values found for other micelles. 13,15 The critical micelle concentration (CMC) of Gd-C3Ms (100% Gd 3+ ) is found to be around 0.015 g L À1 (total concentration of polymer and Gd-L 2 EO 4 ) and the aggregation number (the number of P2MVP 41 -b-PEO 205 per micelle) is around 40, which means that approximately 500 metal ions are contained in one micelle (ESI, † Fig. S3).…”

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

“…To further investigate detailed coordination structures, we also investigated Fe‐L 2 ‐L 3 micelles, which show similar size and salt response behavior as Mn‐L 2 ‐L 3 micelles (Supporting Information, Figure S11). Fully coordinated Fe‐(DPA) 2 features a typical UV/Vis absorption around 370 nm . As shown in Figure b, Fe‐based micelles show differences in UV absorption in the range 320–370 nm, between the typical spectrum of pure L 2 systems (identical to that of fully coordinated Fe‐(DPA) 2 ) and that of mixed systems: the absorption at 350 nm decreases with increasing L 3 /L 2 ratio and levels off at around 60 % of L 3 .…”