biostudies-literatureKabil MFNational Science Foundation under the Established Program to Stimulate Competitive Research (EPSCoR)National Science Foundatione09099https://www.ebi.ac.uk/biostudies/studies/S-EPMC12674095biostudies-literatureUnknown21(48)Superparamagnetic iron oxide nanoparticle (SPION) clusters produce localized magnetic field inhomogeneities that enhance negative contrast in magnetic resonance imaging (MRI). It is shown that high transverse relaxivity (r<sub>2</sub>) can be obtained by clustering hydrophobic SPIONs with an average core diameter of ≈7 nm via self-assembly with amphiphilic polyethylene glycol-b-poly(L-Leucine) block copolymers, PEG<sub>n</sub>-b-p(L-Leu)<sub>m</sub>, where the PEG chains are terminated by methoxy (CH<sub>3</sub>O-PEG<sub>n</sub>) or hydroxyl groups (HO-PEG<sub>n</sub>). Clusters ranging from 65 to 85 nm in diameter are formed by polymer coating and stabilization of hydrophobic SPION aggregates and yield high r<sub>2</sub> values ranging from 226 to 342 s<sup>-1</sup> mm Fe<sup>-1</sup> witSmall (Weinheim an der Bergstrasse, Germany)Multicore SPION Clustering within Poly(amino acid) Corrals for Enhanced MRI Contrast and Drug Release.PMC1267409516552212305402Kabil MFBothun GDMills RScholz CWalsh EGAkinmola ATPan AAnik MIfalseMulticore SPION Clustering within Poly(amino acid) Corrals for Enhanced MRI Contrast and Drug Release.Superparamagnetic iron oxide nanoparticle (SPION) clusters produce localized magnetic field inhomogeneities that enhance negative contrast in magnetic resonance imaging (MRI). It is shown that high transverse relaxivity (r<sub>2</sub>) can be obtained by clustering hydrophobic SPIONs with an average core diameter of ≈7 nm via self-assembly with amphiphilic polyethylene glycol-b-poly(L-Leucine) block copolymers, PEG<sub>n</sub>-b-p(L-Leu)<sub>m</sub>, where the PEG chains are terminated by methoxy (CH<sub>3</sub>O-PEG<sub>n</sub>) or hydroxyl groups (HO-PEG<sub>n</sub>). Clusters ranging from 65 to 85 nm in diameter are formed by polymer coating and stabilization of hydrophobic SPION aggregates and yield high r<sub>2</sub> values ranging from 226 to 342 s<sup>-1</sup> mm Fe<sup>-1</sup> wit2025-01-01T00:00:00Z2025 Dec2026-06-07T04:43:58.44Z2026-06-07T03:07:11.331ZS-EPMC126740954111015410.1002/smll.202509099