Precise-engineering of monodisperse magnetite nanoparticles with low-level of cobalt doping for enhanced MRI contrast performance

The present study focuses on synthesizing and evaluating cobalt-doped magnetite nanoparticles engineered with low cobalt doping levels, namely 1%, 5%, and 10%, for potential use as advanced MRI contrast agents. Various complementary characterization techniques were applied to explore these biocompatible nanoparticles’ structural and magnetic properties, aiming to optimize their performance for imaging applications. • Innovative synthesis of Co-doped Fe 3 O 4 NPs while keeping Fe 3+ /Fe 2+ of 2/1. • Co doping improved MRI contrast without modifying the structure of inverse spinel. • The engineered Co-doped Fe 3 O 4 NPs did not exhibit cytotoxicity. Herein, we designed and synthesized cobalt-modified magnetite nanoparticles (MNPs) in an environmentally safe aqueous medium by using biocompatible Pluronic F127 as dispersant without altering the Fe 3+ /Fe 2+ stoichiometric ratio of 2:1. Gradually increasing amounts of cobalt (1, 5, 10 mol %) were added to this formulation. The obtained MNPs were systematically characterized for their physico-chemical and magnetic properties by ICP-OES, XRD, TEM/EDX, FT-IR, RAMAN, XPS, DLS, Zeta potential, and VSM. Our method ensured that iron oxidation states and their stoichiometry remain unchanged while incorporation of Co was successfully achieved with Co 2+ as the oxidation state, according to XPS. XRD confirmed the inverse spinel structure with cobalt ions mainly occupying the interstitial sites although RAMAN revealed a slight contribution of normal spinel. TEM revealed nanoparticles of ∼ 11.8 nm, displaying a mixed sphere- and cubic-like morphology while DLS and Zeta showed some Co-induced agglomeration and a shift toward positive values, respectively. In vitro cytotoxicity tests indicated good preliminary biocompatibility for all samples. Co-modified MNPs showed enhanced r 2 values in agarose phantoms on 1T MRI apparatus. These outcomes obviously indicate that cobalt-modified magnetite have promising practical implications, being suitable for cancer diagnosis and recommending further in vivo evaluation (e.g, toxicity, biodistribution, immune-response studies).