Octadecylamine-Mediated Versatile Coating of CoFe₂O₄ NPs for the Sustained Release of Anti-Inflammatory Drug Naproxen and in Vivo Target Selectivity

Magnetic nanoparticles (MNPs) can play a distinct role in magnetic drug delivery via their distribution to the targeted area. The preparation of such MNPs is a challenging multiplex task that requires the optimization of size, magnetic, and surface properties for the achievement of desirable target selectivity, along with the sustained drug release as a prerequisite. In that context, CoFe2O4 MNPs with a small size of ∼7 nm and moderate saturation magnetization of ∼60 emu g–1 were solvothermally synthesized in the presence of octadecylamine (ODA) with a view to investigate the functionalization route effect on the drug release. Synthetic regulations allowed us to prepare MNPs with aminated (AmMNPs) and amine-free (FAmMNPs) surface. The addition of the nonsteroidal anti-inflammatory drug with a carboxylate donor, Naproxen (NAP), was achieved by direct coupling with the NH2 groups, rendered by ODA, through the formation of an amide bond in the case of AmMNPs. In the case of FAmMNPs, indirect coupling of NAP was performed through an intermediate linker (polyethylenimine) and on PEG-ylated MNPs. FT-IR, 1H NMR, 13C NMR, and UV–vis data confirmed the addition of NAP, whereas diverse drug-release behavior was observed for the different functionalization approaches. The biological behavior of the MNPs@NAP was evaluated in vitro in rat serum and in vivo in mice, after radiolabeling with a γ-emitting radionuclide, 99mTc. The in vivo fate of MNPs@NAP carriers was in straightforward relation with the direct or indirect coupling of NAP. Furthermore, an inflammation was induced intramuscularly, where the directly coupled 99mTc-MNPs@NAP carriers showed increased accumulation at the inflammation site

Unveiling the Physicochemical Features of CoFe₂O₄ Nanoparticles Synthesized via a Variant Hydrothermal Method: NMR Relaxometric Properties

A series of CoFe₂O₄ nanoparticles were formed through a variant hydrothermal synthesis based on a self-assembled oil–water system in autoclaves at 200 °C in the presence of octadecylamine and the trivalent iron and cobalt acetylacetonates. The variation of the water content, the different valence of the cobalt precursors (Co­(II) and Co­(III)) as well as Fe:Co precursor ratios (2:1 and 1:1) were studied. CoFe₂O₄ nanoparticles with a size range of 9–16 nm of high crystallinity and enhanced saturation magnetization (∼89 emu g^–1) have been isolated and characterized. Raman spectroscopy provided information concerning the lattice strain, while incorporation of Co²⁺ at T_d sites of the spinel indicated a different inversion degree (0.67–0.60) among the samples. EPR studies showed that EPR signal and spin relaxation process were size dependent and influenced by aggregation effects. CoFe₂O₄ nanoparticles were converted to dual agents via a reaction between the free amine groups of the organic coating and the sulfonyl group of the fluorescent dye sulforhodamine B acid chloride (SRB) and NMR relaxometric properties were measured. The relatively high transverse relaxivity values, <i>r</i>₂ (232.0–130.3 mM^–1 s^–1) were attributed to nanocluster effects in aqueous suspensions with respect with the amount of SRB and encourage their potential application as versatile agents in theranostics