Deferoxamine-Modified Hybrid Materials for Direct Chelation of Fe(III) Ions from Aqueous Solutions and Indication of the Competitiveness of In Vitro Complexing toward a Biological System

Abstract

Deferoxamine (DFO) is one of the most potent iron ion complexing agent belonging to a class of trihydroxamic acids. The extremely high stability constant of the DFO-Fe complex (log β = 30.6) prompts the use of deferoxamine as a targeted receptor for scavenging Fe(III) ions. The following study aimed at deferoxamine immobilization on three different supports: poly(methyl vinyl ether-alt-maleic anhydride), silica particles, and magnetite nanoparticles, leading to a class of hybrid materials exhibiting effectiveness in ferric ion adsorption. The formed deferoxamine-loaded hybrid materials were characterized with several analytical techniques. Their adsorptive properties toward Fe(III) ions in aqueous samples, including pH-dependence, isothermal, kinetic, and thermodynamic experiments, were investigated. The materials were described with high values of maximal adsorption capacity q _m, which varied between 87.41 and 140.65 mg g^-1, indicating the high adsorptive potential of the DFO-functionalized materials. The adsorption processes were also described as intense, endothermic, and spontaneous. Moreover, an exemplary magnetically active deferoxamine-modified material has been proven for competitive in vitro binding of ferric ions from the biological complex protoporphyrin IX-Fe(III), which may lead to a further examination of the materials' biological or medical applicability.

Figure 1

(a) Structures of the synthesized deferoxamine-functionalized hybrid materials; (b) formation of the Fe(III)–deferoxamine complex.

Figure 2

(a) FT-IR spectra of the adsorptive materials with indicated specific bands: ν₁ = 1051 cm^–1; ν₂ = 1570 cm^–1; ν₃ = 1640 cm^–1; ν₄ = 1705 cm^–1; ν₅ = 2855 cm^–1; ν₆ = 2930 cm^–1; (b) the thermogravimetric curves obtained during thermal analysis of the materials.

Figure 3

SEM images (A–C) and EDX–SEM mapping of Fe(III) ions (F–H) adsorbed to the hybrid materials: (A, F) PMVEAMA–DFO; (B, G) SiO₂–NCO–DFO; (C, H) SiO₂–maleimide–DFO). SEM images of magnetite-based hybrid materials: (D) Fe₃O₄/SiO₂–NCO–DFO; (E) Fe₃O₄/SiO₂–maleimide–DFO). Fe is visualized in orange.

Figure 4

Influence of the solution pH on the amount of Fe(III) ions adsorbed on the deferoxamine-functionalized hybrid materials (gray dotted line corresponds to the pH of 5 mM aqueous solution of Fe(ClO₄)₃ – 2.45).

Figure 5

Fitting of the experimental data to the Langmuir isotherm model.

Figure 6

Experimental data fitting to kinetic models: (a) pseudo–second–order; (b) intraparticle diffusion.

Figure 7

Plots of the van’t Hoff equation fitted to the thermodynamic studies of ferric ion adsorption on the hybrid materials.

Figure 8

Positive ESI–MS spectra: (a) the formed PPIX–Fe complex; (b) PPIX–Fe complex interaction with pure deferoxamine; (c) PPIX–Fe complex interaction with deferoxamine-loaded Fe₃O₄-based hybrid material 3a.