Reactive Nature of Dopamine as a Surface Functionalization Agent in Iron Oxide Nanoparticles

Abstract

Dopamine forms an initial structure coordinated to the surface of the iron oxide nanoparticle as a result of improved orbital overlap of the five-membered ring and a reduced steric environment of the iron complex. However, through transfer of electrons to the iron cations on the surface and rearrangement of the oxidized dopamine, a semiquinone is formed. Because of free protons in the system, oxygens on the surface are protonated, which allows for the Fe2+ to be released into the solution as a hydroxide. This released fragment of the nanoparticle will then eventually oxidize in air to a form of an iron(III) oxyhydroxide. All of the reported results demonstrate that the reactivity between Fe3+ and dopamine quickly facilitates the degradation of the nanoparticles. The energetic modeling studies substantiate our proposed decomposition mechanism and thus conclude that the use of dopamine as a robust anchor for iron oxide or iron oxide shell particles will not fulfill the need for stable ferrofluids in most biomedical applications.

Superparamagnetic iron oxide nanoparticles as a dual imaging probe for targeting hepatocytes in vivo

“…2). Dopamine was conjugated to the surface of SPION by a ligand replacement reaction method (17). LBA was also conjugated to the free amine groups of dopamine using 1-ethyl-3-(3-(dimethylamino)-propyl) carbodiimide/ N-hydroxysuccinimide after conjugating it to dopamine for introducing the terminal amine on the surface of the SPION.…”

“…Dopamine was used as a capping agent in the surface modification of iron oxide (17). It forms a stable anchor on the surface of iron oxide nanoparticles and can be easily functionalized through amide bonds with LBA.…”

“…After sonication for 2 h, the SPION were washed sequentially with toluene, acetone, and ethanol. Coating of the SPION with dopamine was achieved using the method described by Shultz et al (17). SPION (10 mg in 5 mL of toluene) were mixed with 50 mg of dopamine in methanol and reacted in a sonication bath for 30 min.…”

The design and utility of polymer-stabilized iron-oxide nanoparticles for nanomedicine applications

“…Th is approach has been widely used to attach a range of biologically important molecules, such as peptides and amino acids, to IONPs [16]. However, problems with the stability of this bond in water and biological fl uids have been reported by Carpenter et al after long exposure periods [17].…”

Convenient synthesis of heterobifunctional poly(ethylene glycol) suitable for the functionalization of iron oxide nanoparticles for biomedical applications

“…31 Nevertheless, Fe(III)-mediated oxidation of catechol ligands might induce loss of colloidal stability and produce cytotoxic iron-quinone complexes. 32 The suitability of heterobifunctional PEG molecules 6 and 7 for the pegylation of metal oxide NPs was addressed using USPIO NPs. A suspension of magnetite (Fe 3 O 4 ) NPs (PlasmaChem, $7% nanosuspension in water, average particle core size 8 ± 3 nm), in a mixture of EtOH/toluene (1:1), was ultrasonicated in the presence of AcOH and PEG derivatives 6 and 7 (1:1).…”