Surface Modification of γ-Fe₂O₃@SiO₂ Magnetic Nanoparticles for the Controlled Interaction with Biomolecules

Abstract

Modifying the surface of magnetic nanoparticles (MNPs) to allow for controlled interaction with biomolecules enables their implementation in biomedical applications such as contrast agents for magnetic resonance imaging, labels in magnetic biosensing or media for magnetically assisted bioseparation. In this paper, self-assembly of trialkoxysilanes is used to chemically functionalize the surface of γ-Fe2O3@SiO2 core-shell particles. First, the silane deposition procedure was optimized using infrared analysis in order to obtain maximum packing density of the silanes on the particles. The surface coverage was determined to be ∼8 × 1014 molecules/cm2. It was shown that the magnetic, crystalline, and morphological properties of the MNPs were not altered by deposition of a thin silane coating. The optimized procedure was transferred for the deposition of aldehyde and poly(ethylene glycol) (PEG) presenting silanes. The presence of both silanes on the particle surface was confirmed using XPS and FTIR. The interaction of proteins with silane-modified MNPs was monitored using a Bradford protein assay. Our results demonstrate that, by introducing aldehyde functions, the MNPs are capable of covalently binding human IgG while retaining their specific binding capacity. Maximum surface coverage occurs at 46 μg antibodies per mg article, which corresponds to 35 antibodies bound to an average sized MNP (54 nm in diameter). The human IgG functionalized MNPs exhibit a high degree of specificity (∼90%) and retained a binding capacity of 32%. Using the same approach, streptavidin was coupled onto the MNPs and the biotin binding capacity was determined using biotinylated fluorescein. At maximum surface coverage, a biotin binding capacity of 1500 pmol/mg was obtained, corresponding to a streptavidin activity of 76%. On the other hand, by introducing PEG functions the non-specific adsorption of serum proteins could be significantly suppressed down to ∼3 μg/mg. We conclude that self-assembly of silane films creates a generic platform for the controlled interactions of MNPs with biomolecules.

A magnetically recoverable γ-Fe2O3nanocatalyst for the synthesis of 2-phenylquinazolines under solvent-free conditions

“…The strong bands at 634 and 583 cm À1 and a weak band at 443 cm À1 refer to Fe-O vibration of g-Fe 2 O 3 nanoparticles found in both catalyst samples. 36,37 The FT-IR results are in agreement with the XRD and XPS for the characterization of the maghemite phase of g-Fe 2 O 3 nanoparticles.…”

Facile Characterization of the Immobilization of Streptavidin on Magnetic Submicron Particles with a Fluorescent Probe of Streptavidin

“…When SAV is immobilized on magnetic silica particles without arms, its specific activity for a small probe still can reach about 75% of the free form. 17 Hence, these results supported the effectiveness of the fluorometric assays.…”

“…Many biotin derivatives are effective probes to characterize the immobilization of SAV on solid supports. 6,[15][16][17][18] N-biotin-N 0 -(1-naphthyl)-ethylenediamine (BNE-DA) is successful for homogenous assay of SAV. [4][5][6][7] Herein, we tested the application of BNEDA as a probe for characterizing the immobilization of SAV on MSPs.…”

Isolation methods for particle protein corona complexes from protein-rich matrices

“…Different approaches have been used for this purpose, depending on the experimental question addressed. Some methods quantify the total protein content, such as the Bradford and BCA assays [209][210][211] and UV/vis absorption measurements. 212 The protein amount can be measured by the determination of bound proteins or as a difference in the supernatant.…”