Chemical grafting of a DNA intercalator probe onto functional iron oxide nanoparticles: a physicochemical study

Tri-modal imaging of gold-dotted magnetic nanoparticles for magnetic resonance imaging, computed tomography and intravascular ultrasound: an in vitro study

Aim: To examine the multimodal contrasting ability of gold-dotted magnetic nanoparticles (Au*MNPs) for magnetic resonance (MR), computed tomography (CT) and intravascular ultrasound (IVUS) imaging. Materials & methods: Au*MNPs were prepared by adapting an impregnation method, without using surface capping reagents and characterized (transmission electron microscopy, x-ray diffraction and Fourier-transform infrared spectroscopy) with their in vitro cytotoxicity assessed, followed by imaging assessments. Results: The contrast-enhancing ability of Au*MNPs was shown to be concentration-dependent across MR, CT and IVUS imaging. The Au content of the Au*MNP led to evident increases of the IVUS signal. Conclusion: We demonstrated that Au*MNPs showed concentration-dependent contrast-enhancing ability in MRI and CT imaging, and for the first-time in IVUS imaging due to the Au content. These Au*MNPs are promising toward solidifying tri-modal imaging-based theragnostics.

Enhancement of magnetofection efficiency using chitosan coated superparamagnetic iron oxide nanoparticles and calf thymus DNA

Superparamagnetic iron oxide nanoparticles (MNPs) were prepared and coated with chitosan (CS). The chitosan-magnetic iron oxide nanoparticles (CS-MNPs) were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), and the morphology of the particles was studied by transmission electron microscopy (TEM). Our findings show that the magnetic particles were monodisperse (10nm mean diameter) and exhibited superparamagnetic behavior. The interaction between the particles and calf-thymus DNA (DNA) in physiological buffer was studied with UV-vis, fluorescence and circular dichroism spectroscopy and zeta potential. Spectroscopic studies were indicated DNA conformational changes in the presence of CS-MNPs. Binding and thermodynamic parameters at different temperatures were calculated using the Stern-Volmer, Hill, Scatchard and Van't Hoff equations. The binding process was spontaneous and interactions were electrostatic with the appropriate binding constant (K_b=4.52×10³M^-1, 3.69×10³M^-1 and 3.02×10³M^-1 at 300K, 310K and 320K, respectively). Zeta potential measurements of DNA continually increased with the addition of CS-MNPs, supporting our thermodynamic findings. Moreover, CS-MNPs were able to quench the fluorescence of DNA-intercalated ethidium bromide (DNA-EB) by a static quenching mechanism. Cytotoxicity studies show that the DNA-CS-MNP system is biocompatible with a human foreskin fibroblast cell line, HFFF2. Collectively, these results suggest that surface cationic magnetic chitosan-iron oxide nanoparticles can potentially enhance magnetofection efficiency.

Magnetic nanomaterials with near-infrared pH-activatable fluorescence via iron-catalyzed AGET ATRP for tumor acidic microenvironment imaging

This work provides a fluorescent/magnetic iron oxide nanomaterials prototype to visualize the solid tumor in vivo by sensing the tumor acidic microenvironment, and a satisfactory tumor-to-normal tissue signal ratio (T/N ratio) and a prolonged time-window for 4T1 tumor visualization were observed in vivo.

Electrochemical transduction of DNA hybridization at modified electrodes by using an electroactive pyridoacridone intercalator

A synthetic redox probe structurally related to natural pyridoacridones was designed and electrochemically characterised. These heterocycles behave as DNA intercalators due to their extended planar structure that promotes stacking in between nucleic acid base pairs. Electrochemical characterization by cyclic voltammetry revealed a quasi-reversible electrochemical behaviour occurring at a mild negative potential in aqueous solution. The study of the mechanism showed that the iminoquinone redox moiety acts similarly to quinone involving a two-electron reduction coupled with proton transfer. The easily accessible potential region with respect to aqueous electro-inactive window makes the pyridoacridone ring suitable for the indirect electrochemical detection of chemically unlabelled DNA. Its usefulness as electrochemical hybridization indicator was assessed on immobilised DNA and compared to doxorubicin. The voltamperometric response of the intercalator acts as an indicator of the presence of double-stranded DNA at the electrode surface and allows the selective transduction of immobilised oligonucleotide hybridization at both macro- and microscale electrodes.

Comprehensive study of DNA binding on iron (II,III) oxide nanoparticles with a positively charged polyamine three-dimensional coating

Iron (II,III) oxide Fe3O4 nanoparticles (25 and 50 nm NPs) are grafted with amine groups through silanization in order to generate a positively charged coating for binding negatively charged species including DNA molecules. The spatial nature of the coating changes from a 2-D-functionalized surface (monoamines) through a layer of amine oligomers (diethylenetriamine or DETA, about 1 nm in length) to a 3-D layer of polyamine (polyethyleneimine or PEI, thickness ≥3.5 nm). These Fe3O4-PEI NPs were prepared by binding short-chain PEI polymers to the iodopropyl groups grafted on the NP surface. In this work, the surface charge density, or zeta potential, of the nanoparticles is found not to be the only factor influencing the DNA binding capacity, which also seems not to be affected by their buffering capacity profile in the range of pH 4-10. This study also allows the investigation of this 3-D effect on the surface of a nanoparticle as opposed to conventional 2-D amine functionalization. The flexibility of the PEI coating, which consists of only 1, 2, and 3° amines, on the nanoparticle surface has a significant influence on the overall DNA binding capacity and the binding efficiency (or N/P ratio). These polyamine-functionalized nanoparticles can be used in the purification of biomolecules and the delivery of drugs and large biomolecules.

One-pot synthesis of iron oxide nanoparticles with functional silane shells: a versatile general precursor for conjugations and biomedical applications

Iron oxide nanoparticles (IONPs) and their surface modifications with therapeutic or diagnostic (theranostic, TN) agents are of great interest. Here we present a novel one-pot synthesis of a versatile general TN precursor (aminosilane-coated IONPs [IONP-Sil(NH2)]) with surface amine groups. Surface functional group conversion to carboxylic acid was accomplished by conjugating poly(ethylene glycol) diacid to IONP-Sil(NH2). The NPs were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy. Biocompatibility and cell uptake profile of the nanoparticles were evaluated in-vitro using cultured liver cells (HepG2). Oleylamine (hydrophobic) and bovine serum albumin (BSA) as model drugs were attached to IONP-Sil-PEG(COOH). The ability of IONP-Sil(NH2) to bind small interfering RNA (siRNA) is also shown.

Assessment of DNA complexation onto polyelectrolyte-coated magnetic silica nanoparticles

The polyelectrolyte-DNA complexation method to form magnetoplexes using silica-coated iron oxide magnetic nanoparticles as inorganic substrates is an attractive and promising process in view of the potential applications including magnetofection, DNA extraction and purification, and directed assembly of nanostructures. Herein, we present a systematic physico-chemical study that provides clear evidence of the type of interactions established, reflects the importance of the DNA length, the nanoparticle size and the ionic strength, and permits the identification of the parameters controlling both the stability and the type of magnetoplexes formed. This information can be used to develop targeted systems with properties optimized for the various proposed applications of magnetoplexes.

Engineering the multifunctional surface on magnetic nanoparticles for targeted biomedical applications: a chemical approach

Research on multifunctional magnetic nanoparticles for biomedicines has experienced rapid growth because of the progressive advancements in nanotechnology and in modern biotechnology. However, the design of multifunctional surfaces on magnetic nanoparticles generally lacks a systematic approach. This article will try to unfold the complex chemistry in constructing a multifunctional surface, and layout a simplified guide for researchers to follow, particularly those from nonchemistry backgrounds. A number of design principles with critical rationales are to be introduced and followed by four main strategies: multifunctionality on a polymer chain, use of block copolymers, cocondensation of alkoxysilanes and of the secondary reaction on groups, with a particular reference to the use of alkoxysilanes. Nanoparticles of higher complexity are expected to be reported in the near future. These advanced systems are likely to be designed from some more logical, strategic mechanisms rather than the 'pick-and-mix' approaches we have seen in the last decade.

The effects of magnetite (Fe₃O₄) nanoparticles on electroporation-induced inward currents in pituitary tumor (GH₃) cells and in RAW 264.7 macrophages

Aims

Fe₃O₄ nanoparticles (NPs) have been known to provide a distinct image contrast effect for magnetic resonance imaging owing to their super paramagnetic properties on local magnetic fields. However, the possible effects of these NPs on membrane ion currents that concurrently induce local magnetic field perturbation remain unclear.

Methods

We evaluated whether amine surface-modified Fe₃O₄ NPs have any effect on ion currents in pituitary tumor (GH₃) cells via voltage clamp methods.

Results

The addition of Fe₃O₄ NPs decreases the amplitude of membrane electroporation-induced currents (I_MEP) with a half-maximal inhibitory concentration at 45 μg/mL. Fe₃O₄ NPs at a concentration of 3 mg/mL produced a biphasic response in the amplitude of I_MEP, ie, an initial decrease followed by a sustained increase. A similar effect was also noted in RAW 264.7 macrophages.

Conclusion

The modulation of magnetic electroporation-induced currents by Fe₃O₄ NPs constitutes an important approach for cell tracking under various imaging modalities or facilitated drug delivery.

Multifunctional magnetic mesoporous silica nanocomposites with improved sensing performance and effective removal ability toward Hg(II)

In the present work, a multifunctional inorganic-organic hybrid nanomaterial (MMS-Py) was prepared by the immobilization of a pyrene-based receptor (Py) within the channels of magnetic mesoporous silica nanocomposites (MMS), and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, N(2) adsorption/desorption, superconducting quantum interference device, and photoluminescence spectra. This multifunctional nanomaterial exhibits superparamagnetic behavior, ordered mesoporous characteristics, and significantly improved fluorescence sensing properties that allow for highly sensitive and reproducible Hg(2+) detection. The fluorogenical responses of MMS-Py are stable over a broad pH range. A detection limit of 1.72 ppb is obtained, which is 2 orders of magnitude lower than that based on bulk mesoporous materials. Additionally, this nanomaterial shows high performance in convenient magnetic separability and efficient removal of Hg(2+). These results indicate that these multifunctional nanocomposites may find potential applications for simple detection and easy removal of Hg(2+) in biological, toxicological, and environmental areas.