Preparation of biotinylated glyconanoparticles via a photochemical process and study of their bioconjugation to streptavidin

We report here the preparation of novel biotinylated glyconanoparticles from well-defined biotinylated glycopolymers and poly(N-isopropylacrylamide) (PNIPAAm) synthesized via the reversible addition fragmentation chain transfer (RAFT) polymerization process. The in situ reduction of the biotinylated glycopolymers, PNIPAAm, poly(ethylene glycol), and HAuCl4 via a photochemical process resulted in the formation of biotinylated gold nanoparticles. The multifunctional biotinylated glyconanoparticles were then evaluated for their bioconjugation toward streptavidin using UV-vis spectroscopy and surface plasmon resonance (SPR). The biotinylated nanoparticles underwent aggregation in the presence of streptavidin as revealed by spectrophotometry, which indicates the accessibility of the biotin for conjugation. These results were further confirmed by surface plasmon resonance even in the case of surface-immobilized streptavidin.     

Synthesis and characterization of poly(divinylbenzene)-coated magnetic iron oxide nanoparticles as precursor for the formation of air-stable carbon-coated iron crystalline nanoparticles

Maghemite (gamma-Fe2O3) nanoparticles of 15 +/- 3 nm diameter were prepared by nucleation of gelatin/iron oxide followed by growth of gamma-Fe2O3 films onto these nuclei. The gamma-Fe2O3 nanoparticles were coated with polydivinylbenzene (PDVB) by emulsion polymerization of divinylbenzene (DVB) in an aqueous continuous phase containing the gamma-Fe2O3 nanoparticles. The PDVB-coated gamma-Fe2O3 nanoparticles, dispersed in water, were separated from homo-PDVB nanoparticles using the high gradient magnetic field (HGMF) technique. The influence of DVB concentration on the amount of PDVB coating, on the size and size distribution of the coated gamma-Fe2O3 nanoparticles and on their magnetic properties, has been investigated. Air-stable carbon-coated iron (alpha-Fe/C) crystalline nanoparticles of 41 +/- 12 nm diameter have been prepared by annealing the PDVB-coated gamma-Fe2O3 nanoparticles at 1050 degrees C in an inert atmosphere. These nanoparticles exhibit high saturation magnetization value (83 emu g(-1)) and excellent resistance to oxidation. Characterization of the PDVB-coated gamma-Fe2O3 and of the alpha-Fe/C nanoparticles has been accomplished by TEM, HRTEM, DLS, FTIR, XRD, thermal analysis, zeta-potential, and magnetic measurements.     

Facile preparation of glyconanoparticles and their bioconjugation to streptavidin

Well-defined glycopolymers containing linear and cyclic carbohydrate moieties as pendent groups were prepared by reversible addition fragmentation chain transfer polymerization (RAFT). The RAFT synthesized glycopolymers were used for the aqueous synthesis of stabilized glyconanoparticles. The in situ reduction of the glycopolymers and HAuCl4 resulted in the formation of highly stable modified gold nanoparticles with diameters ranging from 40 to 80 nm in aqueous media. Multifunctional glyconanoparticles were also generated in the presence of varying amounts of biotinylated-polyethyleneglycol (bio-PEG-SH) having terminal thiol groups. The gold nanoparticles underwent aggregation in the presence of streptavidin as revealed by UV-vis spectroscopy. The availability of the biotin for conjugation to streptavidin was also confirmed using surface plasmon resonance (SPR).     

Biotinylation of TiO(2) nanoparticles and their conjugation with streptavidin

Photoactive TiO(2) can be used to mediate a variety of disinfection processes. It was postulated that TiO(2) particles could be directed to specific targets of interest using biotin/streptavidin linkages. Biotinylated TiO(2) nanoparticles (anatase) were obtained by treating TiO(2) nanoparticles with 3-aminopropyltriethoxysilane (APTS) in anhydrous DMSO, followed by reaction with N-hydroxysuccinimidobiotin. 29Si CP-MAS NMR, 13C CP-MAS NMR, and FTIR spectra showed that biotin was covalently bound to the TiO(2) surface. Transmission electron microscopy (TEM) demonstrated that prolonging the silanization reaction times led to increasingly thick silsesquioxane coating layers of up to approximately 10 nm. The specific surface area (SSA) of the TiO2 particles decreased from 16 m(2) g(-1) before treatment to 9.1 m(2) g(-1) after aminosilanization and to 8.4 m(2) g(-)1 after biotinylation, as measured by nitrogen adsorption. Amino surfaces modified for 4, 16, and 26 h had total amino group densities ranging from 2.9 to 26 to 66 nm(-2), respectively, whereas accessible surface amino group densities ranged from 2.7 to 10 to 17 nm(-2) as shown from nitrogen adsorption, polyelectrolyte titration, conductometric titration, and biotin assays. Not all the amino groups were accessible for biotinylation: the densities of active biotin were found to be 2.1, 7.0, and 11.5 nm(-2). The ability of the attached biotin to bind to streptavidin was demonstrated by confocal microscopy with the use of fluorescently labeled streptavidin-FITC. Although streptavidin was readily able to bind to biotinylated TiO(2) particles, it did not act as a strong flocculating agent for the biotinylated TiO2 particles. The implications of these observations, with respect to particle accessibility to tethered streptavidin, are discussed.     

Poly(ethylene oxide)-coated polyamide nanoparticles degradable by glutathione

Poly(adipoyl chloride-alt-cystamine) nanoparticles covalently coated with poly(ethylene oxide) (M _w = 2,000 or 5,000) were prepared as a model of glutathione-degradable drug, protein, or deoxyribonucleic acid delivery systems. The polyamide forming the micellar core has disulfide bonds in the main chain and thus its degradation gives low molecular weight products. The degradation of nanoparticles by the action of glutathione in the reduced or oxidized forms was monitored by time dependencies of the light scattering intensity at 37 °C in media modeling intracellular environment. The lifetimes of nanoparticles were determined. The reductive degradation of the nanoparticles by the reaction with reduced glutathione is an order of magnitude faster than their spontaneous degradation. The effect of nanoparticle concentration and solution pH was also investigated.     

Patterned langmuir-blodgett films of monodisperse nanoparticles of iron oxide using soft lithography

Langmuir-Blodgett (LB) films of monodisperse iron oxide nanoparticles have been successfully deposited onto patterned poly(dimethylsiloxane) surfaces. These patterned LB films of iron oxide nanoparticles were transferred onto solid substrates using micro contact printing.     

Synthesis of monodisperse iron oxide nanocrystals by thermal decomposition of iron carboxylate salts

Iron oxide (Fe(3)O(4), magnetite) nanocrystals of 6 to 30 nm with narrow size distributions (sigma = 5-10%) were prepared by the pyrolysis of iron carboxylate salts.     

Synthesis and electrocatalytic activity of haemin-functionalised iron(II,III) oxide nanoparticles

Haemin-functionalised magnetic iron(II, III) oxide (Fe₃O₄) nanoparticles (Fe₃O₄/haemin) were synthesised by changing the acidity of a solution of the two compounds. The nanoparticles were characterised by transmission electron microscopy, UV–vis absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, measurement of magnetisation, and electrochemical techniques. The properties of both haemin and Fe₃O₄ were retained. Thus, Fe₃O₄/haemin nanoparticles exhibited pronounced electrocatalytic activity towards trichloroacetic acid (TCA) like haemin itself. Interestingly, electrocatalytic activity towards TCA was affected by detection temperature, which was controlled via electrically heated carbon paste electrodes. The maximal catalytic current was 5.8 times higher at 60 °C than at room temperature (25 °C). This proposed electrochemical sensor for TCA possessed a linear detection range of 5–80 μM and a detection limit of 0.3 μM at 60 °C.     

Synthesis of magnetic nanoparticles and their application to bioassays

Magnetic nanoparticles have been attracting much interest as a labeling material in the fields of advanced biological and medical applications such as drug delivery, magnetic resonance imaging, and array-based assaying. In this review, synthesis of iron oxide magnetic nanoparticles via a reverse micelle system and modification of their surface by an organosilane agent are discussed. Furthermore, as a practical biological assay system, the magnetic detection of biomolecular interactions is demonstrated by using the combination of a patterned substrate modified with a self-assembled monolayer and the magnetic nanoparticles.     

Water-dispersible sugar-coated iron oxide nanoparticles. An evaluation of their relaxometric and magnetic hyperthermia properties

Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.     

Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles

The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant.     

Comparison and functionalization study of microemulsion-prepared magnetic iron oxide nanoparticles

Magnetic iron oxide nanoparticles (MION) for protein binding and separation were obtained from water-in-oil (w/o) and oil-in-water (o/w) microemulsions. Characterization of the prepared nanoparticles have been performed by TEM, XRD, SQUID magnetometry, and BET. Microemulsion-prepared magnetic iron oxide nanoparticles (ME-MION) with sizes ranging from 2 to 10 nm were obtained. Study on the magnetic properties at 300 K shows a large increase of the magnetization ~35 emu/g for w/o-ME-MION with superparamagnetic behavior and nanoscale dimensions in comparison with o/w-ME-MION (10 emu/g) due to larger particle size and anisotropic property. Moringa oleifera coagulation protein (MOCP) bound w/o- and o/w-ME-MION showed an enhanced performance in terms of coagulation activity. A significant interaction between the magnetic nanoparticles and the protein can be described by changes in fluorescence emission spectra. Adsorbed protein from MOCP is still retaining its functionality even after binding to the nanoparticles, thus implying the extension of this technique for various applications.     

Synthesis, morphological-structural characterization and magnetic properties of amorphous iron (III)-oxyhydroxy-phosphate nanoparticles

The synthesis, the chemical, morphological, structural characterization and the magnetic properties of amorphous iron oxyhydroxy phosphate nanoparticles are reported. Aggregated spherical particles (diameter: 5-12 nm) are obtained showing a ferrihydrite-like behavior similar to that of the bacterial ferritin iron oxyhydroxy-phosphate core. A superparamagnetic behavior is observed with blocking temperatures ranging from ∼20 to ∼50 K depending on the iron and phosphate content.     

磁性铁氧化物纳米粒子制备及其体内应用研究

磁性铁氧化物纳米粒子由于其生物相容性和低毒性而广泛的应用于生物医学领域。本文总结了近年来制备各种磁性铁氧化物纳米粒子的方法,比较了它们在粒径、结晶度以及制备条件等方面的优缺点,概括了对其进行表面修饰改性材料的种类,阐述近年来磁性铁氧化物纳米粒子在体内应用中药物运输、磁共振成像、磁热疗方面的进展,并指出当前应用中的主要方向和亟待解决的问题。     

Stabilization of magnetic iron oxide nanoparticles in biological media by fetal bovine serum (FBS)

A facile method of stabilizing magnetic iron oxide nanoparticles (MNPs) in biological media (RPMI-1640) via surface modification with fetal bovine serum (FBS) is presented herein. Dynamic light scattering (DLS) shows that the size of the MNP aggregates can be maintained at 190 ± 2 nm for up to 16 h in an RPMI 1640 culture medium containing ≥4 vol % FBS. Under transmission electron microscopy (TEM), a layer of protein coating is observed to cover the MNP surface following treatment with FBS. The adsorption of proteins is further confirmed by X-ray photoelectron spectroscopy (XPS). Gel electrophoresis and LC-MS/MS studies reveal that complement factor H, antithrombin, complement factor I, α-1-antiproteinase, and apolipoprotein E are the proteins most strongly attached to the surface of an MNP. These surface-adsorbed proteins serve as a linker that aids the adsorption of other serum proteins, such as albumin, which otherwise adsorb poorly onto MNPs. The size stability of FBS-treated MNPs in biological media is attributed to the secondary adsorbed proteins, and the size stability in biological media can be maintained only when both the surface-adsorbed proteins and the secondary adsorbed proteins are present on the particle's surface.     

Synthesis and stabilization of monodisperse Fe nanoparticles

Monodisperse Fe nanoparticles are synthesized via a simple one-pot thermal decomposition of Fe(CO)5 in the presence of oleylamine. Controlled oxidation of the iron surface leads to crystalline Fe3O4 shell and results in dramatic increase of chemical and dispersion stability of the nanoparticles. Surface ligand exchange is readily applied to transfer the core/shell nanoparticles from hydrophobic to hydrophilic, and a stable aqueous nanoparticle dispersion in PBS is formed. The functionalized nanoparticles are suitable for biomolecule attachment and biomedical applications.     

A controlled approach to iron oxide nanoparticles functionalization for magnetic polymer brushes

In this article, we report a detailed study of surface modification of magnetite nanoparticles by means of three different grafting agents, functional for the preparation of magnetic polymer brushes. 3-Aminopropyltriethoxysilane (APTES), 3-chloropropyltriethoxysilane (CPTES), and 2-(4-chlorosulfonylphenyl)ethyltrichlorosilane (CTCS) were chosen as grafting models through which a wide range of polymer brushes can be obtained. By means of accurate thermogravimetric analysis a good control over the amount of immobilized molecules is achieved, and optimal operating conditions for each grafting agent are consequently determined. Graft densities ranging from approximately 4 to 7 molecules per nm(2) are obtained, depending on the conditions used. In addition, the surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) carried out with CTCS-coated nanoparticles is presented as an example of polymer brushes, leading to a well-defined and dense polymeric coating of around 0.6 PMMA chains per nm(2).     

Synthesis of iron oxide nanoparticles using chitosan and starch templates

Natural polymers like chitosan and starch have been employed as templates for the preparation of iron oxide nanoparticles. The templates offer selective binding sites for Fe(II) under aqueous conditions. Controlled drying and subsequent removal of the template backbone enables the synthesis of spatially separated iron oxide nanoparticles. The crystalline character of the iron oxide and near narrow particle size distribution pattern have been confirmed through powder XRD, Photon Correlation Spectroscopy, and TEM measurements. The crystallite sizes of the particles were found to be 26–35 nm irrespective of the nature of the template.