Acid-functionalized Magnetic Nanoparticles Research Articles

A highly efficient nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid groups as a solid acid catalyst for synthesis of 1,8-dioxo-octahydroxanthene derivatives

The functionalization of silica-coated Fe3O4 magnetic nanoparticles (Fe3O4@SiO2) using chlorosulfonic acid were afforded sulfonic acid-functionalized magnetic Fe3O4 nanoparticles (Fe3O4@SiO2–SO3H) that can be applied as an organic–inorganic hybrid heterogeneous catalyst. The used Fe3O4 magnetic nanoparticles are 18–30 nm sized that was rapidly functionalized and can be used as catalyst in organic synthesis. The prepared nanoparticles were characterized by X-ray diffraction analysis, magnetization curve, scanning electron microscope, dynamic laser scattering, and FT-IR measurements. The resulting immobilized catalysts have been successfully used in the synthesis of 1,8‐dioxo-octahydroxanthene derivatives under solvent free condition. This procedure has many advantages such as; a much milder method, a shorter reaction time, a wide range of functional group tolerance, and absence of any tedious workup or purification. Other remarkable features include the catalyst can be reused at least five times without any obvious change in its catalytic activity. This procedure also avoids hazardous reagents/solvents, and thus can be an eco-friendly alternative to the existing methods.Graphical A highly efficient nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid groups as a solid acid catalyst for synthesis of 1,8-dioxo-octahydroxanthene derivatives Electronic supplementary materialThe online version of this article (doi:10.1007/s11051-013-2026-2) contains supplementary material, which is available to authorized users.

Sulphamic acid-functionalized magnetic Fe3O4 nanoparticles as recyclable catalyst for synthesis of imidazoles under microwave irradiation

Trisubstituted imidazoles have been synthesized in high yield in the presence of sulphamic acid-functionalized magnetic Fe3O4 nanoparticles (SA–MNPs) as a novel solid acid catalyst under solvent-free classical heating conditions or using microwave irradiation. The heterogeneous catalyst could be recovered easily and reused many times without significant loss of catalytic activity. An efficient procedure for the synthesis of imidazoles has been developed by condensation reaction of 1, 2-diketones, aromatic aldehydes, and ammonium acetate using sulphamic acid-functionalized Fe3O4 nanoparticles under microwave irradiation. This method offers several advantages including high yield, short reaction time, simple work-up procedure and recyclability of the magnetic catalyst.

Magnetic nanoparticles with dendrimer-assisted boronate avidity for the selective enrichment of trace glycoproteins

Boronic acid-functionalized materials have been the subject of increasing attention in recent years due to their capability in the facile selective extraction of glycoproteins. However, boronic acids are associated with weak binding affinity, and it is thereby difficult for boronate affinity materials to extract glycoproteins of low concentration. Here we present for the first time a boronate avidity material, dendrimeric boronic acid-functionalized magnetic nanoparticles, with significantly enhanced binding strength towards glycoproteins. Due to the dendrimer-assisted multivalent synergistic binding, the boronate avidity material exhibited dissociation constants of 10−5 to 10−6 M towards glycoproteins, which are 3–4 orders of magnitude higher than the affinities of single boronic acid binding. Such an avidity enabled the selective extraction of trace glycoproteins; an extractable concentration as low as 2 × 10−14 M was demonstrated. Meanwhile, the boronate avidity material was tolerant of the interference of abundant competing sugars. Moreover, the dendrimeric boronic acid-functionalized magnetic nanoparticles exhibited two additional advantages: high binding capacity and fast binding/desorption speed. Due to these favourable features, the selective enrichment of trace glycoproteins by the boronate avidity material became not only possible but also efficient. Efficient enrichment of trace glycoproteins from human saliva was demonstrated. The dendrimer-assisted synergistic binding strategy is also applicable to other types of boronic acid-functionalized materials and other types of functionalized materials.

A highly efficient magnetic solid acid catalyst for synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation

Fe3O4 nanoparticles were prepared by chemical coprecipitation method and subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction. Grafting of chlorosulfuric acid on the amino-functionalized Fe3O4 nanoparticles afforded sulfamic acid-functionalized magnetic nanoparticles (SA-MNPs). SA-MNPs was found to be a mild and effective solid acid catalyst for the efficient, one-pot, three-component synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation. This protocol afforded corresponding imidazoles in shorter reaction durations, and in high yields. This green procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, easy and quick isolation of the products, excellent yields, short routine, and simplicity of the methodology.

An efficient strategy for unmodified nucleotide-mediated dispersion of magnetic nanoparticles, leading to a highly sensitive MRI-based mercury ion assay

It is highly attractive to develop a detection system that is not only sensitive and selective but also simple, rapid, practical and cost-effective in operation. Here, we report an interesting observation that single-stranded oligonucleotide (ssDNA) can adsorb efficiently on carboxylic acid-functionalized magnetic nanoparticles (CAMNPs) and stabilize the nanoparticles against aggregation in weakly acidic solution. The adsorbing rate closely correlates with the pH of the solution, the temperature and the sequence length of ssDNA. On the basis of this observation, we have designed a highly sensitive, non-sandwich type magnetic relaxation-based detection system for quantitatively probing mercury ion. The assay is independent of the sample's optical properties, requires no covalent modification of the ssDNA or the CAMNPs surfaces, and can be used for high-throughput analysis. By varying the concentration of CAMNPs, four orders of dynamic response range and a detection limit of 0.3nM for Hg2+ are achieved. Moreover, we developed a multi-sample assay to detect Hg2+ in real environmental samples with high sensitivity, selectivity and efficiency.

Acid-Functionalized Nanoparticles for Pretreatment of Wheat Straw

Perfluoroalkylsufonic (PFS) and alkylsufonic (AS) acid-functionalized magnetic nanoparticles were synthesized and characterized, then evaluated for their ability to hydrolyze hemicelluloses. The magnetic core was made of cobalt spinel ferrite and was coated with silica to protect it from oxidation. The silanol groups allowed surface chemical modification of the nanoparticles with the PFS and AS acid functionalities. Thermogravimetric analysis gave a total organic load of 12.6% and 32.5% (w/w) for AS and PFS nanoparticles, respectively. The surface sulfur content was calculated from XPS analysis as 1.37% and 1.93% for PFS and AS nanoparticles, respectively. Wheat straw samples were treated with the acid-functionalized nanoparticles at two different conditions: 80℃ for 24 h and 160℃ for 2 h. These experiments aimed to hydrolyze wheat straw hemicelluloses to soluble oligosaccharides. PFS nanoparticles solubilized significantly higher amounts of hemicelluloses (24.0% ± 1.1%) than their alkyl-sulfonic counterparts (9.1% ± 1.7%) at 80℃, whereas the hydrothermolysis control solubilized 7.7% ± 0.8% of the original hemicelluloses in the sample. At 160℃, PFS and AS nanoparticles gave significantly higher amounts of oligosaccharides (46.3% ± 0.4% and 45 ± 1.2%, respectively) than the control (35.0% ± 1.8%). The hemicelluloses conversion at 160?C reached 66.3% ± 0.9% using PFS nanoparticles and 61.0% ± 1.2% using AS nanoparticles compared with the control experiment, which solubilized 50.9% ± 1.7% of hemicelluloses in the biomass.

Magnetic nanosensors for highly sensitive and selective detection of bacillus Calmette-Guérin

With current concerns of the global threat from tuberculosis, it has become important to rapidly identify the bacteria. Traditional technologies involving isolation and amplification of the pathogenic bacteria are complicated and time-consuming. In this work, we describe a sensitive NMR-based detection method to identify bacteria via bacteria-induced self-assembly of magnetic nanoparticles. Bacillus Calmette-Guérin (BCG) was used as a surrogate for Mycobacterium tuberculosis. We prepared the probes by covalent immobilization of the anti-BCG monoclonal antibody onto carboxylic acid-functionalized magnetic nanoparticles. Once a solution containing BCG was introduced, the probes switched from a well dispersed state to an aggregated one, leading to a distinct and dose-dependent change in the spin-spin relaxation time (T2) of the solution. Thus the qualitative and quantitative detection method for BCG was established. The method provides specific detection of as few as 8 bacterial cells per millilitre in experimental samples within 1 hour, which will be promising for rapid detection of M. tuberculosis in clinical samples.

Facile Synthesis of Boronic Acid-Functionalized Magnetic Mesoporous Silica Nanocomposites for Highly Specific Enrichment of Glycopeptides

In the work, aminophenylboronic acid (APB)-functionalized magnetic mesoporous silica, which holds the attractive features of high magnetic responsivity and large surface area, was developed to enrich glycopeptides. At first, magnetic mesoporous silica nanocomposites were prepared. And then, the nanocomposites were functioned with glycidoxypropyltrimethoxysilane (GLYMO) for boronic acid immobilization. Due to that the boronic acid group on the surface of magnetic mesoporous silica nanocomposites can form tight yet reversible covalent bond with glycopeptides containing cis-1,2-diols groups, the magnetic mesoporous silica nanocomposites were successfully applied to selective enrichment of glycopeptides. APB functionalized magnetic mesoporous silica was also demonstrated to have high selectivity for the glycopeptides in the presence of a 10-fold excess bovine serum albumin (BSA) over horseradish peroxidase (HRP) in the tryptic digest. We also find that magnetic mesoporous silica has better sensitivity in HRP digest compared with that of commercial aminophenylboronic acid-functionalized magnetic nanoparticles beads. The limit of detection for glycopeptides from glycoprotein HRP is about 0.01 ng/µL.

Concanavalin A‐immobilized magnetic nanoparticles for selective enrichment of glycoproteins and application to glycoproteomics in hepatocelluar carcinoma cell line

Protein glycosylation is one of the most important PTMs in biological organism. Lectins such as concanavalin A (Con A) have been widely applied to N-glycosylated protein investigation. In this study, we developed Con A-immobilized magnetic nanoparticles for selective separation of glycoproteins. At first, a facile immobilization of Con A on aminophenylboronic acid-functionalized magnetic nanoparticles was performed by forming boronic acid-sugar-Con A bond in sandwich structure using methyl alpha-D-mannopyranoside as an intermedium. The selective capture ability of Con A-modified magnetic nanoparticles for glycoproteins was tested using standard glycoproteins and cell lysate of human hepatocelluar carcinoma cell line 7703. In total 184 glycosylated sites were detected within 172 different glycopeptides corresponding to 101 glycoproteins. Also, the regeneration of the protein-immobilized nanoparticles can easily be performed taking advantage of the reversible binding mechanism between boronic acid and sugar chain. The experiment results demonstrated that Con A-modified magnetic nanoparticles by the facile and low-cost synthesis provided a convenient and efficient enrichment approach for glycoproteins, and are promising candidates for large-scale glycoproteomic research in complicated biological samples.

Selective Separation of Glycopeptides and Glycoproteins by Aminophenylboronic AcidFunctionalized Magnetic Nanoparticles

Selective Separation of Glycopeptides and Glycoproteins by Aminophenylboronic AcidFunctionalized Magnetic Nanoparticles

Facile synthesis of aminophenylboronic acid-functionalized magnetic nanoparticles for selective separation of glycopeptides and glycoproteins

In this work, aminophenylboronic acid-functionalized magnetic nanoparticles were synthesized, and applied to selective separation of glycopeptides and glycoproteins.

Aptamer-Mediated Magnetic and Gold-Coated Magnetic Nanoparticles as Detection Assay for Prion Protein Assessment

This article reports the chemical synthesis and functionalization of magnetic and gold-coated magnetic nanoparticles. The binding characteristics of streptavidin-conjugated nanoparticles were studied using prion protein as a target to a specific biotinylated aptamer. The size and structure of the particles were determined by transmission electron microscopy, and the binding of the prion to the particle was confirmed by Fourier transform infrared spectroscopy. The rate of prion binding to the aptamer was dose-dependent, and prion immobilization was more effective on L-aspartic acid-functionalized magnetic nanoparticles compared to the carboxyl-functionalized gold-coated magnetic nanoparticles. This study sets the stage for the development of prion detection platforms as well as our long-term goals in structure elucidation at the binding interface.