Selective enrichment of phosphoproteins or phosphopeptides from complex mixtures is essential for MS-based phosphoproteomics, but still remains a challenge. In this article, we described an unprecedented approach to synthesize magnetic mesoporous Fe(3)O(4)@mTiO(2) microspheres with a well-defined core/shell structure, a pure and highly crystalline TiO(2) layer, high specific surface area (167.1 m(2)/g), large pore volume (0.45 cm(3)/g), appropriate and tunable pore size (8.6-16.4 nm), and high magnetic susceptibility. We investigated the applicability of Fe(3)O(4)@mTiO(2) microspheres in a study of the selective enrichment of phosphopeptides. The experiment results demonstrated that the Fe(3)O(4)@mTiO(2) possessed remarkable selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/non-phosphopeptides (1:1000), large enrichment capacity (as high as 225 mg/g, over 10 times as that of the Fe(3)O(4)@TiO(2) microspheres), extreme sensitivity (the detection limit was at the fmol level), excellent speed (the enrichment can be completed in less than 5 min), and high recovery of phosphopeptides (as high as 93%). In addition, the high magnetic susceptibility allowed convenient separation of the target peptides by magnetic separation. These outstanding features give the Fe(3)O(4)@mTiO(2) composite microspheres high benefit for mass spectrometric analysis of phosphopeptides.

The heterostructure Ag–Au bimetallic nanocrystals supported on Fe3O4@carbon composite microspheres were synthesized by one facile and controllable approach, wherein the Ag nanocrystals attached on the Fe3O4@carbon microspheres were prepared first and served as reductant for the galvanic replacement reaction with the Au precursor (HAuCl4). Upon varying the feeding amounts of the Au precursor, the bimetallic compositions on the Fe3O4@carbon microsphere could be readily tuned resulting in a series of composite microspheres with different Au-to-Ag molar ratios. Subsequently, we thus investigated the catalytic activity and selectivity of the magnetic composite catalysts from two sides. First, 4-nitrophenol (4-NP) was applied as a model molecule to study the effect of different Au-to-Ag molar ratios on catalytic capabilities of the resulting composite microspheres. It was found that upon the addition of NaBH4 the catalytic capability was markedly enhanced when the Au content was increased. The maximum activity parameter value reached 1580 s–1 g–1, which is far higher than those of known monometallic composites. Also, they could give the equally high yields for other nitroaromatic compounds with various substituents, irrespective of the linked electron-donating or electron-withdrawing groups. Second, the synergistic effects of the carbon substrate in the catalysis reaction were demonstrated. When compared with colloidal SiO2, TiO2, and poly(styrene-co-acrylic acid) substrates, the carbon support not only facilitated the enhancement of the catalytic performance of the noble metal nanocrystals but was also more suitable for the in situ preparation of Au–Ag bimetallic nanocrystals using the GRR. Besides, the particles’ convenience in terms of their magnetic separability and outstanding reusability was validated through many successive reduction reaction cycles. In light of these unique characteristics, the Fe3O4@C@Ag–Au composite microspheres show promising and great potential for practical applications.

A facile and effective approach to preparation of dual‐responsive magnetic core/shell composite microspheres is reported. The magnetite(Fe3O4)/poly(methacrylic acid) (PMAA) composite microspheres were synthesized through encapsulating γ‐methacryloxypropyltrimethoxysilane (MPS)‐modified magnetite colloid nanocrystal clusters (MCNCs) with crosslinked PMAA shell. First, the 200‐nm‐sized MCNCs were fabricated through solvothermal reaction, and then the MCNCs were modified with MPS to form active vinyl groups on the surface of MCNCs, and finally, a pH‐responsive shell of PMAA was coated onto the surface of MCNCs by distillation‐precipitation polymerization. The transmission electron microscopy (TEM) and vibrating sample magnetometer characterization showed that the obtained composite microspheres had well‐defined core/shell structure and high saturation magnetization value (35 emu/g). The experimental results indicated that the thickness and degree of crosslinking of PMAA shell could be well‐controlled. The pH‐induced change in size exhibited by the core/shell microspheres reflected the PMAA shell contained large amount of carboxyl groups. The carboxyl groups and high saturation magnetization make these microspheres have a great potential in biomolecule separation and drug carriers. Moreover, we also demonstrated that other magnetic polymeric microspheres, such as Fe3O4/PAA, Fe3O4/PAM, and Fe3O4/PNIPAM, could be synthesized by this approach. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

A facile approach has been developed to synthesize Fe3O4/PMG (poly (N,N'-methylenebisacrylamide-co-glycidyl methacrylate)) core/shell microspheres using distillation-precipitation polymerization. Treating PMG shell with iminodiacetic acid (IDA) and Ni2+ yields composite microspheres of Fe3O4/PMG/IDA-Ni2+. The Ni2+ ions loaded on the surface of microspheres provide abundant docking sites for immobilization of histidine-tagged proteins. The high saturation magnetization of Fe3O4/PMG (23 emu/g), determined by vibrating sample magnetometer (VSM), allows an easy separation of the microspheres from solution under an external magnetic field. The composite microspheres were used to purify two His-tagged cellulolytic enzymes (Cel48F and Cel9G) directly from crude cell lysates with high binding affinity, capacity, and specificity. The microspheres can be recycled for many times without significant loss of binding capacity to enzymes. The immobilized enzymes on the surface of microspheres well retain their biological activities in degradation of cellulose. These materials show great potential in the biomedical and biotechnological applications that require low-cost purification of recombinant proteins and instant enzyme immobilization at an industrial scale.

Highly active surface-enhanced Raman scattering (SERS) substrates of Ag nanoparticle (Ag-NP) modified Fe(3)O(4)@carbon core-shell microspheres were synthesized and characterized. The carbon coated Fe(3)O(4) microspheres were prepared via a one-pot solvothermal method and were served as the magnetic supporting substrates. The Ag-NPs were deposited by in situ reduction of AgNO(3) with butylamine and the thickness of the Ag-NP layer was variable by controlling the AgNO(3) concentrations. The structure and integrity of the Fe(3)O(4)@C@Ag composite microspheres were confirmed by TEM, XRD, VSM and UV-visible spectroscopy. In particular, the Ag-NP coated Fe(3)O(4)@carbon core-shell microspheres were shown to be highly active for SERS detections of pentachlorophenol (PCP), diethylhexyl phthalate (DEHP) and trinitrotoluene (TNT). These analytes are representatives of environmentally persistent organic pollutants with typically low SERS activities. The results suggested that the interactions between the carbon on the microsphere substrates and the aromatic cores of the target molecules contributed to the facile pre-concentration of the analytes near the Ag-NP surfaces.

Architectural design is essential to achieve ideal chemical and biological properties of nanomaterials. In this article, a novel route to fabricate high‐quality magnetic composite microspheres composed of a high‐magnetic‐response magnetic colloid nanocrystal cluster (MCNC) core, a poly(methylacrylic acid) (PMAA) interim layer, and a Ti4+‐immobilized poly(ethylene glycol methacrylate phosphate) (PEGMP) shell via two‐step distillation–precipitation polymerization is presented. The unique as‐synthesized MCNC@PMAA@PEGMP‐Ti4+ composite microsphere is investigated for its applicability for selective enrichment of phosphopeptides from complex biological samples. The experiment results demonstrate that, by taking advantage of the pure phosphate–Ti4+ interface and high Ti4+ loading amount, the MCNC@PMAA@PEGMP‐Ti4+ composite microsphere possesses remarkable selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/nonphosphopeptides (1:500). The extreme sensitivity, excellent recovery of phosphopeptides, and high magnetic susceptibility are also proven. These outstanding features demonstrate that the MCNC@PMAA@PEGMP‐Ti4+ composite microspheres have great benefit for the pretreatment before mass spectrometric analysis of phosphopeptides. Furthermore, the performance of the approach in selective enrichment of phosphopeptides from drinking milk and human serum gives powerful evidence for its high selectivity and effectiveness in identifying the low‐abundant phosphopeptides from complicated biological samples.

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Efficient enrichment of specific glycoproteins from complex biological samples is of great importance towards the discovery of disease biomarkers in biological systems. Recently, phenylboronic acid-based functional materials have been widely used for enrichment of glycoproteins. However, such enrichment was mainly carried out under alkaline conditions, which is different to the status of glycoproteins in neutral physiological conditions and may cause some unpredictable degradation. In this study, on-demand neutral enrichment of glycoproteins from crude biological samples is accomplished by utilizing the reversible interaction between the cis-diols of glycoproteins and benzoboroxole-functionalized magnetic composite microspheres (Fe3O4/PAA-AOPB). The Fe3O4/PAA-AOPB composite microspheres are deliberately designed and constructed with a high-magnetic-response magnetic supraparticle (MSP) core and a crosslinked poly(acrylic acid) (PAA) shell anchoring abundant benzoboroxole functional groups on the surface. These nanocomposites possessed many merits, such as large enrichment capacity (93.9 mg/g, protein/beads), low non-specific adsorption, quick enrichment process (10 min) and magnetic separation speed (20 s), and high recovery efficiency. Furthermore, the as-prepared Fe3O4/PAA-AOPB microspheres display high selectivity to glycoproteins even in the E. coli lysate or fetal bovine serum, showing great potential in the identify of low-abundance glycoproteins as biomarkers in real complex biological systems for clinical diagnoses.