磁性微球与牛血清白蛋白的相互作用

以纳米级四氧化三铁为磁性载体,以苯乙烯为单体,用微悬浮聚合法制备了聚苯乙烯磁性微球;以牛血清白蛋白(BSA)为模型蛋白,用荧光光谱仪和紫外-可见吸收光谱仪研究了磁性微球与BSA的相互作用.结果表明,磁性微球与BSA结合反应的猝灭机理为静态猝灭.     

Preparation of Core‐shell Magnetic Molecularly Imprinted Polymer Nanoparticles for Recognition of Bovine Hemoglobin

Imprinting nanoparticles : Core‐shell bovine hemoglobin (BHb) imprinted magnetic nanoparticles (MNPs) with a mean diameter of 210 nm have been synthesized for the first time. The imprinted magnetic nanoparticles could easily reach the adsorption equilibrium and magnetic separation under an external magnetic field, thus avoiding problems related to the bulk polymer.

     

磁性印迹纳米粒子固定血红蛋白修饰磁性电极构建过氧化氢传感器

采用表面印迹技术,以磁性二氧化硅纳米粒子（Fe₃O₄@SiO₂ NPs）作为载体、血红蛋白（Hb）为模板分子、正硅酸乙酯（TEOS）为印迹聚合物单体,制备了Hb印迹Fe₃O₄@SiO₂的磁性印迹纳米粒子（MMIPs NPs）. MMIPs NPs具有磁性内核和血红蛋白印迹壳层的核壳结构,可以富集并固定Hb. 使用壳聚糖将MMIPs NPs固定于磁性电极表面,构建血红蛋白类酶生物传感器,研究了Hb对过氧化氢（H₂O₂）的催化活性. MMIPS NPS相比于磁性非印迹纳米粒子（MNIPS NPS）,催化电流增加了14.3%. 采用磁性电极,MMIPS NPS、Hb和O₂的顺磁性使得该类酶生物传感器对H₂O₂的催化电流增加了60.0%. 血红蛋白类酶生物传感器电流响应与H₂O₂浓度在25 ~ 200 μmol·L^-1间呈线性关系,检出限为3 μmol·L^-1（S/N=3）,表明该类酶传感器对H₂O₂具有良好的催化性能.     

Immobilization of Antibodies on Magnetic Carbonaceous Microspheres for Selective Enrichment of Lysine‐acetylated Proteins and Peptides

Lysine acetylation is a dynamic and reversible modification, which has been proved to be a key posttranslational modification in cellular regulation. However, the low amounts of the acetylated proteins could hardly be detected before enrichment. In this study, for the first time, antibody‐immobilized magnetic carbonaceous microspheres were developed for selective enrichment of acetylated proteins and peptides. At first, standard proteins composed of acetylated bovine serum albumin, myoglobin, α‐casein and ovalbumin were used as model proteins to verify the enrichment efficiency. Then, the synthesized peptide was employed to confirm the selectivity of the method. Besides, the antibody‐immobilized magnetic particles were successfully applied to analyze mouse mitochondrial proteins. After database search, 29 acetylated sites in 26 proteins were identi?ed.     

Slow Magnetic Relaxation from Hard‐Axis Metal Ions in Tetranuclear Single‐Molecule Magnets

We report the synthesis of the novel heterometallic complex [Fe₃Cr(L)₂(dpm)₆]?Et₂O ( Fe₃CrPh ) (Hdpm=dipivaloylmethane, H₃L=2‐hydroxymethyl‐2‐phenylpropane‐1,3‐diol), obtained by replacing the central iron(III) atom by a chromium(III) ion in an Fe₄ propeller‐like single‐molecule magnet (SMM). Structural and analytical data, high‐frequency EPR (HF‐EPR) and magnetic studies indicate that the compound is a solid solution of chromium‐centred Fe₃Cr (S=6) and Fe₄ (S=5) species in an 84:16 ratio. Although SMM behaviour is retained, the |D| parameter is considerably reduced as compared with the corresponding tetra‐iron(III) propeller (D=?0.179 vs. ?0.418 cm^?1), and results in a lower energy barrier for magnetisation reversal (U_eff/k_B=7.0 vs. 15.6 K). The origin of magnetic anisotropy in Fe₃CrPh has been fully elucidated by preparing its Cr‐ and Fe‐doped Ga₄ analogues, which contain chromium(III) in the central position (c) and iron(III) in two magnetically distinct peripheral sites (p1 and p2). According to HF‐EPR spectra, the Cr and Fe dopants have hard‐axis anisotropies with D_c=0.470(5) cm^?1, E_c=0.029(1) cm^?1, D_p1=0.710(5) cm^?1, E_p1=0.077(3) cm^?1, D_p2=0.602(5) cm^?1, and E_p2=0.101(3) cm^?1. Inspection of projection coefficients shows that contributions from dipolar interactions and from the central chromium(III) ion cancel out almost exactly. As a consequence, the easy‐axis anisotropy of Fe₃CrPh is entirely due to the peripheral, hard‐axis‐type iron(III) ions, the anisotropy tensors of which are necessarily orthogonal to the threefold molecular axis. A similar contribution from peripheral ions is expected to rule the magnetic anisotropy in the tetra‐iron(III) complexes currently under investigation in the field of molecular spintronics.     

用于检测重金属离子的磁性荧光复合微球

采用静电逐层自组装的方法,首先将PSS和PAH聚电解质交替沉积在CaCO3中空微球表面,然后将Fe3O4磁性纳米粒子与CdSe量子点负载在中空微球表面不同的聚电解质层中,制备出具有磁性和荧光双重功能的复合微球,并将其作为荧光离子探针,研究了其对Cu2+和Pb2+离子检测的灵敏度、选择性及可行性。结果表明,复合微球显示出良好的磁性和荧光性能,对Cu2+和Pb2+离子的检测具有较高的灵敏度和选择性。尤为重要的是,可通过磁分离的方法将微球快速地从待测液中回收,从而能够避免量子点对环境造成的二次污染。     

用于检测重金属离子的磁性荧光复合微球

采用静电逐层自组装的方法,首先将PSS和PAH聚电解质交替沉积在CaCO₃中空微球表面,然后将Fe₃O₄磁性纳米粒子与CdSe量子点负载在中空微球表面不同的聚电解质层中,制备出具有磁性和荧光双重功能的复合微球,并将其作为荧光离子探针,研究了其对Cu²⁺和Pb²⁺离子检测的灵敏度、选择性及可行性。结果表明,复合微球显示出良好的磁性和荧光性能,对Cu²⁺和Pb²⁺离子的检测具有较高的灵敏度和选择性。尤为重要的是,可通过磁分离的方法将微球快速地从待测液中回收,从而能够避免量子点对环境造成的二次污染。     

Heavy Metal Removal from Synthetic Solutions with Magnetic Beads Under Magnetic Field

The aim of this study is to prepare magnetic beads which can be used for the removal of heavy metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate‐vinyl imidazole) [m‐poly(EGDMA‐VIM)] beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ nano‐powder. The specific surface area of the m‐poly(EGDMA‐VIM) beads was found to be 63.1 m²/g with a size range of 150–200 µm in diameter and the swelling ratio was 85%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA‐VIM) beads was 12.4%. The maximum binding capacities of the m‐poly(EGDMA‐VIM) beads were 32.4 mg/g for Cu²⁺, 45.8 mg/g for Zn²⁺, 84.2 mg/g for Cd²⁺and 134.5 mg/g for Pb²⁺. The affinity order on mass basis is Pb²⁺>Cd²⁺>Zn²⁺>Cu²⁺. Equilibrium data agreed well with the Langmuir model. pH significantly affected the binding capacity of the magnetic beads. Binding of heavy metal ions from synthetic wastewater was also studied. The binding capacities were 26.2 mg/g for Cu²⁺, 33.7 mg/g for Zn²⁺, 54.7 mg/g for Cd²⁺ and 108.4 mg/g for Pb²⁺. The magnetic beads could be regenerated up to about 97% by treating with 0.1 M HNO₃. These features make m‐poly(EGDMA‐VIM) beads a potential candidate for support of heavy metal removal under magnetic field.     

Characterization of Magnetic Nanoiron Oxides for the Removal of Metal Ions from Aqueous Solution

ABSTRACT

Two nanostructured hybrid materials are reported that include uncoated magnetic nanoiron oxides and magnetic nanoiron oxides treated with rose leaf extract. Atomic and molecular absorption spectrometry were used to evaluate the sensitivity of these materials for the isolation of Cr(VI), Zn(II), Pb(II), and Ca(II) from aqueous solution. The structure and physicochemical properties of the resulting nanohybrids were characterized by scanning electron microscopy coupled with energy-dispersive spectroscopy, atomic force microscopy, and X-ray diffraction. The results show that following 15?min of contact in acidic solution, the uncoated magnetic nanoiron oxides removed approximately 90% of Cr(VI), while the magnetic nanoiron oxides coated with rose leaf extract removed 92% of the analyte. These correspond to most industrial wastewater conditions. For the removal of Ca(II) and Zn(II), it was necessary to adjust the pH to neutral to maximize the efficiency. Pb(II) showed maximum removal efficiency when the solution is basic. The simple rose extract suspension was also used for metal removal with high capacity. The results demonstrate that the magnetic nanoiron oxides were uniformly distributed in the rose leaf extract. The extract served as a capping agent due to the presence of polyphenolics.     

One‐Pot Solvothermal Synthesis of Highly Water‐Dispersible Size‐Tunable Functionalized Magnetite Nanocrystal Clusters for Lipase Immobilization

A facile one‐pot synthesis of highly water‐dispersible size‐tunable magnetite (Fe₃O₄) nanocrystal clusters (MNCs) end‐functionalized with amino or carboxyl groups by a modified solvothermal reduction reaction has been developed. Dopamine and 3,4‐dihydroxyhydroxycinnamic acid were used for the first time as both a surfactant and interparticle linker in a polylol process for economical and environment‐friendly purposes. Morphology, chemical composition, and magnetic properties of the prepared particles were investigated by several methods, including FESEM, TEM, XRD, XPS, Raman, FTIR, TGA, zeta potential, and VSM. The sizes of the particles could be easily tuned over a wide range from 175 to 500 nm by varying the surfactant concentration. Moreover, ethylene glycol/diethylene glycol (EG/DEG) solvent mixtures with different ratios could be used as reductants to obtain the particles with smaller sizes. The XRD data demonstrated that the surfactants restrained the crystal growth of the grains. The nanoparticles showed superior magnetic properties and high colloidal stability in water. The cytotoxicity results indicated the feasibility of using the synthesized nanocrystals in biology‐related fields. To estimate the applicability of the obtained MNCs in biotechnology, Candida rugosa lipase was selected for the enzyme immobilization process. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with the free enzyme. This novel strategy would simplify the reaction protocol and improve the efficiency of materials functionalization, thus offering new potential applications in biotechnology and organocatalysis.     

Superoxide Compounds of the Large Pseudo‐Alkali‐Metal Ions Tetramethylammonium, ‐Phosphonium,and ‐Arsonium

Compounds of the three large cations tetramethylammonium, tetramethylphosphonium, and tetramethylarsonium with the superoxide radical anion were synthesized by either metathesis or ion exchange in liquid ammonia. They were obtained from concentrated solutions as ammoniates in the form of long needle‐shaped single crystals. [N(CH₃)₄]‐(O₂)?3NH₃ crystallizes in the monoclinic crystal system, whereas the two compounds [E(CH₃)₄](O₂)?2NH₃ (E=P, As) are isostructural and belong to the orthorhombic crystal system. The cation–anion packing in all three crystal structures is related to the sodium chloride structure. All structures contain hydrogen bonds between the ammonia molecules and between ammonia and the superoxide. The solvent of crystallization was easily released from the crystals upon complete removal of the solvent from the reaction vessel, leading to polycrystalline samples. The Raman spectra of all three solvent‐free compounds show the symmetric stretching mode of the superoxide ion at about 1123 cm^?1. The desolvated [N(CH₃)₄](O₂) was investigated by powder X‐ray diffraction, and the crystal structure was solved by ab initio simulated annealing methods by using rigid‐body models of the constituent molecular ions. The superoxide ion shows rotational disorder. The magnetic susceptibility of tetramethylammonium superoxide follows the Curie–Weiss law with a high‐temperature effective magnetic moment of 1.66(3) μ_B and a paramagnetic Curie temperature of Θ=?13(6) K. Complementary electron paramagnetic resonance spectroscopy revealed that the average g factor is temperature‐dependent. It decreased from 2.15 at 10 K to 1.66 at 100 K, possibly due to the onset of rotational motion of the superoxide ion and in accordance with the lower‐than‐expected effective magnetic moment.     

Direct Electrochemistry of Hemoglobin Immobilized on Carbon‐Coated Iron Nanoparticles for Amperometric Detection of Hydrogen Peroxide

A novel method for preparation of hydrogen peroxide biosensor was presented based on immobilization of hemoglobin (Hb) on carbon‐coated iron nanoparticles (CIN). CIN was firstly dispersed in a chitosan solution and cast onto a glassy carbon electrode to form a CIN/chitosan composite film modified electrode. Hb was then immobilized onto the composite film with the cross‐linking of glutaraldehyde. The immobilized Hb displayed a pair of stable and quasireversible redox peaks and excellent electrocatalytic reduction of hydrogen peroxide (H₂O₂), which leading to an unmediated biosensor for H₂O₂. The electrocatalytic response exhibited a linear dependence on H₂O₂ concentration in a wide range from 3.1 μM to 4.0 mM with a detection limit of 1.2 μM (S/N=3). The designed biosensor exhibited acceptable stability, long‐term life and good reproducibility.     

High Impact of Uranyl Ions on Carrying–Releasing Oxygen Capability of Hemoglobin‐Based Blood Substitutes

The effect of radioactive UO₂²⁺ on the oxygen‐transporting capability of hemoglobin‐based oxygen carriers has been investigated in vitro. The hemoglobin (Hb) microspheres fabricated by the porous template covalent layer‐by‐layer (LbL) assembly were utilized as artificial oxygen carriers and blood substitutes. Magnetic nanoparticles of iron oxide (Fe₃O₄) were loaded in porous CaCO₃ particles for magnetically assisted chemical separation (MACS). Through the adsorption spectrum of magnetic Hb microspheres after adsorbing UO₂²⁺, it was found that UO₂²⁺ was highly loaded in the magnetic Hb microspheres, and it shows that the presence of UO₂²⁺ in vivo destroys the structure and oxygen‐transporting capability of Hb microspheres. In view of the high adsorption capacity of UO₂²⁺, the as‐assembled magnetic Hb microspheres can be considered as a novel, highly effective adsorbent for removing metal toxins from radiation‐contaminated bodies, or from nuclear‐power reactor effluent before discharge into the environment.     

The Synthesis of Magnetic Lysozyme‐Imprinted Polymers by Means of Distillation–Precipitation Polymerization for Selective Protein Enrichment

A protein imprinting approach for the synthesis of core–shell structure nanoparticles with a magnetic core and molecularly imprinted polymer (MIP) shell was developed using a simple distillation–precipitation polymerization method. In this work, Fe₃O₄ magnetic nanoparticles were first synthesized through a solvothermal method and then were conveniently surface‐modified with 3‐(methacryloyloxy)propyltrimethoxylsilane as anchor molecules to donate vinyl groups. Next a high‐density MIP shell was coated onto the surface of the magnetic nanoparticles by the copolymerization of functional monomer acrylamide (AAm), cross‐linking agent N,N′‐methylenebisacrylamide (MBA), the initiator azodiisobutyronitrile (AIBN), and protein in acetonitrile heated at reflux. The morphology, adsorption, and recognition properties of the magnetic molecularly imprinted nanoparticles were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and rebinding experiments. The resulting MIP showed a high adsorption capacity (104.8 mg g^?1) and specific recognition (imprinting factor=7.6) to lysozyme (Lyz). The as‐prepared Fe₃O₄@Lyz‐MIP nanoparticles with a mean diameter of 320 nm were coated with an MIP shell that was 20 nm thick, which enabled Fe₃O₄@Lyz‐MIP to easily reach adsorption equilibrium. The high magnetization saturation (40.35 emu g^?1) endows the materials with the convenience of magnetic separation under an external magnetic field and allows them to be subsequently reused. Furthermore, Fe₃O₄@Lyz‐MIP could selectively extract a target protein from real egg‐white samples under an external magnetic field.     

Graphene‐Based Composite with γ‐Fe2O3 Nanoparticle for the High‐Performance Removal of Endocrine‐Disrupting Compounds from Water

Graphene is a 2D sp²‐hybridized carbon sheet and an ideal material for the adsorption‐based separation of organic pollutants. However, such potential applications of graphene are largely limited, owing to their poor solubility and extensive aggregation properties through graphene? graphene interactions. Herein, we report the synthesis of graphene‐based composites with γ‐Fe₂O₃ nanoparticle for the high‐performance removal of endocrine‐disrupting compounds (EDC) from water. The γ‐Fe₂O₃ nanoparticles partially inhibit these graphene? graphene interactions and offer water dispersibility of the composite without compromising much of the high surface area of graphene. In their dispersed form, the graphene component offers the efficient adsorption of EDC, whilst the magnetic iron‐oxide component offers easier magnetic separation of adsorbed EDC.     

Indirect Transformation of Coordination‐Polymer Particles into Magnetic Carbon‐Coated Mn3O4 (Mn3O4@C) Nanowires for Supercapacitor Electrodes with Good Cycling Performance

Carbon‐coated Mn₃O₄ nanowires (Mn₃O₄@C NWs) have been synthesized by the reduction of well‐shaped carbon‐coated bixbyite networks and characterized by TEM, X‐ray diffraction, X‐ray photoelectron spectroscopy, and electrochemical experiments. To assess the properties of 1D carbon‐coated nanowires for their use in supercapacitors, cyclic voltammetry and galvanostatic charging–discharging measurements were performed. Mn₃O₄@C NWs could be charged and discharged faster and had higher capacitance than bare Mn₃O₄ nanostructures and other commercial materials. The capacitance of the Mn₃O₄@C NWs was 92 % retained after 3000 cycles at a charging rate of 5 A g^?1. This improvement can be attributed to the carbon shells, which promote fast Faradaic charging and discharging of the interior Mn₃O₄ core and also act as barriers to protect the inner core. These Mn₃O₄@C NWs could be a promising candidate material for high‐capacity, low‐cost, and environmentally friendly electrodes for supercapacitors. In addition, the magnetic properties of the as‐synthesized samples are also reported to investigate the influence of the carbon coating.