Removal of aflatoxin B1 from contaminated peanut oils using magnetic attapulgite.

The efficient magnetic adsorbent (Fe3O4@ATP) was prepared by precipitation through the dispersion of Fe3O4 nanoparticles on the natural attapulgite (ATP) and then tested as an adsorbent for aflatoxin B1 (AFB1) removal from contaminated oils. The adsorbent characterization results revealed that the Fe3O4 were incorporated into the ATP, affording the Fe3O4@ATP composite. This magnetic composite displayed a good ability to eliminate AFB1 from contaminated oils with a removal efficiency of 86.82% using a 0.3% dosage. The Fe3O4@ATP possessed paramagnetic character with a saturation magnetization of 50.86 emu/g, enabling its easy separation from the medium using an external magnet. The adsorption process followed the pseudo-second-order model and fitted the Freundlich isotherm well. Moreover, the thermodynamic studies showed that AFB1 adsorption onto Fe3O4@ATP was exothermic and spontaneous. The novelty of this study lies in the fabrication of magnetic composite adsorbents for AFB1 elimination from oils.

Self-assembly of paramagnetic amphiphilic copolymers for synergistic therapy.

Engineering nanoparticles (NPs) with multifunctionality has become a promising strategy for cancer theranostics. Herein, theranostic polymer NPs are fabricated via the assembly of amphiphilic paramagnetic block copolymers (PCL-b-PIEtMn), in which IR-780 and doxorubicin (DOX) were co-encapsulated, for magnetic resonance (MR) and near infrared fluorescence (NIRF) imaging as well as for photo thermal therapy (PTT)-enhanced chemotherapy. The synthesized amphiphilic paramagnetic block copolymers demonstrated high relaxivity (r1 = 7.05 mM-1 s-1). The encapsulated DOX could be released with the trigger of near infrared (NIR) light. In vivo imaging confirmed that the paramagnetic NPs could be accumulated effectively at the tumor sites. Upon the NIR laser irradiation, tumor growth was inhibited by PTT-enhanced chemotherapy. The advantages of the reported system lie in the one-step convergence of multiple functions (i.e., imaging and therapy agents) into a one delivery vehicle and the dual mode imaging-guided synergistic PTT and chemotherapy. This study represents a new drug delivery vehicle of paramagnetic NPs for visualized theranostics.

Predictive Model for Delivery Efficiency: Erythrocyte Membrane-Camouflaged Magnetofluorescent Nanocarriers Study.

Delivery efficiencies of theranostic nanoparticles (NPs) based on passive tumor targeting strongly depend either on their blood circulation time or on appropriate modulations of the tumor microenvironment. Therefore, predicting the NP delivery efficiency before and after a tumor microenvironment modulation is highly desirable. Here, we present a new erythrocyte membrane-camouflaged magnetofluorescent nanocarrier (MMFn) with long blood circulation time (92 h) and high delivery efficiency (10% ID for Ehrlich murine tumor model). MMFns owe their magnetic and fluorescent properties to the incorporation of manganese ferrite nanoparticles (MnFe2O4 NPs) and IR-780 (a lipophilic indocyanine fluorescent dye), respectively, to their erythrocyte membrane-derived camouflage. MMFn composition, morphology, and size, as well as optical absorption, zeta potential, and fluorescent, magnetic, and magnetothermal properties, are thoroughly examined in vitro. We then present an analytical pharmacokinetic (PK) model capable of predicting the delivery efficiency (DE) and the time of peak tumor uptake (tmax), as well as changes in DE and tmax due to modulations of the tumor microenvironment, for potentially any nanocarrier. Experimental PK data sets (blood and tumor amounts of MMFns) are simultaneously fit to the model equations using the PK modeling software Monolix. We then validate our model analytical solutions with the numerical solutions provided by Monolix. We also demonstrate how our a priori nonmechanistic model for passive targeting relates to a previously reported mechanistic model for active targeting. All in vivo PK studies, as well as in vivo and ex vivo biodistribution studies, were conducted using two noninvasive techniques, namely, fluorescence molecular tomography (FMT) and alternating current biosusceptometry (ACB). Finally, histopathology corroborates our PK and biodistribution results.

Screening of the potentially active compounds from Polygonatum sibiricum using RAW264.7 cellular membranes coated magnetic beads fishing followed by HPLC analysis.

Target biomolecule-immobilized magnetic beads could be used as a powerful tool for screening active compounds present in natural products. Low damage rates of the target proteins, associated with the availability of diverse automated online approaches for analysis, make it a valuable tool for affinity studies. RAW264.7 cells (a kind of murine macrophage cell line) were used in this study. These cellular membranes were immobilized onto the surface of MBs and were used for screening the active compounds of Polygonatum sibiricum. Combining this technique with HPLC led to the identification of an active compound and its biological activity was confirmed. This is the first report establishing the use of RAW264.7 cellular membrane-coated magnetic bead fishing followed by HPLC analysis for screening active compounds from natural products.

A "signal-on" chemiluminescence biosensor for thrombin detection based on DNA functionalized magnetic sodium alginate hydrogel and metalloporphyrinic metal-organic framework nanosheets.

A "signal-on" chemiluminescence biosensor was established for detecting thrombin. The thrombin aptamer1-functionalized magnetic sodium alginate (Malg-Apt1) hydrogel was synthesized by physical interaction between sodium alginate and Ca2+, and it was used in the biosensor for separating and enriching thrombin. Ethylenediamine tetraacetic acid (EDTA) was used to chelate with Ca2+ to dissolve the hydrogel and release thrombin. A metalloporphyrinic metal-organic framework nanosheet, named as Cu-TCPP(Co) MOFs, was prepared as signal amplification strategy. Cu-TCPP(Co) MOFs/Au-ssDNA (ssDNA: single-strand DNA) was synthesized for controllable further amplification of chemiluminescent signal. The thrombin aptamer2-functionalized magnetic carbon nanotubes (MCNTs-Apt2) were used as a matrix, and Cu-TCPP(Co) MOFs/Au-ssDNA was adsorbed on the MCNTs by the complementary pairing of the partial bases between ssDNA and Apt2. Compared with ssDNA, Apt2 has a stronger interaction with thrombin. Therefore, thrombin can trigger the release of Cu-TCPP(Co) MOFs/Au-ssDNA to achieve signal amplification. Under the optimal conditions, the biosensor could detect thrombin as low as 2.178 × 10-13 mol/L with the range from 8.934 × 10-13 to 5.956 × 10-10 mol/L and exhibited excellent selectively. Moreover, the "signal-on" chemiluminescence biosensor showed potential application for the detection of thrombin in body fluids.

Periplasmic binding protein-based magnetic isolation and detection of thiamine in complex biological matrices.

Deficiencies in thiamine (vitamin B1) cause a host of neurological and reproductive impairments yielding morbidity and mortality across environmental and clinical realms. In a technique analogous to immunomagnetic separation, we introduce the use of thiamine periplasmic binding protein (TBP)-conjugated magnetic beads to isolate thiamine from complex matrices. TBP expressed in Escherichia coli is highly specific to thiamine and provides an alternative to antibodies for this non-immunogenic target. After incubation with the sample and removal of unbound matrix constituents, thiamine is simultaneously released and converted to its fluorescent oxidation product thiochrome by alkaline potassium ferricyanide. Subsequent measurement of fluorescence at thiochrome-specific wavelengths provides a second layer of specificity for the detection of thiamine. Thiamine could be quantified at concentrations as low as 5 nM ranging up to 240 nM. Within, we apply this technique to selectively capture and quantify thiamine in complex salmonid fish egg and tissue matrices. Our results showed no measurable non-specific binding to the beads by endogenous fluorophores in the fish egg matrix. Thiamine levels as low as 0.2 nmol/g of fish egg can be detected using this approach, which is sufficient to assess deficiencies causing morbidity and mortality in fish that occur at 1.0 nmol/g of egg. This practical method may find application in other resource limited settings for clinical, food, or dietary supplement analyses.

Ferrimagnetic Vortex Nanoring-Mediated Mild Magnetic Hyperthermia Imparts Potent Immunological Effect for Treating Cancer Metastasis.

Cancer metastasis is a serious concern and a major reason for treatment failure. Herein, we have reported the development of an effective and safe nanotherapeutic strategy that can eradicate primary tumors, inhibit metastasizing to lung, and control the metastasis and growth of distant tumors. Briefly, ferrimagnetic vortex-domain iron oxide nanoring (FVIO)-mediated mild magnetic hyperthermia caused calreticulin (CRT) expression on the 4T1 breast cancer cells. The CRT expression transmitted an "eat-me" signal and promoted phagocytic uptake of cancer cells by the immune system to induce an efficient immunogenic cell death, further leading to the macrophage polarization. This mild thermotherapy promoted 88% increase of CD8+ cytotoxic T lymphocyte infiltration in distant tumors and triggered immunotherapy by effectively sensitizing tumors to the PD-L1 checkpoint blockade. The percentage of CD8+ cytotoxic T lymphocytes can be further increased from 55.4% to 64.5% after combining with PD-L1 blockade. Moreover, the combination treatment also inhibited the immunosuppressive response of the tumor, evidenced by significant down-regulation of myeloid-derived suppressor cells (MDSCs). Our results revealed that the FVIO-mediated mild magnetic hyperthermia can activate the host immune systems and efficiently cooperate with PD-L1 blockade to inhibit the potential metastatic spreading as well as the growth of distant tumors.

Poly(deep eutectic solvent)-functionalized magnetic metal-organic framework composites coupled with solid-phase extraction for the selective separation of cationic dyes.

Novel polymeric deep eutectic solvents (PDES) based on 3-acrylamidopropyl trimethylammonium chloride/D-sorbitol functionalized amino-magnetic (Fe3O4NH2) metal-organic framework (HKUST-1-MOF) composites (Fe3O4NH2@HKUST-1@PDES) were synthesized and characterized by field emission transmission electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA), vibrating sample magnetometer (VSM) and zeta potentials. Then the composites were firstly utilized to selectively separate malachite green (MG) and crystal violet (CV) coupled with magnetic solid-phase extraction (MSPE). A response surface methodology (RSM) based on Latin hypercube sampling (LHS) was selected to analytically optimize the extraction parameters including initial concentration of dyes, extraction time, pH value and extraction temperature. The maximum extraction amount and optimal extraction conditions predicted by the RSM model matched well with the actual experimental results, and the extraction amount was 966.93 mg g-1 for MG and 788.90 mg g-1 for CV,respectively. The results indicated that the model possessed higher calculation accuracy through analyzing fewer sample points, thereby achieving theoretical prediction of extraction amount and conditions and being a prefect supplementary to actual experiments. The electrostatic interaction between the composites and cationic dyes played the main roll in the extraction process. The proposed extraction method exhibited lower limit of detection (98.19 ng mL-1 for MG and 23.97 ng mL-1 for CV) and preeminent precision (RSD ˂ 0.4%). Spiked recoveries of fish samples at three spiking levers ranged from 89.43% to 100.65% for MG and 95.29%-98.03% for CV. All results highlighted the excellent potential of Fe3O4NH2@HKUST-1@PDES-MSPE strategy in selective separation of cationic dyes in complex medium.

Magnetic particles-based enzyme immunoassay for rapid determination of secoiridoid glycoside, amarogentin.

Amarogentin (AG) is one of the bitter secoiridoid glycosides, which exerts various pharmacological activities as a bitter stomachic. Recently, there is an increasing demand for AG-containing plants in Japan due to their use as folk medicines and food additives; hence, it is crucial to develop analytical techniques that are specific for AG. In this study, a new magnetic particles-based enzyme immunoassay (MPs-EIA) using a specific monoclonal antibody against AG (MAb 1E9) for the rapid determination of AG in plants of the family Gentianaceae was described. AG directly immobilized onto magnetic particles (MPs) was used as a competitor for free AG against MAb 1E9, thereby increasing the surface area of the solid phase and decreasing the immunoreaction time. In addition, the blocking step required in case of the conventional enzyme-linked immunosorbent assay could be avoided in the proposed MPs-EIA, which enables an even more rapid performance for the immunoassay. In the developed MPs-EIA, AG exhibited linearity in the range of 15.6-500 ng mL-1, with a limit of detection of 8.58 ng mL-1. Validation analysis revealed that MPs-EIA is a sufficiently sensitive and rapid for the quantitative analysis of AG in plant samples. To the best of our knowledge, this is the first MPs-EIA that has been applied to plant samples.

Magnetic silica nanoparticles for use in matrix-assisted laser desorption ionization mass spectrometry of labile biomolecules such as oligosaccharides, amino acids, peptides and nucleosides.

Magnetic silica nanoparticles (MSNPs) were prepared and applied for the first time as a matrix in MALDI MS for analysis of small thermally labile biomolecules including oligosaccharides, amino acids, peptides, nucleosides, and ginsenosides. The matrix was characterized by scanning electron microscopy and UV-vis spectroscopy. It displays good performance in analyses of such biomolecules in the positive ion mode. In addition, the method generates significantly less energetic ions compared to the use of carbon nanotubes or graphene-assisted LDI MS and thus produces intact molecular ions with little or no fragmentation. In addition, the MSNPs have better surface homogeneity and better salt tolerance and cause lower noise. It is assumed that the soft ionization observed when using MSNPs as a matrix is due to the specific surface area and the homogenous surface without large clusters. The matrices were applied to the unambiguous identification and relative quantitation of the water extract of Panax ginseng roots. Any false-positive results as obtained when using graphene and carbon nanotubes as a matrix were not observed. Graphical abstract Schematic presentation of the application of magnetic silica nanoparticles in laser desorption ionization mass spectrometry. Their use results in little or no fragmentation during analysis of small labile biomolecules with some advantages such as better surface homogeneity, high salt tolerance, and lower noise.

Magnetic Semiconductor Gd-Doping CuS Nanoparticles as Activatable Nanoprobes for Bimodal Imaging and Targeted Photothermal Therapy of Gastric Tumors.

Targeted delivery of enzyme-activatable probes into cancer cells to facilitate accurate imaging and on-demand photothermal therapy (PTT) of cancers with high spatiotemporal precision promises to advance cancer diagnosis and therapy. Here, we report a tumor-targeted and matrix metalloprotease-2 (MMP-2)-activatable nanoprobe (T-MAN) formed by covalent modification of Gd-doping CuS micellar nanoparticles with cRGD and an MMP-2-cleavable fluorescent substrate. T-MAN displays a high r1 relaxivity (∼60.0 mM-1 s-1 per Gd3+ at 1 T) and a large near-infrared (NIR) fluorescence turn-on ratio (∼185-fold) in response to MMP-2, allowing high-spatial-resolution magnetic resonance imaging (MRI) and low-background fluorescence imaging of gastric tumors as well as lymph node (LN) metastasis in living mice. Moreover, T-MAN has a high photothermal conversion efficiency (PCE, ∼70.1%) under 808 nm laser irradiation, endowing it with the ability to efficiently generate heat to kill tumor cells. We demonstrate that T-MAN can accumulate preferentially in gastric tumors (∼23.4% ID%/g at 12 h) after intravenous injection into mice, creating opportunities for fluorescence/MR bimodal imaging-guided PTT of subcutaneous and metastatic gastric tumors. For the first time, accurate detection and laser irradiation-initiated photothermal ablation of orthotopic gastric tumors in intraoperative mice was also achieved. This study highlights the versatility of using a combination of dual biomarker recognition (i.e., αvß3 and MMP-2) and dual modality imaging (i.e., MRI and NIR fluorescence) to design tumor-targeting and activatable nanoprobes with improved selectivity for cancer theranostics in vivo.

Monodisperse magnetic poly(glycidyl methacrylate) microspheres for isolation of autoantibodies with affinity for the 46 kDa form of unconventional Myo1C present in autoimmune patients.

Monodisperse nonmagnetic macroporous poly(glycidyl methacrylate) (PGMA) microspheres were synthesized by multistep swelling polymerization of glycidyl methacrylate, ethylene dimethacrylate and 2-[(methoxycarbonyl)methoxy]ethyl methacrylate (MCMEMA). This was followed (a) by ammonolysis to modify the microspheres with amino groups, and (b) by incorporation of iron oxide (γ-Fe2O3) into the pores to render the particles magnetic. The resulting porous and magnetic microspheres were characterized by scanning and transmission electron microscopy (SEM and TEM), atomic absorption and Fourier transform infrared spectroscopy (AAS and FTIR), elemental analysis, vibrating magnetometry, mercury porosimetry and Brunauer-Emmett-Teller adsorption/desorption isotherms. The microspheres are meso- and macroporous, typically 5 µm in diameter, contain 0.9 mM · g-1 of amino groups and 14 wt.% of iron according to elemental analysis and AAS, respectively. The particles were conjugated to p46/Myo1C protein, a potential biomarker of autoimmune diseases, to isolate specific autoantibodies in the blood of patients suffering from multiple sclerosis (MS). The p46/Myo1C loaded microspheres are shown to enable the preconcentration of minute quantities of specific immunoglobulins prior to their quantification via SDS-PAGE. The immunoglobulin M (IgM) with affinity to Myo1C was detected in MS patients. Graphical abstract Monodisperse magnetic poly(glycidyl methacrylate) microspheres were synthesized, conjugated with 46 kDa form of unconventional Myo1C protein (p46/Myo1C) via carbodiimide (DIC) chemistry, and specific autoantibodies isolated from blood of multiple sclerosis (MS) patients; immunoglobulin M (IgM) level increased in MS patients.

Lipase immobilized on ionic liquid-functionalized magnetic silica composites as a magnetic biocatalyst for production of trans-free plastic fats.

The main objective of this study is to develop an efficient and environmentally gentle process for production of trans-free plastic fats. To acheive this, the core-shell structured magnetic composites were prepared, and then imidazole-based ionic liquids (ILs) were covalently grafted on the magnetic composites. Thereafter, Candida rugosa lipase was immobilized on the magnetic IL-functionalized composites. The immobilized lipase could be facilely separated using an external magnetic filed. With the magnetic biocatalyst, enzymatic interesterifications of solid palm stearin and liquid rice bran oil blends were performed at 45 °C. It was shown that the total fatty acid (FA) compositions of the binary blends were almost unchanged after the interesterifications, whereas the FA positional distribution and triacylglycerol species were significantly varied. As compared with the physical blends, the interesterified products had a lower slip melting point, and the interesterification could result in an obvious change in the microstructure of the final products.

Fabrication of a novel magnetic mesoporous molecularly imprinted polymer based on pericarpium granati-derived carrier for selective absorption of bromelain.

Bromelain, a cysteine endopeptidase enzyme of great commercial value, has been widely used in food, pharmaceutical, and cosmetic industries. Conventional methods for purification of bromelain are still limited by a low binding efficiency, time-consuming process, and expensive equipment. Therefore, for selective absorption of bromelain, we developed a facile and effective method to fabricate magnetic mesoporous molecularly imprinted polymers using pericarpium granati-derived carbon as the carrier for the first time. The characterizations of the imprinted polymers indicated that a polydopamine layer was coated on the surface of the carrier and the crystallinity of the carrier did not change. The obtained imprinted polymers exhibited favourable saturation magnetization, a high adsorption capacity of 135.96 mg g-1, a fast equilibrium time, and satisfactory reusability. The imprinted polymers were prepared by an eco-friendly method and exhibited rapid separation and good adsorption performance, thus making the method applicable to biomacromolecular separation, proteomic analysis, and biomedical research.

Biosynthesis of pure hematite phase magnetic iron oxide nanoparticles using floral extracts of Callistemon viminalis (bottlebrush): their physical properties and novel biological applications.

Aqueous floral extracts of Callistemon viminalis were used to synthesize Fe2O3 nanoparticles (IONPs) which were intensively characterized through UV-vis, X-ray diffraction, HR-SEM/HR-TEM, Fourier- transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDS). Their physical properties were studied in response to different annealing temperatures. It was observed that the increase in the annealing temperature produced small-sized nanoparticles. The nanoparticle size was calculated as 32, 26 and 22 nm for annealing at 300, 400 and 500 °C, respectively. The magnetic nature of the bioinspired IONPs was revealed by superconducting quantum interference device (SQUID). Their antibacterial potential was investigated against nine pathogenic bacterial strains (gram positive and gram negative) using disc diffusion method while their MIC was calculated using broth dilution assay. Bioinspired IONPs were found to be highly effective against HepG2 cells (IC50=20 µg/mL). Moderate antileishmanial activities against the promastigotes and amastigotes cultures are reported. Moderate acetylcholine esterase (AchE), butylcholine esterase (BchE) and α-Glycosidase inhibition are reported. Additional assessment of the biocompatibility was performed using haemolytic activity on the freshly isolated human red blood cells and macrophages. Furthermore, the antioxidant activities, including TAC, DPPH and TRP were also performed. Our results indicate that the biogenic and magnetic Fe2O3 can be used for diverse biomedical applications.

Pectin-conjugated magnetic graphene oxide nanohybrid as a novel drug carrier for paclitaxel delivery.

Recent studies have shown that graphene oxide (GO) drug carrier functionalized with biocompatible natural polymers lead to higher loading efficacy and better stability with diminished cellular toxicity. Pectin (PEC) is one of the polysaccharide natural polymers, which has the potential to be used for drug delivery. In this work, we have successfully developed a novel PEC-conjugated magnetic GO nanocarrier for effective delivery of paclitaxel. The structure, surface morphology and thermal stability of the nanohybrid were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and zeta-sizer. Moreover, drug loading and release performance were studied by UV-vis absorption spectra. The cytotoxicity test was also performed by MTT test using L-929 fibroblast normal cell and MCF-7 cancer lines. The prepared nanocarrier showed an improved stability with enhanced drug loading capacity. Additionally, pH-responsive release analysis of the nanohybrid illustrated higher drug release at endosomal pH of cancer cell than that of normal physiological environment. Besides, cytotoxicity test demonstrated the synthesized nanohybrid is biocompatible, having very high relative cell viability. Bearing in mind these findings, the designed multifunctional nanohybrid drug carrier will be a good candidate for cancer drug delivery.

Uniform magnetic targeting of magnetic particles attracted by a new ferromagnetic biological patch.

A new non-toxic ferromagnetic biological patch (MBP) was designed in this paper. The MBP consisted of two external layers that were made of transparent silicone, and an internal layer that was made of a mixture of pure iron powder and silicon rubber. Finite-element analysis showed that the local inhomogeneous magnetic field (MF) around the MBP was generated when MBP was placed in a uniform MF. The local MF near the MBP varied with the uniform MF and shape of the MBP. Therefore, not only could the accumulation of paramagnetic particles be adjusted by controlling the strength of the uniform MF, but also the distribution of the paramagnetic particles could be improved with the different shape of the MBP. The relationship of the accumulation of paramagnetic particles or cells, magnetic flux density, and fluid velocity were studied through in vitro experiments and theoretical considerations. The accumulation of paramagnetic particles first increased with increment in the magnetic flux density of the uniform MF. But when the magnetic flux density of the uniform MF exceeded a specific value, the magnetic flux density of the MBP reached saturation, causing the accumulation of paramagnetic particles to fall. In addition, the adsorption morphology of magnetic particles or cells could be improved and the uniform distribution of magnetic particles could be achieved by changing the shape of the MBP. Also, MBP may be used as a new implant to attract magnetic drug carrier particles in magnetic drug targeting. Bioelectromagnetics. 39:98-107, 2018. © 2017 Wiley Periodicals, Inc.

Physics responsible for heating efficiency and self-controlled temperature rise of magnetic nanoparticles in magnetic hyperthermia therapy.

Magnetic nanoparticles as heat-generating nanosources in hyperthermia treatment are still faced with many drawbacks for achieving sufficient clinical potential. In this context, increase in heating ability of magnetic nanoparticles in a biologically safe alternating magnetic field and also approach to a precise control on temperature rise are two challenging subjects so that a significant part of researchers' efforts has been devoted to them. Since a deep understanding of Physics concepts of heat generation by magnetic nanoparticles is essential to develop hyperthermia as a cancer treatment with non-adverse side effects, this review focuses on different mechanisms responsible for heat dissipation in a radio frequency magnetic field. Moreover, particular attention is given to ferrite-based nanoparticles because of their suitability in radio frequency magnetic fields. Also, the key role of Curie temperature in suppressing undesired temperature rise is highlighted.

An interference-free and label-free sandwich-type magnetic silicon microsphere -rGO-based probe for fluorescence detection of microRNA.

An interference-free and label-free sensing platform was developed for the highly sensitive detection of microRNA-21 (miRNA-21) in vitro by magnetic silicon microsphere (MNP)-reduced graphene oxide (rGO)-based sandwich probe. In this method, DNA capture probes (P1) were connected with MNPs at the 5' end and hybridized with completely complementary target miRNA. Subsequently, rGO was retained and induced the fluorescence quenching in the supernatant. Through the magnetic separation, the supernatant environment was simplified and the interference to analytical signal was eliminated. When DNA capture probe-modified magnetic silicon microspheres (MNP-P1) were adsorbed through rGO in the absence of a target and formed a sandwich structure, the formed nanostructure was easily removed from the solution by a magnetic field and the fluorescence intensity was maximally recovered. This proposed strategy, which both overcame the expensive and cumbersome fluorescent labeling, and eliminated interference to analytical signal for guaranteeing high signal-to-background ratio, exhibited high sensitivity with a detection limit as low as 0.098nM and special selectivity toward miRNA-21. The method was potentially applicable for not only detection of miRNA-21 but also various biomarker analyses just by changing capture probes.

α-Glucosidase immobilization on chitosan-enriched magnetic composites for enzyme inhibitors screening.

In the present study, the chitosan-enriched magnetic composites (MCCs) were prepared by a novel and simple embedding method for the immobilization of α-glucosidase (α-Glu). The immobilized α-Glu could be easily separated from the reaction mixture under an external magnetic field owing to the magnetic support. With the MCCs-immobilized α-Glu, enzyme activity and stability were studied, and enzyme inhibitors were screened from traditional Chinese medicines (TCMs) and vegetables combined with capillary electrophoresis (CE). The MCCs-immobilized α-Glu exhibited enhanced pH and temperature tolerance with unchanged optimum pH and temperature of 4.0 and 60°C comparing with free α-Glu. Reusability of the immobilized α-Glu was significantly improved after immobilization, and it retained 62.2% of its initial activity after 10 repeated cycles. Immobilized α-Glu also showed improved storage stability (84.3±1.2% after 35days of storage at 4°C). The kinetic parameter Km for immobilized α-Glu was calculated to be 0.81mM and the affinity of enzyme towards its substrate was reduced after immobilization. Finally, immobilized α-Glu was used to screen enzyme inhibitors from the extracts of TCMs and vegetables. The enhanced pH and temperature tolerance, improved reusability and storage stability of MCCs-immobilized α-Glu make it a promising candidate for biotechnological applications.