Magnetic Polystyrene Microspheres Research Articles

A novel visual biosensor for mercury detection based on a cleavable phosphorothioate-RNA probe and microfluidic bead trap

Mercury ion (Hg2+) detection plays a crucial role in safeguarding the environment and protecting human health. In this study, we developed a microfluidic biosensing platform that utilizes a phosphorothioate-RNA (PS-RNA) probe and gold-coated magnetic nanoparticles to quantify Hg2+ visually. The PS-RNA probe was linked to gold-coated magnetic nanoparticles via Au–S interaction and biotin–avidin interaction and then combined with polystyrene microspheres to form a self-assembled structure called a magnetic bead-AuNP-probe-polystyrene (MAPP) bead. We designed and fabricated a microfluidic chip that contained only a magnetic separator and a particle trap. The presence of Hg2+ cut the PS-RNA probe, leading to the separation of magnetic beads and polystyrene microspheres. The MAPP was removed by the magnetic separator, while the cut polystyrene microspheres flowed along the channel and accumulated in the particle trap, forming a long visible strip. The length of the polystyrene microsphere strip was proportional to the Hg2+ concentration. The microfluidic biosensing platform exhibited high sensitivity and specificity for Hg2+ detection, with a detection limit of 21.9 nM. By integrating the microfluidic magnetic manipulation system with a sensitive nucleic acid probe, we developed an automated and visual biosensor that is a valuable reference for the on-site visual detection of heavy metal ions.

Fluorescence immunoassay for simultaneous detection typical β-agonists in animal derived food using blue-green upconversion nanoparticles as labels

Common typical β-agonists mainly include ractopamine (RAC), salbutamol (SAL), and clenbuterol (CLB). In view of the harm to human health causes by the ingestion of animal derived food containing β-agonists, and a series of regulations have been issued to restrict the usage of β-agonists as growth promoters. In this work, a fluorescence immunoassay is developed for the simultaneous detection of typical β-agonists based on blue-green upconversion nanoparticles (UCNPs) combine with magnetic separation. Here, blue-green UCNPs act as a signal amplification source, and magnetic polystyrene microspheres (MPMs) act as an ideal separation medium. Based on a competitive form, capture probe competes (RAC-OVA@MPMs and SAL-OVA@MPMs) with targets to bind corresponding signal probe (anti-RAC antibody@NaYF4:Yb, Tm UCNPs and anti-SAL antibody@NaYF4:Yb, Er UCNPs). The fluorescence difference values of the competitive immune-complex obtained via magnetic separation at 483 nm and 550 nm are proportional to concentrations of RAC and SAL, respectively. The immunoassay has the wide detection linear range from 0.001 to 100 μg L−1, and the low limit of detection (LOD) is 5.04 × 10−4 μg L−1 for RAC, 1.97 × 10−4 μg L−1 for SAL, respectively. Meanwhile, use of antibody with same recognition ability for SAL and CLB makes that the fluorescence immunoassay can achieve simultaneous detection of three typical β-agonists (RAC, SAL, and CLB). This fluorescence immunoassay has good application value and practicability for simultaneous detection of typical β-agonists in animal derived food.

Blue-green-red multicolor upconversion nanoparticles based fluorescence immunoassay for simultaneous detection of three mycotoxins in cereals

In this work, a fluorescence immunoassay based on multicolor upconversion nanoparticles (UCNPs) and magnetic separation was established for simultaneous detection of aflatoxin B1 (AFB1), zearalenone (ZEN), and ochratoxin A (OTA) in cereal samples. Anti-AFB1, anti-ZEN, and anti-OTA antibody is connected to blue-green–red UCNPs as multicolor signal probe respectively, and the AFB1, ZEN and OTA coating antigen is connected to magnetic polystyrene microspheres (MPMs) as capture probe respectively. Based on a competitive form, the capture probe and the target competitively bind with signal probe, and the fluorescence intensity of the obtained immune complexes (signal probe@capture probe) at 477 nm, 544 nm, and 662 nm was measured to quantitate AFB1, ZEN, and OTA, respectively. The detection limit (LOD) of AFB1, ZEN, and OTA is 1.0 × 10-3 μg L-1, 9.8 × 10-4 μg L-1, and 5.6 × 10-4 μg L-1, respectively. This assay can achieve rapid, sensitive, accurate, high-throughput, simultaneous quantitative detection of three mycotoxins in cereal samples.

Magnetically-separable quasi-homogeneous catalyst: Brush-type ionic liquid polymer coated magnetic polymer microspheres for tandem reactions to produce 4H-pyrans/biodiesel

Employing magnetic polystyrene microspheres as the core and brush-type alkaline imidazolium ionic liquid polymers as the covalent bonds, a robust magnetically-separable quasi-homogeneous magnetic brush-type ionic liquid polymers ([Im][OH]/MP-B) was synthesized. Due to the features of brush-type ionic liquid polymer (BILPs), [Im][OH]/MP-B demonstrated high catalytic activity. With a broad variety of substrates, [Im][OH]/MP-B was applied in Knoevenagel-Michael tandem reactions for the synthesis of 4 H-pyrans (achieving 99.99% conversion and 93.6% yield) and transesterification tandem reactions for sustainable biodiesel production (achieving 99.9% conversion and 95.2% yield). Furthermore, the catalytic performance of [Im][OH]/MP-B was superior to that of [Im][OH]/MP-CL and [Im][OH]/MP-L and comparable with that of homogeneous catalysts. The reasonable and feasible reaction mechanism of magnetic ionic liquid polymers catalyzing tandem reactions was explored in-depth based on the catalytic performance and kinetics, which clearly demonstrated the catalytic activity and stability of [Im][OH]/MP-B. Notably, [Im][OH]/MP-B was effortlessly recovered by magnetic separation and reutilized numerous times with no evident change in catalytic performance, composition, or microstructure, indicating promising possibilities for ecologically friendly procedures. This work provides a potential strategy for the synthesis of magnetic BILPs for tandem reactions, which could serve as a platform for ecologically friendly and sustainable chemistry.

Fluorescence immunoassay based on magnetic separation and ZnCdSe/ZnS quantum dots as a signal marker for intelligent detection of sesame allergen in foods

To detect sesame allergens, a novel fluorescent immunoassay incorporating a magnetic separation step has been developed via two measurement devices: a fluorescence spectrophotometer and a smartphone equipped with a color reader. Sesame allergen monoclonal antibody (Ab) was covalently bonded with quantum dots (QDs) to act as a signal probe. The capture probes were synthesized as sesame allergen (SA) modified carboxyl-functional magnetic polystyrene microspheres (MPMs). Analytical variables such as the amount of modified SA, the reaction volume of the QDs-Ab, the ionic strength, the pH, and the incubation time of the reaction were optimized. The analytical range and the limit of detection (LOD) of the spectrophotometer-based assay were 80–640 μg/L and 12.75 μg/L, respectively. The analytical range and the LOD with smartphone read-out were 80–640 μg/L and 10.15 μg/L, respectively. Furthermore, the developed assay using the fluorescence spectrophotometer and the smartphone read-out was successfully applied to field testing of SA in solution extracts of biscuits, bread, almond beverage, and energy bars with acceptable results. The recovery rates were in the range 89–108%. It was concluded that the new assay may be used for rapid sesame allergen testing in the laboratory and in the field.

Preparation of Functionalized Magnetic Polystyrene Microspheres and Their Application in Food Safety Detection.

Based on the specific binding of sulfonic acid groups to melamine, β-agonists and other compounds, Fe3O4 nano-magnetic beads were coated with polystyrene using an improved micro-suspension emulsion polymerization method, thus forming core-shell magnetic polystyrene microspheres (Fe3O4@PS) with Fe3O4 as the core and polystyrene as the shell. These functionalized microspheres, which can be used as magnetic solid-phase extraction (MSPE) adsorbent, were prepared after further sulfonation. These microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analysis and saturation magnetization measurement. The results showed that these sulfonated magnetic polystyrene microspheres had favorable sphericity. The particle size of these microspheres ranged from 1 μm to 10 μm. Additionally, these microspheres had good dispersion and magnetic responses in both inorganic and organic solvents. Moreover, these functionalized magnetic polystyrene microspheres were tested and evaluated by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The results indicated that these sulfonated magnetic polystyrene microspheres (Fe3O4@SPS) could effectively adsorb such illegal additives as β-agonists and melamine in the food matrix.

A Smartphone Colorimetric Sensor Based on Pt@Au Nanozyme for Visual and Quantitative Detection of Omethoate.

A smartphone colorimetric sensor based on the Pt@Au nanozyme was successfully developed for the visual and quantitative detection of omethoate in fruit and vegetables. The anti-omethoate antibody was conjugated on the surface of the Pt@Au nanozyme as a catalytic functional signal probe, and coating antigen conjugated on the surface of magnetic polystyrene microspheres (MPMs) was used as a separation capture probe. In the sensing system, when the catalytic functional signal probe was combined with a separation capture probe containing no omethoate, the visible blue color appeared with the addition of tetramethylbenzidine (TMB) chromogenic solution, and the maximum B value of the sensing system was obtained via the smartphone. With increasing concentrations of omethoate, the visualization of the sensing system decreased, and the B-value obtained via the smartphone dropped. Under optimal detection conditions, the omethoate could be detected in a linear range of 0.5–50 μg/L (R2 = 0.9965), with a detection limit of 0.01 μg/L. The accuracy and reliability of the detection results of this colorimetric sensor were successfully confirmed by enzyme linked immunosorbent assay (ELISA) and gas chromatography. This colorimetric sensor provides a technical reference and potential strategy for the immunoassay of hazard factors in resource-scarce laboratories.

Low-Cost and Convenient Microchannel Resistance Biosensing Platform by Directly Translating Biorecognition into a Current Signal.

We report a low-cost and convenient microchannel resistance (MCR) biosensing platform that uses current signal to report biorecognition. The biorecognition behavior between targets and biometric molecules (antigens, antibodies, or oligonucleotides) immobilized on magnetic beads and polystyrene (PS) microspheres induces a quantitative change in the unreacted PS microspheres. After magnetic separation, the unreacted PS microsphere solution is passed through the microchannel, leading to an obvious blocking effect, resulting in an increase in resistance, which can in turn be measured by monitoring the electric current. Thus, the biorecognition is directly converted into a detectable current signal without any bulky instruments or additional chemical reactions. The MCR biosensing platform is cost-effective and user-friendly with high accuracy. It can be an appropriate analysis technique for point-of-care testing in resource-poor settings.

Suspension polymerization for fabrication of magnetic polystyrene microspheres stabilized with Hitenol BC-20

Suspension polymerization for fabrication of magnetic polystyrene microspheres stabilized with Hitenol BC-20

Synthesis and experimental study of liquid dispersions of magnetic fluorescent polystyrene microspheres

Multiplex microsphere-based immunofluorescence assay is a reliable, accurate, and highly sensitive method for the detection of various biomolecules. However, for the moment, the wide application of the method in clinical practice is prevented by the high cost of reagents for analysis - magnetic spectrally encoded microspheres. Therefore, an urgent task is the development of new methods for the synthesis of microspheres with the required properties. The aim of this study was the creation of new magnetic fluorescent microspheres suitable for use in multiplex immunoassay.Samples of magnetic fluorescent polystyrene microspheres were synthesized by dispersion polymerization and two-stage swelling methods. Experimental studies of geometric parameters, fluorescence, magnetic properties of the synthesized microspheres have been carried out.The results of the studies have shown that microspheres synthesized by dispersion polymerization are promising for the use in immunofluorescence analysis. The obtained results can be used for the development of new diagnostic multiplex test systems based on spectrally encoded microspheres.

One-pot label-free dual-aptasensor as a chemiluminescent tool kit simultaneously detect adenosine triphosphate and chloramphenicol in foods

The chemiluminescence (CL) analysis based on label-free dual-aptasensor was developed for simultaneous detection of adenosine triphosphate (ATP) and chloramphenicol (CAP) in food. Magnetic microspheres and polystyrene microspheres used as separating and immobilizing carriers which immobilized the two different captured DNA, respectively. Then these carriers were put in the mixture of ATPs, CAPs, ATP-binding aptamers and CAP-binding aptamers to make one-pot label-free recognized interaction. The more ATP or CAP molecules binding their aptamers, the less aptamers left on the surface of carriers reducing the CL signals. The proposed aptasensor exhibited high selectivity and sensitivity for ATP and CAP with the limits of detection of 3.76 × 10−8 moL/L and 2.48 × 10−8 moL/L, respectively. Finally, this method is further validated by measuring the recovery of ATP/CAP spiked in three different food samples.

An Ultrasensitive Fluorescence Immunoassay Based on Magnetic Separation and Upconversion Nanoparticles as Labels for the Detection of Chloramphenicol in Animal-Derived Foods

In this work, an ultrasensitive fluorescence immunoassay has been proposed for the detection of chloramphenicol. The proposed assay is based on using the carboxyl-functionalized NaYF4: Yb/Tm upconversion nanoparticles with maximum emission at 482 nm under excitation at 980 nm conjugated with anti-chloramphenicol (CAP) antibody as the signal probe and the magnetic polystyrene microspheres conjugated with coating antigen as the sensing probe. The coating antigens on the sensing probes compete with CAPs to bind with the antibodies on the signal probes and the immune complexes form. Via magnetic action, these complexes can be separated to measure their fluorescence intensity. The limit of detection (LOD) of this assay for CAP in PBS is 0.01 pg mL−1, and the linear range extends from 0.05 to 100 pg mL−1 with a linear equation of y = 387.64 lgx + 1153.93 (R2 = 0.9911). The recoveries of CAP in spiked animal-derived foods range from 76.85 to 105.18%. Trace CAP levels have been measured in the real sample by the proposed fluorescence immunoassay, and the results have been verified by commercial ELISA test kit and liquid chromatography-tandem mass spectrometry. The quantitation limits of this immunoassay for CAP in the muscle tissue, milk, and honey samples are 0.25 pg g−1, 0.4 pg g−1, and 0.4 pg g−1, respectively. The fluorescence immunoassay proposed in this study can be used to highly sensitively, accurately, and rapidly detect CAP residues in animal-derived foods.

Upconversion Nanoparticles and Monodispersed Magnetic Polystyrene Microsphere Based Fluorescence Immunoassay for the Detection of Sulfaquinoxaline in Animal-Derived Foods.

A novel fluorescence immunoassay for detecting sulfaquinoxaline (SQX) in animal-derived foods was developed using NaYF4:Yb/Tm upconversion nanoparticles (UCNPs) conjugated with antibodies as fluorescence signal probes, and monodisperse magnetic polystyrene microspheres (MMPMs) modified with coating antigen as immune-sensing capture probes for trapping and separating the signal probes. Based on a competitive immunoassay format, the detection limit of the proposed method for detecting SQX was 0.1 μg L(-1) in buffer and 0.5 μg kg(-1) in food samples. The recoveries of SQX in spiked samples ranged from 69.80 to 133.00%, with coefficients of variation of 0.24-25.06%. The extraction procedure was fast, simple, and environmentally friendly, requiring no organic solvents. In particular, milk samples can be analyzed directly after simple dilution. This method has appealing properties, such as sensitive fluorescence response, a simple and fast extraction procedure, and environmental friendliness, and could be applied to detecting SQX in animal-derived foods.

Reversible immobilization of glucoamylase onto magnetic polystyrene beads with multifunctional groups

A novel and simple process for the surface functionalization of micron-sized monodisperse magnetic polystyrene (PS) microbeads was reported. The polystyrene seed particles were prepared prior to the dispersion polymerization method. Afterwards, series of surface chemical modifications on polystyrene microspheres were conducted, and three end-functional microspheres with carboxyl, imidazolyl and sulphydryl groups were obtained. The functional magnetic polystyrene microspheres were prepared by impregnation and subsequent precipitation of ferric and ferrous ions into the polystyrene particles. Finally, the functional magnetic polystyrene was used for the reversible immobilization of glucoamylase via metal-affinity adsorption. The results indicated that the obtained immobilized glucoamylase presented excellent reusability, applicability, magnetic response and regeneration of supports. The magnetic PS microspheres retained >65% of its initial activity at 65°C over 6h; and the lowest residual activity of immobilized glucoamylase prepared by regenerated supports still remained about 50% of the initial activity after the 10th cycles.

Establishment of magnetic beads-based enzyme immunoassay for detection of chloramphenicol in milk

In this research, magnetic beads-based enzyme immunoassays were investigated for rapid analysis of chloramphenicol (CAP) in milk. To improve sensitivity of CAP determination, two kinds of immunomagnetic separation methods were designed and compared. Magnetic polystyrene microspheres were conjugated with anti-CAP antibody (Method I) or goat-anti-mouse IgG (Method II). The whole determination could be finished in 1.25 h. Both methods showed high sensitivity to CAP in buffer, and obtained an IC(50) value of 0.05 ng mL(-1) for Method I and 0.4 ng mL(-1) for Method II. The methods showed high specificity, only showing a little cross-reaction towards CAP succinate. The two methods were applied to detect CAP in milk. The recovery rates were 80-106% and the coefficients of variation (CVs) were 4.7-15%. The immunomagnetic assay showed promising potential in rapid screening field for CAP analysis. Between the two methods, Method I is more sensitive, and Method II is more suitable for producing a general assay by changing a primary antibody for another analyte.

Fe3O4@PS@PAMAM-Ag Magnetic Nanocatalysts and Their Recoverable Catalytic Ability

Magnetic supports were prepared by coating Fe 3 O 4 nanoparticles with polystyrene (PS). The target nanocomposites were formed by growing polyamidoamine (PAMAM) dendrimers on the magnetic polymer supports with carboxylic groups and then silver nanoparticles were embedded into the PAMAM dendrimer shell. In this way recoverable Fe 3 O 4 @PS@PAMAM-Ag nanocomposites were successfully prepared. The magnetic nanocatalysts were characterized by Fourier transform infrared spectra, scanning electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy. The results demonstrated that the PAMAM dendrimer shell immobilized on the magnetic supports was beneficial for dispersion and stabilization of the silver nanoparticles. The silver content of the Fe 3 O 4 @PS@PAMAM(G7)-Ag nanoparticles was 1.64 wt%. The catalytic activity of the Fe 3 O 4 @PS@PAMAM-Ag nanocomposites was proved using the reduction of 4-nitrophenol as a model catalytic reaction. The nanocomposites could be readily separated by magnetic separation and reused for the next reduction with high efficiency. The catalytic activity remained completely even after the nanocatalyst had been recycled six times. 采用聚苯乙烯 (PS) 包裹 Fe 3 O 4 磁性纳米粒子, 制得 Fe 3 O 4 @PS 复合微球, 以此作为磁性载体, 通过微球表面的羧基将聚酰胺-胺类树形大分子 (PAMAM) 连接到磁性载体上, 然后使 Ag 纳米粒子镶嵌在树形分子层中, 制得可再生的金属复合催化粒子 Fe 3 O 4 @PS@PAMAM-Ag. 并采用红外光谱、扫描电镜、电感耦合等离子体质谱 (ICP-MS) 和 X 射线光电子能谱等方法对复合催化粒子进行了表征, 结果表明, 树形分子可以较好地分散和稳定金属 Ag 纳米粒子, 所制复合催化粒子表面 Ag 含量为 1.64%, 具有较高的催化还原对硝基苯酚的活性. 同时, 利用外加磁场可以方便快捷地从反应体系中分离出来, 继续用于下一次反应中, 复合催化粒子循环使用 6 次后, 仍保持完全的催化性能. A method to prepare magnetic polystyrene microspheres grafted with a dendritic PAMAM-Ag shell and an investigation of their recoverable catalytic activity are presented.

Magnetic P(St-MA) Microspheres：Preparation, Characterization and Interaction with BSA

Taken the nanoparticles Fe3O4 as the magnetic carrier, and styrene ( St ) and Methyl Acrylate (MA) as the monomers, the magnetic polystyrene-methyl acrylate (P(St-MA)) microspheres were prepared by microsuspension copolymerization. The effect of various parameters(e.g. reaction temperature, initiator, Fe3O4/styrene ratio and disperser) on the properties of the P(St-MA) microspheres were studied.The microspheres were characterized by different techniques (e.g. SEM, VSM, TG-DSC, FTIR, ). The interaction of magnetic microspheres and BSA were studied by microcalorimetry. The results showed the P(St-MA) microspheres, with abundant –COOH, superparamagnetic and high magnetic content, were possessed much higher protein adsorbance compared to those of magnetic polystyrene(PS) microspheres.

Preparation of monodisperse magnetic polystyrene microspheres and its surface chemical modification

Monodisperse magnetic polystyrene (PS) microspheres were prepared in the presence of PS seed particles and styrene-based magnetic colloid by the method of magnetic colloid swelling polymerization. The PS seed particles were prepared in advance by soap-free emulsion polymerization. Styrene-based magnetic colloid was used for swelling the PS seed particles in the magnetic colloid swelling polymerization process. After polymerization, functional amino groups were introduced onto the surface of the magnetic PS microspheres by surface Friedel-Crafts acylation reaction. The morphology, size distribution, and magnetic properties of magnetic PS microspheres were characterized with scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM), respectively. SEM showed that the magnetic PS microspheres had an average size of 1078 nm with a narrow size distribution. VSM showed that the magnetic PS microspheres were superparamagnetic, and saturation magnetization was found to be 5.714 emu/g. The concentration of functional amino groups on the surface of magnetic PS microspheres was measured by atomic absorption spectroscopy and UV−Vis spectroscopy, and the concentration of amino groups was found to be 0.168 mmol/g. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis of raspberry-like magnetic polystyrene microspheres

Raspberry-like magnetic polystyrene microspheres were prepared via soap-free emulsion polymerization using 2,2′-azobis(2-methylpropionamidine) dihydrochloride (V50) as initiator. The effect of polymerization parameters, such as initiator type, initiator content and the feeding sequence on the particle size and morphology of magnetic polystyrene microspheres, were examined. The final magnetic polystyrene microspheres were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). The experimental results showed that V50 was a suitable initiator for preparation of raspberry-like magnetic polystyrene microspheres.

Preparation and properties of magnetic polystyrene microspheres

AbstractMagnetic polystyrene nanospheres were efficiently prepared by using a new indirect process based on miniemulsion polymerization of styrene. The samples were characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), and vibrating‐sample magnetometry (VSM), respectively. The experimental results clearly show that the 3‐methacryloxypropyltrimethoxy silane was anchored onto the surface of the magnetic particles to form the vinyl end. The size of the magnetic particle is about 6–30 nm. The size of the magnetic particle capped with polystyrene is about 1–2 μm. The magnetic polystyrene spheres exhibit multidomain character, whereas the pure magnetic particles show single domain character. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3660–3666, 2007