Paramagnetic Microspheres Research Articles

Neonicotinoid Microsphere Immunosensing for Profiling Applications in Honeybees and Bee-Related Matrices.

Neonicotinoids are the most commonly used insecticides due to their effectiveness. However, non-targeted insects, especially bees, are also affected by neonicotinoids. Therefore, neonicotinoid application can contribute to the declining bee populations worldwide. The presented study describes the development of novel competitive, fluorescent microsphere-based suspension immunoassays for neonicotinoid profiling and their application to bees and essential bee-related matrices, using the Multi-Analyte Profiling (xMAP) technology. For the construction of these neonicotinoid microsphere immunoassays (nMIAs), neonicotinoid–ovalbumin conjugates were coupled to unique fluorescent, paramagnetic microspheres, which competed with the free neonicotinoids that were present in test samples for interacting with the corresponding, specific antibodies. In total, five independent nMIA’s were developed for the detection of imidacloprid, acetamiprid, clothianidin, thiacloprid, thiamethoxam, dinotefuran, nitenpyram and imidaclothiz with the limits of detection being for 0.01 ng/mL, 0.01 ng/mL, 0.02 ng/mL, 0.02 ng/mL, 0.003 ng/mL, 2.95 ng/mL, 0.09 ng/mL and 0.04 ng/mL, respectively. The developed nMIAs were applied to fortified matrices including surface water, pollen, honey and honeybees. All of the neonicotinoids, except dinotefuran, could be sensitively detected in all of the tested environmental matrices and bees, with there being sensitivities of 1 ng/mL in water and 10 ng/g in solid materials. These nMIAs provide a rapid profiling method for all of the common neonicotinoids, including those that are banned by the European Union for outdoor use. The developed method can contribute to healthy and sustainable beekeeping, globally, via its application in the apiary environment.

Transverse Magnetic Tweezers Allowing Coincident Epi-Fluorescence Microscopy on Horizontally Extended DNA.

Longitudinal magnetic tweezers (L-MT) have seen wide-scale adoption as the tool of choice for stretching and twisting a single DNA molecule. They are also used to probe topological changes in DNA as a result of protein binding and enzymatic activity. However, in the longitudinal configuration, the DNA molecule is extended perpendicular to the imaging plane. As a result, it is only possible to infer biological activity from the motion of the tethered paramagnetic microsphere. Described here is a "transverse" magnetic tweezers (T-MT) geometry featuring simultaneous control of DNA extension and spatially coincident video-rate epi-fluorescence imaging. Unlike in L-MT, DNA tethers in T-MT are extended parallel to the imaging plane between two micron-sized spheres, and importantly protein targets on the DNA can be localized using fluorescent nanoparticles. The T-MT can manipulate a long DNA construct at molecular extensions approaching the contour length defined by B-DNA helical geometry, and the measured entropic elasticity agrees with the wormlike chain model (force <35 pN). By incorporating a torsionally constrained DNA tether, the T-MT would allow both the relative extension and twist of the tether to be manipulated, while viewing far-red emitting fluorophore-labeled targets. This T-MT design has the potential to enable the study of DNA binding and remodeling processes under conditions of constant force and defined torsional stress.

Immuno-Enriched Microspheres - Magnetic Blade Spray-Tandem Mass Spectrometry for Domoic Acid in Mussels.

Paramagnetic microspheres can be used in planar array fluorescence immunoassays for single or multiplex screening of food contaminants. However, no confirmation of the molecular identity is obtained. Coated blade spray (CBS) is a direct ionization mass spectrometry (MS) technique, and when combined with triple quadrupole MS/MS, it allows for rapid confirmation of food contaminants. The lack of chromatography in CBS, though, compromises the specificity of the measurement for unequivocal identification of contaminants, based on the European Union (EU) regulation. Therefore, a rapid and easy-to-use immuno-magnetic blade spray (iMBS) method was developed in which immuno-enriched paramagnetic microspheres replace the coating of CBS. The iMBS-MS/MS method was fully optimized, validated in-house following the EU 2021/808 regulation, and benchmarked against a commercial lateral flow immunoassay (LFIA) for on-site screening of DA. The applicability of iMBS-MS/MS was further demonstrated by analyzing incurred mussel samples. The combination of immunorecognition and MS/MS detection in iMBS-MS/MS enhances the measurement’s selectivity, which is demonstrated by the rapid differentiation between the marine toxin domoic acid (DA) and its structural analog kainic acid (KA), which cannot be achieved with the LFIA alone. Interestingly, this first-ever reported iMBS-MS/MS method is generic and can be adapted to include any other immuno-captured food contaminant, provided that monoclonal antibodies are available, thus offering a complementary confirmatory analysis approach to multiplex immunoassay screening methods. Moreover, thanks to its speed of analysis, iMBS-MS/MS can bridge the logistics gap between future large-scale on-site testings using LFIAs and classical time-consuming confirmatory MS analysis performed in official control laboratories.

Preparation novel mercaptotriazole-functionalized paramagnetic nickel-zinc ferrite microspheres for absorbing Hg (II) in waste water

A novel paramagnetic adsorbent MMT-M is prepared by functionalizing the Ni0.25Zn0.75Fe2O4 (M) magnetic core using TEOS, 3-chloropropyltriethoxysilane (KH-230) and 3-methyl-4-amino-5-mercapto-1, 2, 4-triazole (MMT) in turn. The MMT-M adsorbent is characterized by VSM, XRD, SEM, TEM, EDS and FTIR. Many critical factors are investigated about its adsorption prosperities in aqueous solution, including Hg (II) ion concentration, pH value, adsorption time, metal ion species, multi ion environment and desorption. MMT-M absorbent shows the best adsorption properties for Hg (II) among metal ions, with the adsorbent capacity beyond 66.25 mg g−1. The series desorption experiments indicate that 0.01 mol/L Na2S solution is the best eluent system for the adsorbent. The MMT-M adsorbent still remains excellent absorbability after five reused cycles. MMT-M adsorbent is good applicable to absorb Hg (II) from real water samples.

Surface treatment-controlled solvothermal synthesis of highly active reduced 1D titania with heterojunctioned carbon allotrope

One-dimensional (1D) nanowire black titania heterojunctioned with multi-wall carbon nanotube (bTiO2 NW/MWCNT) structures were successfully synthesized via a facile single-step hydrothermal procedure, coupled with succeeding surface treatments and a solid-state physiochemical mode of reduction. Paramagnetic SiO2-coated Fe3O4 microspheres were fabricated and used as cores for the seeding and growth of the bTiO2 NW/MWCNT photocatalyst. The as-prepared photocatalysts were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy, Fourier transform infrared spectroscopy, and UV-vis diffuse reflectance spectroscopy. The results of materials characterization confirmed formation of 1D bTiO2 NW structure with chemically bound MWCNT atop the reduced Ti3+ propagated lattice of the predominantly (101) exposed facets of anatase TiO2. Controlling the surface treatment process and NW growth time to maintain the anatase phase and stability of surface morphology upon reduction allowed for superior visible light-driven photoactivity. The visible light-driven photocatalytic degradation of 10 mg/L methylene orange was recorded at 97.4% in 20 min of 0.7 Sun intensity. The apparent reaction rate constant (k) of the as-prepared photocatalyst (0.1439 min−1) is ~ 18 times higher than that of pristine TiO2. Utilization of paramagnetic cores for in situ photocatalyst collection upon water treatment is highly recommended for newly developed materials. Further, performing surface treatment procedures of prepared titania-based photocatalysts has been proven to have a notable advantageous effect on photoactivity and is thus suggested for similar materials.

Propulsion and energetics of a minimal magnetic microswimmer.

In this manuscript we describe the realization of a minimal hybrid microswimmer, composed of a ferromagnetic nanorod and a paramagnetic microsphere. The unbounded pair is propelled in water upon application of a swinging magnetic field that induces a periodic relative movement of the two composing elements, where the nanorod rotates and slides on the surface of the paramagnetic sphere. When taken together, the processes of rotation and sliding describe a finite area in the parameter space, which increases with the frequency of the applied field. We develop a theoretical approach and combine it with numerical simulations, which allow us to understand the dynamics of the propeller and explain the experimental observations. Furthermore, we demonstrate a reversal of the microswimmer velocity by varying the length of the nanorod, as predicted by the model. Finally, we determine theoretically and in experiments the Lighthill's energetic efficiency of this minimal magnetic microswimmer.

Preparation of terpyridine-functionalized paramagnetic nickel-zinc ferrite microspheres for adsorbing Pb(ii), Hg(ii), and Cd(ii) from water.

A paramagnetic microsphere combining special functional groups may be one kind of the most promising methods for heavy metal adsorption, due to their specific separation capacity, selectivity and reusability. In this study, a novel terpyridine-based magnetic solid-phase adsorbent (TPY-M) is successfully constructed. The paramagnetic Ni0.25Zn0.75Fe2O4 microsphere (M) is synthesized and applied as a magnetic core, and is functionalized by terpyridine (TPY) groups. The naked magnetic core and TPY-M are characterized by vibration sample magnetism (VSM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR) techniques. Some parameters of the TPY-M samples are evaluated as potential adsorbents for heavy metal ions in various aqueous solutions. The adsorption capacities of TPY-M for Pb(ii), Hg(ii) and Cd(ii) were 64.75 mg g−1, 33.94 mg g−1 and 24.64 mg g−1 under given conditions, respectively. In the case of Pb(ii), some influencing factors on the TPY-M adsorbent are investigated, including the pH, adsorption time, and ion concentrations. The adsorbent can be easily regenerated by HCl solution after use. The adsorbent revealed good adsorption performance in some real water samples.

Carbon Quantum Dots: Elegant Surface of CoNi Alloys toward Efficient Magnetorheological Performances Realized with Carbon Quantum Dots (Adv. Mater. Interfaces 15/2018)

A series of CoNi based hierarchical microspheres with different surface morphologies, including litchi-like, seed of plane tree-like and waxberry-like shapes, are obtained via surface nucleation of carbon quantum dots (CQDs). Taking both the synergistic benefits of paramagnetic CoNi microspheres and surface architecture, the resulting CoNi microspheres exhibit enhanced interparticle friction for enhancing their MR effects compared with smooth surface microspheres. This work is reported by Wen Ling Zhang, Jingquan Liu and co-workers in article number 1800164.

Magnetically tunable bidirectional locomotion of a self-assembled nanorod-sphere propeller

Field-driven direct assembly of nanoscale matter has impact in disparate fields of science. In microscale systems, such concept has been recently exploited to optimize propulsion in viscous fluids. Despite the great potential offered by miniaturization, using self-assembly to achieve transport at the nanoscale remains an elusive task. Here we show that a hybrid propeller, composed by a ferromagnetic nanorod and a paramagnetic microsphere, can be steered in a fluid in a variety of modes, from pusher to puller, when the pair is dynamically actuated by a simple oscillating magnetic field. We exploit this unique design to build more complex structures capable of carrying several colloidal cargos as microscopic trains that quickly disassemble at will under magnetic command. In addition, our prototype can be extended to smaller nanorods below the diffraction limit, but still dynamically reconfigurable by the applied magnetic field.

Elegant Surface of CoNi Alloys toward Efficient Magnetorheological Performances Realized with Carbon Quantum Dots

AbstractDesigning and fabricating a rational surface architecture is one of the critical factors to achieve desirable physical and chemical properties and still remains an immense challenge. Herein, a series of CoNi‐based hierarchical microspheres with different surface morphologies, including litchi‐like, seed‐of‐plane‐tree‐like, and waxberry‐like shapes, are obtained via surface nucleation of carbon quantum dots (CQDs) with different concentrations in liquid polyol. Microstructure investigations suggest that all the CoNi microspheres are uniformly with enhanced surface roughness with the increasing concentration of CQDs. This study provides insight into the surface dominant magnetorheological (MR) behaviors of these CoNi‐based suspensions. Taking both the synergistic benefits of paramagnetic CoNi microspheres and surface architecture, the resulting CoNi microspheres exhibit enhanced interparticle friction for enhancing their MR effects compared with smooth surface microspheres, opening up the possible mechanism for revealing the MR effect. Moreover, this facile strategy can be extended as an effective path to achieve high‐performance MR behaviors for engineering applications.

Immobilization of penicillin G acylase on paramagnetic polymer microspheres with epoxy groups

Paramagnetic polymer microspheres were synthesized by the inverse suspension polymerization method through polymerization of glycidyl methacrylate, ally glycidyl ether and methacrylamide on the surface of silica-coated Fe3O4 nanoparticles using N,N’-methylene-bis(acrylamide) as a cross-linking agent. Penicillin G acylase (PGA) was covalently immobilized on the surface of the paramagnetic microspheres by reacting the amino groups of the PGA molecules with the epoxy groups of the paramagnetic polymer microspheres. The effect of the SiO2 coating and the amount of paramagnetic Fe3O4 nanoparticles on the initial activity and the operational stability of the immobilized PGA was investigated. The results indicated that SiO2 played an important role in the polymerization process and paramagnetic polymer microspheres with a SiO2-coated Fe3O4 nanoparticles mass content of 7.5% are an optimal support material for PGA immobilization. Immobilized PGA on the paramagnetic polymer microspheres shows a high initial activity of 430 U/g (wet) and retains 99% of its initial activity after recycling 10 times. Furthermore, immobilized PGA exhibits high thermal stability, pH stability and excellent reusability, which can be rapidly recycled by the aid of magnet.

Ultrasensitive chemiluminescence biosensors using nucleic acid-functionalized silver-cysteine nanowires as signal amplifying labels.

Ultrasensitive chemiluminescence (CL) sensors for biomolecules (DNA and proteins) have been developed by adopting DNA-functionalized silver-cysteine hybrid nanowires (p-SCNWs) as signal amplifying labels. The sensing is established from a sandwich-type DNA hybridization, where the target DNA strands are initially hybridized with the capture DNA located at paramagnetic microspheres (PMs) and subsequently hybridized with p-SCNWs functionalized with the signal DNA probe. After magnetic separation, p-SCNWs on the hybrids were completely decomposed with HNO3 to release numerous silver ions. The powerful catalysis of silver ions toward the redox reaction of K2S2O8-Mn2+-H3PO4 causes the generation of KMnO4 that is capable of oxidizing luminol at high pH, triggering an amplified chemiluminescent signal emission. The sensing combines the extraordinary sensitivity of the catalytic chemiluminescence technology and the amplifying strategy via releasing large quantities of silver ions as the catalyst from each hybrid, enabling the assay of target DNA strands at a concentration as low as 0.34 fM. The CL signals associated with single-base pair mismatched DNA strands and non-complementary DNA strands are able to be discriminated well from the CL signal related to the complementary DNA hybridization. Likewise, the combination of p-SCNWs functionalized with an aptamer and PMs/aptamer/thrombin complex allowed the chemiluminescence sensing of thrombin with a low limit of detection corresponding to 0.17 pM.

Enhanced target-specific signal detection using an Escherichia coli lysate in multiplex microbead immunoassays with E. coli-derived recombinant antigens

Diverse techniques have been developed to analyze antibody-mediated responses to infections. However, the most common tests, i.e., enzyme-linked immunosorbent assays, require separate reactions for each antigen and consequently necessitate large sample volumes. Luminex technology allows the detection of multiple antibodies in a single experiment, but nonspecific binding can impair the results. Therefore, we examined the use of Escherichia coli lysates to reduce nonspecific binding and improve the results of liquid microarrays based on Luminex technology. Anti-bacteria antibodies were detected in human serum samples, as evidenced by high median fluorescence intensity (MFI) in assays performed with paramagnetic microspheres coupled with E. coli lysates. Moreover, the addition of an E. coli lysate as a blocker reduced the nonspecific binding of antigens produced by E. coli in a concentration-dependent manner. Tris-HCl reduced MFI values in negative samples, but did not affect MFI for positive samples. For microspheres coupled with different antigens, an E. coli lysate blocker significantly improved the fluorescence signals from positive samples. The addition of Tris-HCl and the E. coli lysate induced antigen-specific differences in MFI. This combination of the E. coli lysate blocker and Tris-HCl yielded a statistically significant improvement in MFI in the assays for Chagas disease and hepatitis C virus samples. However, for the Treponema pallidum p47 antigen improvement in MFI was only observed for the preparation with the E. coli blocker at a concentration of 3%. In conclusion, the addition of an E. coli lysate and Tris-HCl to the microarray assay reduced the nonspecific binding of human anti-bacteria antibodies and, therefore, increased the specific MFI.

Crystal Diagnostics Xpress™ E7 STEC Kit for the Rapid Multiplex Detection of E. coli O157 and non-O157 Shiga toxin-producing E. coli.

The Crystal Diagnostics (CDx) Xpress E7 STEC kit is a rapid and sensitive detection assay for the detection of Escherichia coli O157 and six non-O157 Shiga toxin-producing E. coli (serogroups O26, O45, O1O3, O111, O121, and O145, collectively referred to as STEC) at 1 CFU/325 g of raw ground beef and raw beef trim, or 200 g of spinach. The system comprises an automatic Crystal Diagnostics Xpress System Reader that integrates immunochemical and optical processes for the liquid crystal-based detection of microorganisms, a CDx BioCassette that incorporates antibody-coupled microspheres and liquid crystal for selective identification of the intended microbe, and additional commercially available components. The Crystal Diagnostics Xpress System(TM) combines proprietary liquid crystal technology with antibody-coated paramagnetic microspheres to selectively capture and detect STEC from food matrixes. The Xpress System expeditiously (9.5 h enrichment) provides the sensitivity and specificity of the U. S. Department of Agriculture Food Safety and Inspection Service and the U. S. Food and Drug Administration reference methods in screening as low as 1 STEC CFU/test portion. The inclusivity validation demonstrated detection of 53 of 54 STEC test strains. Shelf life testing of the antibody-coated microspheres and other Crystal Diagnostic consumables indicated that all materials were stable for a minimum of 3 months (ongoing), and lot-to-lot testing demonstrated consistent results between lots (data not shown). The internal and independent laboratory tests demonstrate that the method is rapid and sensitive for screening of the target STEC.

Superresolution imaging of single DNA molecules using stochastic photoblinking of minor groove and intercalating dyes

As proof-of-principle for generating superresolution structural information from DNA we applied a method of localization microscopy utilizing photoblinking comparing intercalating dye YOYO-1 against minor groove binding dye SYTO-13, using a bespoke multicolor single-molecule fluorescence microscope. We used a full-length ∼49kbp λ DNA construct possessing oligo inserts at either terminus allowing conjugation of digoxigenin and biotin at opposite ends for tethering to a glass coverslip surface and paramagnetic microsphere respectively. We observed stochastic DNA-bound dye photoactivity consistent with dye photoblinking as opposed to binding/unbinding events, evidenced through both discrete simulations and continuum kinetics analysis. We analyzed dye photoblinking images of immobilized DNA molecules using superresolution reconstruction software from two existing packages, rainSTORM and QuickPALM, and compared the results against our own novel home-written software called ADEMS code. ADEMS code generated lateral localization precision values of 30–40nm and 60–70nm for YOYO-1 and SYTO-13 respectively at video-rate sampling, similar to rainSTORM, running more slowly than rainSTORM and QuickPALM algorithms but having a complementary capability over both in generating automated centroid distribution and cluster analyses. Our imaging system allows us to observe dynamic topological changes to single molecules of DNA in real-time, such as rapid molecular snapping events. This will facilitate visualization of fluorescently-labeled DNA molecules conjugated to a magnetic bead in future experiments involving newly developed magneto-optical tweezers combined with superresolution microscopy.

Multiplex detection of plant pathogens through the Luminex MagPlex bead system.

Here we describe a versatile multiplex method for both the serological and molecular detection of plant pathogens. The Luminex MagPlex bead system uses small paramagnetic microspheres ("beads"), either coated with specific antibodies or oligonucleotides, which capture respectively viruses and/or bacteria or PCR products obtained from their genetic material. The Luminex MagPlex bead system allows true multiplex detection of up to 500 targets in a single sample on a routine basis. The liquid suspension nature of the method significantly improves (1) assay speed, (2) detection limits and (3) dynamic range. It can also considerably reduce labor and consumables costs.

Crystal Diagnostics MultiPath System™.

The Crystal Diagnostics MultiPath System™ provides rapid detection of Escherichia coli O157 in fresh raw ground beef, raw beeftrim, and spinach. The Crystal Diagnostics system combines patented Liquid Crystal technology with antibody-coated paramagnetic microspheres to selectively capture and detect E. coli O157 in food matrixes. This is the only liquid crystal-based biosensor commercially available for the detection of pathogens. The Crystal Diagnostics system expeditiously provides the sensitivity and accuracy of the U.S. Department of Agriculture Food Safety Inspection Service (USDA-FSIS) and the U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA-BAM) methods for detecting as low as one CFU of E. coli O157 per 375 g of raw ground beef and raw beef trim, or 200 g of raw spinach. An internal inclusivity validation demonstrated detection of all 50 tested strains of . coli O157. The internal and independent laboratory tests demonstrate that the method is rapid and sensitive for detecting of E. coli O157 in fresh raw ground beef, beef trim, and spinach.

Cellphone-based detection platform for rbST biomarker analysis in milk extracts using a microsphere fluorescence immunoassay.

Current contaminant and residue monitoring throughout the food chain is based on sampling, transport, administration, and analysis in specialized control laboratories. This is a highly inefficient and costly process since typically more than 99% of the samples are found to be compliant. On-site simplified prescreening may provide a scenario in which only samples that are suspect are transported and further processed. Such a prescreening can be performed using a small attachment on a cellphone. To this end, a cellphone-based imaging platform for a microsphere fluorescence immunoassay that detects the presence of anti-recombinant bovine somatotropin (rbST) antibodies in milk extracts was developed. RbST administration to cows increases their milk production, but is illegal in the EU and a public health concern in the USA. The cellphone monitors the presence of anti-rbST antibodies (rbST biomarker), which are endogenously produced upon administration of rbST and excreted in milk. The rbST biomarker present in milk extracts was captured by rbST covalently coupled to paramagnetic microspheres and labeled by quantum dot (QD)-coupled detection antibodies. The emitted fluorescence light from these captured QDs was then imaged using the cellphone camera. Additionally, a dark-field image was taken in which all microspheres present were visible. The fluorescence and dark-field microimages were analyzed using a custom-developed Android application running on the same cellphone. With this setup, the microsphere fluorescence immunoassay and cellphone-based detection were successfully applied to milk sample extracts from rbST-treated and untreated cows. An 80% true-positive rate and 95% true-negative rate were achieved using this setup. Next, the cellphone-based detection platform was benchmarked against a newly developed planar imaging array alternative and found to be equally performing versus the much more sophisticated alternative. Using cellphone-based on-site analysis in future residue monitoring can limit the number of samples for laboratory analysis already at an early stage. Therewith, the entire monitoring process can become much more efficient and economical.

Multiplex immunoassay for persistent organic pollutants in tilapia: comparison of imaging- and flow cytometry-based platforms using spectrally encoded paramagnetic microspheres

Recent developments in spectrally encoded microspheres (SEMs)-based technologies provide high multiplexing possibilities. Most SEMs-based assays require a flow cytometer with sophisticated fluidics and optics. A new imaging super-paramagnetic SEMs-based alternative platform transports SEMs with considerably less fluid volume into a measuring chamber. Once there SEMs are held in a monolayer by a magnet. Light-emitting diodes (LEDs) are focused on the chamber to illuminate the SEMs – instead of lasers and they are imaged by a charge-coupled device (CCD) detector, offering a more compact sized, transportable and affordable system. The feasibility of utilising this system to develop a 3-plex SEMs-based imaging immunoassay (IMIA) for the screening of persistent organic pollutants (POPs) was studied. Moreover the performance characteristics of 3-plex IMIA were critically compared with the conventional 3-plex flow cytometric immunoassay (FCIA). Both SEM technologies have potential for the multiplex analysis of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) in buffer and fish extract with insignificant differences in assay sensitivities. Furthermore, we developed a faster and simpler, modified QuEChERS-like generic POPs extraction from tilapia fillet using sodium hydrogen carbonate as one of the salt additives and dispersive solid-phase extraction (dSPE) as a clean-up. Finally, a preliminary in-house validation using 40 different blank and spiked tilapia fillet samples was performed in both systems and the results obtained were critically compared. The lower-cost imaging SEMs-based system performed similarly to the original flow cytometer and, in combination with the new quicker QuEChERS-like extraction, it has high potential for future rapid screening of POPs in several other sample matrices such as other fish species, vegetable refined oils and environmental samples.

Soft colloidal lithography by strong physical contact using swollen magnetic microspheres and magnetic force

Herein we report on pattern formation of a self-assembled monolayer (SAM) using soft colloidal lithography, based on strong physical contact between microspheres and substrate. In typical colloidal lithography, weak contact of microspheres with the substrate does not block the formation of a SAM. To establish conformal contact between microspheres and substrate to block the formation of a SAM, magnetic force was exerted on softened paramagnetic microspheres that had been swollen by a solvent. The soft colloidal lithography with controlled buoyance enables pattern formation through simple wet chemistry.