New monodisperse magnetic polymer microspheres biofunctionalized for enzyme catalysis and bioaffinity separations

Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core-Shell-Shell Catalysts with High Stability and Activity

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core-shell-shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

Silver-decorated gel-shell nanobeads: physicochemical characterization and evaluation of antibacterial properties

We report on the synthesis of composite nanobeads with antibacterial properties. The particles consist of polystyrene cores that are surrounded by sulfonic gel shells with embedded silver nanoparticles. The nanocomposite beads are prepared by sulfonation of polystyrene particles followed by accumulation of silver ions in the shell layer and subsequent reduction with sodium borohydride. The resulting material has been characterized by electron microscopy, vibrational and X-ray photoelectron spectroscopy and several other experimental techniques. It was shown that sodium borohydride reduces silver ions embedded in the gel layer producing silver nanoparticles but also transforms a fraction of sulfonic groups in the polymer to moieties with sulfur in a lower oxidation state, likely thiols. It is hypothesized that the generated thiol groups are anchoring the nanoparticles in the gel shell of the nanobeads stabilizing the whole structure. The silver-decorated nanobeads appear to be a promising material with considerable antimicrobial activity and were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. The determined minimum inhibitory (MIC) and minimum biofilm inhibitory (MBIC) concentrations are comparable to those of non-incorporated silver nanoparticles.

Scalable Production of Monodisperse Functional Microspheres by Multilayer Parallelization of High Aspect Ratio Microfluidic Channels

Droplet microfluidics enables the generation of highly uniform emulsions with excellent stability, precise control over droplet volume, and morphology, which offer superior platforms over conventional technologies for material synthesis and biological assays. However, it remains a challenge to scale up the production of the microfluidic devices due to their complicated geometry and long-term reliability. In this study, we present a high-throughput droplet generator by parallelization of high aspect ratio rectangular structures, which enables facile and scalable generation of uniform droplets without the need to precisely control external flow conditions. A multilayer device is formed by stacking layer-by-layer of the polydimethylsiloxane (PDMS) replica patterned with parallelized generators. By feeding the sample fluid into the device immersed in the carrying fluid, we used the multilayer device with 1200 parallelized generators to generate monodisperse droplets (~45 μm in diameter with a coefficient of variation <3%) at a frequency of 25 kHz. We demonstrate this approach is versatile for a wide range of materials by synthesis of polyacrylamide hydrogel and Poly (l-lactide-co-glycolide) (PLGA) through water-in-oil (W/O) and oil-in-water (O/W) emulsion templates, respectively. The combined scalability and robustness of such droplet emulsion technology is promising for production of monodisperse functional materials for large-scale applications.

On-a-chip tryptic digestion of transthyretin: a step toward an integrated microfluidic system for the follow-up of familial transthyretin amyloidosis

TTR digestion on TE-chip: production of a fragment of interest allowing the therapeutic follow-up of the familial transthyretin amyloidosis.

Magnetic poly(2-hydroxyethyl methacrylate) microspheres for affinity purification of monospecific anti-p46 kDa/Myo1C antibodies for early diagnosis of multiple sclerosis patients

The aim of the present study is to develop new magnetic polymer microspheres with functional groups available for easy protein and antibody binding. Monodisperse macroporous poly(2-hydroxyethyl methacrylate) (PHEMA-COOH) microspheres ~4 µm in diameter and containing ∼1 mmol COOH/g were synthesized by multistep swelling polymerization of 2-hydroxyethyl methacrylate (HEMA), ethylene dimethacrylate (EDMA), and 2-[(methoxycarbonyl)methoxy]ethyl methacrylate (MCMEMA), which was followed by MCMEMA hydrolysis. The microspheres were rendered magnetic by precipitation of iron oxide inside the pores, which made them easily separable in a magnetic field. Properties of the resulting magnetic poly(2-hydroxyethyl methacrylate) (mgt.PHEMA) particles with COOH functionality were examined by scanning and transmission electron microscopy (SEM and TEM), static volumetric adsorption of helium and nitrogen, mercury porosimetry, Fourier transform infrared (FTIR) and atomic absorption spectroscopy (AAS), and elemental analysis. Mgt.PHEMA microspheres were coupled with p46/Myo1C protein purified from blood serum of multiple sclerosis (MS) patients, which enabled easy isolation of monospecific anti-p46/Myo1C immunoglobulin G (IgG) antibodies from crude antibody preparations of mouse blood serum. High efficiency of this approach was confirmed by SDS/PAGE, Western blot, and dot blot analyses. The newly developed mgt.PHEMA microspheres conjugated with a potential disease biomarker, p46/Myo1C protein, are thus a promising tool for affinity purification of antibodies, which can improve diagnosis and treatment of MS patients.

Droplet Microfluidics for the Production of Microparticles and Nanoparticles

Droplet microfluidics technology is recently a highly interesting platform in material fabrication. Droplets can precisely monitor and control entire material fabrication processes and are superior to conventional bulk techniques. Droplet production is controlled by regulating the channel geometry and flow rates of each fluid. The micro-scale size of droplets results in rapid heat and mass-transfer rates. When used as templates, droplets can be used to develop reproducible and scalable microparticles with tailored sizes, shapes and morphologies, which are difficult to obtain using traditional bulk methods. This technology can revolutionize material processing and application platforms. Generally, microparticle preparation methods involve three steps: (1) the formation of micro-droplets using a microfluidics generator; (2) shaping the droplets in micro-channels; and (3) solidifying the droplets to form microparticles. This review discusses the production of microparticles produced by droplet microfluidics according to their morphological categories, which generally determine their physicochemical properties and applications.

Streptavidin-modified monodispersed magnetic poly(2-hydroxyethyl methacrylate) microspheres as solid support in DNA-based molecular protocols

Molecular diagnostics may provide tailored and cost efficient treatment for infectious disease and cancer. Rolling circle amplification (RCA) of padlock probes guarantees high specificity to identify nucleic acid targets down to single nucleotide resolution in a multiplex fashion. This makes the assay suitable for molecular analysis of various diseases, and interesting to integrate into automated devices for point-of-care analysis. A critical prerequisite for many molecular assays is (i) target-specific isolation from complex clinical samples and (ii) removal of reagents, inhibitors and contaminants between reaction steps. Efficient solid supports are therefore essential to enable multi-step, multi-analyte protocols. Superparamagnetic micro- and nanoparticles, with large surface area and rapid liquid-phase kinetics, are attractive for multi-step protocols. Recently, streptavidin-modified magnetic monodispersed poly(2-hydroxyethyl methacrylate) (STV-mag.PHEMA) microspheres were developed by multiple swelling polymerization. They are easily separated by a magnet and exhibit low non-specific protein sorption. In this study, the performance and the binding efficiency of STV-mag.PHEMA was addressed by circle-to-circle amplification (C2CA). A lower number of RCA products were detected as compared to the gold standard Dynabeads. Nevertheless, this study was the first to successfully adapt STV-mag.PHEMA microspheres as solid support in a DNA-based protocol, which is an important finding. The STV-mag.PHEMA microspheres were larger with about 16 times less surface area as compared to the Dynabeads, which might partly explain the lower rolling circle product (RCP) count obtained. Further research is currently ongoing comparing particles of similar sizes and optimizing reaction conditions to establish their full utility in the field. Ultimately, low cost and versatile particles are a great resource to facilitate future clinical molecular diagnostics.

Thionine-Modified Poly(glycidyl methacrylate) Nanospheres as Labels of Antibodies for Biosensing Applications

Monodisperse poly(glycidyl methacrylate) (PGMA) nanospheres were obtained by emulsifier-free emulsion polymerization and characterized by physicochemical methods. The effects of various reaction parameters on the particle properties were investigated. The particle size was controlled in the range of 350-420 nm. To introduce carboxyl groups, the PGMA nanospheres were hydrolyzed and oxidized with KMnO4. Subsequently, the enzyme horseradish peroxidase (HRP) and the electron mediator thionine were covalently attached to the PGMA nanospheres to obtain an antibody indicator suitable for enzyme-based electrochemical immunosensors. Combined HRP and thionine binding to the nanospheres had beneficial effects for the labeling efficiency and at the same time prevented the formation of soluble electron mediators.

Preparation of Monodisperse Porous Silica Particles Using Poly(Glycidyl Methacrylate) Microspheres as a Template

Monodisperse macroporous poly(glycidyl methacrylate) (PGMA) microspheres were used as a template for preparing porous silica particles. The starting polymer microspheres that were 9.3 μm in size were synthesized by multistep swelling polymerization using a modified Ugelstad technique. Subsequently, silica (SiO2) was deposited on the surface and inside the PGMA microspheres to produce poly(glycidyl methacrylate)-silica hybrid particles (PGMA-SiO2). Upon calcination of the PGMA-SiO2 microspheres, porous silica particles were formed. The morphology, particle size, polydispersity and inner structure of the silica microspheres were investigated by scanning and transmission electron microscopy. Thermogravimetric analysis and dynamic adsorption of nitrogen determined the amount of silica formed and its specific surface area. Compared with the starting PGMA microspheres, the size of the porous silica particles decreased by up to 30 %. These porous silica microspheres are promising for chromatography and biomedical applications.

Injectable PEGylated fibrinogen cell-laden microparticles made with a continuous solvent- and oil-free preparation method

A new methodology is reported for the continuous, solvent- and oil-free production of photopolymerizable microparticles containing encapsulated human dermal fibroblasts. A precursor solution of cells in photoreactive poly(ethylene glycol) (PEG)-fibrinogen (PF) polymer was transported through a transparent injector exposed to light irradiation before being atomized in a jet-in-air nozzle. Shear rheometry data revealed the crosslinking kinetics of the PF/cell solution, which was then used to determine the amount of irradiation required to partially polymerize the mixture just prior to atomization. The partially polymerized drops of PF/cells fell into a gelation bath for further crosslinking until fully polymerized hydrogel microparticles were formed. As the drops of solution exited the air-in-jet nozzle, their viscosity was designed to be sufficiently high so as to prevent rapid mixing and/or dilution in the gelation bath, but without undergoing complete gelation in the nozzle. Several parameters of this system were varied to control the size and polydispersity of the microparticles, including the cell density, the flow rate and the air pressure in the nozzle. The system was capable of producing cell-laden microparticles with an average diameter of between 88.1 to 347.1 μm, and a dispersity of between 1.1 and 2.4, depending on the parameters chosen. Varying the precursor flow rate and/or cell density was beneficial in controlling the size and polydispersity of the microparticles; all microparticles exhibited very high cell viability, which was not affected by these parameters. In conclusion, this dropwise photopolymerization methodology for preparing cell-laden microparticles is an attractive alternative to existing techniques that use harsh solvents/oils and offer limited control over particle size and polydispersity.

Monodisperse carboxyl-functionalized poly(ethylene glycol)-coated magnetic poly(glycidyl methacrylate) microspheres: application to the immunocapture of β-amyloid peptides

Identification and evaluation of small changes in β-amyloid peptide (Aβ) levels in cerebrospinal fluid is of crucial importance for early detection of Alzheimer's disease. Microfluidic detection methods enable effective preconcentration of Aβ using magnetic microparticles coated with Aβ antibodies. Poly(glycidyl methacrylate) microspheres are coated with α-amino-ω-methoxy-PEG5000 /α-amino-ω-Boc-NH-PEG5000 Boc groups deprotected and NH2 succinylated to introduce carboxyl groups. Capillary electrophoresis with laser-induced fluorescence detection confirms the efficient capture of Aβ 1-40 peptides on the microspheres with immobilized monoclonal anti-Aβ 6E10. The capture specificity is confirmed by comparing Aβ 1-40 levels on the anti-IgG-immobilized particles used as a control.

Alzheimer's disease biomarkers detection in human samples by efficient capturing through porous magnetic microspheres and labelling with electrocatalytic gold nanoparticles

A nanobiosensor based on the use of porous magnetic microspheres (PMM) as efficient capturing/pre-concentrating platform is presented for detection of Alzheimer's disease (AD) biomarkers. These PMMs prepared by a multistep swelling polymerization combined with iron oxide precipitation afford carboxyl functional groups suitable for immobilization of antibodies on the particle surface allowing an enhanced efficiency in the capturing of AD biomarkers from human serum samples. The AD biomarkers signaling is produced by gold nanoparticle (AuNP) tags monitored through their electrocatalytic effect towards hydrogen evolution reaction (HER). Novel properties of PMMs in terms of high functionality and high active area available for enhanced catalytic activity of the captured AuNPs electrocatalytic tags are exploited for the first time. A thorough characterization by scanning transmission electron microscope in high angle annular dark field mode (STEM-HAADF) demonstrates the enhanced ability of PMMs to capture a higher quantity of analyte and consequently of electrocatalytic label, when compared with commercially available microspheres. The optimized and characterized PMMs are also applied for the first time for the detection of beta amyloid and ApoE at clinical relevant levels in cerebrospinal fluid (CSF), serum and plasma samples of patients suffering from AD.

Magnetic poly(glycidyl methacrylate) microspheres for protein capture

The efficient isolation and concentration of protein antigens from complex biological samples is a critical step in several analytical methods, such as mass spectrometry, flow cytometry and immunochemistry. These techniques take advantage of magnetic microspheres as immunosorbents. The focus of this study was on the development of new superparamagnetic polymer microspheres for the specific isolation of the tumor suppressor protein p53. Monodisperse macroporous poly(glycidyl methacrylate) (PGMA) microspheres measuring approximately 5 μm and containing carboxyl groups were prepared by multistep swelling polymerization of glycidyl methacrylate (GMA), 2-[(methoxycarbonyl)methoxy]ethyl methacrylate (MCMEMA) and ethylene dimethylacrylate (EDMA) as a crosslinker in the presence of cyclohexyl acetate as a porogen. To render the microspheres magnetic, iron oxide was precipitated within their pores; the Fe content in the particles received ∼18 wt%. Nonspecific interactions between the magnetic particles and biological media were minimized by coating the microspheres with poly(ethylene glycol) (PEG) terminated by carboxyl groups. The carboxyl groups of the magnetic PGMA microspheres were conjugated with primary amino groups of mouse monoclonal DO-1 antibody using conventional carbodiimide chemistry. The efficiency of protein p53 capture and the degree of nonspecific adsorption on neat and PEG-coated magnetic microspheres were determined by western blot analysis.

Recent Advances in the Application of Magnetic Nanoparticles as a Support for Homogeneous Catalysts

Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We discuss magnetic core shell nanostructures (e.g., silica or polymer coated magnetic nanoparticles) as substrates for catalyst immobilisation. Then we consider magnetic nanoparticles bound to inorganic catalytic mesoporous structures as well as metal organic frameworks. Binding of catalytically active small organic molecules and polymers are also reviewed. After that we briefly deliberate on the binding of enzymes to magnetic nanocomposites and the corresponding enzymatic catalysis. Finally, we draw conclusions and present a future outlook for the further development of new catalytic systems which are immobilised onto magnetic nanoparticles.