Online Concentration and Affinity Separation of Biomolecules Using Multifunctional Particles in Capillary Electrophoresis under Magnetic Field

Solvophobic-controlled synthesis of smart magneto-fluorescent nanostructures for real-time inspection of metallic fractures

The production of materials that contain more than one functional constituent, the so-called multifunctional materials, is quite relevant in advanced technology. By acting as building blocks, nanoparticles can be suitably explored for generating higher-order multifunctional structures. In this regard, herein, a special clustered magneto-fluorescent superstructure has been developed for non-destructive detection of flaws and shallow subsurface discontinuities in industrial ferromagnetic materials. The strategy consists of the solvophobic-controlled assembly of organic-based maghemite cores and water-based II-VI quantum dots, in the presence of hexadecyltrimethyl-ammonium bromide, CTAB, as a compatibilizer agent. This composite exhibited a high magnetic response (σ _max = 66 emu g^-1) and uniform size, in addition to tunable optical properties (QY = 78%). The strategy of utilizing nanoparticles as magneto-fluorescent nanoprobes to identify tiny slits represents a great advance, for improving the capability of precisely revealing the fracture boundary locations by visual real-time inspection. The nanoscale probes exhibit a low signal-to-noise ratio and a higher competitive performance in relation to the existing micrometric detection systems.

Magnetic Nanoparticle Composites: Synergistic Effects and Applications

Composite materials are made from two or more constituent materials with distinct physical or chemical properties that, when combined, produce a material with characteristics which are at least to some degree different from its individual components. Nanocomposite materials are composed of different materials of which at least one has nanoscale dimensions. Common types of nanocomposites consist of a combination of two different elements, with a nanoparticle that is linked to, or surrounded by, another organic or inorganic material, for example in a core-shell or heterostructure configuration. A general family of nanoparticle composites concerns the coating of a nanoscale material by a polymer, SiO2 or carbon. Other materials, such as graphene or graphene oxide (GO), are used as supports forming composites when nanoscale materials are deposited onto them. In this Review we focus on magnetic nanocomposites, describing their synthetic methods, physical properties and applications. Several types of nanocomposites are presented, according to their composition, morphology or surface functionalization. Their applications are largely due to the synergistic effects that appear thanks to the co-existence of two different materials and to their interface, resulting in properties often better than those of their single-phase components. Applications discussed concern magnetically separable catalysts, water treatment, diagnostics-sensing and biomedicine.

Particle concentrating and sorting under a rotating electric field by direct optical-liquid heating in a microfluidics chip

We demonstrate a functional rotating electrothermal technique for rapidly concentrating and sorting a large number of particles on a microchip by the combination of particle dielectrophoresis (DEP) and inward rotating electrothermal (RET) flows. Different kinds of particles can be attracted (positive DEP) to or repelled (negative DEP) from electrode edges, and then the n-DEP responsive particles are further concentrated in the heated region by RET flows. The RET flows arise from the spatial inhomogeneous electric properties of fluid caused by direct infrared laser (1470 nm) heating of solution in a rotating electric field. The direction of the RET flows is radially inward to the heated region with a co-field (the same as the rotating electric field) rotation. Moreover, the velocity of the RET flows is proportional to the laser power and the square of the electric field strength. The RET flows are significant over a frequency range from 200 kHz to 5 MHz. The RET flows are generated by the simultaneous application of the infrared laser and the rotating electric field. Therefore, the location of particle concentrating can be controlled within the rotating electric field depending on the position of the laser spot. This multi-field technique can be operated in salt solutions and at higher frequency without external flow pressure, and thus it can avoid electrokinetic phenomena at low frequency to improve the manipulation accuracy for lab-on-chip applications.

Nanomaterials for sample pretreatment prior to capillary electrophoretic analysis

Nanomaterials are, in analytical science, used for a broad range of purposes, covering the area of sample pretreatment as well as separation, detection and identification of target molecules.

Electrophoretic separation method for membrane pore-forming proteins in multilayer lipid membranes

In this paper, we report on a novel electrophoretic separation and analysis method for membrane pore-forming proteins in multilayer lipid membranes (MLMs) in order to overcome the problems related to current separation and analysis methods of membrane proteins, and to obtain a high-performance separation method on the basis of specific properties of the lipid membranes. We constructed MLMs, and subsequently characterized membrane pore-forming protein behavior in MLMs. Through the use of these MLMs, we were able to successfully separate and analyze membrane pore-forming proteins in MLMs. To the best of our knowledge, this research is the first example of membrane pore-forming protein separation in lipid membranes. Our method can be expected to be applied for the separation and analysis of other membrane proteins including intrinsic membrane proteins and to result in high-performance by utilizing the specific properties of lipid membranes.

Bifunctional nanoparticles with fluorescence and magnetism via surface-initiated AGET ATRP mediated by an iron catalyst

Fluorescent/magnetic nanoparticles are of interest in many applications in biotechnology and nanomedicine for its living detection. In this study, a novel method of surface modification of nanoparticles was first used to modify a fluorescent monomer on the surfaces of magnetic nanoparticles directly. This was achieved via iron(III)-mediated atom-transfer radical polymerization with activators generated by electron transfer (AGET ATRP). Fluorescent monomer 9-(4-vinylbenzyl)-9H-carbazole (VBK) was synthesized and was grafted from magnetic nanoparticles (ferroferric oxide) via AGET ATRP using FeCl(3)·6H(2)O as the catalyst, tris(3,6-dioxaheptyl)amine (TDA-1) as the ligand, and ascorbic acid (AsAc) as the reducing agent. The initiator for ATRP was modified on magnetic nanoparticles with the reported method: ligand exchange with 3-aminopropyltriethoxysilane (APTES) and then esterification with 2-bromoisobutyryl bromide. After polymerization, a well-defined nanocomposite (Fe(3)O(4)@PVBK) was yielded with a magnetic core and a fluorescent shell (PVBK). Subsequently, well-dispersed bifunctional nanoparticles (Fe(3)O(4)@PVBK-b-P(PEGMA)) in water were obtained via consecutive AGET ATRP of hydrophilic monomer poly(ethylene glycol) methyl ether methacrylate (PEGMA). The chemical composition of the magnetic nanoparticles' surface at different surface modification stages was investigated with Fourier transform infrared (FT-IR) spectra. The magnetic and fluorescent properties were validated with a vibrating sample magnetometer (VSM) and a fluorophotometer. The Fe(3)O(4)@PVBK-b-P(PEGMA) nanoparticles showed an effective imaging ability in enhancing the negative contrast in magnetic resonance imaging (MRI).

The synthesis and bio-applications of magnetic and fluorescent bifunctional composite nanoparticles

Magnetic-fluorescent composite nanoparticles as a new kind of nanoparticle have attracted much attention in recent years. The composite nanoparticles combine the fluorescent properties, magnetic properties and the physical properties of nano-size, so they can offer a range of potential applications, such as bioseparation and bio-imaging, tumor cell localization, and even cancer treatment. This Minireview will introduce the main synthesis strategies for the fabrication of magnetic-fluorescent composite nanoparticles, the current and potential bio-application of magnetic-fluorescent nanocomposites, including protein and DNA separation and detection, bio-imaging and sorting in vitro and in vivo, drug delivery and the cancer treatment.

Ring magnets for magnetic beads trapping in a capillary

This paper introduces the concept of ring magnets for magnetic beads (MBs) trapping in a capillary. Such magnets enable an easy insertion of a capillary simply like a pearl on a string. With this system, high magnetic forces are obtained thanks to the proximity between the magnet and the capillary, giving the opportunity to work at higher flow rates than with classical setups using two magnets with their magnetization perpendicular to the capillary. Moreover, by alternating magnets and non-magnetic spacers either in attraction or repulsion configuration, it is possible to form a chain and as a consequence to adapt the number of magnets to the desired number of plugs, thus controlling the surface available for molecule binding. Magnetic force mapping was first carried out by numerical simulations for a single ring magnet. The usefulness of this concept was then demonstrated with the achievement of an immunoassay and an online preconcentration experiment. To study the formation of multiplugs, the magnetic force was first simulated for a chain of four magnets in repulsion. This force was then introduced into a convection-diffusion model to understand the influence of the flow velocity on their size and position. The numerical simulations were qualitatively corroborated by microscopic visualizations, carried out in a capillary placed between rectangular magnets having a magnetization parallel to the capillary, and quantitatively by bead capture efficiency experiments.

Preparation of P(NIPAM-co-AA) microcontainers surface-anchored with magnetic nanoparticles

P(NIPAM-co-AA) microcontainers surface-anchored with magnetic nanoparticles were prepared using PSt/P(NIPAM-co-AA) core/shell microspheres and amino-modified Fe(3)O(4)@SiO(2) particles as building blocks. At first, the PSt/P(NIPAM-co-AA) core/shell microspheres were prepared by seeded emulsion polymerization, and the amino-modified Fe(3)O(4)@SiO(2) particles were prepared by a modified Stober method followed by functionalized by 3-aminopropyltriethoxysilane. Then, the smaller amino-modified Fe(3)O(4)@SiO(2) particles were assembled onto the surface of PSt/P(NIPAM-co-AA) core/shell microspheres by electrostatic interaction. Subsequently, the two particles were permanently combined through amidation reaction between carboxylic groups and amino groups under the catalysis of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide. By dissolving the PSt core with tetrahydrofuran, novel triple-functional microcontainers with superparamagnetism and pH and temperature sensitivity were obtained.

Rapid and selective concentration of microparticles in an optoelectrofluidic platform

We demonstrate rapid manipulation and selective concentration of microparticles using AC electrokinetics such as dielectrophoresis (DEP) and AC electro-osmosis (ACEO) in an optoelectrofluidic platform based on a liquid crystal display (LCD). When 10 V bias at 10 kHz was applied to the optoelectrofluidic device, only the 1 microm-diameter polystyrene particles were concentrated into the projected LCD image patterns and closely packed, forming the crystalline structure by ACEO flow, while the 6 microm-diameter particles were repelled by negative DEP forces. We have characterized this frequency-dependency of the optoelectrofluidic particle behavior according to the particle diameter. On the basis of these results, we can rapidly concentrate the 1 microm-diameter particles and separate them from the 6 microm particles, by applying an AC signal of 10 kHz frequency. This novel technique can be applied to rapidly concentrate, separate and pattern micro-/nanoparticles in many biological and chemical applications.

Enzyme enhanced quantitative determination of multiple DNA targets based on capillary electrophoresis

In the current paper, enzyme enhanced simultaneous quantitative determination of multiple DNA targets based on capillary electrophoresis (CE) was described. We used three biotin-modified DNA probes, which reacted with avidin-conjugated horseradish peroxidase (avidin-HRP) conjugate to obtain the HRP labeled probes, to hybridize with three corresponding targets. The resulting mixture containing double-strand DNA (dsDNA)-HRP, excess single-strand DNA (ssDNA)-HRP and remaining avidin-HRP was separated by capillary electrophoresis, and then the system of HRP catalyzing H(2)O(2)/o-aminophenol (OAP) reaction was adopted. The catalytic product was detected with electrochemical detection. With this protocol, the limits of quantification for the hybridization assay of 21-, 39- and 80-mer DNA fragments were of 1.2 x 10(-11), 2.4 x 10(-11) and 3.0 x 10(-11)M, respectively. The multiplex assay also provided good specificity without any cross-reaction.

Immunoaffinity capillary electrophoresis as a powerful strategy for the quantification of low-abundance biomarkers, drugs, and metabolites in biological matrices

In the last few years, there has been a greater appreciation by the scientific community of how separation science has contributed to the advancement of biomedical research. Despite past contributions in facilitating several biomedical breakthroughs, separation sciences still urgently need the development of improved methods for the separation and detection of biological and chemical substances. In particular, the challenging task of quantifying small molecules and biomolecules, found in low abundance in complex matrices (e.g., serum), is a particular area in need of new high-efficiency techniques. The tandem or on-line coupling of highly selective antibody capture agents with the high-resolving power of CE is being recognized as a powerful analytical tool for the enrichment and quantification of ultra-low abundance analytes in complex matrices. This development will have a significant impact on the identification and characterization of many putative biomarkers and on biomedical research in general. Immunoaffinity CE (IACE) technology is rapidly emerging as the most promising method for the analysis of low-abundance biomarkers; its power comes from a three-step procedure: (i) bioselective adsorption and (ii) subsequent recovery of compounds from an immobilized affinity ligand followed by (iii) separation of the enriched compounds. This technology is highly suited to automation and can be engineered to as a multiplex instrument capable of routinely performing hundreds of assays per day. Furthermore, a significant enhancement in sensitivity can be achieved for the purified and enriched affinity targeted analytes. Thus, a compound that exists in a complex biological matrix at a concentration far below its LOD is easily brought to well within its range of quantification. The present review summarizes several applications of IACE, as well as a chronological description of the improvements made in the fabrication of the analyte concentrator-microreactor device leading to the development of a multidimensional biomarker analyzer.

Multifunctional Magnetic-fluorescent Nanocomposites for Biomedical Applications

Nanotechnology is a fast-growing area, involving the fabrication and use of nano-sized materials and devices. Various nanocomposite materials play a number of important roles in modern science and technology. Magnetic and fluorescent inorganic nanoparticles are of particular importance due to their broad range of potential applications. It is expected that the combination of magnetic and fluorescent properties in one nanocomposite would enable the engineering of unique multifunctional nanoscale devices, which could be manipulated using external magnetic fields. The aim of this review is to present an overview of bimodal “two-in-one” magnetic-fluorescent nanocomposite materials which combine both magnetic and fluorescent properties in one entity, in particular those with potential applications in biotechnology and nanomedicine. There is a great necessity for the development of these multifunctional nanocomposites, but there are some difficulties and challenges to overcome in their fabrication such as quenching of the fluorescent entity by the magnetic core. Fluorescent-magnetic nanocomposites include a variety of materials including silica-based, dye-functionalised magnetic nanoparticles and quantum dots-magnetic nanoparticle composites. The classification and main synthesis strategies, along with approaches for the fabrication of fluorescent-magnetic nanocomposites, are considered. The current and potential biomedical uses, including biological imaging, cell tracking, magnetic bioseparation, nanomedicine and bio- and chemo-sensoring, of magnetic-fluorescent nanocomposites are also discussed.