Magnetic Biodetection Research Articles

Mechanical Force Acting on Ferrogel in a Non-Uniform Magnetic Field: Measurements and Modeling.

The development of magnetoactive microsystems for targeted drug delivery, magnetic biodetection, and replacement therapy is an important task of present day biomedical research. In this work, we experimentally studied the mechanical force acting in cylindrical ferrogel samples due to the application of a non-uniform magnetic field. A commercial microsystem is not available for this type of experimental study. Therefore, the original experimental setup for measuring the mechanical force on ferrogel in a non-uniform magnetic field was designed, calibrated, and tested. An external magnetic field was provided by an electromagnet. The maximum intensity at the surface of the electromagnet was 39.8 kA/m and it linearly decreased within 10 mm distance from the magnet. The Ferrogel samples were based on a double networking polymeric structure which included a chemical network of polyacrylamide and a physical network of natural polysaccharide guar. Magnetite particles, 0.25 micron in diameter, were embedded in the hydrogel structure, up to 24% by weight. The forces of attraction between an electromagnet and cylindrical ferrogel samples, 9 mm in height and 13 mm in diameter, increased with field intensity and the concentration of magnetic particles, and varied within 0.1–30 mN. The model provided a fair evaluation of the mechanical forces that emerged in ferrogel samples placed in a non-uniform magnetic field and proved to be useful for predicting the deformation of ferrogels in practical bioengineering applications.

Магнитные наночастицы, полученные электрофизическими методами: фокус на биомедицинские приложения

This work describes the possibility of fabrication of the large batches of magnetic nanoparticles using electrophysical methods of electric explosion of the wire, laser target evaporation and spark discharge. Bioapplications of nanoparticles require the production of magnetic materials in the form of stabilized aqueous suspensions or hydrogels with magnetic fillers; therefore, some details of the synthesis of these materials and their certification are discussed. The peculiarities of interaction of magnetic nanoparticles with biological systems, the problem of biocompatibility, the possibility of using ferrogel substrates for the needs of cell technologies and regenerative medicine, as well as implication of biomimetics in the development of magnetic biosensors are considered. The results of the analysis of a number of different biological experiments carried out with suspensions of various types, obtained based on the same batch of MNPs are presented. An analysis of examples of magnetic biodetection and existing theoretical approaches will make it possible to assess the prospects of this scientific direction for the creation of highly sensitive thin film sensors based on the giant magnetoimpedance effect for biomedical applications

Synthesis of Superparamagnetic Iron Oxide Nanoparticles: SWOT Analysis Towards Their Conjugation to Biomolecules for Molecular Recognition Applications.

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) have attracted a great deal of research attention due to their enormous possibilities of utilisation in different bioapplications such as magnetic particle imaging, drug delivery, hyperthermia or magnetic bio-detection. The purpose of this review is to critically analyze the methods for synthesis of SPIONs reported at the literature taking into account their suitability in molecular recognition applications by means of their conjugation to biomolecules. In this work, we have summarized the main synthesis routes, and controlled agglomeration methods for enhancement of sensitivity at molecular recognition events. This includes conventional chemical precipitation methods, thermal decomposition, microemulsions, or microfluidic synthesis, and the main strategies for the preparation of nanocomposites or SPIONs nanoclusters, such as polymer or silica cross-linking reactions, entrapment in nanovesicles or flower-like structures through the appropriate use of different metals to get synergetic properties for the total nanoarquitecture. Since most of the actual applications in biomedicine require their conjugation to biomolecules, an analysis of the Strengths, Weaknesses, Opportunities and Threats of these methods was carried out for the first time, with a view to highlight the best routes for a given application at biomolecular recognition.

Multi‐binding biotinylated iron oxide nanoparticles as a promising versatile material for magnetic biomedical applications

The tetrameric streptavidin and avidin both have four sites that can specifically bind with biotin. Taking advantage of this high affinity binding, it is possible to realise multi-binding of biotinylated nanoparticles to avidin or streptavidin molecules. The iron oxide nanoparticles (IONPs) have been actively investigated in biomedical applications. In this work, biotinylated IONPs (biotin-IONPs) with around 10.5 nm magnetic core size were synthesised. They exhibited long-term hydrophilic stability, and the activity of the biotin content was verified by avidin-horseradish peroxidase induced chromogenic experiment. These biotin-IONPs were then studied as magnetic labels in substrate-based and substrate-free magnetic bio-labelling scheme of alpha-fetoprotein. The multi-binding ability of these biotin-IONPs with streptavidin functionalised detection antibody (streptavidin-detection antibody) was proved both on microplate well surfaces and in solution. Consequently, biotin-IONPs are promising magnetic label materials for the improvement of magnetic biodetection. In addition, the avidin-induced biotin-IONP assemblies were produced in MilliQ water solution and in water-in-oil microemulsion system. In summary, based on their multi-binding nature, the biotin-IONPs can be considered as a versatile material to improve the sensitivity of magnetic biodetection and to be further built into assemblies for future biomedical applications such as magnetic resonance imaging and target drug delivery.

Modelling of thin film magnetoimpedance sensitive element designed for biodetection

Magnetic soft matter (ferrofluids or ferrogels) is one of the rapidly growing areas of research and applications including magnetic biosensing. Giant magnetoimpedance is the effect with proven capacity to magnetic label detection. In this work, we describe a universal model to simulate conditions of magnetic biodetection and to check its validity with giant magnetoimpedance sensitive element based on magnetic multilayer. Finite element method allows calculations of high-frequency current distribution using the Maxwell's equations taking into account the magnetodynamics of iron oxide water-based ferrofluid in small channels similar to the blood vessels. The modelling was realized with the licensed software Comsol©. The calculations were performed on a specialized engineering server based on four processors Intel Xeon E5 and 124 Gb RAM, adapted for parallel computations and suitable for description of individual layers with nanometer dimensions for the number of elements in the mesh structure above 106 cells. The designed model allows calculations of the current density, the outside magnetic flux, resistivity, etc. for each one of the created cells and total values by integration of sub-domains. One can quantitatively describe concentration of ferrofluid, velocity and pressure in the blood vessel. These changes affecting on the giant magnetoimpedance of the FeNi-based multilayer were both calculated and measured.

System based on a ZVA-67 vector network analyzer for measuring high-frequency parameters of magnetic film structures

Thin magnetic films and multilayers are widely used in electronic devices and sensor systems, including systems for magnetic nondestructive testing and magnetic biodetection. Creating sensing elements of a new generation will necessitate the certification of film nanostructures. In this paper, a novel system is presented that allows automated measurement of parameters of thin ferromagnetic film structures at frequencies of 0.1 to 25 GHz in a magnetic field of up to 18 kOe.

Characterization and bio-binding ability study on size-controllable highly monodisperse magnetic nanoparticles

With the advances in micro-/nano-electronic technology, the development of portable lab-on-chip biodetection device by utilizing magnetic nanoparticles as bio-probes and magnetic field sensor as signal detector has attracted considerable interests in healthcare area. Magnetic probes with required sizes are crucial in quantitative magnetic bio-detection for specific bio-analytes. The objective of this study was to synthesize and characterize amphiphilic co-polymer coated magnetic iron oxide nanoparticles with tunable sizes and study their bio-binding ability. Transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectrometer (FT-IR), thermogravimetric analyzer (TGA), and vibrating sample magnetometer (VSM) were employed to investigate the particle dimension, hydrodynamic size, surface property, mass ratio of surface surfactants, and magnetic behavior. The investigation on their biologically binding ability with bovine serum protein was carried out on thin gold film. The results showed iron oxide nanoparticles with controllable sizes were coated by amphiphilic co-polymer successfully and could be completely transferred and well-dispersed in aqueous solutions. The final products with magnetic core sizes ranging from 6nm to 17nm showed superparamagnetic behavior, stable hydrodynamic sizes in aqueous suspensions, and binding ability with bio-molecules, making them promising candidates as magnetic tags for the development of bio-detection devices.

Magnetism of Iron Oxide Nanoparticles and Magnetic Biodetection

Magnetism of Iron Oxide Nanoparticles and Magnetic Biodetection

Spin valve biosensors: Signal dependence on nanoparticle position

Experimental and theoretical studies have been carried out on the spin valve sensor signal dependence on the spatial locations of magnetic nanoparticles as potential biomolecular labels in the magnetic biodetection technology. Superparamagnetic 16 nm magnetite (Fe3O4) nanoparticles were site specifically deposited at different positions relative to a submicron-wide spin valve sensor. The spin valve sensor signal showed both polarity and magnitude differences with the particles at different positions. A theoretical model including magnetic sensor-particle interaction confirms the experimental results and provides a design guide to the sensing area. Moreover, the theoretical calculations reveal a nonmonotonic signal dependence on the vertical particle-to-sensor distance due to the sensor-particle interaction, and show that an optimum distance exists for signal strength and quantification.

Spin valve sensors for ultrasensitive detection of superparamagnetic nanoparticles for biological applications

We present giant magnetoresistance (GMR) spin valve sensors designed for detection of superparamagnetic nanoparticles as potential biomolecular labels in magnetic biodetection technology. We discuss the sensor design and experimentally demonstrate that as few as ∼23 monodisperse 16-nm superparamagnetic Fe 3O 4 nanoparticles can be detected by submicron spin valve sensors at room temperature without resorting to lock-in detection. A patterned self-assembly method of nanoparticles, based on a polymer-mediated process and fine lithography, is developed for the detection. It is found that sensor signal increases linearly with the number of nanoparticles.