Biocompatibility, Pharmaceutical and Biomedical Applications L. Harivardhan Reddy,†,‡ Jose ́ L. Arias, Julien Nicolas,† and Patrick Couvreur*,† †Laboratoire de Physico-Chimie, Pharmacotechnie et Biopharmacie, Universite ́ Paris-Sud XI, UMR CNRS 8612, Faculte ́ de Pharmacie, IFR 141, 5 rue Jean-Baptiste Cleḿent, F-92296 Chat̂enay-Malabry, France Departamento de Farmacia y Tecnología Farmaceútica, Facultad de Farmacia, Campus Universitario de Cartuja s/n, Universidad de Granada, 18071 Granada, Spain ‡Pharmaceutical Sciences Department, Sanofi, 13 Quai Jules Guesdes, F-94403 Vitry-sur-Seine, France

Magnetic nanoparticles: design and characterization, toxicity and biocompatibility, pharmaceutical and biomedical applications.

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Superparamagnetic iron oxide nanoparticles (SPIONs): Development, surface modification and applications in chemotherapy

Magnetic sensors can be classified according to whether they measure the total magnetic field or the vector components of the magnetic field. The techniques used to produce both types of magnetic sensors encompass many aspects of physics and electronics. Here, we describe and compare most of the common technologies used for magnetic field sensing. These include search coil, fluxgate, optically pumped, nuclear precession, SQUID, Hall-effect, anisotropic magnetoresistance, giant magnetoresistance, magnetic tunnel junctions, giant magnetoimpedance, magnetostrictive/piezoelectric composites, magnetodiode, magnetotransistor, fiber optic, magnetooptic, and microelectromechanical systems-based magnetic sensors. The usage of these sensors in relation to working with or around Earth's magnetic field is also presented

Magnetic sensors and their applications

Nanostructures have attracted huge interest as a rapidly growing class of materials for many applications. Several techniques have been used to characterize the size, crystal structure, elemental composition and a variety of other physical properties of nanoparticles. In several cases, there are physical properties that can be evaluated by more than one technique. Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed. In addition, given that the significance of nanoparticles in basic research and applications is constantly increasing, it is necessary that researchers from separate fields overcome the challenges in the reproducible and reliable characterization of nanomaterials, after their synthesis and further process (e.g. annealing) stages. The principal objective of this review is to summarize the present knowledge on the use, advances, advantages and weaknesses of a large number of experimental techniques that are available for the characterization of nanoparticles. Different characterization techniques are classified according to the concept/group of the technique used, the information they can provide, or the materials that they are destined for. We describe the main characteristics of the techniques and their operation principles and we give various examples of their use, presenting them in a comparative mode, when possible, in relation to the property studied in each case.

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Characterization techniques for nanoparticles: comparison and complementarity upon studying nanoparticle properties

A targeted drug delivery system is the need of the hour. Guiding magnetic iron oxide nanoparticles with the help of an external magnetic field to its target is the principle behind the development of superparamagnetic iron oxide nanoparticles (SPIONs) as novel drug delivery vehicles. SPIONs are small synthetic γ-Fe2O3 (maghemite) or Fe3O4 (magnetite) particles with a core ranging between 10 nm and 100 nm in diameter. These magnetic particles are coated with certain biocompatible polymers, such as dextran or polyethylene glycol, which provide chemical handles for the conjugation of therapeutic agents and also improve their blood distribution profile. The current research on SPIONs is opening up wide horizons for their use as diagnostic agents in magnetic resonance imaging as well as for drug delivery vehicles. Delivery of anticancer drugs by coupling with functionalized SPIONs to their targeted site is one of the most pursued areas of research in the development of cancer treatment strategies. SPIONs have also demonstrated their efficiency as nonviral gene vectors that facilitate the introduction of plasmids into the nucleus at rates multifold those of routinely available standard technologies. SPION-induced hyperthermia has also been utilized for localized killing of cancerous cells. Despite their potential biomedical application, alteration in gene expression profiles, disturbance in iron homeostasis, oxidative stress, and altered cellular responses are some SPION-related toxicological aspects which require due consideration. This review provides a comprehensive understanding of SPIONs with regard to their method of preparation, their utility as drug delivery vehicles, and some concerns which need to be resolved before they can be moved from bench top to bedside.

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Superparamagnetic iron oxide nanoparticles: magnetic nanoplatforms as drug carriers

Properties of a flux dam inserted in the pickup coil of a high-T_c superconducting quantum interference device magnetometer

The properties of a flux dam inserted in a pickup coil of a high-Tc superconducting quantum interference device (SQUID) are studied. First, the effect of thermal noise at T=77 K on the magnetic flux entry into in the pickup coil through the flux dam is discussed. It is shown that the thermal noise causes the flux entry even when the circulating current in the pickup coil is less than the critical current of the flux dam. The behavior of this thermally activated flux entry is analyzed using the so-called potential-barrier model. It is shown that the flux entry into the coil proceeds logarithmically with time, indicating the necessity of a long waiting time in the use of the flux dam. It is also shown that the critical current of the flux dam must be large enough to obtain a quasistable state, i.e., a state where no thermally activated flux entry occurs during the measurement time. The critical current should be larger than 50 µA in the magnetic field under operation. Next, in order to satisfy this requirement, the magnetic field dependence of the critical current of the flux dam is studied when the flux dam is made of a wide bicrystal junction. It is shown that the magnetic field dependence of the wide junction can be explained reasonably well if we take into account the so-called overlap-type-junction model and the flux-focusing effect of the bicrystal junction. The obtained results will be useful in the design of the flux dam.

Properties of a flux dam inserted in the pickup coil of a high-Tc superconducting quantum interference device magnetometer

The conversion efficiency between a signal magnetic flux and the output power of a large-β dc SQUID, i.e., a SQUID with a modulation parameter β larger than unity, have been studied theoretically. In our investigation the inductance of the SQUID was shunted by using a damping resistor. The dependence of the output power on such SQUID parameters as β, the McCumber parameter βc and the damping parameter γ=Rs/Rd(Rs and Rd are the shunt and the damping resistances, respectively) was investigated in detail. It has been shown that an order-of-magnitude increase in the output power can be realized with a large-β SQUID without a degradation of noise characteristics, compared with the case of β=1. It has also been shown that the values of βc=0.4 and γ=1 are optimum with regard to a large output power and a low-noise operation of the SQUID.

Conversion Efficiency of a Large-β DC-SQUID with a Resistively Shunted Inductance

When a patient is not capable of eating a meal due to difficulty in swallowing, a nasogastric tube can be inserted through the nose to the stomach to provide nourishment in liquid form. However, it is possible to insert the tube into the lungs by mistake. In this paper, we apply a minimum variance beamformer that is commonly used in brain signal source detection to estimate the position of the magnet attached to the tip of a nasogastric tube. To reduce the computational cost, the signal source power is calculated with two different resolutions. Furthermore, the signal source power calculations are performed in parallel. The position may be estimated in less than 1.0 s, making this method suitable for detecting the tip position of a nasogastric tube in real time.

Application of minimum variance beamformer for estimation of tip position of a nasogastric tube

Experimental and theoretical studies are made of the effect of a microwave on dc current-voltage characteristics of long Josephson junctions. In the case of zero external dc current, dc voltages were observed when the microwave was applied to the junctions. By comparing the observed magnetic-field and microwave-power dependences with theoretical results, it is concluded that these dc voltages resulted from vortex motion which was induced by the applied microwave. When the junctions were in a flux-flow state caused by the external current, a good agreement between theory and experiment concerning the microwave-power and magnetic-field dependences of Shapiro steps demonstrates that an almost ideal traveling-wave type coupling between the applied microwave and a moving vortex array took place in the long Josephson junctions.

Keiji Enpuku

Papers

Properties of a flux dam inserted in the pickup coil of a high-T_c superconducting quantum interference device magnetometer

Properties of a flux dam inserted in the pickup coil of a high-Tc superconducting quantum interference device magnetometer

Conversion Efficiency of a Large-β DC-SQUID with a Resistively Shunted Inductance

Application of minimum variance beamformer for estimation of tip position of a nasogastric tube

Microwave-induced vortex motion in long Josephson junctions.