This paper deals with a magnetic imaging method of magnetic nanoparticles (MNPs). A complete analytical model is developed considering the main parameters of the system. Such analytical modeling of the magnetic induction generated in the space by the MNPs allows to describe the detection system performance and to consider the spatial reconstruction issue. In particular, for a given set of system parameters (sampling step, liftoff, and magnetic noise of the sensor), the ultimate spatial resolution in 2-D can be derived. We discuss the key parameters and compare the analytical model with the experimental data obtained from scanning measurement.

We have designed and fabricated a microfluidic system made of glass and polydimethylsiloxane. A micro-magnetometer has been integrated to the system. This sensor is made of a giant magneto-impedance wire known to have very high magnetic sensitivity at room temperature. A liquid-liquid segmented multiphase flow was generated in the channel using a Y-shaped inlet junction. The dispersed phase plugs contained superparamagnetic iron oxide (20 nm) nanoparticles at a molar concentration of 230 mmol/l. We have shown both theoretically and experimentally that in-flow detection of these nanoparticles is performed by the microsystem for concentration as small as 5.47 × 10−9 mol. These performances show that it is conceivable to use this system for ex-vivo analysis of blood samples where superparamagnetic iron oxide nanoparticles, initially used as magnetic contrast agents, could be functionalized for biomarkers fishing. It opens new perspectives in the context of personalized medicine.

This paper presents a mathematical model of the detection of the magnetic nanoparticles (MNPs) flowing into a microchannel. To validate the model, the experimental measurements were performed using a ferrofluid and a giant magneto impedance microwire made up of CoFeSiBNb alloy as a sensor. The good agreement between theory and measurement implies the possibility of using the numerical simulation to analyze the system performance for the MNPs detection. In addition, a model calculation was performed, which evaluates the optimal signal-to-noise ratio of the detection system as a function of its main parameters and according to the magnetic induction induced by the MNPs.

Il existe un certain nombre d’applications faisant appel aux nanoparticules magnetiques (NPMs). Elles sont generalement utilisees comme marqueurs, agents de ciblage ou agents de contraste. Les travaux de cette these se concentrent sur les performances de methodes magnetiques permettant leur detection. Les potentialites de detection des systemes developpes en termes de localisation et d’evaluation de concentrations dans le cadre de mesure a une ou deux dimensions (1D, 2D) sont les points clefs. Deux systemes ont ete developpes, ils portent sur la detection de NPMs dans des µcanaux pour des applications biomedicales (1D) et l’imagerie magnetique de nanoparticules magnetiques (IMNP) (2D) a l’aide de magnetoimpedance geante. Pour chacune de ces methodes, une modelisation de l’induction magnetique generee par les nanoparticules magnetiques a ete entreprise. Le rapport signal a bruit (RSB) des systemes de detection est egalement decrit. Il tient compte des proprietes des NPMs, du bruit intrinseque du capteur magnetique, du systeme electronique d’excitation et de l’ensemble de la chaine de mesure. Cette modelisation permet d’une part, d’evaluer les seuils theoriques de detection au regard du volume et de la concentration des NPMs en fonction des parametres du dispositif experimental et d’autre part, de decrire la resolution spatiale ultime qu’il est possible d’obtenir, apres reconstruction, en fonction de parametres cles tels que le lift-off, la taille du pixel observe et du bruit magnetique equivalent apparaissant lors de la mesure. Afin de valider ces analyses, les modeles theoriques ont ete confrontes a des mesures experimentales en 1D et 2D. La detection dans un µcanal d’un volume de NPMs de 20 nl et de concentration de 230 mmol/l, ainsi que la reconstruction d’image 2D avec une resolution spatiale inferieure au mm ont pu etre demontrees. L’ensemble des resultats obtenus est en total adequation avec les modeles theoriques.

A complete statistical model taking into account the nature of the magnetic sensor noise is proposed for parameter extraction in magnetorelaxometry experiments on magnetic nanoparticles (MNPs). Apart from the noise, the important factors are the type of the magnetic sensor used as well as the regression model depending on the relaxation mechanism. Whatever the relaxation mechanism is, the models are non-linear. Consequently, the relation between the signal to noise ratio of the measurement and the uncertainty of the extracted parameters is not straightforward. From the model, we derive a figure of merit that enables an a priori performance extrapolation from the characteristics of the magnetometer.

This paper presents the detection of magnetic nanoparticles flowing into a microchannel using giant magnetic impedance (GMI) microwire sensor made up of CoFeSiBNb alloy (40 μm diameter and 1 cm long wire). Detection tests were performed using UltraSmall Particles of Iron Oxyde (USPIO) with diameter of 20 nm. Detection of volume of 180 nl with a concentration of 18 mmol (Fe)/l and flow rate of 260 nl/s was performed. Such type of measurement can find application in biomedical and clinical diagnosis for in vivo noninvasive detection.