Assessing the parameters modulating transducing capacity of magnetic nanoparticles based on ac magnetometry for bio sensing

Résumé

Biomarkers are molecular indicators of physiological or pathogenic states or conditions. Specifically, a biomarker may indicate any change to the progression stages of a disease. Thus, the detection and quantification of biomarkers are essential to diagnose diseases. Recent progress in nanoscience, offers sensing methodologies based on smart materials, as magnetic nanoparticles. In this regard, magnetic detection techniques — such as AC magnetic susceptometry, magnetic particle spectroscopy, SQUID measurements, magneto-optic, and magnetoresistance — are employed to display the variation of magnetic properties of the functionalised nanoparticles (f-MNPs) in presence of biomarkers. Nevertheless, the use of these techniques requires exhaustive sample preparation, large sample volumes, long acquisition times, and/or high-cost instrumentation. This thesis studies the suitability of AC magnetometry to probe a novel magnetic detection methodology, based on the variations of the magnetic and colloidal properties of nanoparticles in presence of a target analyte (i.e., biomarker). Besides, this thesis analyses the influence of several parameters on the transducing capacity for f-MNPs to detect analyte in solutions. The parameters are magnetic relaxation mechanisms, AC magnetic field conditions, analyte multivalency, analyte and MNPs concentrations, and the number of ligands per MNP. Furthermore, we analyse the influence of dendrimer coating to preserve the transducing capability of f-MNPs dispersed in human serum plasma. Finally, we study how the surface of MNPs affects to their AC magnetic response depending on the magnetic relaxation mechanism. Besides, we exploit this phenomenon to assess through the variation of AC magnetization cycles, the thermal unfolding of the proteins attached onto MNP surface