Μαγνητικά νανοσωματίδια οξειδίων του σιδήρου παρασκευάσθηκαν μέσω της αλκαλικής συμπύκνωσης και ελεγχόμενης καταβύθισης συμπλόκων ιόντων FeII, υπό την παρουσία τυχαίου συμπολυμερούς PAA-co-MA. Οι παράμετροι της σύνθεσης μεταβλήθηκαν με σκοπό την απομόνωση προϊόντων που να εμφανίζουν τις καλύτερες μαγνητικές ιδιότητες. Όλα τα προϊόντα εμφάνισαν υψηλή κολλοειδή σταθερότητα σε υδατικά μέσα χαμηλής ιοντικής ισχύος, ενώ ο σιδηρομαγνητικός τους χαρακτήρας έδειξε να ποικίλει από ασθενής μέχρι αρκετά ισχυρός, όπως προέκυψε μετά τον χαρακτηρισμό τους με μαγνητοφόρηση και μαγνητική υπερθερμία με εναλλασόμενο μαγνητικό πεδίο. Το μέσο μέγεθος των νανοκρυσταλλιτών ήταν διαφορετικό σε κάθε προϊόν κυμαινόμενο από περίπου 3 έως 14 nm, όπως προσδιορίστηκε μέσω XRD. Η ανάλυση με ΤΕΜ έδειξε ότι στο προϊόν που εμφανίζει τις καλύτερες μαγνητικές ιδιότητες σχηματίζονται πλειάδες νανοσωματιδίων πυκνής διάταξης, και στις οποίες αποδίδεται η βελτιωμένη απόκριση σε μαγνητικά πεδία. Τα άλλα προϊόντα εμφάνισαν μικρότερα μεγέθη κρυσταλλιτών και διαφορετικά δομικά χαρακτηριστικά. Τα κολλοειδή καταβυθίζονταν κατόπιν αύξησης της ιοντικής ισχύος του διαλύτη. Για τον λόγο αυτό αποφασίστηκε η μελέτη της αντίδρασης σύζευξης των εξωτερικών καρβοξυλικών ομάδων του πολυμερικού φλοιού με mPEG-NH2, δεδομένου ότι η PEG αυξάνει σημαντικά τη σταθερότητα των κολλοειδών. Παρά το γεγονός ότι χρησιμοποιήθηκαν κοινά αντιδραστήρια σύζευξης, μόνο υπό πολύ ειδικές συνθήκες η απόδοση της αντίδρασης ήταν ικανοποιητική, οπότε και προέκυψαν σταθερά κολλοειδή σε συνθήκες υψηλής ιοντικής ισχύος. Τέλος, τα προϊόντα αξιολογήθηκαν για την ικανότητά τους να επάγουν υπερθερμία και μελετήθηκε ο χρόνος χαλάρωσης Τ2, ο οποίος σχετίζεται άμεσα με την ενίσχυση της αντίθεσης στην απεικόνιση μέσω μαγνητικού συντονισμού. Τέλος, ένα από τα προϊόντα, μελετήθηκε in vitro και in νίνο, προκειμένου να αξιολογηθεί η βιοσυμβατότητα του. Τα συστήματα αυτά παρουσιάζουν πολύ ενδιαφέρουσες ιδιότητες ώστε να τροποποιηθούν και να μελετηθούν περεταίρω ως θεραπευτικά ή/και διαγνωστικά νανοϋλικά. / Μagnetic nanoparticles of iron oxides were synthesized through condensation and controlled precipitation of a FeII complex, in alkaline environment, in the presence of a random copolymer PAA-co-MA, as polymeric corona. The synthetic parameters were varied with the aim of isolating products exhibiting the best magnetic properties. All products displayed high colloidal stability in low ionic strength aqueous media, while their ferromagnetic properties varied from weak to quite strong, as deduced after the characterization with magnetophoresis and magnetic hyperthermia with alternating magnetic field. The average crystallite size, as determined through XRD, varied from 8 to 14 nm depending on the product. TEM analysis showed that the product displaying the best magnetic properties formed clusters of densely packed nanocrystallites, leading to interesting superstructural motifs. All the other products displayed smaller crystallite sizes and different structural characteristics. The colloids precipitated upon increase of the ionic strength of the solvent (H2O) with NaCl. Therefore, it was decided to study the conjugation of the outer carboxyl groups of the polymeric corona with mPEG-NH2, since PEG is known to increase significantly the stability of colloids. Despite the fact that common conjugation reagents were used, only under specific conditions the yied of the reaction was appropriately high in order the resultant colloids to be stable in a high ionic strength (isotonic) medium. Finally the products were evaluated for their performance in magnetic hyperthermia and for contrast enhancement in magnetic resonance imaging, by studying the T2 relaxation time. One of the products was furthermore studied by in vitro and in vivo systems, in order to evaluate its biocompatibility. These colloidal systems exhibit very interesting properties in order to be further modified and studied as therapeutic and / or diagnostic (theragnostic) nanomaterials.

Iron oxide magnetic nanoparticle synthesis and their surface functionalization hold a crucial position in the design and fabrication of functional materials for a variety of biomedical applications. Non-uniform nanoparticles with poor crystallinity, prepared by conventional methods, have only limited value in biological areas. Large scale synthesis methods that are able to produce high quality, mono-dispersed iron oxide nanoparticles using low cost and environment friendly chemicals are highly desirable. Following synthesis, appropriate surface functionalization is necessary to direct the dispersibility of nanoparticles in aqueous solution in order to provide them with acceptable colloidal stability against the ion strength and many biomolecules that nanoparticles may encounter under physiological conditions. Poorly stabilized nanoparticles that easily aggregate and form large size agglomerates would be quickly cleared by the liver and other organs and are not suitable for clinical purposes. Additionally, many interesting functionalities such as fluorescence, targeting and anti-cancer properties can be immobilized onto the surface of iron oxide magnetic nanoparticles during the surface functionalization process so as to build multifunctional platforms for disease diagnosis and treatment. Polyol method can be an effective way to prepare magnetite nanoparticles that are suitable for biological applications. In a polyol system, selected surface functionalities were introduced to the nanoparticle surface via a hot injection technique. The morphology, uniformity, crystallinity and magnetic properties were examined to understand the effect of different ligand molecules on the final product. Their surface chemistry, colloidal properties and surface reactivity were also studied to evaluate their practicability in different applications. A high efficiency in-situ method for the preparation of magnetite nanoparticles attached to silica nanospheres was also developed in a polyol system. This approach eliminates several time-consuming processing steps that are in the conventional fabrication route and directly produces water-stable magnetite-silica hybrid materials with surface availability for subsequent modifications. In addition to polyalcohol, the potential of polyamine in the preparation of water-soluble magnetite nanoparticles with amine surface functionalities was also evaluated. And it is suggested that polyamine acts as solvent, stabilizing agent and reducing agent simultaneously during the synthesis. The characterization of polyamine coated nanoparticles, their surface functionalization, and subsequent application for bioseparation and drug delivery were reported.

Magnetite (Fe3O4) and Maghemite (&amp / #947 / -Fe2O3) are well-known iron oxide phases among magnetic nanoparticles due to their magnetic properties, chemical stability, and nontoxicity. They have gained acceptance in several fields of application of nanomaterials such as magnetic recording systems, magnetic refrigeration, magneto-optical devices, magnetic resonance imaging, magnetic separation techniques and separation and purification of biological molecules. Recently, there is a growing interest in the synthesis of magnetic iron oxide nanoparticles in a polymeric, glassy or ceramic matrix since the preparation of pure phase iron oxide composite material involves, presently, some difficulties partially arising from different oxidation states of iron which can lead to the presence of various oxides. Matrix support, in principle, modifies the properties of nanomaterials, thus opening new possibilities for the control of their performance. In addition, the chosen matrix, polymer or sol-gel, provides binding of the functional groups and also prevents grain growth and agglomeration. Therefore, extensive research is conducted on this subject. Sonochemical technique is an effective method to synthesize magnetic nanoparticles with many unique properties due to extreme reaction conditions. Besides, a microscopic mixing in the synthesis procedure is obtained because of the microjet effect which comes from the collapse of the bubbles. This effect creates relatively uniform reaction conditions. Thus, well-dispersed and stable nanoparticles are obtained by using ultrasound. In this study, &amp / #947 / -Fe2O3, maghemite nanoparticles are accommodated in an inert, inorganic, transparent and temperature resistant sol gel matrix to achieve stabilization. The nature and concentration of the salt used, evaporation conditions of the sols, the following heat treatments had been investigated and shown that they had great influence on the particle size and the final iron oxide phase in the sol-gel. The Fe2O3/SiO2 nanocomposites were characterized using X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) techniques. In addition, magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in the presence of poly(methacrylic acid) (PMAA) in aqueous solution. PMAA, which was used as the coating material, prevents magnetite nanoparticles from oxidation towards a lower saturation magnetization iron oxide phases. In order to achieve small particle size and uniform size distribution of the magnetite nanoparticles in PMAA matrix, ultrasonic irradiation was applied during co-precipitation. The polymer coated Fe3O4 nanoparticles were characterized using scanning electron microscopy (SEM), laser particle sizer, X-ray diffraction, (XRD) and vibrating sample magnetometry (VSM) techniques and zeta potential measurements.

Les nanoparticules d’oxyde de fer ont récemment été envisagées comme outils pour l’ingénierie tissulaire. Elles sont internalisées par les cellules qui deviennent alors magnétiques. Des forces magnétiques peuvent ainsi être appliquées à distance sur ces cellules pour contrôler leur organisation spatiale et temporelle, et former un tissu. Ces applications posent la question du devenir des nanoparticules, qui conditionne in fine leur utilisation clinique. Ce travail s’inscrit dans ce cadre et comporte deux axes.La première partie traite de l’étude des propriétés mécaniques et rhéologiques de tissus biologiques modèles, les agrégats multicellulaires. Une combinaison de méthodes magnétiques est proposée pour fabriquer et stimuler des tissus magnétiques de taille et de forme contrôlées. Ces agrégats magnétiques sont soumis à distance à des contraintes magnétiques d’écrasement. L’étude de leur déformation permet d’explorer des caractéristiques statiques et dynamiques rarement étudiées à l’échelle tissulaire (tension de surface, loi puissance, non linéarité). La deuxième partie se concentre sur l'évolution à moyen terme des nanoparticules dans leur environnement tissulaire, au cœur des agrégats. En combinant ce tissu modèle avec des méthodes de quantification magnétique, nous avons pu mettre en évidence une dégradation massive d’origine endosomale, sans pour autant impacter de manière importante l’homéostasie du fer. De plus, le modèle tissulaire mis en place permet d’étudier la biodégradation intracellulaire de n’importe quel type de nanoparticules. Nous l'avons testé avec des nano-architectures plus complexes: nanocubes, nanodimers, ou nanoparticules magnéto-plasmoniques / Iron oxide nanoparticles are promising candidates for applications in nanomedecine (contrast agents, vectors). They were also recently considered as a powerful tool for tissue engineering. Cells, magnetized through nanoparticules internalization, can be organized in space and time thanks to remote magnetic forces. For all those applications the nanoparticles fate inside the cells remains a key issue concerning the final clinical use. The first part of this work focuses on the study of the mechanical and rheological properties of biological tissue models, the multicellular aggregates. An original magnetic molding method and two different experimental setups were developed to produce aggregates with controlled shapes and sizes, to measure their surface tension and to evidence their power law and non linear behavior.In the second part, we investigate the medium term fate of iron oxide nanoparticles in stem cells forming a spheroid as a model tissue. We reveal a massive endosomal degradation. The set of methods and spheroid model we propose allow a comprehensive and quantitative follow up of the biodegradation of any nanomaterials. This was illustrated by investigating the degradation of nanomaterials with more complex nano-architectures (nanocubes, nanodimers) and assessing the efficiency of a protection strategy to modulate the biodegradation

Sample preparation as an essential step in mass spectrometry-based analysis, plays a critical role in proteomics studies. Magnetic nanoparticles (MNPs) have been widely used in protein and peptide sample preparation due to their magnetic properties, biocompatibility, easy synthesis and surface functionalization. MNPs loaded with analyte or analyte modification reagent can be easily separated from the reaction medium by an externally applied magnetic field. The small size of MNPs provides high analyte loading and extraction capacity. Additionally, MNP can be decorated with different functional groups to achieve selective modification or extraction of analyte. In this study we have utilized silica coated iron oxide magnetic nanoparticles (Fe3O4@SiO2 MNPs) for protein and peptide sample preparation. Fluorescence-based methods were utilized for quantitative and qualitative characterization of N-hydrosucccinimidyl (NHS) ester groups on the surface of Fe3O4@SiO2 MNPs. Fluorophore Dansylcadaverine was conjugated to NHS ester functional groups. Fluorometric measurement of cleaved dansylcadaveine was employed to determine the number of NHS ester groups per MNPs that was found to be 2.6 × 102 and 3.4 × 103for 20 nm and 100 nm Fe3O4@SiO2 MNPrespectively. The efficiency of labeling native bovine serum albumin (BSA) by NHS ester coated Fe3O4@SiO2 MNPs was also explored in terms of maximizing the number of MNPs conjugated per BSA molecule or maximizing the number of BSA molecules conjugated per each MNP. Lysine residues of apolipoprotein B-100 (apoB-100) on the surface of intact human low density lipoprotein (LDL) were labeled by NHS ester modified Fe3O4@SiO2 MNPs in aqueous solvents at room temperature. The MNP labeledapoB-100 was treated by SDS to remove lipids and then digested using trypsin. Tryptic peptides were eluted from MNPs by cleaving disulfide linkage between labeled peptides and MNPs. LC-MS/MS analysis found 28 peptides containing labeled lysine residues. These lysine residues should be on the solvent exposed surface of LDL since the large size of MNPs prevents contact of the labeling reagent to those lysines embedded inside the structure of LDL. TCEP- immobilized Fe3O4@SiO2MNPs were fabricated and utilized for reduction of disulfide bonds in bovine pancreas insulin and two different cyclic peptides. Disulfide bonds were efficiently cleaved at room temperature in both organic and aqueous solvents confirmed by LC-MS/MS analysis of reduced/alkylated protein and peptides. Disulfide reduction and alkylation reactions was performed in one step and the reducing agent was simply separated from peptide and protein solution by magnetic separation.