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The preparation of an efficient bimodal single probe for magnetic resonance (MRI) and optical imaging (OI) is reported. Paramagnetic properties have been obtained by the non-covalent encapsulation of the clinically used Gd3+ chelate (i.e., Gd-HP-DO3A) within silica nanoparticles through a water-in-oil microemulsion process. To ensure colloidal stability, the surface of the particles was modified by means of treatment using PEG-silane, and further functionalized photochemically using a diazirine linker bearing carboxylic functions. Optical properties were obtained by the covalent grafting of a near-infrared emitting probe (NIR) on the resulting surface. The confinement of Gd complexes within the permeable matrix resulted in a significant increase in longitudinal relaxivities (>500% at 20 MHz) in comparison with the relaxivities of free chelate, while the post-functionalization process of PEG with fluorescent compounds appeared promising for the derivatization procedure. Several physico-chemical properties attested to the efficient surface modification and confirmed covalent grafting. Preliminary imaging experiments complete this study and confirm the potential of the presented system for preclinical imaging experiments.

International audience; One of the most widely used techniques to obtain anatomical information is magnetic resonance imaging (MRI). Despite its high resolution, it has a low sensitivity which could be enhanced by coupling MRI with a more sensitive technique such as photoacoustic imaging (PAI). The development of a bi-modal agent could thus lead to hybrid images with a high anatomical resolution provided by MRI and a precise localization of the contrast agent thanks to PAI. The probes used in this work

International audience; New pyridine containing triAza; 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) ligands presenting pendant carboxylic acid or alcohol functions have been synthesized and used to form diaqua Gd(III) complexes, which have been immobilized onto dense silica nanoparticles. Cytotoxicity studies of these complexes (free or immobilized on the nanoparticles) on normal 1BR3G cells and cancerous HCT 116 cells indicated a dependence on the pendant chemical group for the free complexes. However, this effect disappeared once the complexes were immobilized on the surface of the nanoparticles, leading to non-toxic nanomaterials. The interest of these complexes (free or immobilized on dense silica nanoparticles) as contrast agents in magnetic resonance imaging (MRI) has been evaluated in comparison with DOTAREM® by recording their nuclear magnetic resonance dispersion (NMRD) profiles, measuring their transversal and longitudinal relaxivities as well as recording images on phantoms at 37 °C. This study has evidenced the high potential of these complexes: first it suggested the possibility to reduce the dose to be injected by a factor of 10, second it evidenced their high efficiency in high field T1-weighted MRI (9.4 T), the key towards images of higher resolution and shorter acquisition times.

This study reports the development of a continuous flow process enabling the synthesis of very small iron oxide nanoparticles (VSION) intended for T1-weighted magnetic resonance imaging (MRI). The influence of parameters, such as the concentration/nature of surfactants, temperature, pressure and the residence time on the thermal decomposition of iron(III) acetylacetonate in organic media was evaluated. As observed by transmission electron microscopy (TEM), the diameter of the resulting nanoparticle remains constant when modifying the residence time. However, significant differences were observed in the magnetic and relaxometric studies. This continuous flow experimental setup allowed the production of VSION with high flow rates (up to 2 mL&middot, min&minus, 1), demonstrating the efficacy of such process compared to conventional batch procedure for the scale-up production of VSION.

Thyroid cancers are the most frequent endocrine cancers and their incidence is increasing worldwide. Thyroid nodules occur in over 19&ndash, 68% of the population, but only 7&ndash, 15% of them are diagnosed as malignant. Diagnosis relies on a fine needle aspiration biopsy, which is often inconclusive and about 90% of thyroidectomies are performed for benign lesions. Galectin-1 has been proposed as a confident biomarker for the discrimination of malignant from benign nodules. We previously identified by phage display two peptides (P1 and P7) targeting galectin-1, with the goal of developing imaging probes for non-invasive diagnosis of thyroid cancer. The peptides were coupled to ultra-small superparamagnetic particles of iron oxide (USPIO) or to a near-infrared dye (CF770) for non-invasive detection of galectin-1 expression in a mouse model of papillary thyroid cancer (PTC, as the most frequent one) by magnetic resonance imaging and fluorescence lifetime imaging. The imaging probes functionalized with the two peptides presented comparable image enhancement characteristics. However, those coupled to P7 were more favorable, and showed decreased retention by the liver and spleen (known for their galectin-1 expression) and high sensitivity (75%) and specificity (100%) of PTC detection, which confirm the aptitude of this peptide to discriminate human malignant from benign nodules (80% sensitivity, 100% specificity) previously observed by immunohistochemistry.

The diagnosis of Alzheimer's disease (AD) is a critical step in the management of patients. We have developed a non-invasive diagnosis tool based on magnetic resonance molecular imaging (MRMI) of amyloid-β peptide using ultra-small particles of iron oxide (USPIO) functionalized with a disulfide constrained cyclic heptapeptide (PHO) identified by phage display (USPIO-PHO). After previously demonstrating the optimal pharmacologic properties of USPIO-PHO and its capacity to cross the blood-brain barrier (BBB), the ability of USPIO-PHO to target amyloid plaques (AP) by MRMI has been validated in the present work on AD transgenic mice. The immunohistochemistry and immunofluorescent detection of USPIO-PHO on brain sections collected after in vivo MRMI studies enabled its colocalization with AP, confirming the BBB passage and specific targeting. The AP targeting by USPIO-PHO has been moreover corroborated by the good correlation between the number of AP detected with anti-amyloid β antibody and Perls'-DAB staining. Finally, the crossing mechanism of USPIO-PHO through the BBB was elucidated, revealing the involvement of non-degradation pathway of caveolae, while the control contrast agent USPIO-PEG was not endocytosed by the human brain endothelial cells.

International audience; The present study reports the preparation of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) polymer vesicles via a nanoprecipitation method and the loading of two different size hydrophobically coated ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (magnetic core size of 4.2 nm and 7.6 nm) into the membrane of these nanovesicles, whose thickness was measured precisely by small angle neutron scattering (SANS). Spherical nano-assemblies with a high USPIO payload and a diameter close to 150 nm were obtained as confirmed by dynamic light scattering (DLS), transmission electron microscopy (TEM) and cryo-TEM. Vesicular structure of these hybrid nano-assemblies was confirmed by multi-angle light scattering (MALS) measurements. Their magnetic properties were evaluated by T1 and T2 measurements (20 and 60 MHz) and by nuclear magnetic relaxation dispersion (NMRD) profiles. The size of USPIO entrapped in the membranes of PEO-b-PCL vesicles has a strong impact on their magnetic properties. It affects both their longitudinal and their transverse relaxivities and thus their magnetic resonance imaging (MRI) sensitivity. Acid-catalyzed hydrolysis of PCL membrane also influences their relaxivities as shown by measurements carried out at pH 7 vs. pH 5. This property was used to monitor the membrane hydrolytic degradation in vitro, as a proof of concept of potential monitoring of a drug delivery by nanomedicines in vivo and non-invasively, by MRI.

The fast development of nanomedicines requires more and more reliable chemical tools in order to accurately design materials and control the surface properties of the nano-objects used in biomedical applications. In this study we describe a smooth and simple photografting technique, i.e., the clip photochemistry, that allows the introduction of molecules of interest in inert polymers or on stealth nanoparticles directly in aqueous solution. First we developed the methodology on polyethylene glycol (PEG) and looked for critical parameters of the process (irradiation times, concentrations, washings) by using several molecular probes and adapted analytical techniques ((19)F qNMR, EA, LSC). We found that the clip photochemistry in water is a robust and efficient method to functionalize PEG. Second we applied it on PEGylated USPIO (USPIO-PEG) magnetic resonance imaging agent and succeeded in introducing RGD peptide and homemade peptidomimetics on their PEG segments. The magnetic abilities of the conjugated nanoparticles were unchanged by the derivatization process as evidenced by their relaxometric properties and their NMRD profile. When tested on Jurkat lymphocyte T Cells, which express αvβ3 integrins, the USPIO conjugated with RGD ligands leads to an increase of the transverse relaxation rate (R2) by a factor 10 to 14 as compared to USPIO-PEG. Consequently, it makes them good candidates for targeted imaging technology in cancer therapy.

The incidence of papillary thyroid cancer has increased these last decades due to a better detection. High prevalence of nodules combined with the low incidence of thyroid cancers constitutes an important diagnostic challenge. We propose to develop an alternative diagnostic method to reduce the number of useless and painful thyroidectomies using a vectorized contrast agent for magnetic resonance imaging. Galectin-1 (gal-1), a protein overexpressed in well-differentiated thyroid cancer, has been targeted with a randomized linear 12-mer peptide library using the phage display technique. Selected peptides have been conjugated to ultrasmall superparamagnetic particles of iron oxide (USPIO). Peptides and their corresponding contrast agents have been tested in vitro for their specific binding and toxicity. Two peptides (P1 and P7) were selected according to their affinity toward gal-1. Their binding has been revealed by immunohistochemistry on human thyroid cancer biopsies, and they were co-localized with gal-1 by immunofluorescence on TPC-1 cell line. Both peptides induce a decrease in TPC-1 cells' adhesion to gal-1 immobilized on culture plates. After coupling to USPIO, the peptides preserved their affinity toward gal-1. Their specific binding has been corroborated by co-localization with gal-1 expressed by TPC-1 cells and by their ability to compete with anti-gal-1 antibody. The peptides and their USPIO derivatives produce no toxicity in HepaRG cells as determined by MTT assay. The vectorized contrast agents are potential imaging probes for thyroid cancer diagnosis. Moreover, the two gal-1-targeted peptides prevent cancer cell adhesion by interacting with the carbohydrate-recognition domain of gal-1.