Delphine Felder-Flesch

The functionalization of superparamagnetic iron oxide nanoparticles (SPION) with PEGylated PAMAM dendrons through a bisphosphonate tweezers yielded 15 and 30 nm dendritic nano-objects stable in physiological media and showing both renal and hepatobiliary elimination.

Current progress in the nuclear medicine field has been exploited in the design of tumour-targeting nanoscale carriers being able to deliver radionuclides in a selective manner to improve the outcome of both cancer diagnosis and therapy. In this field dendrimers have a role to play, thanks to their controlled architecture allowing multivalent attachment possibilities of radionuclide chelators and targeting moieties. This perspective highlights the current research focused on discrete dendritic systems as nanoprobes for nuclear medical imaging, both for Single Photon Emission Computed Tomography (SPECT) ( ^99mTc, ¹¹¹In, ¹²⁵I) and Positron Emission Tomography (PET) ( ⁶⁸Ga). Also a special emphasis is given on radiolabeled ( ⁶⁴Cu, ¹⁸F, ⁷⁶Br, ⁶⁸Ga, ¹¹¹In) dendrimers targeting α_vβ₃ integrin as it is a reliable strategy to assess the presence of angiogenesis, one of the most studied and also targeted biological processes.

The attempt to elaborate organic materials at the nanoscale has attracted broad attention in the last few years. Here, we report the synthesis and characterization of new polypedic organic materials possessing the [60]fullerene as the three-dimensional rigid scaffold. High molecular weight hexakisadducts with different symmetries were obtained in 40 to 60% yield through modulations of the A. Hirsch's and B. Kraütler's methodologies. Such a regioselective grafting of side-connected malonates on C₆₀ put in evidence that not only the size but also the nature of the malonate influences very strongly the optimal reaction conditions to the preparation of multiadducts with very good yields. Characterization was complemented by an investigation of their thermotropic behaviour. Starting from non-mesogenic precursors, the 3D organization stemming from the regioselective polyfunctionalization of the carbon nanosphere allowed highlighting an original nematic self-organization (no literature equivalent) which could be partially oriented under a magnetic field at room temperature.

Covalent attachment, through a phosphonate anchor, of hydrophilic pegylated dendrons on iron oxide nanoparticles results in versatile, robust, and highly relaxing MRI contrast agents.

The spreading behaviour at the air–water interface of a series of [60]fullerene [3 : 3] hexakisadducts has been studied as a function of the hydrophobic–hydrophilic balance of the amphiphiles. More precisely, by changing both the nature and the size of the polar headgroup, by varying the nature of the chemical linker and/or spacer, by modifying the nature and/or the length of the spacer, it has been possible to perform a systematic study. The latter was carried out not only according to the pH of the aqueous subphase but also to its temperature highlighted various behaviours which in particular allowed to us to conclude that the optimal chemical design for this type of amphiphilic molecules is reached with the couples amine polar head/ester linker (Hexa-4) or carboxylic acid polar head/amide linker (Hexa-5).

The synthesis, liquid-crystalline properties and supramolecular organization of a [60]fullerene-based supermolecule are described, and the great potential of the spherical carbonated polyhedron to produce new materials through its multiple and addressable regioselective functionalization is emphasized. Indeed, hexaaddition on the carbon sphere has allowed the preparation, in 50% yield, of the first room-temperature enantiotropic nematic C₆₀-based material, even though the promoter was not mesomorphic. Despite the high molecular weight of such a supermolecule, the resulting material was revealed to be easily oriented in its mesophase by a magnetic field; this has allowed, by small angle X-ray diffraction investigations, a fine description of the molecular organization and of the corresponding relevant interactions involved. These results open the way to multifuntional materials that can take advantage of such an easy orientation of the grafted active chromophores (donor and acceptor) to be particularly efficient (for example in the design of photovoltaic materials).