Innovative SPIONs for multimodal imaging: MRI/PET and MRI/optical imaging

Amongst non-invasive methods, single photon emission computed tomography (SPECT), positron emission tomography (PET) and magnetic resonance imaging (MRI) are routinely used to detect pathological tissues. Each of these imaging... [ view full abstract ]

Amongst non-invasive methods, single photon emission computed tomography (SPECT), positron emission tomography (PET) and magnetic resonance imaging (MRI) are routinely used to detect pathological tissues. Each of these imaging modalities has unique advantages along with intrinsic limitations (for example MRI has an excellent spatial resolution but suffers from a lack of sensitivity). To circumvent these hurdles, ongoing efforts are made to develop multimodal methods. Similarly, bimodal medical imaging relying on MRI coupled to Optical Imaging (OI) may improve the accuracy of a diagnosis by combining the sensitivity of OI and the resolution of MRI.
In this field, nanoparticle (NP) technologies represent the most promising strategy to elaborate multimodal contrast agents. Superparamagnetic iron oxide nanoparticles (SPIONs) are currently being developed for several biological applications such as hyperthermia, drug delivery, or MRI [1-2]. For the latter application, SPIONs are usually used as water proton transverse relaxation time (T2) contrast agents.
The SPIONs presented in this talk for multimodal imaging (MRI/PET and MRI/optical imaging) are developed by taking advantage of (i) the originality of their simultaneous synthesis and colloidal stabilization in one step through a continuous hydrothermal synthesis device (synthesis time <10 s, conditions T, P up to the supercritical water field) [3-4] and (ii) the association of these nanoparticles with innovative chelating agents (NODAGA, MANOTA etc.) [5] or innovative fluorophores like phthalocyanine derivatives for near-IR detection and photodynamic therapy [6].
For all the nanohybrids developed, the grafting of the different ligands is confirmed by exhaustive characterizations. The imaging agents are stable under physiological conditions and show no cytotoxicity. Yields of radiolabeling indicate an efficient chelation and subsequent spectroscopic studies address the imaging capabilities of each probe in the well characterized SPIONs. In vitro, in vivo and biodistribution results of the final NPs will be presented.
[1] L. Maurizi et al., Langmuir, 2009, 8857
[2] L. Maurizi et al., J. Biomed. Nanotechnol. 2015, 126
[3] L. Maurizi et al., Chem. Commun., 2011, 11706
[4] G. Thomas et al., RSC Adv., 2015, 78614
[5] G. Thomas et al., Nanotechnology, 2016, 135604
[6] J. Boudon et al., Chem. Commun., 2013, 7394