Cédric Louis

Ultrasmall Rigid Particles as Multimodal Probes for Medical Applications

Ultrasmall but multifunctional: Rigid imaging particles that are smaller than 5 nm in size can be obtained in a top-down process starting from a core–shell structure (core=gadolinium oxide; shell=polysiloxane). They represent the first multifunctional silica-based particles that are sufficiently small to escape hepatic clearance and enable animal imaging by four complementary techniques

A Top‐Down Synthesis Route to Ultrasmall Multifunctional Gd‐Based Silica Nanoparticles for Theranostic Applications

New, ultrasmall nanoparticles with sizes below 5 nm have been obtained. These small rigid platforms (SRP) are composed of a polysiloxane matrix with DOTAGA (1,4,7,10-tetraazacyclododecane-1-glutaric anhydride-4,7,10-triacetic acid)-Gd(3+) chelates on their surface. They have been synthesised by an original top-down process: 1) formation of a gadolinium oxide Gd2O3 core, 2) encapsulation in a polysiloxane shell grafted with DOTAGA ligands, 3) dissolution of the gadolinium oxide core due to chelation of Gd(3+) by DOTAGA ligands and 4) polysiloxane fragmentation. These nanoparticles have been fully characterised using photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), a superconducting quantum interference device (SQUID) and electron paramagnetic resonance (EPR) to demonstrate the dissolution of the oxide core and by inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry, fluorescence spectroscopy, (29)Si solid-state NMR, (1)H NMR and diffusion ordered spectroscopy (DOSY) to determine the nanoparticle composition. Relaxivity measurements gave a longitudinal relaxivity r1 of 11.9 s(-1)  mM(-1) per Gd at 60 MHz. Finally, potentiometric titrations showed that Gd(3+) is strongly chelated to DOTAGA (complexation constant logβ110 =24.78) and cellular tests confirmed the that nanoconstructs had a very low toxicity. Moreover, SRPs are excreted from the body by renal clearance. Their efficiency as contrast agents for MRI has been proved and they are promising candidates as sensitising agents for image-guided radiotherapy.

Biodistribution study of nanometric hybrid gadolinium oxide particles as a multimodal SPECT/MR/optical imaging and theragnostic agent.

Nanometric hybrid gadolinium oxide particles (Gado-6Si-NP) for diagnostic and therapeutic applications (mean diameter 3-4 nm) were obtained by encapsulating Gd(2)O(3) cores within a polysiloxane shell, which carries organic fluorophore (Cy 5) and is derivatized by a hydrophilic carboxylic layer. As residency time in the living body and methods of waste elimination are crucial to defining a good nanoparticle candidate and moving forward with steps for validation, this study was aimed at evaluating the biodistribution of these multimodal Gado-6Si-NP in rodents. Gado-6Si-NP were imaged following intravenous injection in control Wistar rats and mice using MRI (7 T), optical fluorescent imaging, and SPECT. A clear correlation was observed among MRI, optical imaging, and SPECT regarding the renal elimination. Quantitative biodistribution using gamma-counting of each sampled organ confirmed that these nanoparticles circulated freely in the blood pool and were rapidly cleared by renal excretion without accumulation in liver and RES uptake. These results demonstrate that Gado-6Si-NP display optimal biodistribution properties, enabling them to be developed as multimodal agents for in vivo imaging and theragnostics, especially in oncological applications.

Observation of the gap blueshift on Gd2O3:Eu3+ nanoparticles

We report on the characterization of Gd2O3 nanocrystals of different sizes doped with 2.5 at. % Eu3+ ions. The particles have been synthesized by a sol-lyophilisation process. This method allows the synthesis of 7–100 nm diameter cubic-phase particles. The photoluminescence properties have been studied from visible to vacuum ultraviolet (VUV) wavelengths. Compared to the bulk material properties, some important changes on the luminescence are observed. In particular, some lines are strengthened when the particle’s size is diminished. In another article we had ascribed these bands to doping ions located on sites close to the surface. Both contributions of volume and surface states are observed. VUV spectroscopy performed selectively on the volumes states has allowed in sesquioxide nanoparticles to point out a gap blueshift due to quantum confinement.

Nebulized gadolinium-based nanoparticles: a theranostic approach for lung tumor imaging and radiosensitization.

Lung cancer is the most common and most fatal cancer worldwide. Thus, improving early diagnosis and therapy is necessary. Previously, gadolinium-based ultra-small rigid platforms (USRPs) were developed to serve as multimodal imaging probes and as radiosensitizing agents. In addition, it was demonstrated that USRPs can be detected in the lungs using ultrashort echo-time magnetic resonance imaging (UTE-MRI) and fluorescence imaging after intrapulmonary administration in healthy animals. The goal of the present study is to evaluate their theranostic properties in mice with bioluminescent orthotopic lung cancer, after intrapulmonary nebulization or conventional intravenous administration. It is found that lung tumors can be detected non-invasively using fluorescence tomography or UTE-MRI after nebulization of USRPs, and this is confirmed by histological analysis of the lung sections. The deposition of USRPs around the tumor nodules is sufficient to generate a radiosensitizing effect when the mice are subjected to a single dose of 10 Gy conventional radiation one day after inhalation (mean survival time of 112 days versus 77 days for irradiated mice without USRPs treatment). No apparent systemic toxicity or induction of inflammation is observed. These results demonstrate the theranostic properties of USRPs for the multimodal detection of lung tumors and improved radiotherapy after nebulization.

Automated oligonucleotide solid-phase synthesis on nanosized silica particles using nano-on-micro assembled particle supports.

This article describes an original strategy to enable solid-phase oligodeoxyribonucleotide (ODN) synthesis on nanosized silica particles. It consists of the reversible immobilization of silica nanoparticles (NPs) on micrometric silica beads. The resulting assemblies, called nano-on-micro (NOM) systems, are well adapted to ODN synthesis in an automated instrument. First, NPs are derivatized with OH functions. For NOM assembly preparation, these functions react with the silanols of the microbeads under specific experimental conditions. Furthermore, OH groups allow ODN synthesis on the nanoparticles via phosphoramidite chemistry. The stability of the NOM assemblies during ODN solid-phase synthesis is confirmed by scanning and transmission electron microscopy (SEM and TEM, respectively), together with dynamic light scattering analyses. Then, the release of ODN-functionalized nanoparticles is performed under mild conditions (1% NH(4)OH in water, 1 h, 60 degrees C). Our technique provides silica nanoparticles well functionalized with oligonucleotides, as demonstrated by hybridization experiments conducted with the cDNA target.

Paramagnetic nanoparticles to track and quantify in vivo immune human therapeutic cells

This study aims to investigate gadolinium-based nanoparticles (Gd-HNP) for in vitro labeling of human plasmacytoid dendritic cells (HuPDC) to allow for in vivo tracking and HuPDC quantifying using magnetic resonance imaging (MRI) following parenteral injection. Human plasmacytoid DC were labeled (LabHuPDC) with fluorescent Gd-HNP (Gd-FITC-HNP) and injected via intraperitoneal and intravenous routes in 4-5 NOD-SCID β2m(-/-)mice (treated mice = TM). Control mice (CM) were similarly injected with unlabeled HuPDC. In vivo 7 T MRI was performed 24 h later and all spleens were removed in order to measure Gd and fluorescence contents and identify HuPDC. Gd-FITC-HNP efficiently labeled HuPDC (0.05 to 0.1 pg per cell), without altering viability and activation properties. The magnetic resonance (MR) signal was exclusively due to HuPDC. The normalized MR splenic intensity for TM was significantly higher than for CM (p < 0.024), and highly correlated with the spleen Gd content (r = 0.97), and the number of HuPDC found in the spleen (r = 0.94). Gd-FITC-HNP allowed for in vivo tracking and HuPDC quantifying by means of MRI following parenteral injection, with very high sensitivity (<3000 cells per mm(3)). The safety of these new nanoparticle types must be confirmed via extensive toxicology tests including in vivo stability and biodistribution studies.

Oligonucleotide solid-phase synthesis on fluorescent nanoparticles grafted on controlled pore glass{

Oligonucleotide solid-phase synthesis is now possible on nano-sized particles, thanks to the use of controlled pore glass-nanoparticle assemblies. We succeeded in anchoring silica nanoparticles (NPs) inside the pores of micrometric glass via a reversible covalent binding. The pore diameter must be at least six times the diameter of the nanoparticle in order to maintain efficient synthesis of oligonucleotides in the synthesizer. We demonstrated that the pores protect NP anchoring during DNA synthesis without decreasing the coupling rate of the phosphoramidite synthons. This bottom-up strategy for NP functionalization with DNA results in unprecedented DNA loading efficiency. We also confirmed that the DNA synthesized on the nanoparticle surface was accessible for hybridization with its complementary DNA strand.

One-pot direct synthesis for multifunctional ultrasmall hybrid silica nanoparticles

Ultrasmall silica nanoparticles (NPs), having hydrodynamic diameters under 10 nm are promising inorganic platforms for imaging and therapeutic applications in medicine. Herein is described a new way for synthesizing such kind of NPs in a one-pot scalable protocol. These NPs bear DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) ligands on their surface that can chelate different metals suitable for a wide variety of biomedical applications. By varying the ratio of the precursors, the hydrodynamic diameters of the particles can be controlled over the range of 3 to 15 nm. The resulting NPs have been characterized extensively by complementary techniques like dynamic light scattering (DLS), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), mass spectrometry (MS), phosphorescence titration, photophysical measurements, relaxometry and elemental analysis to elucidate their structures. Chelation of gadolinium (Gd) allowed its use as an effective intravenous contrast agent in MRI and was illustrated in mice bearing colorectal CT26 tumors. The new particle appears to sufficiently accumulate in the tumors and efficiently clear out of animal bodies through kidneys. This new synthesis is an original, time/material-saving and very flexible process that can be applied for creating versatile ultrasmall multifunctional nanomedicines.