Assembly of Poly(vinylphosphonic acid)-Based Double Hydrophilic Block Copolymers by Gadolinium Ions for the Formation of Highly Stable MRI Contrast Agents.

Mixing double-hydrophilic block copolymers containing a poly(vinylphosphonic acid) block with gadolinium ions in water leads to the spontaneous formation of polymeric nanoparticles. With an average diameter near 20 nm, the nanoparticles are stable after dilution or change of pH and ionic strength. High magnetic relaxivities were measured in vitro, and in vivo magnetic resonance imaging on rats demonstrates the high potential of such polymeric assemblies.

In Cellulo Evaluation of the Therapeutic Potential of NHC Platinum Compounds in Metastatic Cutaneous Melanoma.

We describe here the evaluation of the cytotoxic efficacy of two platinum (II) complexes bearing an N-heterocyclic carbene (NHC) ligand, a pyridine ligand and bromide or iodide ligands on a panel of human metastatic cutaneous melanoma cell lines representing different genetic subsets including BRAF-inhibitor-resistant cell lines, namely A375, SK-MEL-28, MeWo, HMCB, A375-R, SK-MEL-5-R and 501MEL-R. Cisplatin and dacarbazine were also studied for comparison purposes. Remarkably, the iodine-labelled Pt-NHC complex strongly inhibited proliferation of all tested melanoma cells after 1-h exposure, likely due to its rapid uptake by melanoma cells. The mechanism of this inhibitory activity involves the formation of DNA double-strand breaks and apoptosis. Considering the intrinsic chemoresistance of metastatic melanoma cells of current systemic treatments, these findings are promising and could give research opportunities in the future to improve the prognosis of patients suffering from unresectable metastatic melanoma that are not eligible or that do not respond to the most effective drugs available to date, namely BRAF inhibitors and the anti-PD-1 monoclonal antibody (mAb).

Gadolinium-based contrast agents: From gadolinium complexes to colloidal systems.

Nowadays, most of the clinically used contrast agents are based on the use of gadolinium molecular complexes like Dotarem®, Magnevist®…. Nevertheless, developing new gadolinium based contrast agents with enhanced relaxivity properties while avoiding gadolinium release in human tissue is still of paramount importance. We describe here two promising families of contrast agents which meets these criteria and compared their properties to the ones of clinically used Gd complexes. The first one is based on contrast agents obtained by covalent or non-covalent interactions of gadolinium molecular complexes with polymers, nanoparticles or liposomes. The second family is based on the formation of gadolinium particles (Gd2O3, GdPO4, NaGdF4, GdF3…) of controlled morphology and composition. The performance of these two families is described as well as their development perspective.

Iron Oxide Colloidal Nanoclusters as Theranostic Vehicles and Their Interactions at the Cellular Level.

Advances in surfactant-assisted chemical approaches have led the way for the exploitation of nanoscale inorganic particles in medical diagnosis and treatment. In this field, magnetically-driven multimodal nanotools that perform both detection and therapy, well-designed in size, shape and composition, are highly advantageous. Such a theranostic material—which entails the controlled assembly of smaller (maghemite) nanocrystals in a secondary motif that is highly dispersible in aqueous media—is discussed here. These surface functionalized, pomegranate-like ferrimagnetic nanoclusters (40⁻85 nm) are made of nanocrystal subunits that show a remarkable magnetic resonance imaging contrast efficiency, which is better than that of the superparamagnetic contrast agent Endorem©. Going beyond this attribute and with their demonstrated low cytotoxicity in hand, we examine the critical interaction of such nanoprobes with cells at different physiological environments. The time-dependent in vivo scintigraphic imaging of mice experimental models, combined with a biodistribution study, revealed the accumulation of nanoclusters in the spleen and liver. Moreover, the in vitro proliferation of spleen cells and cytokine production witnessed a size-selective regulation of immune system cells, inferring that smaller clusters induce mainly inflammatory activities, while larger ones induce anti-inflammatory actions. The preliminary findings corroborate that the modular chemistry of magnetic iron oxide nanoclusters stimulates unexplored pathways that could be driven to alter their function in favor of healthcare.

Effect of the Functionalization Process on the Colloidal, Magnetic Resonance Imaging, and Bioelimination Properties of Mono- or Bisphosphonate-Anchored Dendronized Iron Oxide Nanoparticles.

The functionalization process of iron oxide nanoparticles (NPs) is a major step and has to ensure a small particle size distribution (below 100 nm) and to preserve good magnetic properties suitable for in vivo applications. Two functionalization processes are here compared to coat iron oxide NPs, synthesized by thermal decomposition, with dendron molecules bearing either a mono- or a bisphosphonate anchoring group. The two processes are direct ligand exchange and the simultaneous ligand exchange and phase transfer process. The latter process led to a larger size distribution than the former. The phosphonate group is confirmed to be a strong anchoring agent from X-ray photoelectron spectroscopy (XPS) and IR characterizations whatever the grafting process and the number of phosphonate groups, it also confirms the preservation of the NPs' magnetic properties. All dendronized NPs display good in vitro MRI properties and those obtained by direct exchange showed no cell internalization, an efficient in vivo MRI contrast enhancement, and elimination by both urinary and hepato-biliary ways.

Assembly of Double-Hydrophilic Block Copolymers Triggered by Gadolinium Ions: New Colloidal MRI Contrast Agents.

Mixing double-hydrophilic block copolymers containing a poly(acrylic acid) block with gadolinium ions in water leads to the spontaneous formation of polymeric nanoparticles. With an average diameter near 20 nm, the nanoparticles are exceptionally stable, even after dilution and over a large range of pH and ionic strength. High magnetic relaxivities were measured in vitro for these biocompatible colloids, and in vivo magnetic resonance imaging on rats demonstrates the potential utility of such polymeric assemblies.

Radiolabeled dendritic probes as tools for high in vivo tumor targeting: application to melanoma.

In bioimaging, targeting allows refining the diagnosis by improving the sensitivity and especially the specificity for an earlier diagnosis. Two 111In-radiolabeled dendritic nanoprobes (DPs) (111In-2, 111In-3) and their model counterparts (111In-1, 111In-4) are designed and assessed for in vitro and in vivo tumor targeting efficiency in a murine melanoma models. Tumor uptake is correlated to dendrimer multivalency and reaches values as high as 12.7 ± 1.6% ID g-1 at 4 h post intravenous injection for 111In-3vs. 1.5 ± 0.5% ID g-1 for the unfunctionalized DP, and over 11% ID g-1 for any tumor weight whatsoever.

Combining ultrasmall gadolinium-based nanoparticles with photon irradiation overcomes radioresistance of head and neck squamous cell carcinoma.

Gadolinium based nanoparticles (GBNs, diameter 2.9±0.2nm), have promising biodistribution properties for theranostic use in-vivo. We aimed at demonstrating the radiosensitizing effect of these GBNs in experimental radioresistant human head and neck squamous cell carcinoma (SQ20B, FaDu and Cal33 cell lines). Combining 0.6mM GBNs with 250kV photon irradiation significantly decreased SQ20B cell survival, associated with an increase in non-reparable DNA double-strand breaks, the shortening of G2/M phase blockage, and the inhibition of cell proliferation, each contributing to the commitment of late apoptosis. Similarly, radiation resistance was overcome for SQ20B stem-like cells, as well as for FaDu and Cal33 cell lines. Using a SQ20B tumor-bearing mouse model, combination of GBNs with 10Gy irradiation significantly delayed tumor growth with an increase in late apoptosis and a decrease in cell proliferation. These results suggest that GBNs could be envisioned as adjuvant to radiotherapy for HNSCC tumors.

Small rigid platforms functionalization with quaternary ammonium: targeting extracellular matrix of chondrosarcoma.

This work takes place in the "cartilage targeting strategy", consisting in using the quaternary ammonium (QA) function as a vector to proteoglycans (PGs) of extracellular matrix (ECM). The objective was to demonstrate that QA could address gadolinium based small rigid platforms (SRP) to PG-rich tumors. SRP were functionalized with QA, radiolabeled with (111)Indium and evaluated for biodistribution in vivo, respectively to non functionalized SRP, in two experimental models: (i) the HEMCSS human xenograft model; (ii) the Swarm rat chondrosarcoma (SRC) orthotopic model. The contribution of cellular uptake to tumoral accumulation of nano-objects was also determined from in vitro binding. In the SRC model expressing a highly and homogeneously distributed PG content, tumor accumulation and retention of SRP@QA were increased by 40% as compared to non-functionalized SRP. When considering the radiosensitizing potential of gadolinium based SRP, these results provide hopes for the radiobiological approach of highly resistant tumor such as chondrosarcoma. FROM THE CLINICAL EDITOR: In this study, gadolinium-based complexing DOTA-surfaced small polysiloxane nanoparticles were functionalized with quaternary ammonium derivatives that target the extracellular matrix of chondrosarcoma. The authors demonstrate in a rat model that the use of these constructs results in a 40% increase of tumor accumulation and retention compared to non-functionalized (and otherwise same) platforms. Similar approaches would be welcome additions to the clinical armamentarium addressing chondrosarcoma.

The in vivo radiosensitizing effect of gold nanoparticles based MRI contrast agents.

Owing to the high atomic number (Z) of gold element, the gold nanoparticles appear as very promising radiosensitizing agents. This character can be exploited for improving the selectivity of radiotherapy. However, such an improvement is possible only if irradiation is performed when the gold content is high in the tumor and low in the surrounding healthy tissue. As a result, the beneficial action of irradiation (the eradication of the tumor) should occur while the deleterious side effects of radiotherapy should be limited by sparing the healthy tissue. The location of the radiosensitizers is therefore required to initiate the radiotherapy. Designing gold nanoparticles for monitoring their distribution by magnetic resonance imaging (MRI) is an asset due to the high resolution of MRI which permits the accurate location of particles and therefore the determination of the optimal time for the irradiation. We recently demonstrated that ultrasmall gold nanoparticles coated by gadolinium chelates (Au@DTDTPA-Gd) can be followed up by MRI after intravenous injection. Herein, Au@DTDTPA and Au@DTDTPA-Gd were prepared in order to evaluate their potential for radiosensitization. Comet assays and in vivo experiments suggest that these particles appear well suited for improving the selectivity of the radiotherapy. The dose which is used for inducing similar levels of DNA alteration is divided by two when cells are incubated with the gold nanoparticles prior to the irradiation. Moreover, the increase in the lifespan of tumor bearing rats is more important when the irradiation is performed after the injection of the gold nanoparticles. In the case of treatment of rats with a brain tumor (9L gliosarcoma, a radio-resistant tumor in a radiosensitive organ), the delay between the intravenous injection and the irradiation was determined by MRI.

The In Vivo Radiosensitizing Effect of Gold Nanoparticles Based MRI Contrast Agents.

Owing to the high atomic number (Z) of gold element, the gold nanoparticles appear as very promising radiosensitizing agents. This character can be exploited for improving the selectivity of radiotherapy. However, such an improvement is possible only if irradiation is performed when the gold content is high in the tumor and low in the surrounding healthy tissue. As a result, the beneficial action of irradiation (the eradication of the tumor) should occur while the deleterious side effects of radiotherapy should be limited by sparing the healthy tissue. The location of the radiosensitizers is therefore required to initiate the radiotherapy. Designing gold nanoparticles for monitoring their distribution by magnetic resonance imaging (MRI) is an asset due to the high resolution of MRI which permits the accurate location of particles and therefore the determination of the optimal time for the irradiation. We recently demonstrated that ultrasmall gold nanoparticles coated by gadolinium chelates (Au@DTDTPA-Gd) can be followed up by MRI after intravenous injection. Herein, Au@DTDTPA and Au@DTDTPA-Gd were prepared in order to evaluate their potential for radiosensitization. Comet assays and in vivo experiments suggest that these particles appear well suited for improving the selectivity of the radiotherapy. The dose which is used for inducing similar levels of DNA alteration is divided by two when cells are incubated with the gold nanoparticles prior to the irradiation. Moreover, the increase in the lifespan of tumor bearing rats is more important when the irradiation is performed after the injection of the gold nanoparticles. In the case of treatment of rats with a brain tumor (9L gliosarcoma, a radio-resistant tumor in a radiosensitive organ), the delay between the intravenous injection and the irradiation was determined by MRI.

A bisphosphonate tweezers and clickable PEGylated PAMAM dendrons for the preparation of functional iron oxide nanoparticles displaying renal and hepatobiliary elimination.

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.

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 ß2m(-/-)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.

The biodistribution of gold nanoparticles designed for renal clearance.

Owing to their tunable optical properties and their high absorption cross-section of X- and γ-ray, gold nanostructures appear as promising agents for remotely controlled therapy. Since the efficiency of cancer therapy is not limited to the eradication of the tumour but rests also on the sparing of healthy tissue, a biodistribution study is required in order to determine whether the behaviour of the nanoparticles after intravenous injection is safe (no accumulation in healthy tissue, no uptake by phagocytic cell-rich organs (liver, spleen) and renal clearance). The biodistribution of Au@DTDTPA nanoparticles which are composed of a gold core and a DTDTPA (dithiolated polyaminocarboxylate) shell can be established by X-ray imaging (owing to the X-ray absorption of the gold core) and by magnetic resonance imaging (MRI) since the DTDTPA shell was designed for the immobilization of paramagnetic gadolinium ions. However scintigraphy appears better suited for a biodistribution study owing to a great sensitivity. The successful immobilization of radioelements ((99m)Tc, (111)In) in the DTDTPA shell, instead of gadolinium ions, renders possible the follow up of Au@DTDTPA by scintigraphy which showed that Au@DTDTPA nanoparticles exhibit a safe behaviour after intravenous injection to healthy rats.

Effect of the nanoparticle synthesis method on dendronized iron oxides as MRI contrast agents.

Aqueous suspensions of dendronized iron oxide nanoparticles (NPs) have been obtained after functionalization, with two types of dendrons, of NPs synthesized either by coprecipitation (leading to naked NPs in water) or by thermal decomposition (NPs in situ coated by oleic acid in an organic solvent). Different grafting strategies have been optimized depending on the NPs synthetic method. The size distribution, the colloidal stability in isoosmolar media, the surface complex nature as well as the preliminary biokinetic studies performed with optical imaging, and the contrast enhancement properties evaluated through in vitro and in vivo MRI experiments, have been compared as a function of the nature of both dendrons and NPs. All functionalized NPs displayed good colloidal stability in water, however the ones bearing a peripheral carboxylic acid function gave the best results in isoosmolar media. Whereas the grafting rates were similar, the nature of the surface complex depended on the NPs synthetic method. The in vitro contrast enhancement properties were better than commercial products, with a better performance of the NPs synthesized by coprecipitation. On the other hand, the NPs synthesized by thermal decomposition were more efficient in vivo. Furthermore, they both displayed good biodistribution with renal and hepatobiliary elimination pathways and no consistent RES uptake.

Biodistribution of ultra small gadolinium-based nanoparticles as theranostic agent: application to brain tumors.

Gadolinium-based nanoparticles are novel objects with interesting physical properties, allowing their use for diagnostic and therapeutic applications. Gadolinium-based nanoparticles were imaged following intravenous injection in healthy rats and rats grafted with 9L gliosarcoma tumors using magnetic resonance imaging and scintigraphic imaging. Quantitative biodistribution using gamma-counting of each sampled organ confirmed that these nanoparticles were rapidly cleared essentially by renal excretion. Accumulation of these nanoparticles in 9L gliosarcoma tumors implanted in the rat brain was quantitated. This passive and long-duration accumulation of gadolinium-based nanoparticles in tumor, which is related to disruption of the blood-brain barrier, is in good agreement with the use of these nanoparticles as radiosensitizers for brain tumors.

Multifunctional Peptide-conjugated hybrid silica nanoparticles for photodynamic therapy and MRI.

Photodynamic therapy (PDT) is an emerging theranostic modality for various cancer as well as non-cancer diseases. Its efficiency is mainly based on a selective accumulation of PDT and imaging agents in tumor tissue. The vascular effect is widely accepted to play a major role in tumor eradication by PDT. To promote this vascular effect, we previously demonstrated the interest of using an active- targeting strategy targeting neuropilin-1 (NRP-1), mainly over-expressed by tumor angiogenic vessels. For an integrated vascular-targeted PDT with magnetic resonance imaging (MRI) of cancer, we developed multifunctional gadolinium-based nanoparticles consisting of a surface-localized tumor vasculature targeting NRP-1 peptide and polysiloxane nanoparticles with gadolinium chelated by DOTA derivatives on the surface and a chlorin as photosensitizer. The nanoparticles were surface-functionalized with hydrophilic DOTA chelates and also used as a scaffold for the targeting peptide grafting. In vitro investigations demonstrated the ability of multifunctional nanoparticles to preserve the photophysical properties of the encapsulated photosensitizer and to confer photosensitivity to MDA-MB-231 cancer cells related to photosensitizer concentration and light dose. Using binding test, we revealed the ability of peptide-functionalized nanoparticles to target NRP-1 recombinant protein. Importantly, after intravenous injection of the multifunctional nanoparticles in rats bearing intracranial U87 glioblastoma, a positive MRI contrast enhancement was specifically observed in tumor tissue. Real-time MRI analysis revealed the ability of the targeting peptide to confer specific intratumoral retention of the multifunctional nanoparticles.

Toward an image-guided microbeam radiation therapy using gadolinium-based nanoparticles.

Ultrasmall gadolinium-based nanoparticles (GBNs) induce both a positive contrast for magnetic resonance imaging and a radiosentizing effect. The exploitation of these characteristics leads to a greater increase in lifespan of rats bearing brain tumors since the radiosensitizing effect of GBNs can be activated by X-ray microbeams when the gadolinium content is, at the same time, sufficiently high in the tumor and low in the surrounding healthy tissue. GBNs exhibit therefore an interesting potential for image-guided radiotherapy.

Dendronized iron oxide nanoparticles for multimodal imaging.

The synthesis of small-size dendrons and their grafting at the surface of iron oxide nanoparticles were achieved with the double objective to obtain a good colloidal stability with a mean hydrodynamic diameter smaller than 100 nm and to ensure the possibility of tuning the organic coating characteristics including morphology, functionalities, physico-chemical properties, grafting of fluorescent or targeting molecules. Magnetic resonance and fluorescence imaging are then demonstrated to be simultaneously possible using such versatile superparamagnetic iron oxide nanocrystals covered by a dendritic shell displaying either carboxylate or ammonium groups at their periphery which could be further labelled with a fluorescent dye. The grafting conditions of these functionalized dendrons at the surface of SPIO NPs synthesized by co-precipitation have been optimized as a function of the nature of the peripheral functional group. The colloidal stability has been investigated in water and osmolar media, and in vitro and in vivo MRI and optical imaging measurements have been performed showing encouraging biodistribution.

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.