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.

Ex Vivo and In Vivo Imaging and Biodistribution of Aptamers Targeting the Human Matrix MetalloProtease-9 in Melanomas.

The human Matrix MetalloProtease-9 (hMMP-9) is overexpressed in tumors where it promotes the release of cancer cells thus contributing to tumor metastasis. We raised aptamers against hMMP-9, which constitutes a validated marker of malignant tumors, in order to design probes for imaging tumors in human beings. A chemically modified RNA aptamer (F3B), fully resistant to nucleases was previously described. This compound was subsequently used for the preparation of F3B-Cy5, F3B-S-acetylmercaptoacetyltriglycine (MAG) and F3B-DOTA. The binding properties of these derivatives were determined by surface plasmon resonance and electrophoretic mobility shift assay. Optical fluorescence imaging confirmed the binding to hMMP-9 in A375 melanoma bearing mice. Quantitative biodistribution studies were performed at 30 min, 1h and 2 h post injection of 99mTc-MAG-aptamer and 111In-DOTA-F3B. 99mTc radiolabeled aptamer specifically detected hMMP-9 in A375 melanoma tumors but accumulation in digestive tract was very high. Following i.v. injection of 111In-DOTA-F3B, high level of radioactivity was observed in kidneys and bladder but digestive tract uptake was very limited. Tumor uptake was significantly (student t test, p<0.05) higher for 111In-DOTA-F3B with 2.0%ID/g than for the 111In-DOTA-control oligonucleotide (0.7%ID/g) with tumor to muscle ratio of 4.0. Such difference in tumor accumulation has been confirmed by ex vivo scintigraphic images performed at 1h post injection and by autoradiography, which revealed the overexpression of hMMP-9 in sections of human melanomas. These results demonstrate that F3B aptamer is of interest for detecting hMMP-9 in melanoma tumor.

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.

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.

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.

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.

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.