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.

Dendronized iron oxide nanoparticles as contrast agents for MRI

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

Multi-luminescent hybrid gadolinium oxide nanoparticles as potential cell labeling

This manuscript analyses the use of newly developed hybrid gadolinium oxide nanoparticles as cell-labeling tracers. The nanoparticles are core-shell particles composed of a core of gadolinium oxide of [2-4] nm and a protecting shell of polysiloxane [1-3 nm] where different organic dyes (fluoresceine isothiocyanate (FITC) or rhodamine B isothiocyanate (RBITC)) are embedded. They are functionalized with poly(ethylene glycol)bis(carboxymethyl) to ensure their colloidal stability in biological buffers. These particles are potential multi-labeling tracers (magnetic and optical). In this paper, we show by optical imaging that they can be efficiently internalized in cells without cell alteration. The in-vitro uptake of the nanoparticles was followed in two cell lines (human fibroblasts and a human adenocarnima cell lines MCF7 cells). Nanoparticles distribution within cells was analysed by confocal analysis, and gadolinium concentration within cells was quantified by mass spectrometry (ICP-MS analysis). Nanoparticles uptake is found to be fast and efficient for both cell lines, with fluorescent labeling visible after 10 min of incubation whatever the nature of the fluorophore. The fluorescent intensity is mainly found as concentrated dots in the perinuclear region of the cells and decreases with the number of days in culture, but is still easily detectable after 3 days in culture. No significant effect on cell growth was detected. Finally, we show in this study the protective effect of the polysiloxane layer: encapsulation of RBITC within the polysiloxane shell, leads to a better photostability of this low cost dye than Cy3 and even reach a level comparable to Alexa 595. With their high photostability and long-lasting contrast properties, these hybrid luminescent nanoparticles appears thus as a versatile solution to assess multiple cell fate both in in-vitro cell model as well as in-vivo.

Core/shell nanoparticles for multiple biological detection with enhanced sensitivity and kinetics

The paper shows the different methods to attach a molecule to detect streptavidin to a dielectric particle made of a rare-earth oxide core and a polysiloxane shell containing fluorescein. First, the detection of streptavidin binding on a biotinylated gold substrate can be achieved in three ways: the shift of the surface plasmon resonance of the substrate and the double luminescence (organic and inorganic) of the core/shell particle. Second, these detections are efficient even after elimination upon thermal annealing of all the undesired molecules that skew the assays. Finally, the particle that ballasts the protein enhances its binding kinetics and increases the localized surface plasmon resonance shift that detects the binding.

Gadolinium chelate coated gold nanoparticles as contrast agents for both X-ray computed tomography and magnetic resonance imaging

Functionalized gold nanoparticles were applied as contrast agents for both in vivo X-ray and magnetic resonance imaging. These particles were obtained by encapsulating gold cores within a multilayered organic shell which is composed of gadolinium chelates bound to each other through disulfide bonds. The contrast enhancement in MRI stems from the presence of gadolinium ions which are entrapped in the organic shell, whereas the gold core provides a strong X-ray absorption. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in the lungs, spleen, and liver.

Apport de la tomographie par émission de positons pour le diagnostic de sarcoïdose au cours d'une myopathie granulomateuse

INTRODUCTION

Granulomatous myositis is a rare condition that has been described in association with sarcoidosis. In the absence of sarcoidosis or other underlying disease, a diagnosis of isolated granulomatous myositis is considered.

OBSERVATION

A 61-year-old African man presented with progressive limitation in running and proximal atrophy of the lower limbs for the past year. Quadricipital muscle biopsy revealed non-caseating epithelioid granulomas and multinuclear giant cells. Whole body fluorodeoxyglucose positron emission tomography ((18)FDG-PET) revealed hypermetabolic activity of salivary and lachrymal glands, and mild hypermetabolism in the mediastinal lymph nodes. Minor salivary gland biopsy was consistent with sarcoidosis.

CONCLUSION

To our knowledge, this is the first reported case of sarcoid myopathy demonstrating the diagnostic usefulness of (18)FDG-PET.

Hybrid Gadolinium Oxide Nanoparticles: Multimodal Contrast Agents for in Vivo Imaging

Luminescent hybrid nanoparticles with a paramagnetic Gd2O3 core were applied as contrast agents for both in vivo fluorescence and magnetic resonance imaging. These hybrid particles were obtained by encapsulating Gd2O3 cores within a polysiloxane shell which carries organic fluorophores and carboxylated PEG covalently tethered to the inorganic network. Longitudinal proton relaxivities of these particles are higher than the positive contrast agents like Gd-DOTA which are commonly used for clinical magnetic resonance imaging. Moreover these particles can be followed up by fluorescence imaging. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in lungs and liver.

The role of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography in disseminated carcinoma of unknown primary site

BACKGROUND

The authors conducted a comprehensive review of the efficacy of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (FDG-PET) in the detection of primary tumors in patients with disseminated carcinoma of unknown primary site.

METHODS

Ten studies (involving a total of 221 patients) tat were published between 1998 and 2006 were reviewed. Each study evaluated the role of FDG-PET in the detection of unknown primary tumors after a conventional diagnostic workup. Although 94% of patients had a single site of metastases, the studies otherwise were very heterogeneous in the studied population, study design, and additional diagnostic workup.

RESULTS

In 41% of patients, FDG-PET detected primary tumors that were not apparent after conventional workup. In this group of patients, the overall sensitivity, specificity, and accuracy rates of FDG-PET in detecting unknown primary tumors were 91.9%, 81.9%, and 80.5%, respectively. FDG-PET imaging also led to the detection of previously unrecognized metastases in 37% of patients. Lung cancers represented 59% of the detected tumors. FDG-PET had a notably high false-positive rate (58.3%) in tumors of the lower digestive tract. FDG-PET altered the clinical management in 34.7% of patients. Most of those patients (53%) received specific chemotherapy for lung and pancreatic cancers; whereas 12% received specific therapy for breast, ovarian, and prostate cancers; and 14% underwent surgery with curative intent.

CONCLUSIONS

FDG-PET was an efficient method for detecting primary tumors that were undetected by other modalities and was sensitive for the detection of previously unrecognized metastases. FDG-PET significantly changed clinical management in approximately one-third of the patients studied.

[Feasibility and technical problems of sentinel node analysis in melanoma]

BACKGROUND

Development of the sentinel lymph node (SLN) biopsy the last 10 years has changed surgical approach of solid tumor treatment and particularly of melanoma. The aim of our study was to analyze in our hospital, the feasibility of the SLN biopsy technique in order to define a better prognostic classification of melanomas.

PATIENTS AND METHODS

Between July 1999 and October 2003, 97 patients were included in this study in our center. Criteria for inclusion were cutaneo-mucosal melanoma of Breslow >or=1,5 mm, and/or Clarck >or=IV, and/or ulceration, and/or signs of regression, before any surgical margins.

RESULTS

Lymphoscintigraphy (LS) identified at least 1 SLN in 94 cases/97 (97%), thus permitting intraoperative SLN mapping and sentinel node biopsy of at least 1 lymph node in 88 cases/94 (94%). Failure of the SLN procedure was noted in 9 cases: in 3 cases, no lymph node was individualized by LS, in 1 patient, intraoperative SLN mapping failed to find the previously identified SLN and in 5 cases, a SLN was identified by LS and intraoperative mapping but could not be removed because of its deep location and difficulty of dissection. In 17 patients, removal of one or two "non sentinel lymph node(s)" was (were) made by the surgeon because of its (their) suspected aspect (black or large). Among the 88 patients who had dissection of at least 1 SLN, a micrometastasis was detected by standard histological evaluation and/or immunohistochemical stains in 14 cases (16%) and into a "non SLN" in 2 cases (2,3%). The median follow up of patients was 16 months (1- 48 months). Among the 14 patients with positive SLN, 6 (43%) relapsed. The other eight were in complete remission of their melanoma with a mean follow up of 11,44 months . Among the 74 patients with negative SLN, 7 (9,5%) developed a recurrence. Among the 9 patients in whom any sentinel lymph node have been removed, 3 had a relapse (one in transit than on lymph nodes, and two on lymph nodes).

CONCLUSION

Our results are in accordance with the literature, and confirm the feasibility of SLN mapping and of SLN histological analysis in our center. We described in this study technical problems we encountered. Our study also show the prognostic value of this technique. However, advantage in global survey of sentinel node dissection and regional lymph node dissection in cases of micrometastases has still to be demonstrated.

T-cell homing to the pancreas in autoimmune mouse models of diabetes: in vivo MR imaging

PURPOSE

To evaluate the efficiency of T-cell labeling with anionic magnetic nanoparticles (AMNPs) and in vivo magnetic resonance (MR) imaging monitoring of T-cell homing to the pancreas.

MATERIALS AND METHODS

In vivo MR images of pancreas were obtained with a 7-T MR system in 12 NOD (nonobese diabetic) mice at 11 and 20 days after injection of AMNP-loaded or unloaded T cells. Homing of loaded T cells in pancreatic lymph nodes was detected by the presence of a focal dark spot with T2* effect in a caudal area of the pancreas. Detection of loaded T cells in pancreatic islets was evaluated by comparison of histograms of MR signal intensity generated in whole pancreas in mice injected with loaded and unloaded T cells. Homing of loaded T cells was confirmed at transmission electronic microscopy (TEM). Fifty-six mice underwent all experiments.

RESULTS

Focal dark spots with T2* effect were observed at 11 days in all three mice injected with loaded T cells and in none of the three mice injected with unloaded T cells. At 20 days, a more diffuse negative enhancement of the whole pancreas was noticed in one mouse injected with loaded T cells than in three mice injected with unloaded T cells. Presence of loaded T cells was confirmed with TEM. In vitro and in vivo tests confirmed that survival and function were not altered by loading.

CONCLUSION

The ability of MR imaging to depict cell homing in living organisms at least 20 days after cell labeling was demonstrated, opening the way of follow-up in autoimmune diseases and cell therapy.

Cell internalization of anionic maghemite nanoparticles: quantitative effect on magnetic resonance imaging

Anionic iron oxide nanoparticles are efficiently internalized into macrophages where they concentrate within micrometric endosomes, conferring on them a high magnetic susceptibility. The uptake of anionic maghemite nanoparticles by macrophages was quantified by an electron spin resonance (ESR) experiment. MR spin-echo sequences were performed with various TEs and TRs. The contrast enhancement was compared between two types of agarose phantoms with the same equivalent ferrite concentrations but containing either dispersed isolated nanoparticles or magnetically labeled macrophages. It is shown that the intracellular confinement of maghemite nanoparticles within micrometric endosomes results in a significant decrease of the longitudinal relaxivity and a moderate decrease of the transverse relaxivity compared to the relaxivities of the dispersed isolated nanoparticles. As a consequence, the signature of endosomal magnetic labeling consists of a negative contrast on T(1)-weighted images in the whole ferrite concentration range, whereas the presence of extracellular isolated nanoparticles can result in a positive enhancement.

Intracellular uptake of anionic superparamagnetic nanoparticles as a function of their surface coating

A new class of superparamagnetic nanoparticles bearing negative surface charges is presented. These anionic nanoparticles show a high affinity for the cell membrane and, as a consequence, are captured by cells with an efficiency three orders of magnitude higher than the widely used dextran-coated iron oxide nanoparticles. The surface coating of anionic particle with albumin strongly reduces the non specific interactions with the plasma membrane as well as the overall cell uptake and at the same time restores the ability to induce specific interactions with targeted cells by the coadsorption on the particle surface of a specific ligand. Kinetics of cellular particle uptake for different cell lines are quantitated using two new complementary assays (Magnetophoresis and Electron Spin Resonance).