David Kryza

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.

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.

Development of gadolinium based nanoparticles having an affinity towards melanin

Small Rigid Platforms (SRPs) are sub-5 nanometre gadolinium based nanoparticles that have been developed for multimodal imaging and theranostic applications. They are composed of a polysiloxane network surrounded by gadolinium chelates. A covalent coupling with quinoxaline derivatives has been performed. Such derivatives have proven their affinity for melanin frequently expressed in primary melanoma cases. Three different quinoxaline derivatives have been synthesised and coupled to the nanoparticles. The affinity of the grafted nanoparticles for melanin has then been shown in vitro by surface plasmon resonance on a homemade melanin grafted gold chip.

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.

Influence of multidrug resistance on 18 F-FCH cellular uptake in a glioblastoma model

PurposeMultidrug resistance, aggressiveness and accelerated choline metabolism are hallmarks of malignancy and have motivated the development of new PET tracers like 18F-FCH, an analogue of choline. Our aim was to study the relationship of multidrug resistance of cultured glioma cell lines and 18F-FCH tracer uptake.MethodsWe used an in vitro multidrug-resistant (MDR) glioma model composed of sensitive parental U87MG and derived resistant cells U87MG-CIS and U87MG-DOX. Aggressiveness, choline metabolism and transport were studied, particularly the expression of choline kinase (CK) and high-affinity choline transporter (CHT1). FCH transport studies were assessed in our glioblastoma model.ResultsAs expected, the resistant cell lines express P-glycoprotein (Pgp), multidrug resistance-associated protein isoform 1 (MRP1) and elevated glutathione (GSH) content and are also more mobile and more invasive than the sensitive U87MG cells. Our results show an overexpression of CK and CHT1 in the resistant cell lines compared to the sensitive cell lines. We found an increased uptake of FCH (in % of uptake per 200,000 cells) in the resistant cells compared to the sensitive ones (U87MG: 0.89u2009±u20090.14; U87MG-CIS: 1.27u2009±u20090.18; U87MG-DOX: 1.33u2009±u20090.13) in line with accelerated choline metabolism and aggressive phenotype.ConclusionsFCH uptake is not influenced by the two ATP-dependant efflux pumps: Pgp and MRP1. FCH would be an interesting probe for glioma imaging which would not be effluxed from the resistant cells by the classic MDR ABC transporters. Our results clearly show that FCH uptake reflects accelerated choline metabolism and is related to tumour aggressiveness and drug resistance.

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.

Granulocyte Colony-Stimulating Factor Nanocarriers for Stimulation of the Immune System (Part I): Synthesis and Biodistribution Studies

In the field of cancer immunotherapy, an original approach consists of using granulocyte colony-stimulating factor (G-CSF) to target and activate neutrophils, cells of the innate immune system. G-CSF is a leukocyte stimulating molecule which is commonly used in cancer patients to prevent or reduce neutropenia. We focused herein on developing a G-CSF nanocarrier which could increase the in vivo circulation time of this cytokine, keeping it active for targeting the spleen, an important reservoir of neutrophils. G-CSF-functionalized silica and gold nanoparticles were developed. Silica nanoparticles of 50 nm diameter were functionalized by a solid phase synthesis approach. The technology enabled us to incorporate multiple functionalities on the surface such as a PEG as hydrophilic polymer, DTPA as 111In chelating agent and G-CSF. The gold nanocarrier consisted of nanoparticles of 2-3 nm diameter elaborated with DTPA groups on the surface and functionalized with G-CSF. We studied the particle biodistribution in mice with special attention to organs involved in the immune system. The two nanocarriers with similar functionalization of surface showed different pathways in mice, probably due to their difference in size. Considering the biodistribution after G-CSF functionalization, we confirmed that the protein was capable of modifying the pharmacokinetics by increasing the nanocarrier concentration in the spleen, a reservoir of G-CSF receptor expressing cells.

Radio-UHPLC: a tool for rapidly determining the radiochemical purity of technetium-99m radiopharmaceuticals?

Determining the radiochemical purity (RCP) of technetium-99m ((99m)Tc) radiopharmaceuticals using the method described in the package insert is a time-consuming process, requiring particular attention in order to achieve accurate RCP results. The purpose of this study was to evaluate whether radio-ultra high performance liquid chromatography (radio-UHPLC) may be an alternative method for RCP testing of (99m)Tc-tetrofosmin, (99m)Tc-MAG3 and (99m)Tc-sestamibi. Results obtained using radio-UHPLC were in excellent agreement with the standard method, with total analysis time being reduced to less than 3 min.

Granulocyte-Colony Stimulating Factor Nanocarriers for Stimulation of the Immune System (Part II): Dose-Dependent Biodistribution and In Vivo Antitumor Efficacy in Combination with Rituximab

The purpose of immuno-modulation is to increase or restore the action of immunocompetent cells against tumors with or without the use of monoclonal antibodies. The innate immune system is a key player in various pathological situations, but cells of this system appear to be inhibited or insufficiently active in malignancy or severe infectious diseases. The present study was designed to investigate therapeutic value of nanoparticles (NPs) coupled with bioactive hematopoietic growth factors acting on the innate immune system. The use of nanoparticles (NPs) allowing multimodal detection and multifunctional grafting are currently of great interest for theranostic purposes. In the present work, we have evaluated the impact of the number of granulocyte-colony stimulating factor (G-CSF) grafted on the surface on the NPs on the biodistribution in mice thanks to indium 111 radiolabeling. Furthermore, we have investigated whether grafted G-CSF NPs could stimulate the immune innate system and enhance the therapeutic efficacy of the monoclonal antibody rituximab in mice bearing human lymphoma xenografts. Following intravenous (i.v.) administration of NP-DTPA and NP-DTPA/G-CSF-X high levels of radioactivity were observed in the liver. Furthermore, spleen uptake was correlated with the number of G-CSF molecules grafted on the surface of the NPs. Combining NP-DTPA/G-CSF-34 with rituximab strongly reduced RL tumor growth compared to rituximab alone or in combination with conventional G-CSF + rituximab. The use of highly loaded G-CSF NPs as immune adjuvants could enhance the antitumor activity of therapeutic monoclonal antibodies by amplifying tumor cell destruction by innate immune cells.