Drug development in oncology assisted by noninvasive optical imaging.

International audienceEarly and accurate detection of tumors, like the development of targeted treatments, is a major field of research in oncology. The generation of specific vectors, capable of transporting a drug or a contrast agent to the primary tumor site as well as to the remote (micro-) metastasis would be an asset for early diagnosis and cancer therapy. Our goal was to develop new treatments based on the use of tumor-targeted delivery of large biomolecules (DNA, siRNA, peptides, or nanoparticles), able to induce apoptosis while dodging the specific mechanisms developed by tumor cells to resist this programmed cell death. Nonetheless, the insufficient effectiveness of the vectorization systems is still a crucial issue. In this context, we generated new targeting vectors for drug and biomolecules delivery and developed several optical imaging systems for the follow-up and evaluation of these vectorization systems in live mice. Based on our recent work, we present a brief overview of how noninvasive optical imaging in small animals can accelerate the development of targeted therapeutics in oncology

Highly efficient cell adhesion on beads functionalized with clustered peptide ligands

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Targeted delivery of activatable fluorescent pro-apoptotic peptide into live cells

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: Drug vectorization via a RGD-tetrameric peptide

International audienceRGD peptides recognize the α(v)β(3) integrin, a receptor that is overexpressed on the surface of both tumor blood vessels and cancerous cells. These peptides are powerful tools that act as single antiangiogenic molecules, but recently also have been used for tumor imaging and drug targeting. We designed the molecule RAFT-(c[-RGDfK-])(4), a constrained and chemically defined entity that can be produced at clinical-grade quality. This scaffold was covalently coupled via a labile bridge to the proapoptotic peptide (KLAKLAK)(2) (RAFT-RGD-KLA). A fluorescent, activatable probe was also introduced, allowing intracellular localization. At 2.5 µM, this molecule induced the intracellular release of an active KLA peptide, which in turn caused mitochondrial depolarization and cell death in vitro in tumor cells. In a mouse model, the RAFT-RGD-KLA peptide was found to prevent the growth of remote subcutaneous tumors. This study demonstrated that the antitumor peptide is capable of killing tumor cells in an RGD-dependent manner, thus lowering the nonspecific cytotoxic effects expected to occur when using cationic cytotoxic peptides. Thus, this chemistry is suitable for the design of complex, multifunctional molecules that can be used for both imaging and therapeutics, representing the next generation of perfectly controlled, targeted drug-delivery systems

PEP-RSV: Targeting the replication mechanism of respiratory syncytial virus

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In vivo optical imaging of integrin alphaV-beta3 in mice using multivalent or monovalent cRGD targeting vectors.

International audienceBACKGROUND: The cRGD peptide is a promising probe for early non-invasive detection of tumors. This study aimed to demonstrate how RAFT-c(-RGDfK-)4, a molecule allowing a tetrameric presentation of cRGD, improved cRGD-targeting potential using in vivo models of alphaVbeta3-positive or negative tumors. RESULTS: We chose the human embryonic kidney cells HEK293(beta3) (high levels of alphaVbeta3) or HEK293(beta1) (alphaVbeta3-negative but expressing alphaV and beta1) engrafted subcutaneously (s.c.) in mice. Non-invasive in vivo optical imaging demonstrated that as compared to its monomeric cRGD analogue, Cy5-RAFT-c(-RGDfK-)4 injected intravenously had higher uptake, prolonged retention and markedly enhanced contrast in HEK293(beta3) than in the HEK293(beta1) tumors. Blocking studies further demonstrated the targeting specificity and competitive binding ability of the tetramer. CONCLUSION: In conclusion, we demonstrated that Cy5-RAFT-c(-RGDfK-)4 was indeed binding to the alphaVbeta3 receptor and with an improved activity as compared to its monomeric analog, confirming the interest of using multivalent ligands. Intravenous injection of Cy5-RAFT-c(-RGDfK-)4 in this novel pair of HEK293(beta3) and HEK293(beta1) tumors, provided tumor/skin ratio above 15. Such an important contrast plus the opportunity to use the HEK293(beta1) negative control cell line are major assets for the community of researchers working on the design and amelioration of RGD-targeted vectors or on RGD-antagonists

High-relaxivity molecular MRI contrast agent to target Gb3-Expressing cancer cells

International audienceTargeted contrast agents (CAs) can improve magnetic resonance imaging (MRI) for accurate cancer diagnosis. In this work, we used the Shiga toxin B-subunit (STxB) as a targeting agent, which binds to Gb3, a glycosphingolipid highly overexpressed on the surface of tumor cells. We developed STxB-targeted MRI probes from cyclic peptide scaffolds functionalized with six to nine monoamide DO3A[Gd(III)] chelates. The influence of structural constraints on the longitudinal relaxivity ($r_1$) of the CAs has been studied. The cyclic peptide carrying nine monoamide DO3A[Gd(III)] exhibited a r1 per compound of 32 and 93 mM$^{–1}$s$^{–1}$ at 9.4 and 1.5 T, respectively. Its conjugation to the pentameric STxB protein led to a 70 kDa compound with a higher $r_1$ of 150 and 475 mM$^{–1}$ s$^{–1}$ at 9.4 and 1.5 T, respectively. Specific accumulation and cellular distribution of this conjugate in Gb3-expressing cancer cells were demonstrated using immunofluorescence microscopy and quantified by an inductively coupled plasma–mass spectrometry dosage of Gd(III). Such an agent should enable the in vivo detection by MRI of tumors expressing Gb3 receptors

Fullerene-functionalized carbon nanotubes as improved optical limiting devices

International audienceWe report the synthesis, characterization and optical limiting behavior of a nanohybrid built by grafting C60-fullerenes on carbon nanotubes (CNTs). The nonlinear optical limiting properties of the CNT-C60 complex were investigated at wavelengths where C60 does not absorb. We found that the nanohybrid had superior performances to those of CNTs and fullerenes, either taken individually or as a mixture. This enhanced optical limitation of the nanohybrid suggests not only cooperative but also synergistic effects between the two carbon forms. A mechanism involving higher excitonic states of the CNTs formed by Auger recombination of low energy excitons is proposed

Disordered, fuzzy and sticky: NMR insights into respiratory syncytial virus phosphoprotein, an adaptor-like protein.

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