Improvement of the anti-proliferative activity of the peptide ERα17p in MCF-7 breast cancer cells using nanodiamonds.

Nanodiamonds (NDs) are emerging delivery systems with biomedical applications and interesting perspectives in oncology. Their use has been proposed to assist the internalization of anticancer drugs and to decrease administered drug doses. The pro-apoptotic peptide ERα17p, which is issued from the hinge/N-terminus parts of the AF2 region of the human estrogen receptor α (ERα), is active at a concentration of 10µM on breast cancer cells and particularly on those cancer cells that are ERα-positive. We have synthesized ND@ERα17p conjugates by physisorption of the cationic peptide ERα17p on the surface of anionic NDs. Resulting ND@ERα17p suspensions were characterized by far-UV electronic circular dichroism (ECD), dynamic light scattering (DLS) and zetametry. We then tested the anti-proliferative action of ND@ERα17p on ERα-positive MCF-7 breast carcinoma cells. ND@ERα17p allowed a decrease of the active concentration to 0.1nM (ND@ERα17p), revealing unambiguously that NDs could be used to improve the anti-proliferative action of this peptide. This preliminary study proposes a novel approach for enhancing the apoptotic action displayed by ERα17p, in the context of breast cancer.

Probing the in-air growth of large area of 3D functional structures into a 2D supramolecular nanoporous network.

Surface-confined host-guest chemistry at the air/solid interface is used for trapping a functionalized 3D Zn-phthalocyanine complex into a 2D porous supramolecular template allowing the large area functionalization of an sp2-hybridized carbon-based substrate as evidenced by STM, resonance Raman spectroscopy, and water contact angle measurements.

How to unveil self-quenched fluorophores and subsequently map the subcellular distribution of exogenous peptides.

Confocal laser scanning microscopy (CLSM) is the most popular technique for mapping the subcellular distribution of a fluorescent molecule and is widely used to investigate the penetration properties of exogenous macromolecules, such as cell-penetrating peptides (CPPs), within cells. Despite the membrane-association propensity of all these CPPs, the signal of the fluorescently labeled CPPs did not colocalize with the plasma membrane. We studied the origin of this fluorescence extinction and the overall consequence on the interpretation of intracellular localizations from CLSM pictures. We demonstrated that this discrepancy originated from fluorescence self-quenching. The fluorescence was unveiled by a "dilution" protocol, i.e. by varying the ratio fluorescent/non-fluorescent CPP. This strategy allowed us to rank with confidence the subcellular distribution of several CPPs, contributing to the elucidation of the penetration mechanism. More generally, this study proposes a broadly applicable and reliable method to study the subcellular distribution of any fluorescently labeled molecules.

Antibody recognition in multiple sclerosis and Rett syndrome using a collection of linear and cyclic N-glucosylated antigenic probes.

Antibody detection in autoimmune disorders, such as multiple sclerosis (MS) and Rett syndrome (RTT) can be achieved more efficiently using synthetic peptides. The previously developed synthetic antigenic probe CSF114(Glc), a type I' ß-turn N-glucosylated peptide structure, is able to recognize antibodies in MS and RTT patients' sera as a sign of immune system derangement. We report herein the design, synthesis, conformational analysis, and immunological evaluation of a collection of glycopeptide analogs of CSF114(Glc) to characterize the specific role of secondary structures in MS and RTT antibody recognition. Therefore, we synthesized a series of linear and cyclic short glucosylated sequences, mimicking different ß-turn conformations, which were evaluated in inhibition enzyme-linked immunosorbent assays (ELISA). Calculated IC50 ranking analysis allowed the selection of the candidate octapeptide containing two (S)-2-amino-4-pentynoic acid (L-Pra) residues Ac-Pra-RRN(Glc)GHT-Pra-NH2 , with an IC50 in the nanomolar range. This peptide was adequately modified for solid-phase ELISA (SP-ELISA) and surface plasmon resonance (SPR) experiments. Pra-RRN(Glc)GHT-Pra-NH2 peptide was modified with an alkyl chain linked to the N-terminus, favoring immobilization on solid phase in SP-ELISA and differentiating IgG antibody recognition between patients and healthy blood donors with a high specificity. However, this peptide displayed a loss in IgM specificity and sensitivity. Moreover, an analog was obtained after modification of the octapeptide candidate Ac-Pra-RRN(Glc)GHT-Pra-NH2 to favor immobilization on SPR sensor chips. SPR technology allowed us to determine its affinity (KD = 16.4 nM), 2.3 times lower than the affinity of the original glucopeptide CSF114(Glc) (KD = 7.1 nM).

Accumulation of cell-penetrating peptides in large unilamellar vesicles: A straightforward screening assay for investigating the internalization mechanism.

The internalization of cell-penetrating peptides (CPPs) into liposomes (large unilamellar vesicles, LUVs) was studied with a rapid and robust procedure based on the quenching of a small fluorescent probe, 7-nitrobenz-2-oxa-1,3-diazole (NBD). Quenching can be achieved by reduction with dithionite or by pH jump. LUVs with different compositions of phospholipids (PLs) were used to screen the efficacy of different CPPs. In order to "validate" the composition of the membrane models, a control cationic peptide, which does not enter eukaryotic cells, was included in the study. It was found that pure DOPG or DOPG within ternary mixtures with cholesterol are the most appropriate models for studying CPP translocation. An anionic lipid, such as DOPG, is required for the adsorption of the basic peptides on the surface of LUVs. In addition, it acts as transfer agent through the lipid bilayer. A fluid phase and/or the presence of phase defects also appear mandatory for the internalization to occur. The neutralization of charges within an inverted micelle demonstrated in the case of DOPG and also proposed for a ternary mixture of PLs might not be the only mechanism for the CPP translocation. Finally, it is shown that oleic acid facilitates the entry inside LUVs in gel phase of a series of cationic peptides including CPPs and also the negative control peptide PKCi.

The efficacies of cell-penetrating peptides in accumulating in large unilamellar vesicles depend on their ability to form inverted micelles.

In this study, the direct translocation of cell-penetrating peptides (CPPs) into large unilamellar vesicles (LUVs) was shown to be rapid for all the most commonly used CPPs. This translocation led within a few minutes to intravesicular accumulation up to 0.5 mM, with no need for a transbilayer potential. The accumulation of CPPs inside LUVs was found to depend on CPP sequence, CPP extravesicular concentration and phospholipid (PL) composition, either in binary or ternary mixtures of PLs. More interestingly, the role of anionic phospholipid flip-flopping in the translocation process was ascertained. CPPs enhanced the flipping of PLs, and the intravesicular CPP accumulation directly correlated with the amount of anionic PLs that had been transferred from the external to the internal leaflet of the LUV bilayer, thus demonstrating the transport of peptide/lipid complexes as inverted micelles.

Nanodiamond as a vector for siRNA delivery to Ewing sarcoma cells.

The ability of diamond nanoparticles (nanodiamonds, NDs) to deliver small interfering RNA (siRNA) into Ewing sarcoma cells is investigated with a view to the possibility of in-vivo anticancer nucleic-acid drug delivery. siRNA is adsorbed onto NDs that are coated with cationic polymer. Cell uptake of NDs is demonstrated by taking advantage of the NDs' intrinsic fluorescence from embedded color-center defects. Cell toxicity of these coated NDs is shown to be low. Consistent with the internalization efficacy, a specific inhibition of EWS/Fli-1 gene expression is shown at the mRNA and protein level by the ND-vectorized siRNA in a serum-containing medium.

Peptide-grafted nanodiamonds: preparation, cytotoxicity and uptake in cells.

Nanodiamonds that were prepared by high pressure/high temperature were functionalized with biomolecules for biological applications. Nanodiamonds (NDs, < or =35 nm) that were coated by silanization or with polyelectrolyte layers were grafted with a fluorescent thiolated peptide via a maleimido function; this led to an aqueous colloidal suspension that was stable for months. These substituted NDs were not cytotoxic for CHO cells. Their capacity to enter mammalian cells, and their localisation inside were ascertained after labelling the nucleus and actin, by examining the cells by confocal, reflected light and fluorescence microscopy.