A solid-phase synthesis of three aza-, iminoaza- and reduced aza-peptides from the same precursor

Using the Boc-strategy, a step-by-step synthesis on the PAM solid supportof three aza-, iminoaza- and reduced aza-peptide homologues is described.From the same hydrazinocarbonyl peptide-PAM precursor, the coupling ofeither a Boc-amino acid or a Boc-amino aldehyde gives rise to an aza-peptideor an iminoaza-peptide containing theC-CO-NH-N-CO-NH-C orC-CH=N-N-CO-NH-C surrogate of the peptide motif, respectively. In situreduction of the latter by NaBH₃CN leads to a reducedaza-peptide containing theC-CH₂-NH-N-CO-NH-C moiety. The key step synthesis of thehydrazinocarbonyl peptide-PAM precursor is carried out by coupling on thegrowing peptide chain the N-Boc-aza-amino acid chloride obtained by theaction of triphosgene on the corresponding N-Boc-hydrazine. Thesemodifications have been introduced in position 1-2 of the YLGYLEQLLRbenzodiazepine-like decapeptide     

Molecular modelling,synthesis and biological evaluation of peptide inhibitors as anti-angiogenic agent targeting neuropilin-1 for anticancer application

Vascular endothelial growth factor (VEGF) and its co-receptor neuropilin-1 (NRP-1) are important targets of many pro-angiogenic factors. In this study, nine peptides were synthesized and evaluated for their molecular interaction with NRP-1 and compared to our previous peptide ATWLPPR. Docking study showed that the investigated peptides shared the same binding region as shown by tuftsin known to bind selectively to NRP-1. Four pentapeptides (DKPPR, DKPRR, TKPPR and TKPRR) and a hexapeptide CDKPRR demonstrated good inhibitory activity against NRP-1. In contrast, peptides having arginine residue at sites other than the C-terminus exhibited low activity towards NRP-1 and this is confirmed by their inability to displace the VEGF₁₆₅ binding to NRP-1. Docking study also revealed that replacement of carboxyl to amide group at the C-terminal arginine of the peptide did not affect significantly the binding interaction to NRP-1. However, the molecular affinity study showed that these peptides have marked reduction in the activity against NRP-1. Pentapeptides having C-terminal arginine showed strong interaction and good inhibitory activity with NRP thus may be a good template for anti-angiogenic targeting agent.     

Triazinyl porphyrin-based photoactive cotton fabrics: preparation, characterization, and antibacterial activity

In the present work, we report on the synthesis of cellulose cotton fibers bearing different types of photosensitizers with the aim to prepare new efficient polymeric materials for antimicrobial applications. Anionic, neutral, and cationic amino porphyrins have been covalently grafted on cotton fabric, without previous chemical modification of the cellulosic support, using a 1,3,5-triazine derivative as the linker. The obtained porphyrin-grafted cotton fabrics were characterized by infrared (ATR-FTIR), diffuse reflectance UV-vis (DRUV) spectroscopies, and thermogravimetric analysis (TGA) to confirm the triazine linkage. Antimicrobial activity of porphyrin-cellulose materials was tested under visible light irradiation against Staphylococcus aureus and Escherichia coli . The results showed excellent activity on the Gram-positive bacterium, showing structure-activity relationship, although no photodamage of the Gram-negative microorganism was recorded. A mechanism of bacterial inactivation by photosensitive surfaces is proposed.     

New photodynamic molecular beacons (PMB) as potential cancer-targeted agents in PDT

Further improvements in Photodynamic therapy (PDT) necessitate that the dye targets more selectively tumour tissues or neovascularization than healthy cells. Different enzymes such as matrix metalloproteinases (MMPs) are overexpressed in tumour areas. Among these MMPs, gelatinases (MMP-2 and MMP-9) and its activator MMP-14 are known to play a key role in tumour angiogenesis and the growth of many cancers such as glioblastoma multiforme (GBM), an aggressive malignant tumour of the brain. These last years, the concept of photodynamic molecular beacons (PMB) became interesting for controlling the photosensitizer’s ability to generate singlet oxygen (¹O₂) close to target biomolecules as MMPs. We report herein novel PMBs triggered by MMP-2 and/or MMP-9 and/or MMP-14, comprising a photosensitizer and a singlet oxygen quencher linked by MMP cleavable peptide linker (H-GRIGFLRTAKGG-OH). First of all, we focused on the synthesis and the photophysical study of different derivatives photosensitizer-peptide. This preliminary work concluded on an influence of the nature and the distance from the peptide, but not of the position of the photosensitizer in these derivatives on the proteolytic enzymatic action. The nature of the quencher used (a blackberry quencher (BBQ-650) or a black hole quencher (BHQ3)) does not influence the enzymatic action. We also studied the influence of an additional PEG spacer. Finally, the synthesis, the singlet oxygen quenching efficiency and the enzymatic activation of these new MMP- cleavable-PMBs were compared.     

Real-Time Monitoring of Photocytotoxicity in Nanoparticles-Based Photodynamic Therapy: A Model-Based Approach

Nanoparticles are widely suggested as targeted drug-delivery systems. In photodynamic therapy (PDT), the use of multifunctional nanoparticles as photoactivatable drug carriers is a promising approach for improving treatment efficiency and selectivity. However, the conventional cytotoxicity assays are not well adapted to characterize nanoparticles cytotoxic effects and to discriminate early and late cell responses. In this work, we evaluated a real-time label-free cell analysis system as a tool to investigate in vitro cyto- and photocyto-toxicity of nanoparticles-based photosensitizers compared with classical metabolic assays. To do so, we introduced a dynamic approach based on real-time cell impedance monitoring and a mathematical model-based analysis to characterize the measured dynamic cell response. Analysis of real-time cell responses requires indeed new modeling approaches able to describe suited use of dynamic models. In a first step, a multivariate analysis of variance associated with a canonical analysis of the obtained normalized cell index (NCI) values allowed us to identify different relevant time periods following nanoparticles exposure. After light irradiation, we evidenced discriminant profiles of cell index (CI) kinetics in a concentration- and light dose-dependent manner. In a second step, we proposed a full factorial design of experiments associated with a mixed effect kinetic model of the CI time responses. The estimated model parameters led to a new characterization of the dynamic cell responses such as the magnitude and the time constant of the transient phase in response to the photo-induced dynamic effects. These parameters allowed us to characterize totally the in vitro photodynamic response according to nanoparticle-grafted photosensitizer concentration and light dose. They also let us estimate the strength of the synergic photodynamic effect. This dynamic approach based on statistical modeling furnishes new insights for in vitro characterization of nanoparticles-mediated effects on cell proliferation with or without light irradiation.     

Tissue distribution and pharmacokinetics of an ATWLPPR-conjugated chlorin-type photosensitizer targeting neuropilin-1 in glioma-bearing nude mice.

Destruction of the neovasculature is essential for efficient tumor eradication by photodynamic therapy (PDT). The PDT anti-vascular effect can be promoted by developing addressed photosensitizers localized preferentially to the tumor vascular compartment. A new photosensitizer conjugated to an heptapeptide [H-Ala-Thr-Trp-Leu-Pro-Pro-Arg-OH (ATWLPPR)] targeting neuropilin-1, a Vascular Endothelial Growth Factor (VEGF) co-receptor, has been synthesized. It was administered intravenously for an easier access to endothelial cells lining the vasculature in human malignant glioma-bearing nude mice. Plasma pharmacokinetic parameters were derived from plasma concentration-time data using a non-compartmental analysis and validated a relatively rapid elimination from the blood compartment with an elimination rate constant of 0.062 h(-1) and a biological half-life of 11.0 h. The photosensitizer was mainly concentrated in organs such as liver, spleen and kidneys, which are rich in reticuloendothelial cells. In these organs, the elimination profiles of the photosensitizer were comparable, with half-lives as short as 12.2, 15.1 and 19.7 h, respectively. The peptidic moiety of the conjugated photosensitizer was degraded to various rates depending on the organ considered, most of the degradation process occurred in organs of the reticuloendothelial system. A metabolic product resulting from the enzymatic cleavage of the peptide bond between Ala and Thr was detected in plasma at all the examined time points from 2 h post-injection. The conjugated photosensitizer accumulated rapidly and at high levels in the tumor, with 2.3% of injected dose per gram of tumor tissue at 1 h after injection. Taking into account the aspecific uptake of the degradation product, the tumor levels of total photoactivable compounds might exhibit an interesting photodynamic activity. On the contrary, levels of total photoactivable compounds remained low in the skin. This study provides essential information for the choice of the time interval not to exceed to activate the photosensitizer.     

A solid-phase synthesis of three aza-, iminoaza- and reduced aza-peptides from the same precursor

Summary Using the Boc-strategy, a step-by-step synthesis on the PAM solid support of three aza-, iminoaza- and reduced aza-peptide homologues is described. From the same hydrazinocarbonyl peptide-PAM precursor, the coupling of either a Boc-amino acid or a Boc-amino aldehyde gives rise to an aza-peptide or an iminoaza-peptide, containing the C^α-CO-NH-N^α-CO-NH-C^α or C^α-CH=N-N^α-CO-NH-C^α surrogate, of the peptide motif, respetively. In situ reduction of the latter by NaBH₃CN leads to a reduced aza-peptide containing the C^α-CH₂-NH-N^α-CO-NH-C^α moiety. The key step synthesis of the hydrazinocarbonyl peptide-PAM precursor is carried out by coupling on the growing peptide chain theN-Boc-azaamino acid chloride obtained by the action of triphosgene on the, correspondingN-Boc-hydrazine. These modifications have been introduced in position 1–2 of the YLGYLEQLLR benzodiazepine-like decapeptide.