Plasmonic Properties of Gold Nanostructures on Gold Film

This paper reports on a systematic study of the plasmonic properties of periodic arrays of gold cylindrical nanoparticles in contact with a gold thin film. Depending on the gold film thickness, it observes several plasmon bands. Using a simple analytical model, it is able to assign all these modes and determine that they are due to the coupling of the grating diffraction orders with the propagating surface plasmons travelling along the film. With finite difference time domain (FDTD) simulations, it demonstrates that large field enhancement occurs at the surface of the nanocylinders due to the resonant excitation of these modes. By tilting the sample, it also observes the evolution of the spectral position of these modes and their tuning through nearly the whole visible range is possible. Such plasmonic substrates combining both advantages of the propagative and localised surface plasmons could have large applications in enhanced spectroscopies.

     

Zinc accumulation patterns in four Anthyllis vulneraria subspecies supplemented with mineral nitrogen or grown in the presence of their symbiotic bacteria

Aims

This work examines Zn accumulation in four Anthyllis vulneraria subspecies supplemented with mineral nitrogen or grown in the presence of their symbiotic bacteria.

Methods

Anthyllis vulneraria subspecies were grown hydroponically in the presence of high levels of ZnSO₄. The plants were either grown in symbiosis with one of two non-metallicolous or metallicolous Mesorhizobium inoculants or in the presence of KNO₃.

Results

When exposed to 1,000 μM Zn, shoot and root biomass of three out of our four Anthyllis subspecies cultivated with NO₃ dropped significantly by about 24–28 %; carpatica, the fourth subspecies, was not affected. Subspecies carpatica Zn tolerance was confirmed when in symbiosis with the metallicolous strain. In the presence of 1,000 μM Zn, the different Anthyllis subspecies concentrated more Zn in their roots than in their shoots and only subsp. carpatica accumulated a significant amount of Zn in its shoots. The most remarkable feature was the drastic decrease in Zn concentration in both roots (up to 2.5–3 fold) and shoots (2.6-fold) of subsp. carpatica exposed to 1,000 μM Zn and nodulated whatever the Mesorhizobium strain used, compared to the N-grown plants.

Conclusions

Our results bring new perspectives as regards phytostabilization, with the potential use of a rhizobium-inoculated leguminous subspecies displaying unusual Zn tolerance.     

Enzymatic synthesis of fructooligosaccharides from date by-products using an immobilized crude enzyme preparation of <Emphasis Type="Italic">β</Emphasis>-D-fructofuranosidase from <Emphasis Type="Italic">Aspergillus awamori</Emphasis> NBRC 4033

Aqueous extracts from date by-products of the sucrose-rich variety “Deglet Nour” were used as a starting substrate to achieve the enzymatic synthesis of fructooligosaccharides (FOS) commonly used as prebiotics. A crude β-fructofuranosidase (Ffase) preparation from Aspergillus awamori NBRC4033 was immobilized on chitosan by covalent binding through glutaraldehyde linkages (Yi = 88%, Ya = 54%), and used for this purpose. The effect of water-extraction volume on the FOS synthesis by transfructosylation was studied. It was found that 150 mL/100 g of date by-products gave the best FOS concentration and productivity (123 g/L and 18.5 g/h/100 g respectively), related to an optimal sucrose conversion of 53.26%. The main FOS product was purified via a biogel-P2 gel filtration column. Its structure was determined as 1-kestose: α-Dglucopyranosyl-( 1→2)-β-D-fructofuranosyl-(2→1)-β-Dfructofuranoside by combination of ¹H, ¹³C and 2D-NMR techniques. Our results provide new insights into the enzymatic synthesis of FOS from an alternative source of sucrose, namely date by-products.     

Role of carbohydrate moiety of bleomycin-A2 in caspase-3 activation and internucleosomal chromatin fragmentation in apoptosis of laryngeal carcinoma cells

Bleomycin (BLM), an antitumor antibiotic, is currently used during anticancer therapy. The therapeutic efficiency of BLM for the treatment of malignant tumors is related to its ability to cleave DNA. However, little is known about the biological activity of the glycannic moiety in BLM-induced cytotoxicity. In this study, cell death induced by BLM-A2 and deglycosylated BLM-A2 was studied in a laryngeal carcinoma cell line (HEp-2 cells). Our results indicate that HEp-2 cells showed morphological and biochemical changes associated with apoptosis in the presence of low concentrations of BLM-A2. In contrast, the same changes, except activation of caspase-3 and internucleosomal digestion of genomic DNA, were observed when cells were exposed to high concentrations of deglycosylated BLM-A2. These observations indicate that the glycannic moiety from the bleomycin molecule has important biological effects on the cytotoxicity of the drug.     

Innovative surface characterization techniques applied to immunosensor elaboration and test: Comparing the efficiency of Fourier transform-surface plasmon resonance, quartz crystal microbalance with dissipation measurements, and polarization modulation-reflection absorption infrared spectroscopy

Three sensitive and original transduction techniques have been used to monitor the immobilization of anti-rabbit immunoglobulins (anti-rIgGs) and the detection of rIgGs on gold transducers. Polarization modulation-reflection absorption infrared spectroscopy (PM-RAIRS), quartz crystal microbalance with dissipation measurements (QCM-D), and Fourier transform-surface plasmon resonance (FT-SPR) were combined to achieve the best sensitivity and a large dynamic range in the target detection step. Their performances were compared after having checked that the layers adsorbed on the three different gold substrates were identical. The studied immunosensors were elaborated by building a thiolamine layer on gold surface, followed by its derivatization by glutaraldehyde and covalent binding of a monoclonal secondary IgG. The antibody attachment step was monitored in a wide range of concentrations (1-50 μg/ml). Then the built immunosensors were used to detect the rIgG recognition. PM-RAIRS analyses, performed under air, supplied ex situ data, whereas FT-SPR and QCM techniques were used in situ, enabling on-line detection of recognition processes. Interestingly, the three techniques suggested that the antibody coverage gets saturated for approximately 20 μg/ml in solution. In the very low concentration range (1 μg/ml), antibody binding was detected by the three techniques, but FT-SPR leads to an intense signal with a wavenumber shift of approximately 30 cm⁻¹; one may expect, by FT-SPR, a detection limit of the order of a few tenths of μg/ml. Ongoing experiments aim at determining the limit of detection and dynamic range of the very promising FT-SPR technique.     

Involvement of C-jun NH2-terminal kinase and apoptosis induced factor in apoptosis induced by deglycosylated bleomycin in laryngeal carcinoma cells

In our previous studies, we demonstrated that the deglycosylation of bleomycin-A2 (BLM-A2) does not affect the capacity of this drug to induce cell death by apoptosis in a caspase-independent manner in laryngeal cancer cells (HEp-2), but suppresses the ability of BLM-A2 to induce ROS formation. We have now investigated the consequence of BLM-A2 deglycosylation in terms of the involvement of apoptotic pathways in HEp-2 cells. Apoptosis induced by bleomycin-A2 and deglyco-BLM-A2 is associated with the release of cytochrome c and AIF. Only Bax was oligomerized with BLM-A2-induced HEp-2 cell death. BLM-A2 and deglyco-BLM-A2-induced apoptosis depended on JNK activation but was independent of death receptors expression. In contrast, both of these drugs would sensitize HEp-2 cells to death receptor ligand-induced cell death. These observations indicate that the deglycosylation of BLM does not impair the ability of the drug to trigger cell death through activation of the intrinsic pathway by the release of AIF responsible for mitochondrial permeability and chromatin condensation independent of caspases activation.     

Cytotoxicity, intracellular distribution and uptake of doxorubicin and doxorubicin coupled to cell-penetrating peptides in different cell lines: A comparative study

One of the major obstacles which are opposed to the success of anticancer treatment is the cell resistance that generally develops after administration of commonly used drugs. In this study, we try to overcome the tumour cell resistance of doxorubicin (Dox) by developing a cell-penetrating peptide (CPP)-anticancer drug conjugate in aim to enhance its intracellular delivery and that its therapeutic effects. For this purpose, two cell-penetrating peptides, penetratin (pene) and tat, derived from the HIV-1 TAT protein, were chemically conjugated to Dox. The cytotoxicity, intracellular distribution and uptake were accessed in CHO cells (Chinese Hamster Ovarian carcinoma cells), HUVEC (Human Umbilical Vein Endothelial Cells), differentiated NG108.15 neuronal cell and breast cancer cells MCF7drug-sensitive or MDA-MB 231 drug-resistant cell lines. The conjugates showed different cell killing activity and intracellular distribution pattern by comparison to Dox as assessed respectively by MTT-based colorimetric cellular cytotoxicity assay, confocal fluorescence microscopy and FACS analysis. After treatment with 3 μM with Dox-CPPs for 2 h, pene increase the Dox cytotoxicity by 7.19-fold in CHO cells, by 11.53-fold in HUVEC cells and by 4.87-fold in MDA-MB 231 cells. However, cytotoxicity was decreased in NG108.15 cells and MCF7. Our CPPs-Dox conjugate proves the validity of CPPs for the cytoplasmic delivery of therapeutically useful molecules and also a valuable strategy to overcome drug resistance.     

Integrated analysis for identifying Portulaca oleracea and its sub-species based on chloroplastic and nuclear DNA barcoding

The taxonomy of Portulaca oleracea has been considered as being complex since the aggregate is composed of many subspecies or a group of micro-species based on seed-coat characters, seed size, and chromosome number. In order to enlarge the background of the extent of genetic variability between and within Tunisian P. oleracea accessions, a combined morphological and molecular approach was adapted, in the present survey. The morphological analyses of the spontaneous Tunis population display high intra population variability characterized by two distinct morphotypes corresponding to the botanical forms (wild and cultivated plant). Furthermore, the molecular approach based on sequences data related to chloroplastic and ribosomal DNA, was used to understand this variability. The obtained results highlighted the greater molecular variability of this plant and allowed to segregate between morphotypes and genotypes of Portulaca. Mostly, this work shows the important contribution of DNA barcoding approach in resolving low-level-taxonomy problems to distinguish between natural populations and varieties.