Redox and ion-exchange properties in surface-tethered DNA-conducting polymers

A poly(cyclopentadithiophene) matrix modified by DNA covalently fixed to the surface has been designed to study the redox and ion-exchange properties in surface-tethered DNA-conducting polymers. Voltammetric investigations show an improvement in conductivity, originating from DNA modification, probably due to changes in charged-density and size of dopant species. Cyclic voltammetry with concomitant QCM measurements indicate that the mass changes are consistent with an ejection of Na+ cations associated to the anionic phosphate groups, attesting a DNA contribution to the p-doping process. So, in contrast to the classic doping patterns, the p-doping process of surface-tethered DNA-copolymer exhibits a cation-controlled transport mechanism. Impedimetric investigations indicate that for long enough DNA target sequence, nucleic acid preserves certain flexibility and is involved in the p-doping process through a diffusion-like motion. These results give new opportunities for genesensors development and for a better understanding of bioactive conducting surfaces

Hybridization-induced interfacial changes detected by non-Faradaic impedimetric measurements compared to Faradaic approach

A biosensor for direct label-free DNA detection based on a polythiophene matrix is investigated by electrochemical impedance spectroscopy (EIS). Impedimetric experiments are performed with and without redox probe in solution. The non-Faradaic impedance measurements reveal two relaxation processes located at 50 Hz and 5 kHz, respectively. The first relaxation process, located at low frequencies, allows to detect biorecognition events by measuring the phase angle decrease, in accordance with a hindrance of the polaronic conduction. The second relaxation process, located at 5 kHz and originating from DNA modification, seems to increase with the length of the target sequence. These results suggest that this loaded support provides a platform for impedimetric detection of hybridization at high frequencies, leading to less time-consuming detection procedure. For a better understanding, results obtained in non-Faradaic mode are compared with Faradaic approach

Preparation of New Polyols Based on Cis-1,4-Polyisoprene by Using 1,3-Dipolar Cycloaddition

This research focuses on synthesis and modification of polyol precursors derived from cis-1,4-polyisoprene (PI). These new polyol precursors can be converted to high value-added polyurethane (PU). The epoxidized hydroxytelechelic PI (EHTPI) prepared by chemical modification from PI was used as starting material for polyol synthesis. 1,3-Dipolar cycloaddition between a terminal alkyne and an azide has rapidly become the most popular click reaction. We applied this reaction to couple azide-functionalized PI and alkyne-functionalized sugar for preparing polyols. For azide functionalization, 1-methyl epoxidized cyclohexane was used as a model molecule, and various conditions for epoxide ring opening of 1-methyl epoxidized cyclohexane and EHTPI were investigated. The cycloaddition of alkyne and azide was carried out in the presence of sodium ascorbate and copper sulfate. The polyol precursors obtained might be used to prepare biodegradable polyol PU

Antifouling activity of novel polyisoprene-based coatings made from photocurable natural rubber derived oligomers

Natural rubber is a renewable resource with a potential as precursor of a very wide range of novel polymers, including polyisoprene-based surfaces with antifouling (AF) activity. In this work, new ionic and non-ionic coatings were prepared by the photocrosslinking reaction of photosensitive cis-1,4- oligoisoprenes, bearing a variable number of ammonium groups. The photochemical crosslinking was achieved using radical (via acrylate groups) or cationic (via epoxy groups) processes. Surface properties of these coatings were studied by static contact angle measurements and AFM imaging. Assessment of bioactivity demonstrated that most of the resulting coatings showed AF potential against fouling organisms: growth inhibition of marine bacteria (Pseudoalteromonas elyakovii, Shewanella putrefaciens, Cobetia marina, Polaribacter irgensii, Vibrio aestuarianus) and fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata, Zalerion sp., Monodictys pelagica); decreased adhesion of microalgae (Navicula jeffreyi, Cylindrotheca closterium, Chlorarachnion globosum, Pleurochrysis roscoffensis, Exanthemachrysis gayraliae, Amphora coffeaeformis); inhibition of attachment and/or germination of spores of Ulva intestinalis. The best AF activity was obtained with the ionic surfaces. These new coatings prepared from precursors obtained from natural rubber are in essence active by contact. As the biocidal functions are fixed covalently to the polymer chain, detectable release of biocidal products in the marine ecosystem is prevented so that a valuable environment-friendly alternative for new AF coatings is hereby proposed

Metabolite profiling in developing Camelina sativa seeds.

International audienceCamelina sativa is a Brassicaceae with interesting agronomic potential and is considered an alternative oilseed crop. Currently, Camelina is grown mainly for its seed, which shows a high oil content with an unusual fatty acid profile particularly rich in polyunsaturated fatty acids. Camelina seeds contain other potentially valuable compounds and their composition is now relatively well described. However, little information is available on the accumulation dynamics of these compounds during seed development.Our aim is to describe the dynamics of metabolites accumulation during C. sativa seed development.After purification by HPLC, the fractions were analyzed by LC–MS and NMR to characterize new compounds. The dynamic of metabolites accumulation during seed development was monitored during 15, 25 and 35 days after flowering, and metabolic profilings were performed by LC–MS and GC–MS.This study describes for the first time two compounds (quercetin-5b-O-sinapyl-2″-O-apiosyl-3-O-rutinoside and epicatechin-7-O-glucose) that have not previously been identified in the seeds of C. sativa. We also show the accumulation kinetics of various metabolites involved in seed development. These investigations highlight a major reorganization of the metabolome with a depletion of the content of most primary metabolites and a high accumulation of most fatty acids, glucosinolates, flavonoids and sinapic acid derivatives.This study resulted in the metabolic profile of C. sativa during seed development and enabled to identify two novel compounds in Camelina seeds