Tuning the functional properties of lignocellulosic films by controlling the molecular and supramolecular structure of lignin.

This study investigated the relationships between lignin molecular and supramolecular structures and their functional properties within cellulose-based solid matrix, used as a model biodegradable polymer carrier. Two types of derivatives corresponding to distinct structuration levels were prepared from a single technical lignin sample (PB1000): phenol-enriched oligomer fractions and colloidal nanoparticles (CLP). The raw lignin and its derivatives were formulated with cellulose nanocrystals or nanofibrils to prepare films by chemical oxidation or pressure-assisted filtration. The films were tested for their water and lignin retention capacities, radical scavenging capacity (RSC) and antimicrobial properties. A structural investigation was performed by infrared, electron paramagnetic resonance spectroscopy and microscopy. The composite morphology and performance were controlled by both the composition and structuration level of lignin. Phenol-enriched oligomers were the compounds most likely to interact with cellulose, leading to the smoothest film surface. Their RSC in film was 4- to 6-fold higher than that of the other samples. The organization in CLP led to the lowest RSC but showed capacity to trap and stabilize phenoxy radicals. All films were effective against S. aureus (gram negative) whatever the lignin structure. The results show the possibility to tune the performances of these composites by exploiting lignin multi-scale structure.

EPR and electrochemical quantification of oxygen using newly synthesized para-silylated triarylmethyl radicals.

Novel silylated triarylmethyl (TAM) radicals based on TAM core CT-03 and their electron paramagnetic resonance (EPR) spectra are evaluated as a function of oxygen concentration. Combination of peak-to-peak linewidth of the EPR signal and electrochemical determination allows designing a method for oxygen quantification in phosphate buffer, dimethylsulfoxide, and dichloromethane, which can be extended to other solvents.

Reduction of nilutamide by NO synthases: implications for the adverse effects of this nitroaromatic antiandrogen drug.

Nitric oxide synthases (NOSs) are flavohemeproteins that catalyze the oxidation of l-arginine to l-citrulline with formation of the widespread signal molecule NO. Beside their fundamental role in NO biosynthesis, these enzymes are also involved in the formation of reactive oxygen species and in the interactions with some xenobiotic compounds. Nilutamide is a nonsteroidal antiandrogen that behaves as a competitive antagonist of the androgen receptors and is proposed in the treatment of metastatic prostatic carcinoma. However, therapeutic effects of nilutamide are overshadowed by the occurrence of several adverse reactions mediated by toxic mechanism(s), which remain(s) poorly investigated. Here, we studied the interaction of NOSs with nilutamide. Our results show that the purified recombinant neuronal NOS reduced the nitroaromatic nilutamide to the corresponding hydroxylamine. The reduction of nilutamide catalyzed by neuronal NOS proceeded with intermediate formation of a nitro anion free radical easily observed by EPR, was insensitive to the addition of the usual heme ligands and l-arginine analogues, but strongly inhibited by O(2) and a flavin/NADPH binding inhibitor. Involvement of the reductase domain of nNOS in the reduction of nilutamide was confirmed by (i) the ability of the isolated reductase domain of nNOS to catalyze the reaction and (ii) the stimulating effect of Ca(2+)/calmodulin on the accumulation of hydroxylamine and nitro anion radical. In a similar manner, the recombinant inducible and endothelial NOS isoforms also displayed nitroreductase activity, albeit with lower yields. The selective reduction of nilutamide to its hydroxylamino derivative by the NOSs could explain some of the toxic effects of this drug.