Rezumat

Rezumat

Rezumat

Rezumat

Rezumat

The goal of this paper aimed the development of an inexpensive, reliable and easy-to-use biodevice for detection and monitoring of phenol and phenolic endocrine disruptors in water samples. X-Ray (XRD) diffraction technique was employed for physical characterization of the modified electrode surface, results revealing nanostructured layers assemblies of polycrystalline gold with (200) growth preferred orientation and gold crystallite size of 33.19 nm. Investigation of the modified surface charge transfer properties was performed using cyclic voltammetry technique highlighting a significant enhancement of the electron transfer rate. Dual signal amplification offered by synergistic effect of gold nanoparticle and reduced graphene oxide layers and tyrosinase led to competitive detection limits (7.2 x 10(-8) mol L-1 for phenol and 4.8 x 10(-7) mol L-1 for octylphenol) and sensitivities (416 nA/mu mol for phenol and 155 nA/mu mol for octylphenol). The obtained values of the K-m(app) and I-max/K-m(app) ratio confirmed a strongly dependence of the immobilized tyrosinase catalytic efficiency on the steric and electronic properties of the bulky side chain in the para position of the phenolic compound. The biodevice showed a percent recovery between 87 +/- 8% and 94 +/- 11% demonstrating a suitable degree of accuracy and confirming the application potential to the detection and monitoring of phenol and several endocrine disruptors in water samples. (C) 2015 Elsevier B.V. All rights reserved.

Rezumat

Indium doped tin oxide (ITO) electrodes were functionalized with gold nanoparticles (GNPs) and cysteamine monolayer to enhance the heterogeneous electron transfer process of laccase from Trametes versicolor. The assembly of GNP on ITO support was performed through generation of H+ species at the electrode surface by hydroquinone electrooxidation at 0.9 V vs Ag/AgCl. Uniform distribution of gold nanoparticle aggregates on electrode surfaces was confirmed by atomic force microscopy. The size of GNP aggregates was in the range of 200-500 nm. The enhanced charge transfer at the GNP functionalized ITO electrodes was observed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Electrocatalytic behavior of laccase immobilized on ITO modified electrode toward oxygen reduction reaction was evaluated using CV in the presence of 2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfuric acid (ABTS). The obtained sigmoidal-shaped voltammograms for ABTS reduction in oxygen saturated buffer solution are characteristic for a catalytic process. The intensity of catalytic current increased linearly with mediator concentration up to 6.2 x 10(-4) M. The registered voltammogram in the absence of ABTS mediator clearly showed a significant faradaic current which is the evidence of the interfacial oxygen reduction. (C) 2014 Elsevier B.V. All rights reserved.

Rezumat

We are presenting a bienzymatic sensor for the determination of polyphenols. An ITO electrode was modified with multiwalled carbon nanotubes, and the enzymes laccase and tyrosinase were co-entrapped into a chitosan matrix. The resulting biosensor was calibrated at -50 mV (vs. the Ag/AgCl reference electrode) using rosmarinic acid, caffeic acid and gallic acid as the substrates. The new biosensor resulted in a 10.7-fold increase in response sensitivity and a considerable improvement of the detection limit (42 nM for rosmarinic acid). Fouling of the surface of the biosensor was prevented by applying the surfactant Tween 20. The data recorded in surfactant medium revealed a significant improvement of the operational stability and an enlarged linear concentration ranges (up to 12 mu M for rosmarinic acid). The sensor was used to evaluate the total phenolic content from extracts of Salvia officinalis and cultures of Basilicum callus.

Rezumat

The present paper addresses the radical scavenger properties evaluation of different extracts from plants and berries, in order to prove the feasibility of electrochemical approach to such an application. The radical scavenging properties of extracts of acclimatised Lonicerae caerulea fructus, Myrtilli fructus, Equiseti herba, Millefolii herba and Medicagini herba were evaluated using as model a long lifetime free radical 2,2'-diphenyl-1-pycrilhydrazil (DPPH). An electro-analytical method (square-wave voltammetry) devoted to the evaluation of extract properties was developed and results were confirmed using spectrochemical methods. The results were expressed in Trolox equivalent radical scavenging activity on mg dry base. In the case of Lonicera caerulea fruits the results (12385.63 mu mol TE/mg dry fruit for aqueous extract; 12455.27 mu mol TE/mg dry fruit for alcoholic extract and 3918.05 mu mol TE/mg dry fruit for total extract) proved that berries from acclimatised plant provide a high content of antioxidants.

Rezumat

The EU project Nutra-Snack established an integrated scientific and technological framework to introduce conventional and new biotechnologies into the nutraceutical industry. The purpose was to promote novel ready-to-eat snacks enriched with natural antioxidant/radical-scavenging compounds. Enhancement of valuable compounds production in plant cells and in vitro cultures were achieved by different elicitation strategies, and exhaustive metabolites profiling obtained by high-resolution analytical techniques. Finally, innovative enzyme-based biosensors were developed for food products functional activity and safety properties assessment. This review provides an overview of the technologies selected, integrated and tested in NUTRA-SNACK and recent literature strengthening integrated approaches in modern food process manufacturing.

Rezumat