Exploiting Energy Transfer in Hybrid Metal and Semiconductor Nanoparticle Systems for Biosensing and Energy Harvesting

In this work, gold and semiconductor nanoparticles are used as building blocks for nanostructures, in which energy transfer is investigated. Nanoparticles have size-dependent controllable optical properties. Therefore, they are interesting objects to study different aspects and applications of energy transfer. Fluorescence quenching by gold nanoparticles is investigated and used to develop novel immunoassays for medically relevant molecules. The range of fluorescence quenching by gold nanoparticles is effective over longer distances than for dye molecules. The reason for this is the large absorption cross-section of gold nanoparticles and the radiative rate suppression of dyes caused by gold nanoparticles. The influence of gold nanoparticles on radiative and non-radiative rates of Cy3 and Cy3B dyes is studied here. A competitive, homogeneous immunoassay for digoxigenin and digoxin, a drug used to cure heart diseases, is developed. Dye-labeled digoxigenin is bound to the gold nanoparticles functionalized with anti-digoxigenin antibodies, quenching the dye fluorescence. Unlabeled digoxigenin partially replaces the dye-labeled digoxigenin leading to an increase of fluorescence. The assay has a limit of detection of 0.5 nM in buffer and 50 nM in serum. Time resolved spectroscopy reveals that the quenching is due to energy transfer with an efficiency of 70%. A homogeneous sandwich immunoassay for cardiac troponin T, an indicator of damage to the heart muscle, is developed. Gold nanoparticles and fluorophores are functionalized with anti-troponin T antibodies. In the presence of troponin T the nanoparticles and fluorophores form a sandwich structure, in which the dye fluorescence is quenched by a gold nanoparticle. The limit of detection of the immunoassay in buffer is 0.02 nM and 0.11 nM in serum. Energy transfer, with up to 95% efficiency, is responsible for the fluorescence quenching, as found through time resolved spectroscopy. Energy transfer is demonstrated in clusters of CdTe nanocrystals assembled using three methods. In the first method, clusters of differently-sized water soluble CdTe nanocrystals capped by negatively charged mercaptoacid stabilizers are produced through electrostatic interactions with positively charged Ca(II) cations. The two other methods employ covalent binding through dithiols and thiolated DNA as linkers between nanocrystals. Energy transfer from smaller nanocrystals to larger nanocrystals in aggregates is demonstrated by means of steady-state and time-resolved photoluminescence spectroscopy, paving the way for nanocrystal-based light harvesting structures in solution. Multi-shell onion-like CdSe/ZnS/CdSe/ZnS nanocrystals are presented. In these structures the CdSe core and the CdSe shell produce two emission peaks upon UV light excitation. When the emission peaks are well matched, the resulting emission appears as pure white light. The shade of the white light can be controlled by annealing the particles. Evidence for intra-nanocrystal energy transfer is presented

miTuner - a kit for microRNA based gene expression tuning in mammalian cells

The purpose of this RFC is to introduce a modular expression tuning kit for use in mammalian cells. The kit enables the regulation of the gene expression of any gene of interest (GOI) based on synthetic microRNAs, endogenous microRNAs or a combination of both

Fluorescence Quenching of Alpha-Fetoprotein by Gold Nanoparticles: Effect of Dielectric Shell on Non-Radiative Decay

Fluorescence quenching spectrometry was applied to study the interactions between gold colloidal nanoparticles and alpha-fetoprotein (AFP). Experimental results show that the gold nanoparticles can quench the fluorescence emission of adsorbed AFP effectively. Furthermore, the intensity of fluorescence emission peak decreases monotonously with the increasing gold nanoparticles content. A mechanism based on surface plasmon resonance–induced non-radiative decay was investigated to illuminate the effect of a dielectric shell on the fluorescence quenching ability of gold nanoparticles. The calculation results show that the increasing dielectric shell thickness may improve the monochromaticity of fluorescence quenching. However, high energy transfer efficiency can be obtained within a wide wavelength band by coating a thinner dielectric shell

miMeasure – a standard for miRNA binding site characterization in mammalian cells

This RFC proposes a standard for the quantitative characterization of miRNA binding sites (miRNA-BS) in mammalian cells. The miMeasure standard introduces a ready-to-use standard measurement plasmid (pSMB_miMeasure, BBa_K337049) enabling rapid experimental characterization of any miRNA-BS of choice. We recommend a new standard unit, RKDU (relative knock-down unit) to describe the knock-down efficiency of a miRNA-BS in a specific cell type. pSMB_miMeasure allows for an easy and fast measurement of RKDU while providing effective normalization against variance stemming from differences in transfection efficiency and from other sources

Noble Metal Nanoparticles for Biosensing Applications

In the last decade the use of nanomaterials has been having a great impact in biosensing. In particular, the unique properties of noble metal nanoparticles have allowed for the development of new biosensing platforms with enhanced capabilities in the specific detection of bioanalytes. Noble metal nanoparticles show unique physicochemical properties (such as ease of functionalization via simple chemistry and high surface-to-volume ratios) that allied with their unique spectral and optical properties have prompted the development of a plethora of biosensing platforms. Additionally, they also provide an additional or enhanced layer of application for commonly used techniques, such as fluorescence, infrared and Raman spectroscopy. Herein we review the use of noble metal nanoparticles for biosensing strategies—from synthesis and functionalization to integration in molecular diagnostics platforms, with special focus on those that have made their way into the diagnostics laboratory

Parler de la langue en Ukraine contemporaine : une analyse historico-épistémologique des travaux de Larysa Masenko

Dans notre travail, nous étudions le discours sur la langue en Ukraine indépendante à partir de 1991. Ce discours porte essentiellement sur la politique linguistique, le bilinguisme et la régulation de la langue, qui font l'objet d'études de la sociolinguistique ukrainienne. Parmi les sociolinguistes ukrainiens contemporains, Larysa Terentijivna Masenko; auteure de plusieurs livres consacrés à la situation linguistique en Ukraine et à l'histoire de la politique linguistique soviétique, occupe une place importante dans le monde académique et public. Le but de notre travail consiste à examiner le discours de L. T. Masenko sur la langue du point de vue de l'histoire des idées linguistiques. L'analyse des concepts-clés utilisés dans les textes de la linguiste nous permet de déterminer sa compréhension des divers aspects de la langue

L. Masenko et les racines romantiques des idées sur la politique linguistique en Ukraine contemporaine

Dans cet article sont examinées les propositions de la linguiste ukrainienne L. Masenko concernant la politique linguistique en Ukraine contemporaine. Nous montrons les racines historiques de ses idées en les comparant avec les propos de plusieurs linguistes du passé. Il se trouve que les idées de Masenko proviennent du «paradigme» de la période du Romantisme, dans lequel la langue était identifiée à la «nation».</jats:p