DNA-basierte molekulare Nanokonstruktion: ein Modellbeispiel und Applikationen unter Verwendung von DNA/DNA- und DNA-Nanopartikel-Komplexen in planartechnischer Umgebung

In der Arbeit wurde eine Machbarkeitsstudie eines nanobiotechnologischen Baukastensystems mit molekularen Techniken (auf DNA-Basis) erstellt. Die Komponenten des Systems waren Planarsubstrate (Chips), metallische Nanopartikel und Nukleinsäuren. Das Grundprinzip der Konstruktion basierte auf der Selbstorganisation von Nukleinsäuren auf Oberflächen (in Form von sogenannten selbstorganisierenden Monoschichten) und der Bindung verschiedener Komponenten durch die Affinität der Nukleinsäuren (Hybridisierung). Durch die Kombination der Komponenten untereinander wurden verschiedene Immobilisierungs- und Markierungsprozesse realisiert. In der Arbeit wurden Produkte dieser Prozesse erzeugt und charakterisiert. Auch wurden erste umfassende Quantifizierungsversuche zu einer neuartigen Nanopartikel-Markierung durchgeführt. Das vorgestellte nanobiotechnologische System ermöglichte mit einfachen Komponenten und Techniken einen definierten Aufbau von Molekülkonstrukten aus DNA und DNA-Nanopartikel-Komplexen in planarer Anordnung

A nyílt kormányzati adatok kutatási kihívásai

Habár a nyílt adatok koncepciója már régóta ismert, komolyabb praktikus érdeklődésről a közszféra részéről körülbelül egy évtizede lehet beszélni. Ez a momentum megmozgatta az e-kormányzás ’fősodrába’ tartozó kutatók érdeklődését is, mely meg is látszik a vonatkozó publikációk megemelkedett számán. Habár két-három éve visszaesni látszott a lendület, az újrahasznosítás jelensége újabb muníciót szolgáltatott a kutatásoknak. Jelen tanulmány a legfrissebb irodalom és esettanulmányok segítségével tekinti át a nyílt kormányzati adatok kutatásának jellemző területeit és javaslatokat fogalmaz meg olyan kutatási kérdésekre, melyek nemcsak előrébb vihetik a nyílt kormányzati adatok újrahasznosításának kérdéseit, de irányt mutathatnak hazai kutatóknak is a sikeres nemzetközi megjelenéshez

Propagating and localized surface plasmon resonance sensing — A critical comparison based on measurements and theory

With its potential for ultrasensitive, label-free detection of molecular interactions, sensing methods based on the surface plasmon resonance (SPR) effect fully meet the requirements for modern analytical techniques. Already established by using propagating SPR in thin gold layers, the last years witnessed the emergence of another related technique utilizing extremely miniaturized noble metal sensor structures, based on a localized SPR. This paper provides a critical comparison of these kinds of SPR sensing, reviews the foundation of both general approaches, presents experimental data on exactly the same molecular model system using both techniques, as well as theoretical considerations in order to allow reasonable comparison. It highlights the specific features and effects, in order to provide guidance in choosing the right technique for given bioanalytical tasks. The study demonstrated the capabilities of LSPR for sensing of molecular layers even in the lower nanometer dimension. For the detection of small (bio)molecules, smaller particle diameters are favored regarding highest sensitivity. It also presents an approach to obtain refractive index and the thickness of a molecular film by analyzing the signal response of plasmonic sensors with metal nanoparticles. Moreover, an additional method for the improvement of the parameters' determination is introduced

Modification of Surface Bond Au Nanospheres by Chemically and Plasmonically Induced Pd Deposition

In this work we investigated methods of modifying gold nanospheres bound to a silicon surface by depositing palladium onto the surfaces of single nanoparticles. Bimetallic Au-Pd nanoparticles can thus be gained for use in catalysis or sensor technology. For Pd deposition, two methods were chosen. The first method was the reduction of palladium acetate by ascorbic acid, in which the amounts of palladium acetate and ascorbic acid were varied. In the second method we utilized light-induced metal deposition by making use of the plasmonic effect. Through this method, the surface bond nanoparticles were irradiated with light of wavelengths capable of inducing plasmon resonance. The generation of hot electrons on the particle surface then reduced the palladium acetate in the vicinity of the gold nanoparticle, resulting in palladium-covered gold nanospheres. In our studies we demonstrated the effect of both enhancement methods by monitoring the particle heights over enhancement time by atomic force microscopy (AFM), and investigated the influence of ascorbic acid/Pd acetate concentration as well as the impact of the irradiated wavelengths on the enhancement effect. It could thus be proven that both methods were valid for obtaining a deposition of Pd on the surface of the gold nanoparticles. Deposition of Pd on the gold particles using the light-assisted method could be observed, indicating the impact of the plasmonic effect and hot electron for Pd acetate reduction on the gold particle surface. In the case of the reduction method with ascorbic acid, in addition to Pd deposition on the gold nanoparticle surface, larger pure Pd particles and extended clusters were also generated. The reduction with ascorbic acid however led to a considerably thicker Pd layer of up to 54 nm in comparison to up to 11 nm for the light-induced metal deposition with light resonant to the particle absorption wavelength. Likewise, it could be demonstrated that light of non-resonant wavelengths was not capable of initiating Pd deposition, since a growth of only 1.6 nm (maximum) was observed for the Pd layer

2-LED-μspectrophotometer for rapid on-site detection of pathogens using noble-metal nanoparticle-based colorimetric assays

Novel point-of-care compatible methods such as colorimetric assays have become increasingly important in the field of early pathogen detection. A simple and hand-held prototype device for carrying out DNA-amplification assay based on plasmonic nanoparticles in the colorimetric detection is presented. The low-cost device with two channels (sample and reference) consists of two spectrally different light emitting diodes (LEDs) for detection of the plasmon shift. The color change of the gold-nanoparticle-DNA conjugates caused by a salt-induced aggregation test is examined in particular. A specific and sensitive detection of the waterborne human pathogen Legionella pneumophila is demonstrated. This colorimetric assay, with a simple assay design and simple readout device requirements, can be monitored in real-time on-site. © 2020 by the authors

A new strategy for silver deposition on Au nanoparticles with the use of peroxidase-mimicking DNAzyme monitored by Localized Surface Plasmon Resonance technique

Peroxidase-mimicking DNAzyme was applied as a catalyst of silver deposition on gold nanoparticles. This DNAzyme is formed when hemin binds to the G-quadruplex-forming DNA sequence. Such a system is able to catalyze a redox reaction with a one- or two-electron transfer. The process of silver deposition was monitored via a localized surface plasmon resonance technique (LSPR), which allows one to record scattering spectrum of a single nanoparticle. Our study showed that DNAzyme is able to catalyze silver deposition. The AFM experiments proved that DNAzyme induced the deposition of silver shells of approximately 20 nm thickness on Au nanoparticles (AuNPs). Such an effect is not observed when hemin is absent in the system. However, we noticed non-specific binding of hemin to the capture oligonucleotides on a gold NP probe that also induced some silver deposition, even though the capture probe was unable to form G-quadruplex. Analysis of SEM images indicated that the surface morphology of the silver layer deposited by DNAzyme is different from that obtained for hemin alone. The proposed strategy of silver layer synthesis on gold nanoparticles catalyzed by DNAzyme is an innovative approach and can be applied in bioanalysis (LSPR, electrochemistry) as well as in material sciences

Wet-chemical Passivation of Anisotropic Plasmonic Nanoparticles for LSPR-sensing by a Silica Shell

Metal nanoparticles showing the effect of localized surface plasmon resonance (LSPR), a collective oscillation of the conduction electrons upon interaction with light, represent an interesting tool for bioanalytics. This resonance is influenced by changes in the environment, and can be therefore used for the detection of molecular layers. The sensitivity, this means the extent of wavelength resonance shift per change in refractive index in the environment, represents an important performance parameter. It is higher for silver compared to gold particles, and is also increased for anisotropic particles. So silver triangles show a high potential for highly sensitive plasmonic nanoparticles. However, the stability under ambient conditions is rather poor. The paper demonstrates the passivation of silver triangles by silica coating using a wet-chemical approach. It compares the sensitivity for particles with and without passivation, and visualizes the passivation effect in a high resolution, single particle TEM study

Shape-Dependent Catalytic Activity of Gold and Bimetallic Nanoparticles in the Reduction of Methylene Blue by Sodium Borohydride

In this study the catalytic activity of different gold and bimetallic nanoparticle solutions towards the reduction of methylene blue by sodium borohydride as a model reaction is investigated. By utilizing differently shaped gold nanoparticles, i.e., spheres, cubes, prisms and rods as well as bimetallic gold–palladium and gold–platinum core-shell nanorods, we evaluate the effect of the catalyst surface area as available gold surface area, the shape of the nanoparticles and the impact of added secondary metals in case of bimetallic nanorods. We track the reaction by UV/Vis measurements in the range of 190–850 nm every 60 s. It is assumed that the gold nanoparticles do not only act as a unit transferring electrons from sodium borohydride towards methylene blue but can promote the electron transfer upon plasmonic excitation. By testing different particle shapes, we could indeed demonstrate an effect of the particle shape by excluding the impact of surface area and/or surface ligands. All nanoparticle solutions showed a higher methylene blue turnover than their reference, whereby gold nanoprisms exhibited 100% turnover as no further methylene blue absorption peak was detected. The reaction rate constant k was also determined and revealed overall quicker reactions when gold or bimetallic nanoparticles were added as a catalyst, and again these were highest for nanoprisms. Furthermore, when comparing gold and bimetallic nanorods, it could be shown that through the addition of the catalytically active second metal platinum or palladium, the dye turnover was accelerated and degradation rate constants were higher compared to those of pure gold nanorods. The results explore the catalytic activity of nanoparticles, and assist in exploring further catalytic applications

Chip-based duplex real-time PCR for water quality monitoring concerning Legionella pneumophila and Legionella spp.

Based on biomolecular methods, rapid and selective identification of human pathogenic water organisms becomes an important issue. Legionella spp., are pathogenic water bacteria with worldwide significance. Prevalent detection methods for these microorganisms are time and/or cost intensive. We describe a detection setup and relating DNA assay. A miniaturized real-time polymerase chain reaction (real-time PCR) for direct on-line discrimination of Legionella pneumophila and Legionella spp. was established and integrated into a real-time PCR-chip-system. The PCR-chip device combines a temperature controlling unit and a fluorescence intensity measurement. It was designed to achieve rapid amplification, using an approach of real-time fluorescence read out with the intercalating dye EvaGreen® and melting curve analysis, without requiring multiple probes. The presented results exhibit reproducibility and good sensitivity, showing that the setup is suitable for robust, rapid and cost-efficient detection and monitoring of a variety of Legionella spp.in urban water samples

Aszpartám édesítőszer élelmiszerekből származó bevitelének becslése és a kockázat értékelése = Estimation of the aspartame intake coming from foods and its risk assessment

A NÉBIH Élelmiszerbiztonsági Kockázatértékelési Igazgatósága vizsgálatot végzett annak megállapítására, hogy a hazai élelmiszerfogyasztási adatok alapján mennyire biztonságos az aszpartám fogyasztása, azaz mennyire közelíti meg a hazai aszpartámbevitel a nemzetközileg elfogadott megengedhető napi bevitel (ADI, Acceptable Daily Intake) értéket. Az aszpartám expozíciójának becslését a NÉBIH-ÉKI három módszerrel végezte. Az EFSA honlapjáról letölthető ún. FAIM modell Excel templáttal (Food Additives Intake Model) az értékelni kívánt adalékanyag határértékeinek (a megengedett maximális felhasználási szinteknek) megadásával, valamint az EFSA adatbázisában rendelkezésre álló, a modellbe beépített tagországi élelmiszerfogyasztási adatok alapján becsülhető az átlagos és nagy bevitel. Másrészt egy 2013 végén rendelkezésre bocsátott, probabilisztikus elven működő ún. FACET (Flavourings, Additives and Contact Materials Exposure Task) szoftver segítségével, amely Magyarországról szintén az EFSA adatbázisában rendelkezésre álló 2003-as élelmiszerfogyasztási adatokat tartalmazza. Harmadrészt pedig egy saját kidolgozású probabilisztikus módszer alkalmazásával, a legújabb, 2009. évi hazai élelmiszerfogyasztási adatok alapján, 4992 fő napi fogyasztási adatait figyelembe véve történt a magyar lakosság aszpartám bevitelének becslése. Az eredmények alapján levonható a következtetés, hogy a magyar lakosság élelmiszerekből származó aszpartám expozíciója egészségügyi szempontból nem aggályos. A FAIM modell szerint, felnőttek esetén a nagy bevitel az ADI 20%-a, míg időseknél az ADI 13,8%-a. Az átlagos bevitel ennél alacsonyabb, felnőtteknél az ADI 5,8%-a, idősek esetén 4,8%-a. A FACET modellel számítva az átlagos (felnőtt és idős) fogyasztó aszpartám bevitele az ADI 4,4%-a, a nagy bevitel (P95) az ADI 14%-a. A saját, probabilisztikus módszerrel, 2009-es élelmiszerfogyasztási adatokkal számított átlagos bevitel az ADI 3,6%-a, míg a nagy bevitel az ADI 14,4%-a. Az adalékanyagok étrendi bevitelének becslésére alkalmazott többlépcsős, egymásra épülő megközelítés második szintjén végzett becslés konzervatív (a legrosszabb esetet feltételezi), a további pontosítás (harmadik lépcső) eredményeként a becsült expozíció ennél is alacsonyabb lenne. A közlemény kitér a különböző módszerek összehasonlítására is. Az aszpartám élelmiszerekkel, italokkal történő bevitele az átlagos magyar fogyasztóknál a szokásos étrend esetén nem ad okot aggodalomra. Érdemes azonban megjegyezni, hogy a gyermekek expozíciója nagy mennyiségű aszpartámmal édesített üdítőital- és gyümölcsjoghurt- fogyasztás esetén elérheti az ADI -értéket. A study was performed by the Directorate of Risk Assessment of Food Safety of NÉBIH in order to determine how safe the consumption of aspartame is, based on domestic food consumption data, i.e. how close domestic aspartame intake is to the internationally accepted Acceptable Daily Intake (ADI) value. Aspartame exposition was estimated by NÉBIH-ÉKI using three methods. Average and high intake levels can be estimated using the so-called FAIM (Food Additives Intake Model) model Excel template that can be downloaded from the homepage of EFSA, by entering the limit values (allowed maximum usage levels) of the additive to be evaluated, and also based on food consumption data of member states, incorporated in the model and available in the EFSA database. The second method is with the help of a so-called FACET (Flavourings, Additives and Contact Materials Exposure Task) software operating on probabilistic principles, made available to us at the end of 2013 and containing 2003 Hungarian food consumption data available also in the EFSA database. And the third method for estimation of the aspartame intake of the Hungarian population was by using our own developed probabilistic method based on the latest, 2009 domestic food consumption data, taking into consideration the daily consumption data of 4992 individuals. Based on the data it can be concluded that the aspartame exposition of the Hungarian population coming from foods is not cause for a health concern. According to the FAIM model, the high intake is 20% of the ADI for adults and 13.8% for the elderly. The average intake is lower than this, 5.8% of the ADI for adults and 4.8% for the elderly. Calculating with the FACET model, aspartame intake of the average (adult and elderly) consumer is 4.4% of the ADI, while the high intake (P95) is 14% of the ADI. The average intake calculated with the own probabilistic method, using 2009 food consumption data, is 3.6% of the ADI, while the high intake is 14.4% of the ADI. The estimation performed at level two of the multistage tiered approach used for the estimation of the dietary intake of additives is conservative (it assumes a worst-case scenario), the estimated exposition obtained as the result of a further refinement (third stage) would be even lower. The paper also includes the comparison of the different methods. Aspartame intake with foods and beverages is not a cause for concern for the average Hungarian consumer in case of the usual diet. However, it is worth noting that the exposition of children, in case of consumption of large quantities of aspartame-sweetened beverages and fruit yogurts, may reach the ADI value