Nanoszemcsés szerkezetek és vékonyrétegek ellipszometriai modellezése bioszenzorikai és (opto)elektronikai alkalmazásokhoz = Ellipsometric modelling of nanograin structures and thin films for biological and (opto)electronical applications

Folyadékcellát, in situ mérési eljárást és optikai modelleket fejlesztettünk fehérjék leválasztás közbeni ellipszometriai mérésére. Az általunk fejlesztett 0,5 ml térfogatú és az előzőleg vásárolt 5 ml térfogatú kereskedelmi folyadékcella szisztematikus összehasonlító vizsgálatával, folyadékdinamikai szimulációval elemeztük és teszteltük a cellák legjobb beállítását és használhatóságának határait (pl. ablakkorrekció, szükséges folyadékmennyiség). Elsőként vizsgáltuk flagellinből polimerizált filamentumok rögzítését, a rögzített rétegek szerkezetét és a leválasztás kinetikáját. Megmutattuk, hogy a flagellin-leválasztás kinetikája többréteges ellipszometriai modellel vizsgálható. Ezáltal részletes betekintést nyerünk a rétegépülés folyamatába. Megvizsgáltuk a szubsztrát-minőség és az aktiválás hatását az immobilizációra. MATLAB nyelven kifejlesztettünk egy teljes moduláris ellipszometriai kiértékelő rendszert, amelyben implementálni tudtuk saját modelljeinket, és amelyet az MFA 128-node-os szuperszámítógépén Octave/Linux alatt futtatni tudtunk. Szoftverünkkel megmutattuk, hogy a parametrizált dielektromos függvény modell jól használható porózus szilícium, leválasztással létrehozott nanokristályos szilícium, ionimplantált szilícium és vegyületfélvezető szerkezetek rétegvastagságának, összetételének, kristályosságának és szemcseméretének meghatározására. A fenti anyagszerkezetek és a rendezett felületi struktúrák vizsgálatához paraméter-kereső algoritmusokat fejlesztettünk. | We have developed a flow cell, in situ measurement, and optical models for the ellipsometric measurement of proteins during deposition. We have tested and evaluated the best conditions and the limit of capabilities (e.g. windows correction, needed volume of solution) through systematic comparative studies of a home-made 0,5-ml cell and a commercial 5-ml flow cell. We were the first who investigated the immobilization, structure and deposition kinetics of flagellar filaments. We have shown that the deposition kinetics can be studied in detail using multi-layer optical models. Using these models we have a detailed view of the mechanisms of layer growth. We have investigated the effect of activation and substrate properties on the immobilization. We have developed a complete modular ellipsometric software package in MATLAB to implement our special models, and to enable to run the programs on the 128-node super computer of the MFA using Octave/Linux. With our software we have shown that using parameterized dielectric functions the layer thickness, structure, composition, crystallinity, and grain size of porous silicon, deposited nanocrystalline silicon, ion implanted silicon, and compound semiconductors can be determined with a high sensitivity. We have developed parameter search algorithms to evaluate the above materials, as well as order surface structures

Sample handling in surface sensitive chemical and biological sensing : a practical review of basic fluidics and analyte transport

This paper gives an overview of the advantages and associated caveats of the most common sample handling methods in surface-sensitive chemical and biological sensing.We summarize the basic theoretical and practical considerations one faces when designing and assembling the fluidic part of the sensor devices. The influence of analyte size, the use of closed and flow-through cuvettes, the importance of flow rate, tubing length and diameter, bubble traps, pressure-driven pumping, cuvette dead volumes, and sample injection systems are all discussed. Typical application areas of particular arrangements are also highlighted, such as themonitoring of cellular adhesion, biomolecule adsorption–desorption and ligand–receptor affinity binding. Our work is a practical review in the sense that for every sample handling arrangement considered we present our own experimental data and critically reviewour experience with the given arrangement. In the experimental partwe focus on sample handling in optical waveguide lightmode spectroscopy (OWLS) measurements, but the present study is equally applicable for other biosensing technologies in which an analyte in solution is captured at a surface and its presence is monitored. Explicit attention is given to features that are expected to play an increasingly decisive role in determining the reliability of (bio)chemical sensingmeasurements, such as analyte transport to the sensor surface; the distorting influence of dead volumes in the fluidic system; and the appropriate sample handling of cell suspensions (e.g. their quasi-simultaneous deposition). At the appropriate places, biological aspects closely related to fluidics (e.g. cellular mechanotransduction, competitive adsorption, blood flow in veins) are also discussed, particularly with regard to their models used in biosensing

Vezetőképesség moduláció ZnO nanoszálakon bioreceptorokkal = Conductivity Modulation of ZnO Nanowires by Bioreceptors (CoMoNano)

Kimutattuk, hogy az egyszerű és alacsony hőmérsékletű nedves kémiai eljárásban a vizes cinknitrát/hexametiltetramin oldat koncentrációjának csökkentésével csökken a növesztett ZnO nanoszálak vastagsága. Újszerű módszert dolgoztunk ki a nanoszál növesztésére, amelyben a ZnO magrétegre leválasztott Stöber szilika nanogömbök monorétegével nemcsak vékony de hosszabb nanoszálak is növeszthetőek. Kimutattuk, hogy az ilyen szálnak jobb az UV fénnyel történő modulálhatósági hatásfoka. Megmutattuk, hogy rendezett, lokalizált nanoszálak növeszthetők a magrétegre felvitt PMMA fedőrétegben kialakított nukleációablakokon keresztül. Az így növesztett nanoszálak rendezettsége, minősége inkább az alkalmazott magréteg kristályi minőségétől függ, semmint a felületi durvaságától. Eljárást dolgoztunk ki az IC planár technológiába jobban integrálható horizontális nanoszálak növesztésére. A kontaktusokról induló és oxidon tovább növő szálak lehetővé teszik az eszköz térvezérlésű tranzisztorként hátsó gate általi vezérelhetőségét, amivel növelhető a szál modulálhatósági hatásfokát, modulálási sebességét. Demonstráltuk a horizontális szálak modulálhatóságát UV fényre (kb. öt nagyságrend változás ) illetve az IgG fehérjére Z domén receptorokkal. A modulálás már nagyon kis IgG (25 nM) koncentrációnál megfigyelhető, de a koncentráció növekedésével telítési jelleget mutat. Ennek valószínűleg a szálon szabadon maradt receptorok csökkenő száma lehet az oka. | We have shown that in the chemical bath deposition the thickness of the grown ZnO nanowires (NWs) is reduced with decreasing concentration of the aqueous zinc nitrate and hexamethylentetramine. A novel route has been developed using a monolayer of silica nanospheres deposited on ZnO seedlayer to grow thin but much longer NWs than usual. Such NWs were observed to have better UV modulation property than those formed without nanosphere layer. We demonstrated that the selective growth of NWs could be well realized via the nucleation windows pre-formed in the PMMA cap-layer over the seed layer. The crystal quality and alignment of such NWs was determined by the dispersion in the crystallographic orientation of the seed layer while the role of its surface roughness was negligible. Method to grow horizontal NWs which is integrable into IC planar technology has been developed. Being nucleated from the electrodes then grown along oxide surface, the NWs can be gated by a back electrode as a field effect transistor, thus their modulation efficiency, speed can be further achieved. Modulation of the horizontal NWs has been demonstrated for UV illumination (five order of magnitude change) and IgG with Z domain receptors. The modulation effect of IgG can be observed even at very low concentration (25 nM), which showed a saturation tendency with increasing IgG concentration, probably due to the limitation of the available binding sites of the Z domains on the NW surface for the IgGs

Human primary endothelial label-free biochip assay reveals unpredicted functions of plasma serine proteases

Tissue-on-a-chip technologies are more and more important in the investigation of cellular function and in the development of novel drugs by allowing the direct screening of substances on human cells. Constituting the inner lining of vessel walls, endothelial cells are the key players in various physiological processes, moreover, they are the first to be exposed to most drugs currently used. However, to date, there is still no appropriate technology for the label-free, real-time and high-throughput monitoring of endothelial function. To this end, we developed an optical biosensor-based endothelial label-free biochip (EnLaB) assay that meets all the above requirements. Using our EnLaB platform, we screened a set of plasma serine proteases as possible endothelial cell activators, and first identified the endothelial cell activating function of three important serine proteases – namely kallikrein, C1r and mannan-binding lectin-associated serine-protease 2 (MASP-2) – and verified these results in well-established functional assays. EnLaB proved to be an effective tool for revealing novel cellular mechanisms as well as for the high-throughput screening of various compounds on endothelial cells

Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically

The interaction of the anti-adhesive coating, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its Arg-Gly-Asp (RGD) functionalized form, PLL-g-PEG-RGD, with the green tea polyphenol, epigallocatechin-gallate (EGCg) was in situ monitored. After, the kinetics of cellular adhesion on the EGCg exposed coatings were recorded in real-time. The employed plate-based waveguide biosensor is applicable to monitor small molecule binding and sensitive to sub-nanometer scale changes in cell membrane position and cell mass distribution; while detecting the signals of thousands of adhering cells. The combination of this remarkable sensitivity and throughput opens up new avenues in testing complicated models of cell-surface interactions. The systematic studies revealed that, despite the reported excellent antifouling properties of the coatings, EGCg strongly interacted with them, and affected their cell adhesivity in a concentration dependent manner. Moreover, the differences between the effects of the fresh and oxidized EGCg solutions were first demonstrated. Using a semiempirical quantumchemical method we showed that EGCg binds to the PEG chains of PLL-g-PEG-RGD and effectively blocks the RGD sites by hydrogen bonds. The calculations supported the experimental finding that the binding is stronger for the oxidative products. Our work lead to a new model of polyphenol action on cell adhesion ligand accessibility and matrix rigidity

Kinetics and Structure of Self-Assembled Flagellin Monolayers on Hydrophobic Surfaces in the Presence of Hofmeister Salts: Experimental Measurement of the Protein Interfacial Tension at the Nanometer Scale

In the present study, we monitor the adsorption–desorption kinetics and adsorbed layer structure of the bacterial protein flagellin in the presence of Hofmeister salts by a surface sensitive label-free optical biosensor (optical waveguide lightmode spectroscopy, OWLS). The recorded OWLS data were analyzed by a computer code using a set of coupled differential equations modeling the adsorption–desorption process. By supposing reversibly and irreversibly adsorbed protein states with different adsorption footprints, the kinetic data could be perfectly fitted. We revealed that the proteins adsorbing in the presence of kosmotropic salts had smaller footprints, leading to a more oriented and densely packed layer. Kosmotropic salts increased both the adsorption rate constant and the transition rate constants from the reversibly to the irreversibly adsorbed state. In contrast, chaotropic salts increased the desorption rate constant and led to decreased adsorbed mass and a more loosely packed film. Neither circular dichroism spectroscopy in bulk solutions or Fourier transform infrared spectroscopy of surface-adsorbed flagellins could reveal significant structural changes due to the presence of the Hofmeister salts, and supported our conclusions about the adsorption mechanism. On the basis of the measured kinetic and structural data (footprints of adsorbed proteins), we developed a model to calculate the protein–water-substrate interfacial tension in the presence of Hofmeister salts, and compared the experimentally obtained values with related literature data. The calculated values are consistent with previously published data of surface tension changes, andto the best of our knowledgerepresent the first experimental results for this quantity