The problems related to the development of a multielement immunosensor device with the prism type of excitation of a surface plasmon resonance in the Kretschmann configuration and with the scanning of the incidence angle of monochromatic light aimed at the reliable determination of the levels of three molecular markers of the system of hemostasis (fibrinogen, soluble fibrin, and D-dimer) are considered. We have analyzed the influence of a technology for the production of a gold coating, modification of its surface, and noise effects on the enhancement of sensitivity and stability of the operation of devices. A means of oriented immobilization of monoclonal antibodies on the surface of gold using a multilayer film of copper aminopentacyanoferrate is developed. For the model proteins of studied markers, the calibrating curves (maximum sensitivity of 0.5 μg/ml) are obtained, and the level of fibrinogen in blood plasma of donors is determined. A four-channel modification of the device with an application of a reference channel for comparing the elimination of the noise of temperature fluctuations has been constructed. This device allows one to execute the express-diagnostics of prethrombotic states and the monitoring of the therapy of diseases of the blood circulation system.
The goal of a present research is to develop a method for production of multilevel Diffractive Optical Elements
(DOEs) for use in Digital Security Holograms, using the direct-writing maskless lithography system.
The results of experimental and theoretical investigations aimed at applying non-organic photoresists for mastering optoelectronic devices are represented. Samples for investigations were prepared using thermal evaporation of the glass with different As-S-Se compositions in vacuum onto a glass substrate. When exposing photoresist to obtain interference 2D/3D patterns, we used He-Cd laser irradiation with the wavelength 440 nm. The exposure was chosen from 20 to 150 mJ/cm2, and spatial frequencies of obtained gratings were from 600 to 3600 mm-1. The resist samples were processed using a waterless organic selective etchant based on amines. Results of investigations showed that As40S60-xSex (x=0-20) photoresist is characterized by higher holographic sensitivity (i.e. energetic expose necessary for providing given value of the diffraction efficiency). This enables us to create various combined optical-digital protective elements and master-copies for all types of optical disks (CD, DVD).
The represented work is aimed at the problem of optimization of optical biosensors based on the surface plasmon
resonance (SPR) effect in thin gold films. Using it, one can characterize biomolecular interactions by detection of the
resonance angle shift in a real time scale without any labels.
To provide reliable operation of a sensor chip, we deposited a sensitive gold film onto glass substrates using an
intermediate chromium layer capable to improve adhesion of the following layers. Performed is the analysis of the
chromium layer influence on structural and optical properties of the gold film as well as on processes of transducer
regeneration after operation cycles.
The influence of low-temperature annealing (80÷300°C) on gold film properties was investigated. As it was observed with
SPR spectroscopy and atomic force microscopy, minimal energy losses during excitation of surface polariton states as well
as smoothing the small-scale relief of polycrystalline gold surface are reached with annealing temperatures close to 120°C.
It is these samples that provide formation of defectless self-organized thiol monolayers, which results in stabilization and
passivation of SPR transducer sensitive surface.
Modification of the transducer gold surface with a monolayer matrix system containing two types of mercaptanes of
different lengths and structure enabled to realize the idea of molecular recognizing some low-molecular compounds
(barbituric acid) against the background of close structural analogs (veronal).
To avoid influence of non-specific sorption, for the first time, we used the electrochemically deposited films of nickel
hydroxide Ni(OH)2.
The work is devoted to investigations of physical and chemical processes taking place at the boundary between a thin gold film subjected to low-temperature annealing and gas or liquid media. Besides, the work is aimed to research formation of protective, stabilizing and orienting ones in optimization of characteristics inherent to biochemical sensors based on the effect of optical excitation of the surface electromagnetic wave in the thin gold film as well as in investigations of the reflection angular function when using the mode of attenuated internal total reflection. Shown is the necessity to apply the procedure of 120°C temperature annealing that can result in smoothing a small-scale relief of the gold surface and obtaining some optimal parameters of a resonance curve as well as in formation of defectless protective and stabilizing nano-dimensional layers. To protect gold surface, studied are several mechanisms of layer formation in the cases of gold thiolate and gold sulfide. The way of oriented fixation of a sensitive molecular layer using the non-organic cooper aminopentacyanoferrate layer is worked out.
The formation of AuxSy interfacial layer by reactive annealing of gold films in H2S atmosphere is investigated. This seems to be a technologically favorable technique for the large-scale and low-cost fabrication of nondestructive immobilization support for biological molecules. Formation of phases with different chemical functionality and surface topography as a function of reaction time was studied using Atomic Force Microscopy (AFM), Surface Plasmon Resonance (SPR) measurements and biomolecular interaction analysis [trypsin -- Soybean Trypsin Inhibitor (STI) reaction]. The results obtained confirm the classical two-step model for the sulfide phase formation during reactive annealing. This includes an intermediate formation of a dispersed phase of sulfur followed by its reconstruction to a close-packed sulfide layer. Adsorption of proteins onto a certain sulfide layer passes with retention of a native state of adsorbed molecules. The proposed strategy for formation of biochemical structures (gold/sulfide/proteins) on the surface of physical transducers open a new way for design and development of novel artificial smart sensing systems. They not only maintain optimal functioning of bioreceptors but also are responsive to their environment.
Multifractal analysis is performed for description of the surface topography of thin polycrystalline gold film. The film was obtained by thermal evaporation in vacuum. Its structure was modified by annealing at different temperatures in the range 20 - 200 degree(s)C. All films were imaged by Atomic Force Microscopy. Image was analyzed as a collection of layers taken parallel to the mean surface. Fractal subsets with different scaling properties were described by multifractal divergence (e.g. the difference between maximal and minimal values of the f((alpha) ) spectrum). This allowed us to highlight the effect of the temperature of film annealing on the surface structure. We found that fractal diversity jumps down in the temperature range 130 divided by 140 degree(s)C. Therefore, phase transition occurs in the system. Below the temperature of the phase transition the surface topography is characterized by high roughness and existence of small-scale irregularities. The melting also results in a decrease of the surface roughness due to the flowing down of gold crystallites. We also illustrate that surface transformation under low-temperature annealing changes the power spectral density and probability distribution of height functions.
The peculiarities of interfacial structure of self-assembled layer of dodecanthiol on the gold surface determined by quasi-elastic light scattering were employed to probe the lateral distribution and preferred orientation of the thiol molecules within the monolayer. The analysis of Angle Resolved Scattering in the framework of theoretical description involving both scattering on surface roughness and nonuniformities of dielectric permittivity of the near- surface layer allowed to establish the presence of correlation in counterphase between distribution of the thickness of the thiol coating and the relief of the gold surface. The distribution of the scatters in the thiol film is similar to that in as-deposited film of gold that is evidence of the dominant role of the structure of the relief of gold film in formation of the thiol layers. The formation of thiol layer on surface of polycrystalline gold is a complex process including adsorption, local self-assembly and surface-induced distortion of organized structure primary in the region of surface cavities. This study confirmed the utility of the proposed approach based on the nondestructive analysis of organized interfacial layers for detection spatial distribution and chemical functionality of self-assembled monolayers in practical sensing devices.
The interaction of DD-fragment of fibrinogen with antibodies immobilized on the surface of polycrystalline gold films monoclonal has been studied by means of Surface Plasmon Resonance (SPR) biosensor instrument as a model system for real-time biomolecular interaction analysis. A BioHelper Plasmon-002 device (ISP NASU, Kiev, Ukraine), that exploits the SPR phenomenon to detect the interactions between sensor layer and analyte has been used for investigation. The results show that the kinetic parameters of antigen-antibody interactions are directly related to concentration of DD- fragment of fibrinogen in the examined solutions in the range from 102 to 105 ng/ml. The binding kinetic data can be described by a set of several time-division binding equilibrium, each of them correlated well with an ideal binding first-order reactions. The influence of the procedure of antibody immobilization on the quasi flat gold surface has been examined as well.
Surface plasmon resonance (SPR) is a technique, which is extremely sensitive for changes of dielectric characteristic of thin biology layers, present on top of metals, which supports SPR. This fact defines increased interest to development of immunosensors, based on this effect. The working characteristics of such sensors are dependent on many factors, both physic peculiarity and stable surface characteristics of the metal layer, which supports plasmon oscillation (silver, gold), is primary. The experiments show that type of treatment of glass substrate can change significant silver properties such as plasmon carrier and define character of absorption activity to protein molecules. Sensitivity of SPR immunosensors for change of adsorption cover thickness dependents of pH and ionic strength of protein solution also of silver surface hydrophilicity or hydrophobicity. In particular, we see a bovine serum albumin (BSA) adsorption maximum for such technology parameters: ion-plasma treatment before silver evaporation on the glass slides, pH equals 5, ion strength 20 mmol, and the surface of the silver must be highly hydrophobic.
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