Aleksey Nabok

Comparative Studies on Optical Biosensors for Detection of Bio-Toxins

A number of optical bio-sensing methods were reviewed with their principles and main characteristics outlined. The advantages and disadvantages of optical methods were discussed in a view of their application in detection of bio-toxins. A case study presented the comparative analysis of results in detection of mycotoxins obtained with the method of total internal reflection ellipsometry. The future prospects of optical biosensing technologies were discussed with the main focus on development of portable and highly sensitive biosensors suitable for in-field analysis.

Optical detection of microcystin produced by cyanobacteria

Microcystin (MC-LR) produced by cyanobacteria (blue-green algae) was detected in direct immunoassay with specific monoclonal antibody MC10E7 using an optical method of Total Internal Reflection Ellipsometry (TIRE). The minimal detected concentration of MC-LR of 0.1 ng/ml is a remarkable achievement for direct immunoassay against such low molecular weight analyte molecule. The study of binding kinetics of MC-LR to MC10E7 antibody allowed the evaluation of the association constant KA of about 108 (l/Mol) typical for highly specific immune reactions. Concentration of MC-LR in aqueous solutions was reduced using an absorbent made of polyelectrolyte-coated microparticles functionalized with MC10E7 antibodies.

Analysis of Toxic Amyloid Fibril Interactions at Natively Derived Membranes by Ellipsometry

There is an ongoing debate regarding the culprits of cytotoxicity associated with amyloid disorders. Although small pre-fibrillar amyloid oligomers have been implicated as the primary toxic species, the fibrillar amyloid material itself can also induce cytotoxicity. To investigate membrane disruption and cytotoxic effects associated with intact and fragmented fibrils, the novel in situ spectroscopic technique of Total Internal Reflection Ellipsometry (TIRE) was used. Fibril lipid interactions were monitored using natively derived whole cell membranes as a model of the in vivo environment. We show that fragmented fibrils have an increased ability to disrupt these natively derived membranes by causing a loss of material from the deposited surface when compared with unfragmented fibrils. This effect was corroborated by observations of membrane disruption in live cells, and by dye release assay using synthetic liposomes. Through these studies we demonstrate the use of TIRE for the analysis of protein-lipid interactions on natively derived lipid surfaces, and provide an explanation on how amyloid fibrils can cause a toxic gain of function, while entangled amyloid plaques exert minimal biological activity.

Investigation of Zinc phthalocyanine films for QCM sensing applications

A Quartz Crystal Microbalance (QCM) with 1 0 MHz fundamental resonance was used as the sensing element(s) to monitor changes in the properties of Zinc Phthalocyanine (ZnPc) films caused by adsorption of different types of selected organic vapour, such as hexane and benzene. The experimental admittance spectra of (QCM) around resonance were fitted to an equivalent circuit model (BVD circuit) and parameters relating to film thickness and viscosity were extracted. LabVIEW software was used to control the experimental setup and curve fitting. (ZnPc) films with a range of different substitutes were studied. Additionally, characterization of the film properties has been carried out using parameters obtained from QCM measurements in conjunction with suitable data analysis and modeling techniques. Validation of the film properties has been established (thickness and structure) using complementary existing methods such as AFM and Ellipsometry.

Detection of γ-radiation and heavy metals using electrochemical bacterial-based sensor

The main aim of this work is to develop a simple electrochemical sensor for detection of γ-radiation and heavy metals using bacteria. A series of DC and AC electrical measurements were carried out on samples of two types of bacteria, namely Escherichia coli and Deinococcus radiodurans. As a first step, a correlation between DC and AC electrical conductivity and bacteria concentration in solution was established. The study of the effect of γ-radiation and heavy metal ions (Cd2+) on DC and AC electrical characteristics of bacteria revealed a possibility of pattern recognition of the above inhibition factors.

A synthetic biological quantum optical system

Strong coupling between plasmon modes and chlorins in synthetic light-harvesting maquette proteins yields hybrid light–matter states (plexcitons) whose energies are controlled by design of protein structure, enabling the creation of new states not seen under weak coupling.