Viter R., Savchuk, M., Iatsunskyi I., Pietralik Z., Starodub N., Shpyrka, N., Ramanaviciene A., Ramanavicius A.
Analytical, thermodynamical and kinetic characteristics of photoluminescence immunosensor for the determination of Ochratoxin A Ochratoxin A (OTA) is one of the most widespread and dangerous food contaminants. Therefore, rapid, label free and precise detection of low OTA concentrations requires novel gensing elements with advanced bioanalytical properties. In the present paper we report photoluminescence (PL) based immunosensor for the detection of OTA. During the development of immunosensor photoluminescent ZnO nanorods (ZnO-NRs) were deposited on glass substrate. Then the ZnO-NRs were silanized and covalently modified by Protein-A (Glass/ ZnO-NRs/Protein-A). The latest structure was modified by antibodies against OTA (Anti-OTA) in order to form OTA-selective layer (Glass/ZnO-NRs/Protein-A/Anti-OTA). In order to improve immunosensors selectivity the surface of Glass/ZnO-NRs/Protein-A/Anti-OTA was additionally blocked by BSA. Formed Glass/ZnO-NRs/ Protein-A/BSA &Anti-OTA structures were integrated within portable fiber optic detection system, what is important for the development of low cost and portable immunosensors. The immunosensor has been tested in a wide range of OTA concentrations from 10(-4) ng/ml until 20 ng/ml. Interaction isotherms were derived from atialytical signals of immunosensor. Association constant and Gibbs free energy for the interaction of Glass/ ZnO-NRs/Protein-A/Anti-OTA with OTA were calculated, analyzed and compared with some other related results. Sensitivity range and limit of detection were determined as 0.1-1 ng/ml and 10(-2) ng/ml, respectively. Interaction kinetics of ZnO-NRs with OTA was evaluated. Response time of the immunosensor toward OTA was in the range of 500-800 s. Some insights related to the mechanism of PL-signal generation are proposed and discussed.
Structural and dynamical study of PDMS and PS based block copolymers Block copolymers represent an interesting class of materials, combining properties of individual components and capable of developing nanoscopic domain morphologies. Copolymers which comprise polystyrene and poly(dimethylsiloxane) attract special attention due to their effective segregation and the highly contrasting thermal properties of individual blocks. This work covers structural studies of copolymeric domain architecture and investigates the molecular dynamics observed in bulk PDMS, diblock PS-PDMS and triblock PS-PDMS-PS. Utilization of atomic force microscopy and NMR spin diffusion provide a thorough picture of phase separated systems. Dielectric spectroscopy reveals the dynamic heterogeneity of PDMS amorphous phase. Two distinct structural relaxations, namely ? and ?c, were observed and attributed correspondingly to PDMS mobile amorphous fraction and PDMS rigid amorphous fraction. Unexpectedly, the segmental reorientations observed in the case of copolymers were faster that that observed for bulk PDMS.