P1.3 - Immune-Enzymatig Biosensors Based on the Oxide Cerium Isfets: Some Physical and Functional Characteristics at the Determination of Simazine and T2-Mycotoxin

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
P1 - Medical / Bio-Sensors
N. Starodub - , National University of Life and Environ¬mental Sciences, Kiev (Ukraine), A. Shmiryeva - Kiev National Technical University (Ukraine)
680 - 685


Input and output characteristics of the IsFET’s with the Si3N4 and CeOх dielectrics shown the increasing of the pH-sensitivity in the respect of the drain current in case of the CeOх. It is due to high density of the surface sensitive centers (up to 1020 м -2), large level of the permittivity (ε = 26) and the band-gap energy (3.6 eV) of cerium. All these effects lead to decreasing of the current losses through the dielectric.
The CeOx IsFETs had the increased pH-sensitivity (about 58 mV/pH) that was near to the maximal possible index (59 mV/pH) for the structures of the semiconductor-insulator-solution. We tested the efficiency of this structure at the control of herbicide simazine and such toxic substances as mycotoxin T2 in the model solution. Analysis was fulfilled in two way: competitive and so called “to saturation”. In first one simazine or mycotoxin T2 labeled by horse radish peroxidase (HRP) competed with that which should be analyzed. In second one at first the immobilized Ab interacted with simazina or mycotoxin T2 in the sample and then with the solution of this analyte but labeled by HRP. The activity of HRP was registered in the presence of the special working buffer containing tris-HCl (pH 7.5), NaCl, ascorbic acid and H2O2. The concentrations of the HRP–simazine or T2 conjugates were varied in the range 0.05–0.4 μg ml−1 and it was found that the maximal sensor output (about 100 mV) corresponded to 0.1 μg ml-1 of the conjugate. The concentration of the above mentioned HRP-labeled substances during the competitive analysis was equal to 0.1 μg ml-1. Reliable decrease of the sensor signal was observed down to 1.0 and 3.0 ng ml-1 of simazine and T2 mycotoxin in the analyzed mixture, accordingly. The linearity of signal decrease was observed in the range of T2 mycotoxin concentrations from 5 to 190 ng ml-1. The similar situation was occurred in case of simazine (2-150 ng ml- 1). The overall time of the assay including the duration of all preparation stages was 30 min. The limiting stage of the analysis is the competition between the labeled and native substances for binding with Ab (up to 10 min). In case of the analysis by “to saturated way” allowed reaching sensitivity 0.5 ng ml-1 and linearity in the range 1.0-200 ng ml-1 and 0.5-170 for T2 mycotoxin and simazine, respectively. The overall time of the incubations was the same 10 min (5 min for the staying chip in the solution of the native and the labeled substances). There is necessary to note that the sensitivity and the stability of the biosensors based on the Si3N4 and CeOx IsFETs are much better for last one.