Abstract
This work focuses on the development of the novel label-free optical apta-sensors for detection of mycotoxins. A highly sensitive analytical method of total internal reflection ellipsometry (TIRE) combined with Localized Surface Plasmon Resonance (LSPR) phenomenon in nano-structured gold films was exploited here for the first time for detection of aflatoxin B1 and M1 in direct assay with specific aptamers immobilized on the surface of gold. The achieved detection of low molecular weight molecules, such as aflatoxin B1 and M1, in a wide range of concentrations from 100 ng/mL down to 0.01 ng/mL is remarkable for the LSPR method. The study of binding kinetics of aflatoxin molecules to their respective aptamers using dynamic TIRE measurements yielded the values of affinity constants in the range of 10−8–10−7 mol, which is characteristic for highly specific aptamer/target interactions similar to that for monoclonal antibodies. The effect of aptamers’ DNA chain length on their binding characteristics was analyzed.
Highlights
This work is dedicated to the detection of mycotoxins produced by different fungi species that may grow on various agricultural products, such as grains, nuts, coffee beans, spices, fruits, and associated food and animal feed, stored at inappropriate conditions, i.e., elevated temperatures and high humidity [1]
Optical biosensors lead this development with a number of biosensors based on the different instrumentation and principles (i.e., Surface Plasmon Resonance (SPR), Total Internal Reflection Ellipsometry (TIRE), Optical Waveguide Lightmode Spectroscopy (OWLS), Mach–Zehnder (MZ) interferometers, etc.) [3]
We recently reported on the use of aptamers in conjunction with the total internal reflection ellipsometry (TIRE) method for the detection of ochratoxin A
Summary
This work is dedicated to the detection of mycotoxins produced by different fungi species that may grow on various agricultural products, such as grains, nuts, coffee beans, spices, fruits, and associated food and animal feed, stored at inappropriate conditions, i.e., elevated temperatures and high humidity [1]. Toxins 2018, 10, 291 suitable for express and cost-effective detection of mycotoxins is of great demand nowadays [3] Optical biosensors lead this development with a number of biosensors based on the different instrumentation and principles (i.e., Surface Plasmon Resonance (SPR), Total Internal Reflection Ellipsometry (TIRE), Optical Waveguide Lightmode Spectroscopy (OWLS), Mach–Zehnder (MZ) interferometers, etc.) [3]. We would like to highlight the method of total internal reflection ellipsometry (TIRE) which was developed in the last 10–15 years, as a highly sensitive analytical tool in bio-sensing, attractive for the detection of low molecular weight analytes, and mycotoxins in particular [4,5,6,7,8] Another interesting optical phenomenon of localized surface plasmon resonance (LSPR) [9] has recently attracted the attention of researches because of its potentially high sensitivity allowing the detection of single molecules [10]. We attempted the detection of aflatoxins B1 and M1 in assay with specific aptamers using a combination of the Localized Surface Plasmon Resonances phenomenon in nanostructured gold films with the method of TIRE
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