[INVITED] Novel optical biosensing technologies for detection of mycotoxins

This work reviews our recent progress in development of novel optical methods of detection of mycotoxins in direct assay with either specific antibodies or aptamers. The main method in this work was the total internal reflection ellipsometry (TIRE) combined with LSPR transducers based on gold nano-structures produced by annealing of thin gold films. The gold nano-islands produced were characterised with SEM, AFM, UV–visible absorption spectroscopy, and spectroscopic ellipsometry. The combination of TIRE and LSPR offers superior refractive index sensitivity as compared to traditional UV–vis absorption spectroscopy. The limitations of LSPR related to a short evanescent field decay length can be overcome using small-size bio-receptors, such as half-antibodies and aptamers. The achieved sensitivity of detection of mycotoxins in 0.01 ppb level of concentration is sufficient for the use of this method for analysis of agriculture products, food and feed on the presence of mycotoxins. Even higher sensitivity in sub-ppt level was achieved with another optical biosensor developed recently; it is based on optical planar waveguide operating as polarization interferometer (PI). This method is promising for development of portable, highly sensitive, and simple to use biosensors suitable for point-of-need detection of mycotoxins

Highly sensitive label-free in vitro detection of aflatoxin B1 in an aptamer assay using optical planar waveguide operating as a polarization interferometer

This work reports on further development of an optical biosensor for the in vitro detection of mycotoxins (in particular, aflatoxin B1) using a highly sensitive planar waveguide transducer in combination with a highly specific aptamer bioreceptor. This sensor is built on a SiO2–Si3N4–SiO2 optical planar waveguide (OPW) operating as a polarization interferometer (PI), which detects a phase shift between p- and s-components of polarized light propagating through the waveguide caused by the molecular adsorption. The refractive index sensitivity (RIS) of the recently upgraded PI experimental setup has been improved and reached values of around 9600 rad per refractive index unity (RIU), the highest RIS values reported, which enables the detection of low molecular weight analytes such as mycotoxins in very low concentrations. The biosensing tests yielded remarkable results for the detection of aflatoxin B1 in a wide range of concentrations from 1 pg/mL to 1 μg/mL in direct assay with specific DNA-based aptamers

Automated oligonucleotide solid-phase synthesis on nanosized silica particles using nano-on-micro assembled particle supports

International audienceThis article describes an original strategy to enable solid-phase oligodeoxyribonucleotide (ODN) synthesis on nanosized silica particles. It consists of the reversible immobilization of silica nanoparticles (NPs) on micrometric silica beads. The resulting assemblies, called nano-on-micro (NOM) systems, are well adapted to ODN synthesis in an automated instrument. First, NPs are derivatized with OH functions. For NOM assembly preparation, these functions react with the silanols of the microbeads under specific experimental conditions. Furthermore, OH groups allow ODN synthesis on the nanoparticles via phosphoramidite chemistry. The stability of the NOM assemblies during ODN solid-phase synthesis is confirmed by scanning and transmission electron microscopy (SEM and TEM, respectively), together with dynamic light scattering analyses. Then, the release of ODN-functionalized nanoparticles is performed under mild conditions (1% NH4OH in water, 1 h, 60 °C). Our technique provides silica nanoparticles well functionalized with oligonucleotides, as demonstrated by hybridization experiments conducted with the cDNA target