Evanescent Wave Optical-Fiber Aptasensor for Rapid Detection of Zearalenone in Corn with Unprecedented Sensitivity

Abstract

Zearalenone (ZEN) is a common mycotoxin pollutant found in agricultural products. Aptamers are attractive recognition biomolecules for the development of mycotoxin biosensors. Even though numerous aptasensors have been reported for the detection of ZEN in recent years, many of them suffer from problems including low sensitivity, low specificity, tedious experimental steps, high-cost, and difficulty of automation. We report here the first evanescent wave optical-fiber aptasensor for the detection of ZEN with unprecedented sensitivity, high specificity, low cost, and easy of automation. In our aptasensor, a 40-nt ZEN-specific aptamer (8Z31) is covalently immobilized on the fiber. The 17-nt fluorophore Cy5.5-labeled complementary DNA strand and ZEN competitively bind with the aptamer immobilized on the fiber, enabling the signal-off fluorescent detection of ZEN. The coating of Tween 80 enhanced both the sensitivity and the reproducibility of the aptasensor. The sensor was able to detect ZEN spiked-in the corn flour extract with a semilog linear detection range of 10 pM-10 nM and a limit of detection (LOD, S/N = 3) of 18.4 ± 4.0 pM (equivalent to 29.3 ± 6.4 ng/kg). The LOD is more than 1000-fold lower than the maximum ZEN residue limits set by China (60 μg/kg) and EU (20 μg/kg). The sensor also has extremely high specificity and showed negligible cross-reactivity to other common mycotoxins. In addition, the sensor was able to be regenerated for 28 times, further decreasing its cost. Our sensor holds great potential for practical applications according to its multiple compelling features.

Recent Progress in Functional-Nucleic-Acid-Based Fluorescent Fiber-Optic Evanescent Wave Biosensors

“…The most popularly used route consists of several steps: (1) oxidation to form hydroxyl groups, (2) silanization to convert the hydroxyl groups into an amino group, (3) the transformation of the amino to an aldehyde group by amine aldehyde condensation reaction, (4) covalently coupling the amino-modified nucleic acid probes, and (5) reduction of the less-stable imine bond into a C-N single bond and the unreacted aldehyde groups into hydroxyl groups by NaBH 4 reduction [ 50 ]. Many works use a similar approach to immobilize amino aptamers on the fiber surface with slight differences [ 51 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ]. For examples, glycine [ 60 , 79 ] and NaCNBH 3 [ 60 , 80 ] were used to deplete the remaining aldehyde sites after the coupling of aptamers.…”

“…Different from the target or cDNA-immobilized strategies, the NADL-FOEW sensor enables in situ target enrichment, purification, and sensing on the same surface simultaneously, therefore dramatically improving the LOD down to the unprecedented femtomolar ranges. So far, we have demonstrated the ultrasensitive and specific detection of kanamycin [ 50 ], sulfadimethoxine [ 50 ], di-(2-ethylhexyl) phthalate [ 50 ], zearalenone [ 77 ], sulfonamides [ 71 ], and alternariol [ 72 ] in diverse matrices including environmental water, fresh milk, wine, wheat, and corn extracts. Both the detection sensitivity and the dynamic range all meet the practical applications.…”

“… The separation-free detection of small-molecule targets using FNA-FOEW sensors installed with fibers functionalized by ( A ) target [ 85 , 86 ]; ( B ) cDNA [ 75 ]; ( C ) aptamer [ 71 , 72 , 77 ]; ( D ) cDNA complementary to one of the split aptamer fragments [ 73 ]; or ( E ) one fragment of the split aptamer [ 76 , 80 ]. …”

Recent Advances in Optical Hydrogen Sensor including Use of Metal and Metal Alloys: A Review

“…The basic sensing mechanism of the EF-based hydrogen sensor depends on the interaction of evanescent field at the interface of the optical core fiber and sensing layer. These evanescent field decays exponentially corresponding to increasing the distance from the exposed core, and the attenuation coefficient depends on the refractive index of the fiber cladding [63]. These techniques were exploited to increase the intensity of the evanescent field at interface and improve the light-matter interaction to the hydrogen.…”

Developments in mycotoxin analysis: an update for 2021-22

“…The innate stability of synthetic receptors makes them well-suited for sensor platforms where the limited shelfstability of antibodies could be problematic. Zhao et al (2022) reported on a portable evanescent wave opticalfibre sensor that employed a ZEN specific aptamer as the recognition layer. The sensor consisted of the optical system (laser, optical fibre coupler, filter, photodiode, and signal amplifier) and a fluidic system (peristaltic pump, tubes, reaction chamber).…”