Fabrication of a disposable aptasensing chip for simultaneous label-free detection of four common coexisting mycotoxins

Self-designed portable dual-mode fluorescence device with custom python-based analysis software for rapid detection via dual-color FRET aptasensor with IoT capabilities

An innovative aptasensor incorporating MoS2-modified bicolor quantum dots and a portable spectrometer, designed for the simultaneous detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1) in corn was developed. Carbon dots and CdZnTe quantum dots were as nano-donors to label OTA and AFB1 aptamers, respectively. These labeled aptamers were subsequently attached to MoS2 receptors, enabling fluorescence resonance energy transfer (FRET). With targets, the labeled aptamers detached from the nano-donors, thereby disrupting the FRET process and resulting in fluorescence recovery. Furthermore, a portable dual-mode fluorescence detection system, complemented with customized python-based analysis software, was developed to facilitate rapid and convenient detection using this dual-color FRET aptasensor. The developed host program is connected to the spectrometer and transmits data to the cloud, enabling the device to have Internet of Things (IoT) characteristics. Connected to the cloud, this IoT-enabled device offers convenient and reliable fungal toxin detection for food safety.

Simultaneous detection of multiple mycotoxins using MXene-based electrochemical aptasensor array and a self-developed multi-channel portable device

In response to the pressing need for highly efficient simultaneous detection of multiple mycotoxins, which are often found co-occurring in food raw materials and feed, an MXene-based electrochemical aptasensor array (MBEAA) was developed. This aptasensor array utilizes high-specificity aptamers as recognition elements, enabling the capture of electrical signal changes in the presence of target mycotoxins. Based on this platform, a multi-channel portable electrochemical device, enabling rapid, cost-effective, and simultaneous detection of aflatoxin B1 (AFB1), ochratoxin A (OTA), and zealenone (ZEN) was further developed. The developed system boasts a wide detection range of 1.0 × 10-1 to 10.0 ng mL-1, with remarkable performance characterized by ultra-low detection limits of 41.2 pg mL-1, 27.6 pg mL-1, and 33.0 pg mL-1 for AFB1, OTA, and ZEN, respectively. Successfully applied in corn samples, this method offers a portable, easy-to-operate, and cost-effective solution for simultaneous multi-mycotoxin detection. Moreover, the application of the self-developed detection system could be expanded for simultaneous detection of many different targets when their specific aptamers or antibodies were available.

Magnetic metal-organic frameworks as sensitive aptasensors for coronavirus spike protein

Electrochemical biosensors, known for their low cost, sensitivity, selectivity, and miniaturization capabilities, are ideal for point-of-care devices. The magnetic metal-organic framework (MMOF), synthesized using the in-situ growth method, consists of ferric salt, magnetic nanoparticles, histidine, and benzene tetracarboxylic acid. MMOF was sequentially modified with aptamer-biotin and streptavidin-horseradish peroxidase, serving as a detector for spike protein and a transducer converting electrochemical signals using H2O2-hydroquinone on a screen-printed electrode. MMOF facilitates easy washing and homogeneous deposition on the working electrode with a magnet, enhancing sensitivity and reducing noise. The physical and electrochemical properties of the modified MMOFs were thoroughly characterized using various analytical techniques. The aptasensors' performance achieved a detection limit of 6 pM for voltammetry and 5.12 pM for impedance spectroscopy in human serum samples. This cost-effective, portable MMOF platform is suitable for rapid point-of-care testing for SARS-CoV-2 spike proteins.

Dual modal improved enzyme-linked immunosorbent assay for aflatoxin B1 detection inspired by the interaction of amines with Prussian blue nanoparticles

This work reports an improved enzyme-linked immunosorbent assay (ELISA) via the interaction between prussian blue nanoparticles (PBNPs) and amines for aflatoxin B1 (AFB1) detection. The effect of different amines on the structure and properties of PBNPs was systematically investigated. Amines with pKb < 7, like ethylenediamine (EDA), can decompose structure of PBNPs, leading to the reduction of extinction coefficient and photothermal effect. Whereas, amines with large pKb > 7, such as o-phenylenediamine (OPD), could undergo catalytic oxidation by PBNPs, resulting in the production of fluorescent and colored oxidation products. Accordingly, EDA and OPD were used to construct improved ELISA. Specifically, silica nanoparticles, on which AFB1 aptamer and amino binding agent (ethylenediaminetetraacetic acid disodium salt, EDTA•2Na) were previously assembled via carboxyl-amino linkage, are anchored to microplates by AFB1 and antibody. EDA concentration can be regulated by EDTA•2Na to affect extinction coefficient and photothermal effect of PBNPs, thereby achieving visual colorimetric and portable photothermal signal readout (Model 1). OPD concentration can also be controlled by EDTA•2Na, thus generating colorimetric and ultrasensitive fluorescent signals through PBNPs catalysis (Model 2). The proposed strategy not only opens new avenue for signal readout mode of biosensing, but also provides universal technique for hazards.

DNA-induced assembly of biocatalytic nanocompartments for sensitive and selective aptasensing of aflatoxin B1

Enzyme cascade with high specificity and catalytic efficiency has significant applications for developing efficient bioanalysis methods. In this work, a sensitive and selective aptasensor was constructed based on the DNA-induced assembly of biocatalytic nanocompartments. Different from the conventional co-immobilization in one pot, the cascade enzymes of glucose oxidase (GOX) and horseradish peroxidase (HRP) were separately encapsulated in ZIF-90 nanoparticles. After conjugating complementary DNA or aptermer on enzyme@ZIF-90, DNA hybridization drove enzyme@ZIF-90 connected into clusters or linked on other DNA modified biocatalytic nanocompartment (such as invertase loaded Fe3O4@SiO2). Owing to the shortened distance between enzymes, the catalytic efficiency of connected clusters was significantly enhanced. However, the specifically interaction between the substrate molecule and aptermer sequence would lead to the disassembly of DNA duplexes, resulting in the gradual "switching-off" of cascade reactions. With aflatoxin B1 (AFB1) as the model substrate, the compartmentalized three-enzyme nanoreactors showed good analytical performance in the linear range from 0.01 ng mL-1 to 50 ng mL-1 with a low detection limit (3.3 pg mL-1). In addition, the proposed aptasensor was applied to detect AFB1 in corn oil and wheat powder samples with total recoveries ranging from 94 % to 109 %. As a result, this DNA-induced strategy for enzyme cascade nanoreactors opens new avenues for stimuli-responsive applications in biosensing.