Recent advances of ratiometric sensors in food matrices: mycotoxins detection.

The public health problem caused by mycotoxins contamination has received a great deal of attention worldwide. Mycotoxins produced by filamentous fungi widely distributed in foodstuffs can cause adverse impacts on humans and livestock, posing serious health threats. Particularly worth mentioning is that mycotoxins can accumulate in organisms and be enriched through the food chain. Improving early trace detection and control from the source is a more desirable approach than the contaminated food disposal process to ensure food safety. Conventional sensors are susceptible to interference from various components in intricate food matrices when detecting trace mycotoxins. The application of ratiometric sensors avoids signal fluctuations, and reduce background influences, which casts new light on developing sensors with superior performance. This work is the first to provide an overview of the recent progress of ratiometric sensors in the detection of mycotoxins in intricate food matrices, and highlight the output types of ratiometric signal with respect to accurate quantitative analysis. The prospects of this field are also included in this paper and are intended to have key ramifications on the development of sensing detection conducive to food safety.

An ultrasensitive ratiometric aptasensor based on the dual-potential electrochemiluminescence of Ru(bpy)32+ in a novel ternary system for detection of Patulin in fruit products.

To sensitively monitor trace-level of toxic patulin (PAT), an ultrasensitive PAT ratiometric aptasensor based on the dual-potential electrochemiluminescence (ECL) of Ru(bpy)32+ was first proposed. Noteworthily, Ru(bpy)32+-doped trimetallic nanocube (Ru@Tri) innovatively integrated the luminophore and cathode coreaction accelerator (CCA), which could generate strong cathodic ECL in the existence of low concentration of K2S2O8. Simultaneously, anthocyanin-derived carbon quantum dots (anth-CQDs) prepared from purple potato skins was first served as a green anodic coreactant. And SiO2-coated anth-CQDs (anth-CQDs@SiO2) exhibited excellent performance for enhancing anodic ECL of Ru@Tri. Based on this, a novel ternary ECL system was established. In the presence of PAT, the ECL intensity ratio of anode to cathode (IECL-A/IECL-C) was significantly increased, and a low detection limit of 0.05 pg mL-1 was obtained. Moreover, when proposed method and high performance liquid chromatography (HPLC) were simultaneously applied to series of fruit products, the obtained results were completely consistent, reflecting its practicability.

A replacement-type electrochemiluminescent aptasensor for lysozyme based on full-electric modification electrode coupled to silica-coated Ru(bpy)32+/silver nanospheres.

This research proposed a replacement-type electrochemiluminescent (ECL) aptasensor for lysozyme (LYZ) detection at trace levels based on a full-electric modification electrode (FEMG) coupled to silica-coated Ru(bpy)32+/silver nanospheres (Ru/SNs@SiO2). The multi-walled carbon nanotubes-doped-thionine (MWCNTs/PTn) electropolymerized modified electrode was decorated with electrodeposited gold nanoparticles (GNs) to form the FEMG. Then, the FEMG was utilized as sensing substrates for the immobilization of the anti-lysozyme aptamer (LA); the stability and number of LA attaching onto the FEMG were dramatically increased. The ECL measurement was used to evaluate the hybridization reaction of LA and the Ru/SNs@SiO2 marked DNA probe, and it was noted as Ia. After the combination of the LA with the LYZ, the target-triggered replacement of the DNA probe was actualized and the ECL measurement descended to Ib. The ECL difference (ΔIECL = Ia - Ib) before and after the replacement event was utilized for quantitation of LYZ. As a result, the fabricated aptasensor with great sensitivity and specificity achieved a wide linear range (10 fM-10 pM) and a low limit of detection (5 fM). It obtained satisfactory recovery for the detection of LYZ in human serum, and the results were identified with the LYZ ELISA kit. Therefore, the proposed ECL sensor is expected to become a promising approach in the field of biomolecule detection.

An excellent electrochemical aptasensor for amyloid-ß oligomers based on a triple-helix aptamer switch via target-triggered signal transduction DNA displacement events.

An excellent aptasensor for electrochemical detection of amyloid-ß oligomers (AßOs) at trace levels was fabricated based on a triple-helix aptamer switch (THAS) via target-triggered signal transduction DNA displacement events. Specifically, a single-stranded anti-AßO aptamer (Apt) carrying two symmetrical arm segments was first attached via Au-S binding to an Au electrode. Gold nanoparticle (GNP)-tagged signal transduction probes (GNP-STPs) were simultaneously hybridized with the two arm segments of the Apt, and a rigid THAS was formed on the Au electrode. Compared to the conventional hybrid, the number of GNPs on the Au electrode increased significantly with the THAS, effectively improving the stability of the Apt to avoid lodging. Trithiocyanuric acid (TA) was utilized to further gather the GNPs and form network-like TA/GNPs. As a result, the differential pulse voltammetry (DPV) response of GNPs was clearly enhanced. When AßOs were present, target-triggered signal transduction DNA displacement events were carried out from THAS via the reaction of the Apt with the AßOs, which caused the GNP-STP to dissociate from the Au electrode, and thus a significant reduction in the DPV response was observed. The assay was able to sensitively detect trace AßOs by monitoring the AßO-controlled DPV response change. It exhibited a wide linear range from 1 fM to 10 pM with a low detection limit of 0.5 fM, and was successfully employed for the determination of AßOs in 20 serum samples, with good recovery. Moreover, the developed assay can provide a sensitive and selective platform for many studies or investigations related to Alzheimer's disease (AD) monitoring and treatment.

Recent Advances in Ochratoxin A Electrochemical Biosensors: Recognition Elements, Sensitization Technologies, and Their Applications.

Ochratoxin A (OTA) is a class of mycotoxin that are mainly produced by Aspergillus and Penicillium and widely found in plant origin food. OTA-contaminated foods can cause serious harm to animals and humans, while high stability of OTA makes it difficult to remove in conventional food processing. Thus, sensitive and rapid detection of OTA undoubtedly plays an important role in OTA prevention and control. In this paper, the conventional and novel methods of OTA at home and abroad are summarized and compared. The latest research progress and related applications of novel OTA electrochemical biosensors are mainly described with a new perspective. We innovatively divided the recognition element into single and combined recognition elements. Specifically, signal amplification technologies applied to the OTA electrochemical aptasensor are proposed. Furthermore, summary of the current limitations and future challenges in OTA analysis is included, which provide reference for the further research and applications.