A switchable electrochemical hairpin-aptasensor for ochratoxin A detection based on the double signal amplification effect of gold nanospheres

An OTA electrochemical sensor based on h-DNA and the double effect of gold nanospheres that can be applied for actual sample detection.

Establishment of a Chemiluminescence Immunoassay Combined with Immunomagnetic Beads for Rapid Analysis Of Ochratoxin A

BACKGROUND

Ochratoxins A (OTA), as the harmful mycotoxins, are toxic secondary metabolite produced by several species of Aspergillus and Penicillium. Hence, it is of vital important to establish a sensitive method to detect OTA in various grains.

OBJECTIVE

Herein a novel highly sensitive chemiluminescence immunoassay was developed to determination of ochratoxin A in wheat, corn, and poultry feed.

METHODS

The immunomagnetic beads were used as solid phase carrier and separator in the competitive chemiluminescence method, the monoclonal antibodies anti-OTA coated on immunomagnetic beads were applied as the capturing antibody, in which OTA would compete with Ochratoxin A-alkaline phosphatase (OTA-ALP) in binding with OTA antibodies.

RESULTS

The proposed method exhibited good linearity (R2 ≥ 0.999), adequate OTA recovery rate (83.60% to 102.50%), and good repeatability. The sensitivity of the proposed method was 2.05 pg/mL. In addition, the method was highly selective, it did not have cross-reaction with other mycotoxin (e.g., AFB1, DON, ZEN). Furthermore, the developed method was applied in the analysis of wheat, corn and two animal feeds successfully, the results obtained by the chemiluminescence method showed the high correlation with those obtained by HPLC method (correlation coefficient 0.9958) when testing each extract by both methods.

CONCLUSIONS

This strategy shows great potential application for other toxic and harmful mycotoxin detection.

HIGHLIGHTS

A novel highly rapid and sensitive chemiluminescence immunoassay was established to quantitation for ochratoxin A.

DNA walker-assisted aptasensor for highly sensitive determination of Ochratoxin A

Ochratoxin A (OTA), a toxic secondary metabolite produced via various fungus, poses a serious threat to the health of human beings and animals. In this paper, an aptasensor for OTA detection based on gold nanoparticles decorated molybdenum oxide (AuNPs-MoO_x) nanocomposites, hybridization chain reaction (HCR) and a restriction endonuclease (Nb.BbvCI)-aided walker DNA machine was successfully constructed. In this electrochemical platform, the HCR was also used to embed more electrical signal molecules of methylene blue (MB) on silver nanoparticles (AgNPs) to achieve signal amplification. Under the optimum conditions, after adding OTA and Nb.BbvCI in turn and responding adequately under appropriate conditions, aptamer-DNA (6-DNA) carries the OTA away from the electrode surface, and walker DNA was hybridized autonomously with 5-DNA, releasing a large amount of 5'-DNA with the help of Nb.BBVCI. Finally, the electrochemical signal obtained by differential pulse voltammetry (DPV) was weakened. As an artificial and popular signal amplification technique, the DNA walking machine greatly improved the sensitivity. The proposed biosensor exhibited excellent analytical performance in the range of 0.01-10000 pg mL^-1 with a detection limit as low as 3.3 fg mL^-1. Furthermore, direct comparison with ultraperformance liquid chromatography (UPLC) indicates excellent agreement to actual samples such as apple juice, orange juice, red wine and serum.

Trends and Advances in Electrochemiluminescence Nanobiosensors

The rapid and increasing use of the nanomaterials (NMs), nanostructured materials (NSMs), metal nanoclusters (MNCs) or nanocomposites (NCs) in the development of electrochemiluminescence (ECL) nanobiosensors is a significant area of study for its massive potential in the practical application of nanobiosensor fabrication. Recently, NMs or NSMs (such as AuNPs, AgNPs, Fe₃O₄, CdS QDs, OMCs, graphene, CNTs and fullerenes) or MNCs (such as Au, Ag, and Pt) or NCs of both metallic and non-metallic origin are being employed for various purposes in the construction of biosensors. In this review, we have selected recently published articles (from 2014-2017) on the current development and prospects of label-free or direct ECL nanobiosensors that incorporate NCs, NMs, NSMs or MNCs.