A Non-Enzyme and Non-Label Sensitive Fluorescent Aptasensor Based on Simulation-Assisted and Target-Triggered Hairpin Probe Self-Assembly for Ochratoxin a Detection

Development and analysis of a universal label-free micro/nano component for three-channel detection of silver ions, mercury ions, and tetracycline

In this paper, an enzyme-free and label-free fluorescent nanomodule is proposed for rapid, simple and sensitive detection of Ag+, Hg2+ and tetracycline (TC). The strategy is cleverly designed to enable multiple-purpose detection with as little as 31 nt of ssDNA. Both the embedded dye SYBR Green I and the nanomaterial graphene oxide (GO) are able to distinguish single-stranded DNA from double-stranded DNA; thus, the combination of the two instead of using traditional molecular beacon (MB)-labeled fluorophores and quencher groups can effectively reduce the cost of experiments while efficiently reducing the background noise. Performance testing experiments confirmed the stability and selectivity of the platform; the limits of detection (LODs) of Ag+ and Hg2+ were 1.41 nM and 1.79 nM, respectively, and the detection range were within the WHO standards. In addition, only some base sequences in the flexible functional domain of the nanoloop needed to be programmed to build a universal platform, which was feasible using TC as a target. Therefore, the designed nanomodule has the potential to detect various types of targets, such as antibiotics, proteins, and target genes, and has broad application prospects in environmental monitoring, food testing, and disease diagnosis.

Fluorescence-based aptasensors for small molecular food contaminants: From energy transfer to optical polarization

Small molecular food contaminants, such as mycotoxins, pesticide residues and antibiotics, are highly probable to be passively introduced in food at all stages of its processing, including planting, harvest, production, transportation and storage. Owing to the high risks caused by the unknowing intake and accumulation in human, there is an urgent need to develop rapid, sensitive and efficient methods to monitor them. Fluorescence-based aptasensors provide a promising platform for this area owing to its simple operation, high sensitivity, wide application range and economical practicability. In this paper, the common sorts of small molecular contaminants in foods, namely mycotoxins, pesticides, antibiotics, etc, are briefly introduced. Then, we make a comprehensive review, from fluorescence resonance energy transfer (in turn-on, turn-off, and ratiometric mode, as well as energy upconversion) to fluorescence polarization, of the fluorescence-based aptasensors for the determination of these food contaminants reported in the last five years. The principle of signal generation, the advances of each sort of fluorescent aptasensors, as well as their applications are introduced in detail. Additionally, we also discussed the challenges and perspectives of the fluorescent aptasensors for small molecular food contaminants. This work will offer systematic overview and inspiration for amateurs, researchers and developers of fluorescence-based aptasensors for the detection of small molecules.

Signal enhancing strategies in aptasensors for the detection of small molecular contaminants by nanomaterials and nucleic acid amplification

Small molecular contaminants (such as mycotoxins, antibiotics, pesticide residues, etc.) in food and environment have given rise to many biological and ecological toxicities, which has attracted worldwide attention in recent years. Meanwhile, due to the advantages of aptamers such as high specificity and stability, easy synthesis and modification, as well as low cost and immunogenicity, various aptasensors for the detection of small molecular contaminants have been flourishing. An aptasensor as a whole is composed of an aptamer-based target recognizer and a signal transducer, which are fields of concentrated research. In the practical detection applications, in order to achieve the quantitative detection of small molecular contaminants at low abundance in real samples, a large number of signal enhancing strategies have been utilized in the development of aptasensors. Recent years is a vintage period for efficient signal enhancing strategies of aptasensors by the aid of nanomaterials and nucleic acid amplification that are applied in the elements for target recognition and signal conversion. Therefore, this paper meticulously reviews the signal enhancing strategies based on nanomaterials (including the (quasi-)zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanomaterials) and nucleic acid amplification (including enzyme-assisted nucleic acid amplification and enzyme-free nucleic acid amplification). Furthermore, the challenges and future trends of the abovementioned signal enhancing strategies for application are also discussed in order to inspire the practitioners in the research and development of aptasensors for small molecular contaminants.

Contribution of Nanomaterials to the Development of Electrochemical Aptasensors for the Detection of Antimicrobial Residues in Food Products

The detection of antimicrobial residues in food products of animal origin is of utmost importance. Indeed antimicrobial residues could be present in animal derived food products because of animal treatments for curative purposes or from illegal use. The usual screening methods to detect antimicrobial residues in food are microbiological, immunological or physico-chemical methods. The development of biosensors to propose sensitive, cheap and quick alternatives to classical methods is constantly increasing. Aptasensors are one of the major trends proposed in the literature, in parallel with the development of immunosensors based on antibodies. The characteristics of electrochemical sensors (i.e., low cost, miniaturization, and portable instrumentation) make them very good candidates to develop screening methods for antimicrobial residues in food products. This review will focus on the recent advances in the development of electrochemical aptasensors for the detection of antimicrobial residues in food products. The contribution of nanomaterials to improve the performance characteristics of electrochemical aptasensors (e.g., Sensitivity, easiness, stability) in the last ten years, as well as signal amplification techniques will be highlighted.

Recent Progress and Development of G-Quadruplex-Based Luminescent Assays for Ochratoxin A Detection

Ochratoxin A (OTA) is a mycotoxin that is widespread throughout the world. It contaminates foods such as vegetables, fruits, and rice. It harms human health and has potential carcinogenic effects. The G-quadruplex (G4) is a tetraplexed DNA structure generated from guanine-rich DNA that has found emerging use in aptamer-based sensing systems. This review outlines the status of OTA contamination and conventional detection methods for OTA. Various G4-based methods to detect OTA developed in recent years are summarized along with their advantages and disadvantages compared to existing approaches.