Detection of Cadmium(II) in Aquatic Products Using a Rolling-Circle Amplification-Coupled Ratio Fluorescent Probe Based on an Aptamer–Peptide Conjugate

Abstract

The existing aptamers for cadmium (Cd 2+ ), the common toxic heavy metal contaminant in food, cannot meet the requirements for detecting Cd 2+ in rapid detection methods. In previous work, we found that coupling aptamer−peptide conjugates (APCs) with peptides and aptamers can provide a less disruptive method with a significantly improved affinity. Moreover, we found that the spatial conformation of aptamers and peptides is crucial for obtaining proper affinity in APC. Therefore, we describe a simple design strategy to obtain a series of APCs with different affinities by designing peptide orientations (N-terminal, C-terminal). The best affinity was found for APC(C1−N) with a binding constant (K a ) of 2.23 × 10 6 M −1 , indicating that the APC(C1−N) affinity was significantly increased by 829.17% over aptamer. Finally, a rolling-circle amplification (RCA)-coupled ratio fluorescencebased biosensor for Cd 2+ detection was established with a detection limit of 0.0036 nM, which has great potential for practical aquatic product detection.

An Ochratoxin a DNA Aptamer-Mediated Transcriptional Regulatory Riboswitch Biosensor

“…Ochratoxin A (OTA) is a toxic secondary metabolite mainly produced by Penicillium verrucosum and Aspergillus carbosporus and is present in foods such as cereals, grapes, coffee, spices, and cocoa. − OTA has cumulative toxicity, so animals ingesting feed contaminated with OTA may result in OTA residues in animal-derived foods, further affecting human health throughout the food chain. − Therefore, it is always necessary to establish an analysis method that is simple, fast, and sustainable and can be directly detected at the sampling location.…”