Label-Free Fluorescence Sensing Strategy Based on Functional Nucleic Acids via Energy Transfer between DNA-Templated Silver Nanoclusters and Gold Nanorods

Abstract

A simple and low-cost fluorescence signal-on sensing strategy has been developed based on functional nucleic acids (FNAs) via energy transfer between DNA-templated silver nanoclusters (DNA-AgNCs) and gold nanorods (GNRs). FNAs were used as highly selective recognition probes, in which an aptamer was used to detect small molecules represented by tetracycline, and DNAzyme was used to detect heavy metal ions represented by Pb2+. The fluorescent DNA-AgNCs were synthesized by the designed oligonucleotide sequences, which consisted of three parts: AgNCs synthesis template C6G5C6, spacer T5, and complementary sequences of the aptamer or enzyme strand. The difference in electrostatic interactions between ss/dsDNA and positively charged GNRs leads to energy transfer with different efficiencies. The analytes represented by tetracycline and Pb2+ can destroy the dsDNA structure and reduce the energy-transfer efficiency between DNA-AgNCs and GNRs, thus achieving fluorescence recovery and a signal-on analytical strategy. This strategy has excellent specificity and sensitivity with limit of detections of 4.411 nM for tetracycline and 1.416 nM for Pb2+ and has been successfully applied to detect tetracycline in milk and Pb2+ in river water. Using DNA-AgNCs formed in situ as signal probes, this strategy does not require labels or modifications and can be completed without complex analytical instruments. Moreover, this strategy can be extended to detect other targets by replacing FNA sequences. Therefore, it has promising prospects in the sensitive, simple, and rapid detection of contaminants in food and environment samples.

RNA-cleaving DNAzymes for accurate biosensing and gene therapy

“…Sun et al developed a simple and low-cost fluorescence signal-on sensing strategy based on DNAzymes to detect tetracycline in milk (detection limit of 4.411 nM). 45 Escherichia coli ( E. coli ) is a food-borne pathogen with widespread sources and low infectious doses from contaminated milk, water, and other routes, which seriously threatens human health. 46 Nonspecific binding is one of the severe challenges in food detection.…”

Recent Advances in Design and Application of Nanomaterials-Based Colorimetric Biosensors for Agri-food Safety Analysis

“…Recently, emerging novel nanomaterials, such as metal–organic frameworks (MOFs), nanoclusters, covalent–organic frameworks, and MXenes have also been reported for food safety assays. Among them, MOFs with diverse skeleton composition, abundant organic ligands, high specific surface area and good biocompatibility have broad application prospects .…”

Fluorescent Features and Applicable Biosensing of a Core–Shell Ag Nanocluster Shielded by a DNA Tetrahedral Nanocage

“…The locally concentrated Ag + adducts are chemically reduced, allowing the agglomeration of Ag 0 to form DNA/AgNCs. − The DNA/AgNCs entity develops discrete and sparsely organized electronic states and becomes an optical chromophore. Because of the strong molecular brightness, robust emission, high quantum yields (QYs), and long fluorescence lifetimes, these label-free emitters have been an intriguing class of fluorescent probes with well-defined perspectives for applications in the biological sensing of disease-related markers at ultralow levels, , enzyme activity, cellular imaging, and environment or food analysis . Their intrinsic photophysics and spectral features can be tuned by the primary bases, length, and secondary structure of DNA hosts, which dictate the discrete electron energy levels dependent on the cluster stoichiometry, size, and doping, endowing them with wide spectral spanning from visible to near-infrared regions .…”