DNA-templated fluorescent nanoclusters (NCs) have attracted increasing research interest on account of their prominent features, such as DNA sequence-dependent fluorescence, easy functionalization, wide availability, water solubility, and excellent biocompatibility. Coupling DNA templates with complementary DNA, aptamers, G-quadruplex, and so on has generated a large number of sensors. Additionally, the preparation and applications of DNA-templated fluorescent NCs in these sensing have been widely studied. This review firstly focuses on the properties of DNA-templated fluorescent NCs, and the synthesis of DNA-templated fluorescent NCs with different metals is then discussed. In the third part, we mainly introduce the applications of DNA-templated fluorescent NCs for sensing metal ions. At last, we further discuss the future perspectives of DNA-templated fluorescent NCs in the synthesis and sensing metal ions in the environmental and biological fields.

Ochratoxin A (OTA) is one of the most toxic mycotoxins and exists in various food commodities. Herein, a sensitive fluorescence method was developed for OTA detection which combines the advantages of label-free dsDNA-templated copper nanoparticles (CuNPs), high selectivity of OTA aptamer and high efficiency of exonuclease-catalyzed target recycling amplification. OTA aptamer was hybridized with its complementary DNA (cDNA), and the obtained dsDNA acted as the template for fluorescent CuNPs. In the presence of its target (OTA), the aptamer prefers to form an OTA–aptamer complex in lieu of an aptamer–DNA duplex, which results in the dissociation of the aptamer–DNA duplex. The released cDNA and aptamer could be digested into mononucleotides by the RecJ_f exonuclease (single-stranded DNA specific exonuclease), and the target was liberated and could participate in the next reaction cycle. The above process resulted in the degradation of a large amount of template dsDNA, which prevented the synthesis of CuNPs, thus resulting in low fluorescence of the system. Based on this strategy, a label-free and sensitive detection of OTA was developed with a low detection limit of 5 ng mL⁻¹ (S/N = 3). Our strategy was further validated and evaluated successfully by assaying OTA in real samples. The proposed assay has great potential as an OTA quantification method for use in the food safety field.

In this work, we reported a highly rapid and non-enzymatic method for cholesterol measuring based on carbon nitride quantum dots (CNQDs) as fluorescent nanoprobes, which were synthesized through chemical oxidation. The obtained CNQDs displayed high quantum yield up to 35% as well as excellent photostability, water solubility and low toxicity. We found that the fluorescence of CNQDs could be quenched more than 90% within 30 seconds by cholesterol through the formation of hydrogen bonds between –NH₂, –NH on the surface of CNQDs and cholesterol containing –OH. According to this phenomenon, a cholesterol detection method was constructed with a wide linear region over the range of 0–500 μmol L⁻¹ and a detection limit as low as 10.93 μmol L⁻¹, and it possessed the obvious advantages of being a very rapid process and avoiding the use of enzymes. In addition, this method showed high selectivity in the presence of various interfering reagents and applicability to the measurement of cholesterol in fetal bovine serum, which indicated its potential application value in clinical settings.