DNA-stabilized, fluorescent, metal nanoclusters for biosensor development

• A review of DNA-templated gold, silver and copper nanoclusters.
• Summary of synthesis, characterization, and analytical applications of nanoclusters.
• Biosensor development reviewed based on the reactions unique to the nanoclusters.
• Future development trends discussed from fundamental and application perspectives.

Fluorescent silver, gold and copper nanoclusters (NCs) have emerged for biosensor development. Compared to semiconductor quantum dots, there is less concern about the toxicity of metal NCs, which can be more easily conjugated to biopolymers. These NCs need a stabilizing ligand. Many polymers, proteins and nucleic acids stabilize NCs, and many DNA sequences produce highly-fluorescent NCs. Coupling these DNA stabilizers with other sequences, such as aptamers, has generated a large number of biosensors.We summarize the synthesis of DNA and nucleotide-templated NCs; and, we discuss their chemical interactions. We briefly review properties of NCs, such as fluorescence quantum yield, emission wavelength and lifetime, structure and photostability.We categorize sensor-design strategies using these NCs into:(1)fluorescence de-quenching;(2)generation of templating DNA sequences to produce NCs;(3)change of nearby environment; and,(4)reacting with heavy metal ions or other quenchers.Finally, we discuss future trends.