A dual-mode nanosensor based on carbon quantum dots and gold nanoparticles for discriminative detection of glutathione in human plasma

Metal nanoclusters (NCs) are emerging as a new class of functional nanomaterials in the area of biological sensing, labelling, imaging and therapy due to their unique physical and chemical properties, such as ultrasmall size, HOMO–LUMO transition, strong luminescence together with good photostability and biocompatibility. A recent surge of interest in this field is the surface functionalization of these metal NCs through which one can tailor their physicochemical properties, such as stability in solution, and strong luminescence, as well as their biodistribution and toxicity in biological systems, which in turn can empower these functionalized NCs with desirable targeting, imaging, and therapeutic ability for biomedical applications. In this review, we first introduce the functionalization strategies for the metal NCs developed in the past few years, followed by highlighting some biomedical applications of these functionalized metal NCs. We then discuss the difference of in vitro and in vivo fate as well as toxicity between various functionalized metal NCs. Finally, we present a short discussion on the current challenges and provide an outlook of the future developments of these functional metal NCs.

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Functionalization of metal nanoclusters for biomedical applications

Copper is a highly toxic environmental pollutant with bioaccumulative properties. Therefore, sensitive Cu2+ detection is very important to prevent over-ingestion, and visual detection using unaugmented vision is preferred for practical applications. In this study, hyperbranched polyethyleneimine-protected silver nanoclusters (hPEI-AgNCs) were successfully synthesized using a facile, one-pot reaction under mild conditions. The hPEI-AgNCs were very stable against extreme pH, ionic strength, temperature, and photoillumination and could act as sensitive and selective Cu2+ sensing nanoprobes in aqueous solutions with a 10 nM limit of detection. In addition, hPEI-AgNCs-doped agarose hydrogels were developed as an instrument-free and regenerable platform for visual Cu2+ and water quality monitoring.

Sensitive and Selective Detection of Copper Ions with Highly Stable Polyethyleneimine-Protected Silver Nanoclusters

Metal nanoclusters (NCs) containing a few to a few hundreds of atoms bridge the gap between nanoparticles and molecular compounds. The last decade evidenced impressive developments of noble metal NCs such as Au and Ag. Copper is an earth abundant, inexpensive metal from the same group of the periodic table, which is increasingly coming into focus for NC research. This review specifically addresses wet chemical synthesis methods, optical properties and some emerging applications of Cu NCs. As surface protecting templates/ligands play an important role in the stability and properties of Cu NCs, we classified the synthetic methods by the nature of the capping agents. The optical properties of Cu NCs are discussed from the point of view of the effects of the metal core, surface ligands and environment (solvents and aggregation) on the emission of the clusters. Applications of luminescent Cu NCs in biological imaging and light emitting devices are considered.

Synthesis, optical properties and applications of light-emitting copper nanoclusters

Metal nanoclusters (MNCs) are composed of several to tens of atoms and have drawn considerable research interest due to their unique electrical, physical and optical properties. However, in comparison to the extensively investigated Au NCs and Ag NCs, analytical applications of the copper nanoclusters (Cu NCs) are relatively limited and still at an early stage. In this review, we focus on recent advances in the analytical applications of Cu NCs based on their optical, electrochemical, and catalytical properties for the detection of various analytes, including metal ions, anions, biomoleculars (proteins, nucleic acids etc.), small molecules and pH. In addition, their applications in biological labeling and bioimaging were summarized.

Na Zhang

Papers

Sensitive and selective detection of biothiols based on target-induced agglomeration of silvernanoclusters

Fluorescent detection of hydrogen peroxide and glucose with polyethyleneimine-templated Cu nanoclusters

Sensitive signal-on fluorescent sensing for copper ions based on the polyethyleneimine-capped silver nanoclusters-cysteine system.