Viruses are real menace to human safety that cause devastating viral disease. The high prevalence of these diseases is due to improper detecting tools. Therefore, there is a remarkable demand to identify viruses in a fast, selective and accurate way. Several biosensors have been designed and commercialized for detection of pathogenic viruses. However, they present many challenges. Nanotechnology overcomes these challenges and performs direct detection of molecular targets in real time. In this overview, studies concerning nanotechnology-based biosensors for pathogenic virus detection have been summarized, paying special attention to biosensors based on graphene oxide, silica, carbon nanotubes, gold, silver, zinc oxide and magnetic nanoparticles, which could pave the way to detect viral diseases and provide healthy life for infected patients.

Nanomaterial-based biosensors for detection of pathogenic virus

The preparation of dual-functional hybrid nanoflower and its application in the ultrasensitive detection of disease-related biomarker.

Atomically precise metal nanoclusters (MNCs) have gained tremendous research interest in recent years due to their extraordinary properties. The molecular-like properties that originate from the quantized electronic states provide novel opportunities for the construction of unique nanomaterials possessing rich molecular-like absorption, luminescence, and magnetic properties. The field of monolayer-protected metal nanoclusters, especially copper, with well-defined molecular structures and compositions, is relatively new, about two to three decades old. Nevertheless, the massive progress in the field illustrates the importance of such nanoobjects as promising materials for various applications. In this respect, nanocluster-based catalysts have become very popular, showing high efficiencies and activities for the catalytic conversion of chemical compounds. Biomedical applications of clusters are an active research field aimed at finding better fluorescent contrast agents, therapeutic pharmaceuticals for the treatment and prevention of diseases, the early diagnosis of cancers and other potent diseases, especially at early stages. A huge library of structures and the compositions of copper nanoclusters (CuNCs) with atomic precisions have already been discovered during last few decades; however, there are many concerns to be addressed and questions to be answered. Hopefully, in future, with the combined efforts of material scientists, inorganic chemists, and computational scientists, a thorough understanding of the unique molecular-like properties of metal nanoclusters will be achieved. This, on the other hand, will allow the interdisciplinary researchers to design novel catalysts, biosensors, or therapeutic agents using highly structured, atomically precise, and stable CuNCs. Thus, we hope this review will guide the reader through the field of CuNCs, while discussing the main achievements and improvements, along with challenges and drawbacks that one needs to face and overcome.

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Copper nanoclusters: designed synthesis, structural diversity, and multiplatform applications.

In this study, we have reported a new approach for sequence specific microRNA-155 (miRNA-155) detection by water soluble luminescent copper nanoclusters. The method is based on the shifts in the fluorescence emissions of oligonucleotide-templated copper nanoclusters (DNA-CuNCs) and can be regarded as the first instance of using fluorescent CuNCs for the detection of microRNA by forming DNA-RNA heteroduplex. The as-prepared CuNCs exhibited a strong fluorescence enhancement at 510 nm and a red shift (60 nm) when bonded to the target miRNA-155 (DNA-RNA heteroduplex formation). Under the optimal conditions, the fluorescent intensity of DNA-CuNCs increased by the increasing the target miRNA-155 with in a dynamic range from 5.0 × 10 −12 to 1.0 × 10 −8  M down to a detection limit (LOD) of 2.2 × 10 −12  M. The target miRNA is selectively discriminated from mismatched miRNA by this method. The method was further applied to the determination of miRNA spiked human serum samples. Overall, the nanobiosensor showed the potential of becoming a potential alternative tool for the detection of miRNA-155 in biomedical research and early clinical diagnostic studies.

Label-free fluorescent detection of microRNA-155 based on synthesis of hairpin DNA-templated copper nanoclusters by etching (top-down approach)

Copper nanoclusters (Cu NCs) have emerged as a valuable member of the family of ligand-protected few-atomic metal nanoparticles and show fascinating properties of color-controlled light emission, combined with the advantages of versatile solution-based chemical synthesis at low cost. Synthetic methods of Cu NCs using various types of functional ligands and scaffolds allow tuning their emission wavelength and improving their environmental stability. Depending on the method of preparation and the ligands used, Cu NCs have already been applied for a wide variety of applications in catalysis, sensing, bioimaging, theranostics, and optoelectronics. This review highlights the potential of Cu NCs and links synthetic procedures and functionalization with different ligands with their properties and applications.

https://pubs.rsc.org/en/content/articlepdf/2019/qm/c9qm00492k

Ligand functionalized copper nanoclusters for versatile applications in catalysis, sensing, bioimaging, and optoelectronics

Colorimetric detection of hepatitis B virus (HBV) DNA based on DNA-templated copper nanoclusters.

Today, a consensus that DNA working as a molecular wire shows promise in nanoscale electronics is reached. Considering that the “ON-OFF” switch is the basis of a logic circuit, the switch of DNA-mediated charge transport (DNA CT) should be conquered. Here, on the basis of chemical or electrochemical deposition and stripping of DNA-templated copper nanoclusters (CuNCs), we develop an “ON-OFF” nanoswitch for DNA CT. While CuNCs are deposited, the DNA CT is blocked, which can be also recovered after stripping the CuNCs. A switch cycle can be completed in a few seconds and can be repeated for many times. Moreover, by regulating the amount of reagents, deposition/stripping time, applied potential, etc., the switch is adjustable to make the wire at either an “ON-OFF” state or an intermediate state. We believe that this concept and the successful implementation will promote the practical application of DNA wire one step further.

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Siyu Liu

Papers

Colorimetric detection of hepatitis B virus (HBV) DNA based on DNA-templated copper nanoclusters.

Switchable DNA wire: deposition-stripping of copper nanoclusters as an "ON-OFF" nanoswitch.