Poly(adenine) DNA-Templated Gold Nanocluster-Based Fluorescent Strategy for the Determination of Thiol-Containing Pharmaceuticals

Gold nanoclusters: An ultrasmall platform for multifaceted applications

Gold nanoclusters (Au NCs) with a core size below 2 nm form an exciting class of functional nano-materials with characteristic physical and chemical properties. The properties of Au NCs are more prominent and extremely different from their bulk counterparts. The synthesis of Au NCs is generally assisted by template or ligand, which impart excellent cluster stability and high quantum yield. The tunable and sensitive physicochemical properties of Au NCs open horizons for their advanced applications in various interdisciplinary fields. In this review, we briefly summarize the solution phase synthesis and origin of the characteristic properties of Au NCs. A vast review of recent research work introducing biosensors based on Au NCs has been presented along with their specifications and detection limits. This review also highlights recent progress in the use of Au NCs as bio-imaging probe, enzyme mimic, temperature sensing probe and catalysts. A speculation on present challenges and certain future prospects have also been provided to enlighten the path for advancement of multifaceted applications of Au NCs.

Blue-emitting glutathione-capped copper nanoclusters as fluorescent probes for the highly specific biosensing of furazolidone

Herein, a facile, straightforward and green method was developed to prepare copper nanoclusters by using glutathione (GSH) as the protecting agent and ascorbic acid as the reducing agent. The glutathione-templated copper nanoclusters (GSH-Cu NCs) were characterized through fluorescence spectroscopy, UV-vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and fluorescence lifetime analysis. The as-synthesized Cu NCs showed blue fluorescence with a peak centered at 426 nm. The Cu NCs had excellent water solubility, stability and dispersibility. Based on the inner filter effect and static quenching mechanism, Cu NCs were employed to detect furazolidone in bovine serum samples. Under optimal detection conditions, a good linear relationship was observed between F₀/F and the furazolidone concentration from 0.05 to 60 μM. The detection limit (LOD) was 0.012 μM. Furthermore, the fluorescence probe was successfully used in the quantification of furazolidone in bovine serum samples. In addition, this analytical method provides a rapid, easy and ultrasensitive fluorescence platform for the detection of furazolidone.

Fabrication of multiple molecular logic gates made of fluorescent DNA-templated Au nanoclusters

A universal platform of label-free multiple molecular logic gates have been constructed by taking the advantage of DNA-AuNCs.

A turn-on fluorescence strategy for biothiols determination by blocking Hg(II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters

Fluorescent adenine (A)-rich DNA-templated gold nanoclusters were demonstrated to be a novel probe for determination of biothiols (including cysteine, glutathione, and homocysteine). Fluorescence intensity of adenine-rich DNA-templated gold nanoclusters could be greatly quenched by Hg(II) ions through the formation of a gold nanoclusters-Hg(II) system. When biothiols (cysteine as the model) were introduced into the system, the fluorescence intensity recovered due to the formation of a more stable Hg(II)-thiol coordination complex using Hg-S metal-ligand bonds, which inhibited the Hg(II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters. Based on this fluorescence phenomenon, an on-off-on fluorescence strategy was designed for the sensitive determination of biothiols. The method allowed sensitive detection of cysteine with a linear detection range from 100 nM to 5 μM and a limit of detection of 30 nM. Additionally, the assay can be applied for detection of biothiol levels in human plasma samples. Therefore, it can provide a simple and rapid fluorescent platform for biothiol detection.

A novel fluorescent nanoprobe that based on poly(thymine) single strand DNA-templated copper nanocluster for the detection of hydrogen peroxide

In this paper, a label-free fluorescence nanoprobe is constructed based on poly(thymine) single strand DNA-templated Copper nanocluster (denote as: T-CuNCs) for the detection of hydrogen peroxide. In the assay, the fluorescent T-CuNCs will generate though the reaction of Cu²⁺, poly(thymine) and sodium ascorbate. However, the hydroxyl radical (^.OH) will generated in the presence of H₂O₂, which is able to induced the oxidative lesions of poly(thymine) single chain DNA and lead to the poly(thymine) being splitted into shorter or single oligonucleotide fragments and lose the ability to template the fluorescent T-CuNCs again. Therefore, H₂O₂ can be detected by monitoring the fluorescence strength change of T-CuNCs. The experimental results show that the fluorescence intensity change of T-CuNCs has fantastic linearity versus H₂O₂ concentration in the range of 1-30 μM (R² = 0.9947) and 30-80 μM (R² = 0.9972) with the limit of detection (LOD) as low as 0.5 μM (S/N = 3). More important, the fluorescent nanoprobe was also successfully utilized on the detection of H₂O₂ in serum samples. Therefore, a label-free, costless and effective fluorescence method has been established for the detection of H₂O₂, the intrinsic properties of the nanoprobe endow its more potential applications in chemical and biological study.

DNA functionalized metal and metal oxide nanoparticles: principles and recent advances in food safety detection

The frequent occurrence of food safety incidents has given rise to unprecedented concern about food contamination issues for both consumers and the industry. Various contaminations in food pose serious threats to food safety and human health. Many detection methods were studied to address the challenge. Recently, biosensors relying on deoxyribonucleic acid (DNA)-functionalized nanoparticles have been developed as an efficient and effective detection method. In the current review, the strategies for DNA assembly metal and metal oxide nanoparticles are elaborated, recent applications of the sensors based on DNA-functionalized nanoparticles in food contaminant detection are discussed. Pathogenic bacteria, heavy metal ions, mycotoxins, antibiotics, and pesticides are covered as food contaminants. Additionally, limitations and future trends of functionalized nanoparticles-based technology are also presented. The current review indicates that DNA-functionalized metal and metal oxide nanoparticles are a novel nanomaterial with unique biological and physical properties for developing electrochemical, fluorescent, colourimetric and surface-enhanced Raman spectroscopy (SERS) sensors, etc. Compared with conventional detection techniques, DNA-functionalized metal and metal oxide nanoparticles have considerable advantages with high accuracy, high specificity, micro-intelligence, and low cost. Nevertheless, the stability of these sensors and the limitations of real-time detection are still under discussion. Therefore, more tolerant, portable, and rapid DNA sensors should be developed to better the real-time monitoring of harmful contaminants.

Ascorbic acid stabilised copper nanoclusters as fluorescent sensors for detection of quercetin

In this report, green-emitting fluorescence copper nanoclusters (Cu NCs) were synthesized using ascorbic acid as reducing agent and protecting agent. The ascorbic acid capped Cu NCs (AA-Cu NCs) were characterized using fluorescence spectroscopy, UV-vis absorption spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The analysis data demonstrated that the AA-Cu NCs were highly dispersed with an average diameter of 2 nm. The as-prepared Cu NCs possessed good water solubility, excellent photostability and displayed excitation-dependent fluorescence characteristics. More importantly, the fluorescence intensity of AA-Cu NCs was linearly quenched in the presence of quercetin from 0.7 to 50 μM and the detection limit (LOD) was 0.19 μM. Finally, the fluorescence sensor was successfully employed to detect quercetin in bovine serum samples.

A fluorescent sensor based on ascorbic acid-functionalized copper nanoclusters (AA-Cu NCs) were prepared for the sensitive detection of quercetin.