Fluorescent Biosensor Based on Hairpin DNA Stabilized Copper Nanoclusters for Chlamydia trachomatis Detection

Chlamydia trachomatis (C. trachomatis) is a kind of intracellular parasitic microorganism, which can causes many diseases such as trachoma. In this strategy, a specific hairpin DNA with the probe loop as specific regions to recognize C. trachomatis DNA with strong affinity was designed, and its stem consisted of 24 AT base pairs as an effective template for hairpin DNA-CuNCs formation. In the absence of C. trachomatis DNA, the detection system showed strong orange fluorescence emission peaks at 606 nm. In the presence of C. trachomatis DNA, the conformation of DNA probe changed after hybridizing with C. trachomatis DNA. Then, the amount of hairpin DNA-CuNCs was reduced and resulted in low fluorescence emission. C. trachomatis DNA displayed a significant inhibitory effect on the synthesis of fluorescent hairpin DNA-CuNCs due to the competition between C. trachomatis DNA and the specific hairpin DNA. Under the optimal experimental conditions, different concentrations of C. trachomatis were tested and the results showed a good linear relationship in the range of 50 nM to 950 nM. Moreover, the detection limit was 18.5 nM and this detection method possessed good selectivity. Finally, the fluorescent biosensor had been successfully applied to the detection of C. trachomatis target sequence in HeLa cell lysate, providing a new strategy for the detection of C. trachomatis.

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

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.

Fluorescence resonance energy transfer using DNA-templated copper nanoparticles for ratiometric detection of microRNAs

We examined the effectiveness of a ratiometric method using DNA-templated copper nanoparticles, which can function as a probe for fluorescence resonance energy transfer. This method in combination with PCR successfully detected the target microRNA, which corresponded well with the results obtained by quantitative reverse transcription PCR.

A label-free protamine-assisted colorimetric sensor for highly sensitive detection of S1 nuclease activity

A label-free, simple and rapid colorimetric method for the sensitive detection of S1 nuclease activity based on protamine-assisted aggregation of gold nanoparticles.

Recent advances in the synthesis and application of copper nanomaterials based on various DNA scaffolds

Fluorescent copper nanomaterials (CuNMs), including copper nanoparticles (CuNPs) and copper nanoclusters (CuNCs), become more and more popular with the abundant raw materials and low cost. A wide range of applications has been explored due to their fascinating properties such as low toxicity, remarkable water solubility, facile synthesis, large Stokes shifts, and good biocompatibility. As a kind of genetic material, DNA exhibits its molecular recognition function and diversity. The marriage between CuNMs and DNA endows DNA-templated CuNMs (DNA-CuNMs) with unique properties such as fluorescence, electrochemiluminescence and catalytic features. In this review, we summarize the synthesis and recent applications of DNA-CuNMs. Fluorescent CuNMs can be grown on various DNA scaffolds with special sequence design. T base plays an important role in the formation of CuNMs on DNA templates. These fluorescent DNA-CuNMs hold great prospect in logic gate construction, staining and biosensing of DNAs and RNAs, ions, proteins and enzymes, small molecules and so on.

Ultrasensitive Biosensor for Detection of Mercury(II) Ions Based on DNA-Cu Nanoclusters and Exonuclease III-assisted Signal Amplification

This paper describes a novel method for label-free mercury(II) ion detection based on exonuclease III-induced target signal recycling amplification using double-stranded DNA templated copper nanoclusters. The synthesized DNA-Cu nanoclusters were used with exonuclease III loop amplification technology for ultra-high sensitivity detection of mercury(II) ions, which were detected by significantly decreased fluorescence intensity. Under the optimal experimental conditions, there was a clear linear relationship between Hg²⁺ concentration in the range of 0.04 to 8 nM and fluorescence intensity. The detection limit for Hg²⁺ was 4 pM. In addition, the interference of other metal ions on the mercury(II) ion detection was also studied. To confirm the application of the fluorescent sensor, it was applied to determine the concentrations of mercury(II) ions in tap water, and the results showed that the method can be used to detect mercury(II) ions in water samples successfully.