DNA Nanoribbon-Templated Self-Assembly of Ultrasmall Fluorescent Copper Nanoclusters with Enhanced Luminescence

Fructose@histone synergistically improve the performance of DNA-templated Cu NPs: rapid analysis of LAM in tuberculosis urine samples using a handheld fluorometer and a smartphone RGB camera

This study presented a nanoparticle-enhanced aptamer-recognizing homogeneous detection system combined with a portable instrument (NASPI) to quantify lipoarabinomannan (LAM). This system leveraged the high binding affinity of aptamers, the high sensitivity of nanoparticle cascade amplification, and the stabilization effect of dual stabilizers (fructose and histone), and used probe-Cu2+ to achieve LAM detection at concentrations ranging from 10 ag mL-1 to 100 fg mL-1, with a limit of detection of 3 ag mL-1 using a fluorometer. It can also be detected using an independently developed handheld fluorometer or the red-green-blue (RGB) camera of a smartphone, with a minimum detection concentration of 10 ag mL-1. We validated the clinical utility of the biosensor by testing the LAM in the urine of patients. Forty urine samples were tested, with positive LAM results in the urine of 18/20 tuberculosis (TB) cases and negative results in the urine of 6/10 latent tuberculosis infection cases and 10/10 non-TB cases. The assay results revealed a 100% specificity and a 90% sensitivity, with an area under the curve of 0.9. We believe that the NASPI biosensor can be a promising clinical tool with great potential to convert LAM into clinical indicators for TB patients.

Nanosensors Monitor Intracellular GSH Depletion: GSH Triggers Cu(II) for Tumor Imaging and Inhibition

Glutathione (GSH) is the primary antioxidant in cells, and GSH consumption will break the redox balance in cells. Based on this, a method that uses high concentrations of GSH in the tumor microenvironment to trigger the redox reaction of Cu(II) to generate copper nanoprobes with fluorescence and tumor growth inhibition properties is proposed. The nanoprobe mainly exists in the form of Cu(I) and catalyzes the decomposition of hydrogen peroxide into hydroxyl radicals. At the same time, a simple and controllable carbon micro-nano electrode is used to construct a single-cell sensing platform, which enable the detection of glutathione content in single living cells after Cu(II) treatment, providing an excellent example for detecting single-cell biomolecules.

Leveraging Concentration Imbalance-Driven DNA Circuit as an Operational Amplifier to Enhance the Sensitivity of Hepatitis B Virus DNA Detection with Hybridization-Responsive DNA-Templated Silver Nanoclusters

Hepatitis B virus (HBV) infection remains a major global health concern, necessitating the development of sensitive and reliable diagnostic methods. In this study, we propose a novel approach to enhance the sensitivity of HBV DNA detection by leveraging a concentration imbalance-driven DNA circuit (CIDDC) as an operational amplifier, coupled with a hybridization-responsive DNA-templated silver nanocluster (DNA-AgNCs) nanoprobe named Q·C6-AgNCs. The CIDDC system effectively converts and amplifies the input HBV DNA into an enriched generic single-stranded DNA output, which subsequently triggers the fluorescence of the DNA-AgNCs reporter upon hybridization, generating a measurable signal for detection. By incorporating the DNA circuit, we not only achieved enhanced sensitivity with a lower detection limit of 0.11 nM but also demonstrated high specificity with single-base mismatch discriminability for HBV DNA detection. Additionally, this mix-and-detect assay format is simple, user-friendly, and isothermal. This innovative strategy holds promise for advancing molecular diagnostics and facilitating the effective management of HBV-related diseases.

Self-Assembly-Induced Enhancement of Cathodic Electrochemiluminescence of Copper Nanoclusters for a Split-Type Matrix Metalloproteinase 14 Sensing Platform

The unique optoelectronic and tunable luminescent characteristics of copper nanoclusters (Cu NCs) make them extremely promising as luminophores. However, the limited luminescence intensity and stability of Cu NCs have restricted their application in the field of electrochemiluminescence (ECL). Herein, a self-assembly-induced enhancement strategy was successfully employed to enhance the cathodic ECL performance of flexible ligand-stabilized Cu NCs. Specifically, Cu NCs form ordered sheetlike structures through intermolecular force. The restriction of ligand torsion in this self-assembled structure leads to a significant improvement in the ECL properties of the Cu NCs. Experimental results demonstrate that the assembled nanoscale Cu NC sheets exhibit an approximately three-fold increase in cathodic ECL emission compared to the dispersed state of Cu NCs. Furthermore, assembled nanoscale Cu NCs sheets were utilized as signal probes in conjunction with a specific short peptide derived from the catalytic structural domain of matrix metalloproteinase 14 (MMP 14) as the identification probe, thereby establishing a split-type ECL sensing platform for the quantification of NMP 14. The investigation has revealed the exceptional performance of assembled nanoscale Cu NCs sheets in ECL analysis, thus positioning them as novel and promising signal probes with significant potential in the field of sensing.

Confined Unimolecular Micelles for Directed Self-Assembly of Ultrastable Multiple-Responsive Ratiometric Fluorescent Ultrasmall Nanoparticle Assemblies

Ultrasmall fluorescent nanomaterials have been widely studied as novel fluorescent probes; however, these nanomaterials are prone to structural damage or aggregation, and the sensitivity and accuracy of most single emission fluorescence probes were very low. Therefore, the controlled synthesis of stable dual-emission ratiometric fluorescence ultrasmall assembly probes still remains a challenge. Herein, star-like polymer unimolecular micelles were utilized as a scaffold template to encapsulate fluorescent ultrasmall carbon quantum dots (CQDs) and gold nanoclusters (AuNCs) via the polymer template directed self-assembly strategy to obtain multiple-responsive ratiometric fluorescent assemblies. The assemblies were ultrastable, well-defined, and nearly monodispersed with controlled size, regular morphology, and pH- and thermal-responsiveness. The assemblies can be applied to realize rapid, sensitive, quantitative, and specific detection of Cu2+ and GSH. Moreover, the convenient rapid real-time detection was realized via the combination of the visualized paper-based sensor, and the multilevel information encryption was also achieved.

Fluorescent metal nanoclusters: From luminescence mechanism to applications in enzyme activity assays

Metal nanoclusters (MNCs) have outstanding fluorescence property and biocompatibility, which show widespread applications in biological analysis. Particularly, evaluation of enzyme activity with the fluorescent MNCs has been developed rapidly within the past several years. In this review, we first introduced the fluorescent mechanism of mono- and bi-metallic nanoclusters, respectively, whose interesting luminescence properties are mainly resulted from electron transfer between the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels. Meanwhile, the charge migration within the structure occurs through ligand-metal charge transfer (LMCT) or ligand-metal-metal charge transfer (LMMCT). On such foundation, diverse enzyme activities were rigorously evaluated, including three transferases and nine hydrolases, in turn harvesting rapid research progresses within past 5 years. Finally, we summarized the design strategies for evaluating enzyme activity with the MNCs, presented the major issues and challenges remained in the relevant research, coupled by showing some improvement measures. This review will attract researchers dedicated to the studies of the MNCs and provide some constructive insights for their further applications in enzyme analysis.

Self-Assembled DNA Machine and Selective Complexation Recognition Enable Rapid Homogeneous Portable Quantification of Lung Cancer CTCs

In this study, we systematically investigated the interactions between Cu2+ and various biomolecules, including double-stranded DNA, Y-shaped DNA nanospheres, the double strand of the hybridization chain reaction (HCR), the network structure of cross-linked HCR (cHCR), and small molecules (PPi and His), using Cu2+ as an illustrative example. Our research demonstrated that the coordination between Cu2+ and these biomolecules not only is suitable for modulating luminescent material signals through complexation reactions with Cu2+ but also enhances signal intensities in materials based on chemical reactions by increasing spatial site resistance and local concentration. Building upon these findings, we harnessed the potential for signal amplification in self-assembled DNA nanospheres and the selective complexation modulation of calcein in conjunction with the aptamer targeting mucin 1 as a recognition probe. We applied this approach to the analysis of circulating tumor cells, with the lung cancer cell line A549 serving as a representative model. Our assay, utilizing both a fluorometer and a handheld detector, achieved impressive detection limits of ag/ml and single-cell levels for mucin 1 and A549 cells, and this approach was successfully validated using 46 clinical samples, yielding 100% specificity and 86.5% sensitivity. Consequently, our strategy has paved the way for more portable and precise disease diagnosis.

Self-assembly of Copper Nanoclusters Using DNA Nanoribbon Templates for Sensitive Electrochemical Detection of H2O2 in Live Cells

The excessive secretion of H2O2 within cells is closely associated with cellular dysfunction. Therefore, high sensitivity in situ detection of H2O2 released from living cells was valuable in clinical diagnosis. In the present work, a novel electrochemical cells sensing platform by synthesizing copper nanoclusters (CuNCs) at room temperature based on DNA nanoribbon (DNR) as a template (DNR-CuNCs). The tight and ordered arrangement of nanostructured assemblies of DNR-CuNCs conferred the sensor with superior stability (45 days) and electrochemical performance. The MUC1 aptamer extending from the DNR template enabled the direct capture MCF-7 cells on electrode surface, this facilitated real-time monitoring of H2O2 release from stimulated MCF-7 cells. While the captured MCF-7 cells on the electrode surface significantly amplified the current signal of H2O2 release compared with the traditional electrochemical detection H2O2 released signal by MCF-7 cells in PBS solution. The approach provides an effective strategy for the design of versatile sensors and achieving monitored cell release of H2O2 in long time horizon (10 h). Thereby expanding the possibilities for detecting biomolecules from live cells in clinical diagnosis and biomedical applications.

Concept and Development of Algebraic Topological Framework Nucleic Acids

Nucleic acids are considered as promising materials for developing exquisite nanostructures from one to three dimensions. The advances of DNA nanotechnology facilitate ingenious design of DNA nanostructures with diverse shapes and sizes. Especially, the algebraic topological framework nucleic acids (ATFNAs) are functional DNA nanostructures that engineer guest molecules (e. g., nucleic acids, proteins, small molecules, and nanoparticles) stoichiometrically and spatially. The intrinsic precise properties and tailorable functionalities of ATFNAs hold great promise for biological applications, such as cell recognition and immunotherapy. This Perspective highlights the concept and development of precisely assembled ATFNAs, and outlines the new frontiers and opportunities for exploiting the structural advantages of ATFNAs for biological applications.

Copper Nanoclusters as Multienzymes Mimic Activities of Oxidase and Ascorbic Acid Oxidase in the Presence of Imidazole

Artificial nanoenzymes based on metal nanoclusters have received great attention for multienzyme activities nowadays. In this work, pepsin-capped copper NCs (Cu-Pep NCs) are used as oxidase, ascorbic acid oxidase (AAO), and peroxidase mimics, and their activities are enhanced by the introduction of imidazole. The oxidase activity increased almost 7.5-fold, while 5-fold and 2-fold increases were observed for the peroxidase and AAO-like activity, respectively. The enhanced radical formation in the presence of imidazole moieties facilitates the enzymatic activity of the Cu-Pep-NCs/Imid system. This work describes the different enzymatic activities of the NCs, paving a new way for artificial nanoenzymes having enhanced activities.

DNA-Modulated and Mechanoresponsive Excitonic Couplings Reveal Chiroptical Correlation of Conformation, Tension, and Dynamics of DNA Self-Assembly

Study of the conformational and mechanical behaviors of biomolecular assemblies is vital to the rational design and realization of artificial molecular architectures with biologically relevant functionality. Here, we revealed DNA-modulated and mechanoresponsive excitonic couplings between organic chromophores and verified strong correlations between the excitonic chiroptical responses and the conformational and mechanical states of DNA self-assemblies irrespective of fluorescence background interference. Besides, the excitonic chiroptical effect allowed sensitive monitoring of DNA self-assembled nanostructures due to small molecule bindings or DNA strand displacement reactions. Moreover, we developed a new chiroptical reporter, a DNA-templated dimer of an achiral cyanine5 and an intrinsically chiral BODIPY, that exhibited unique multiple-split spectral line shape of exciton-coupled circular dichroism, largely separated response wavelengths, and enhanced anisotropy dissymmetry factor (g-factor). These results shed light on a promising chiroptical spectroscopic tool for studying biomolecular recognition and binding, conformation dynamics, and soft mechanics in general.

Ratiometric fluorescence determination of alkaline phosphatase activity based on carbon dots and Ce3+-crosslinked copper nanoclusters

A new ratiometric fluorescent probe for efficient determination of ALP was developed. The probe was constructed by combining Ce3+-crosslinked copper nanoclusters (Ce3+-CuNCs) which exhibit the aggregation-induced emission (AIE) feature with carbon dots (CDs). The introduction of phosphate (Pi) induced the generation of CePO4 precipitation, resulting in significant decrease of fluorescence emission of CuNCs at 634 nm. At the same time, the fluorescence of CDs at 455 nm was obviously enhanced, thus generating ratiometric fluorescence response. Based on the fact that the hydrolysis of pyrophosphate (PPi) by ALP can produce Pi, the CD/Ce3+-CuNCs ratiometric probe was successfully used to determine ALP. A good linear relationship between the ratiometric value of F455/F634 and ALP concentrations ranging from 0.2 to 80 U·L- 1 was obtained, with a low detection limit of 0.1 U·L- 1. The ratiometric responses of the probe resulted in the visible fluorescence color change from orange red to blue with the increase of ALP concentration. The smartphone-based RGB recognition of the fluorescent sample images was used for ALP quantitative determination. A novel ratiometric fluorescent system based on Ce3+-CuNCs with AIE feature and CDs were constructed for efficient detection of ALP.

Hybrid chain reaction and selective recognition-based homogeneous dual-fluorescence analysis of circulating tumor cells in clinical ovarian cancer samples

BACKGROUND

Oncological analysis is important in tumor diagnosis. We constructed a dual-fluorescence and binary visual analysis system for circulating tumor cells (CTCs) using the folate receptor as a biomarker, combined with hybridization chain reaction and nanomaterial amplification. This strategy integrates terminal protection, selective recognition properties of N-methyl mesoporphyrin IX and CdTe quantum dots for Cu2+ and double-stranded templated copper nanoparticles, and inkjet printing technology.

RESULTS

In fluorescence mode, folate receptor and A2780 ovarian cancer cells were specifically detected with a limit of detection of 0.1 fg mL-1, and 10 cells mL-1 were observed. The detection limits of both the color and distance reading modes were comparable to those obtained in fluorescence mode. The applicability of the method for quantifying CTCs was validated using 27 (6 negative and 21 positive) clinical ovarian cancer samples; the results agreed with those of both the clinical folate receptor-polymerase chain reaction kit and radiological and pathological results.

SIGNIFICANCE

This dual-fluorescence and binary visual CTCs detection method provides multiple options for clinical tumor liquid biopsy.

Ligand-induced Assembly of Copper Nanoclusters with Enhanced Electrochemical Excitation and Radiative Transition for Electrochemiluminescence

Copper nanoclusters (CuNCs) are emerging electrochemiluminescence (ECL) emitters with unique molecule-like electronic structures, high abundance, and low cost. However, the synthesis of CuNCs with high ECL efficiency and stability in a scalable manner remains challenging. Here, we report a facile gram-scale approach for preparing self-assembled CuNCs (CuNCsAssy ) induced by ligands with exceptionally boosted anodic ECL and stability. Compared to the disordered aggregates that are inactive in ECL, the CuNCsAssy shows a record anodic ECL efficiency for CuNCs (10 %, wavelength-corrected, relative to Ru(bpy)3 Cl2 /tripropylamine). Mechanism studies revealed the unusual dual functions of ligands in simultaneously facilitating electrochemical excitation and radiative transition. Moreover, the assembly addressed the limitation of poor stability of conventional CuNCs. As a proof of concept, an ECL biosensor for alkaline phosphatase detection was successfully constructed with an ultralow limit of detection of 8.1×10-6  U/L.

DNA Framework Programmed Conformational Reconstruction of Antibody Complementary Determining Region

The conformation of complementary determining region (CDR) is crucial in dictating its specificity and affinity for binding with an antigen, making it a focal point in artificial antibody engineering. Although desirable, programmable scaffolds that can regulate the conformation of individual CDRs with nanometer precision are still lacking. Here, we devise a strategy to program the CDR conformation by anchoring both ends of a free CDR loop to specific sites of a DNA framework structure. This method allows us to define the span of a single CDR loop with an ∼2 nm resolution. Using this approach, we create a series of DNA framework based artificial antibodies (DNFbodies) with varied CDR loop spans, leading to different antibody-antigen binding affinities. We find that an optimized single CDR loop (∼2.3 nm span) exhibits ∼3-fold improved affinity relative to natural antibodies, confirming the critical role of the CDR conformation. This study may inspire the rational design of artificial antibodies.

Fluorescent Features and Applicable Biosensing of a Core-Shell Ag Nanocluster Shielded by a DNA Tetrahedral Nanocage

The DNA frame structure as a natural shell to stably shield the sequence-templated Ag nanocluster core (csAgNC) is intriguing yet challenging for applicable fluorescence biosensing, for which the elaborate programming of a cluster scaffold inside a DNA-based cage to guide csAgNC nucleation might be crucial. Herein, we report the first design of a symmetric tetrahedral DNA nanocage (TDC) that was self-assembled in a one-pot process using a C-rich csAgNC template strand and four single strands. Inside the as-constructed soft TDC architecture, the template sequence was logically bridged from one side to another, not in the same face, thereby guiding the in situ synthesis of emissive csAgNC. Because of the strong electron-repulsive capability of the negatively charged TDC, the as-formed csAgNC displayed significantly improved fluorescence stability and superb spectral behavior. By incorporating the recognizable modules of targeted microRNAs (miRNAs) in one vertex of the TDC, an updated TDC (uTDC) biosensing platform was established via the photoinduced electron transfer effect between the emissive csAgNC reporter and hemin/G-quadruplex (hG4) conjugate. Because of the target-interrupted csAgNC switching in three states with the spatial proximity and separation to hG4, an "on-off-on" fluorescing signal response was executed, thus achieving a wide linear range to miRNAs and a limit of detection down to picomoles. Without complicated chemical modifications, this simpler and more cost-effective strategy offered accurate cell imaging of miRNAs, further suggesting possible therapeutic applications.

DNA Nanoribbon-Assisted Intracellular Biosynthesis of Fluorescent Gold Nanoclusters for Cancer Cell Imaging

Metal nanoclusters (NCs) have emerged as a promising class of fluorescent probes for cellular imaging due to their high resistance to photobleaching and low toxicity. Nevertheless, their widespread use in clinical diagnosis is limited by their unstable intracellular fluorescence. In this study, we develop an intracellularly biosynthesized fluorescent probe, DNA nanoribbon-gold NCs (DNR/AuNCs), for long-term cellular tracking. Our results show that DNR/AuNCs exhibit a 4-fold enhancement of intracellular fluorescence intensity compared to free AuNCs. We also investigated the mechanism underlying the fluorescence enhancement of AuNCs by DNRs. Our findings suggest that the higher synthesis efficiency and stability of AuNCs in the lysosome may contribute to their fluorescence enhancement, which enables long-term (up to 15 days) fluorescence imaging of cancer cells (enhancement of ∼60 times compared to free AuNCs). Furthermore, we observe similar results with other metal NCs, confirming the generality of the DNR-assisted biosynthesis approach for preparing highly bright and stable fluorescent metal NCs for cancer cell imaging.

Fluorescence Enhancement Method for Aptamer-Templated Silver Nanoclusters and Its Application in the Construction of a β-Amyloid Oligomer Sensor

DNA-templated silver nanoclusters (DNA-AgNCs) have attracted significant attention due to their unique fluorescence properties. However, so far, the relatively low quantum yields of the DNA-AgNCs and the complex design of DNA-AgNC-based sensors have limited their application in biosensing or bioimaging. Herein, we report a novel fluorescence enhancement method. The β-Amyloid Oligomer (AβO) aptamer (Apt_AβO) with A₁₀/T₁₀ at its 3' end can be directly used as the template to fabricate the AgNCs. When the AgNCs were hybridized with the complementary strand that has 12 bases suspended at its 3' terminal, being the same or complementary to the A/T at the 3' end of the Apt_AβO, and two-base mismatches in the complementary region of the aptamer excluded A₁₀/T₁₀, a dramatic fluorescence enhancement (maximum: ∼500-fold; maximum quantum yield: 31.5%) can be realized. The fluorescence enhancement should result from the aggregation-induced emission of the AgNCs, which can be attributed to forming the reticular structure of the hybridized product. To some extent, the method developed in this work is extendable. The fluorescence enhancement was also realized from the thrombin aptamer-templated AgNCs through designing the aptamer and the corresponding complementary strand according to the method. Based on the fluorescence enhancement of the Apt_AβO-templated AgNCs, an "on-off" fluorescence sensor was constructed for the sensitive and selective detection of AβO. This work provides a rational strategy to realize fluorescence enhancement for the aptamer-templated AgNCs and design an aptamer-based fluorescence sensor.

DNA-templated copper nanocluster: A robust and universal fluorescence switch for bleomycin assay

Bleomycin (BLM) is widely utilized for cancer treatment due to the outstanding antitumor activity, but BLM with imprecisely controlled dosage may lead to lethal consequences. It is thus a profound task to accurately monitor the BLM levels in clinical settings. Herein, we propose a straightforward, convenient, and sensitive sensing method for BLM assay. Poly-T DNA-templated copper nanoclusters (CuNCs) are fabricated with strong fluorescence emission and uniform size distribution and served as fluorescence indicators for BLM. The high binding affinity of BLM for Cu²⁺makes it able to inhibit fluorescence signals generated from CuNCs. This is the underlying mechanism rarely explored and can be utilized for effective BLM detection. A detection limit of 0.27 μM (according to 3σ/s rule) is achieved in this work. And the precision, producibility, and practical useability are also confirmed with satisfactory results. Furthermore, the accuracy of the method is verified by high-performance liquid chromatography (HPLC). To sum up, the established strategy in this work exhibits the advantages of convenience, rapidness, low cost, and high precision. The construction of BLM biosensors is important to achieve the best therapeutic effect with minimal toxicity, which opens a new avenue for monitoring antitumor drugs in clinical settings.

Copper nanoclusters stabilized by D-penicillamine for ultrasensitive and visual detection of oxytetracycline

Copper nanoclusters (DPA@CuNCs) with red fluorescence were successfully synthesized by a one-step method based on D-penicillamine (DPA), which acted not only as a reducing agent but also as a stabilizer. The products were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, particle-size analysis, ultraviolet-visible spectrophotometry, and fluorescence spectrometry. When the excitation wavelength was 280 nm, DPA@CuNCs emitted bright red fluorescence at 640 nm with a fluorescence quantum yield of 5.8 %. Due to the inner filter effect, oxytetracycline (OTC) effectively quenched the fluorescence of DPA@CuNCs, and then DPA@CuNCs were applied to the trace detection of OTC. The method showed a good linear range for OTC from 5 to 60 μmol/L, with a detection limit of 0.026 μmol/L and a correlation coefficient R² of 0.9983. Moreover, a paper-based sensor for the visual detection of OTC has been developed, which can conveniently and rapidly distinguish the concentration ranges of OTC through the color changes of the test papers.

Cu2+-mediated turn-on fluorescence biosensor based on DNA-templated silver nanoclusters for label-free and sensitive detection of adenosine triphosphate

A Cu²⁺-mediated turn-on fluorescence biosensor based on the DNA-templated green-emitting silver nanoclusters (DNA@g-AgNCs) was developed for label-free and sensitive detection of adenosine 5'-triphosphate (ATP). Cu²⁺ was able to quench the bright green fluorescence of DNA@g-AgNCs because of the coordination and photoinduced electron transfer between DNA@g-AgNCs and Cu²⁺. Therefore, a unique and effective fluorescence biosensor can be constructed with the formation of DNA@g-AgNCs/Cu²⁺/ATP ternary-competition system. With the introduction of ATP, the DNA@g-AgNCs/Cu²⁺ fluorescence sensing system will be disrupted and the fluorescence of DNA@g-AgNCs was recovered due to higher affinity of ATP towards Cu²⁺. On the basis of this feature, the DNA@g-AgNCs/Cu²⁺ fluorescence sensing system demonstrated quantitative determination of ATP in the range 0.05 - 3 μM and a detection limit of 16 nM. Moreover, the fluorescence sensing system was successfully applied to the quantitative determination of ATP in human urine and serum samples with recoveries ranging from 98.6 to 106.5%, showing great promise to provide  a label-free, cost-efficient, and rapid platform for ATP-related clinical disease diagnosis.

DNA Nanoribbon for Efficient Anti-miRNA Peptide Nucleic Acid Delivery and Synergistic Enhancement of Cancer Cell Apoptosis

Antisense peptide nucleic acid (asPNA), an effective antisense drug, has been employed as a gene therapy agent and a useful tool in molecular biology. Gaining control over the delivery of asPNA to target tissues has been a major hindrance to its wide application in clinical practice. A simple and efficient DNA nanoribbon (DNR)-based drug delivery process has been designed in this study that releases the asPNA agent to inhibit oncogenic microRNAs (miRNAs). Furthermore, we demonstrated how the AS1411 aptamer that binds nucleolin on the cell membranes works as a control mechanism capable of identifying target cancer cells and enhancing the enrichment capacity of DNR. With the biodegradability of DNR, we can efficiently initiate the release of asPNA into the cytoplasm, particularly targeting the intended miR-21 and synergistically increasing programmed cell death 4 (PDCD4) expression to enhance cell apoptosis. We assume that this well-defined delivery mechanism will aid in designing antisense site-specific treatments for various diseases, including cancer.

Nanotrains of DNA Copper Nanoclusters That Triggered a Cascade Fenton-Like Reaction and Glutathione Depletion to Doubly Enhance Chemodynamic Therapy

Many current chemodynamic therapy (CDT) strategies suffer from either low therapeutic efficiency or the deficiency of poor targeting. The low therapeutic efficiency is mainly ascribed to the intracellular antioxidant system and the inefficient Fenton reaction in the weakly acidic tumor microenvironment (TME). Herein, by exploitation of the diverse function and programmability of functional nucleic acid, aptamer-tethered nanotrains of DNA copper nanoclusters (aptNTDNA-CuNCs) were assembled to simultaneously achieve targeted recognition, loading, and delivery of CDT reagents into tumor cells without an external carrier. The intracellular hydrogen peroxide (H₂O₂) oxidized nanotrains of DNA-CuNCs to produce a lot of Cu²⁺ and Cu⁺ ions, which can generate reactive oxygen species (ROS) in the weakly acidic TME based on the pH-independent Fenton-like reaction of Cu⁺/H₂O₂. Meanwhile, the redox reaction between intracellular glutathione (GSH) and Cu²⁺ depleted GSH and generated Cu⁺ ions, which weakened the antioxidant ability of cancer cells and further enhanced the Fenton-like reaction of Cu⁺/H₂O₂, respectively. Thus, the cascade Fenton-like reaction and GSH depletion doubly improved the efficacy of CDT. The in vivo and in vitro study solidly confirmed that aptNTDNA-CuNCs have excellent antitumor efficacy and no cytotoxicity to healthy cells. Therefore, aptNTDNA-CuNCs can act as CDT reagents to achieve highly efficient, biocompatible, and targeted CDT.

Fluorescence Aptasensor of Tuberculosis Interferon-γ in Clinical Samples Regulated by Steric Hindrance and Selective Identification

Although there are many interferon gamma (IFN-γ)-based tools for tuberculosis (TB) diagnosis, they are less sensitive and laborious. Here, we developed an IFN-γ aptasensor using pyrophosphate-cerium coordination polymeric nanoparticles (PPi-Ce CPNs) as signal reporters and a double-stranded DNA as a probe. The sensor was realized by sterically regulating the polymerization elongation of terminal deoxynucleotidyl transferase (TdT) and the selective recognition reaction of PPi-Ce CPNs. This method employs PPi-Ce CPNs to selectively identify Cu²⁺ and polyT-templated copper nanoparticles (Cu NPs), as well as a TdT-assisted amplification technique. Our data showed that under optimized experimental conditions, a limit of detection of as low as 0.25 fg/mL was achieved, with a linear range of 1-100 fg/mL, and a good target protein specificity. The detection sensitivity was an order of magnitude higher than that observed with Cu NPs when used as signal reporters. This IFN-γ quantification technique was further validated in clinical samples using 57 clinical TB patients (22 negative and 35 positive). Our findings agreed with those from enzyme-linked immunosorbent assay, GeneXpert MTB/rifampin assay, and polymerase chain reaction detection of TB-DNA and those from clinical imaging techniques. Therefore, our analytical system may provide an additional and more sensitive tool for the early diagnosis of TB.

A label-free cyclic amplification strategy for microRNA detection by coupling graphene oxide-controlled adsorption with superlong poly(thymine)-hosted fluorescent copper nanoparticles

Herein, based on a terminal deoxynucleotidyl transferase (TdT)-mediated superlong poly-T-templated-copper nanoparticles (poly T-CuNPs) strategy, a simple, universal and label-free fluorescent biosensor for the detection of miRNA was constructed by employing graphene oxide (GO) and DNase I. In this strategy, GO and DNase I were used as a switch and amplifier of the signal generation pathway, respectively, and the fluorescence of poly T-CuNPs was used as the signal output. In the presence of target miRNA, the DNA dissociated from the GO surface by forming a miRNA/DNA duplex and was degraded by DNase I. The short oligos with 3'-OH, the product of DNase I degradation, could be recognized by the TdT and added to a long poly-T tail. Finally, the fluorescence signal was output through the synthesis of poly T-CuNPs. As a proof of concept, let-7a was analyzed. The method showed good sensitivity and selectivity with a linear response in the 50 pM-10,000 pM let-7a concentration range and a 30 pM limit of detection (LOD = 30 pM, R² = 0.9954, the relative standard deviation were 2.79%-5.30%). It was also successfully applied to the determination of miRNA in spiked human serum samples. It showed good linearity in the range of 500-10000 pM (R² = 0.9969, the relative standard deviation were 1.61%-3.85%). Moreover, both the adsorption of GO and the degradation of DNase I are DNA sequence-independent; thus, this method can be applied to the detection of any miRNA simply by changing the assisted-DNA sequence.

Homogeneous Binary Visual and Fluorescence Detection of Tetanus Toxoid in Clinical Samples Based on Enzyme-Free Parallel Hybrid Chain Reaction

Here, we report a simple aptamer-based toxoid test with both fluorescence and binary visual readouts. This test is established based on our recent finding that CdTe quantum dots could differentiate DNA templated Cu NPs from Cu²⁺. Through the further integration with enzyme-free triple parallel hybridization chain reaction, cation exchange reaction, and inkjet printing, we demonstrated specific detection of tetanus toxoid with a limit-of-detection (LOD) of 0.25 fg/mL using fluorescence readout. Using color- and distance-based binary visual readouts, we were able to achieve LODs of 10 fg/mL and 1 fg/mL, respectively. The quantitative test results for tetanus toxoid using both fluorescence and visual readouts were successfully validated in 84 clinical serum samples. Moreover, our strategy also enabled accurate monitoring of tetanus toxoid levels in patients before and after drug treatment. On the basis of our clinical test results, we recommend a cutoff value of 5 fg/mL for tetanus infection.

DNA Nanotechnology-Enabled Fabrication of Metal Nanomorphology

In recent decades, DNA nanotechnology has grown into a highly innovative and widely established field. DNA nanostructures have extraordinary structural programmability and can accurately organize nanoscale materials, especially in guiding the synthesis of metal nanomaterials, which have unique advantages in controlling the growth morphology of metal nanomaterials. This review started with the evolution in DNA nanotechnology and the types of DNA nanostructures. Next, a DNA-based nanofabrication technology, DNA metallization, was introduced. In this section, we systematically summarized the DNA-oriented synthesis of metal nanostructures with different morphologies and structures. Furthermore, the applications of metal nanostructures constructed from DNA templates in various fields including electronics, catalysis, sensing, and bioimaging were figured out. Finally, the development prospects and challenges of metal nanostructures formed under the morphology control by DNA nanotechnology were discussed.

Controlling the Chemistry of Nanoclusters: From Atomic Precision to Controlled Assembly

Metal nanoclusters have gained prominence in nanomaterials sciences, owing to their atomic precision, structural regularity, and unique chemical composition. Additionally, the ligands stabilizing the clusters provide great opportunities for linking the clusters in higher order dimensions, eventually leading to the formation of a repertoire of nanoarchitectures. This makes the chemistry of atomic clusters worth exploring. In this mini review, we aim to focus on the chemistry of nanoclusters. Firstly, we summarize the important strategies developed so far for the synthesis of atomic clusters. For each synthetic strategy, we highlight the chemistry governing the formation of nanoclusters. Next, we discuss the key techniques in the purification and separation of nanoclusters, as the chemical purity of clusters is deemed important for their further chemical processing. Thereafter which we provide an account of the chemical reactions of nanoclusters. Then, we summarize the chemical routes to the spatial organization of atomic clusters, highlighting the importance of assembly formation from an application point of view. Finally, we raise some fundamentally important questions with regard to the chemistry of atomic clusters, which, if addressed, may broaden the scope of research pertaining to atomic clusters.

Intrinsic-to-extrinsic emission tuning in luminescent Cu nanoclusters by in situ ligand engineering

Enhancement of the emission quantum yield and expansion of the emission tunability spectrum are the key aspects of an emitter, which direct the evolution of future generation light harvesting materials. In this regard, small molecular ligand-protected Cu nanoclusters (SLCuNCs) have emerged as prospective candidates. Herein, we report the broadband emission tunability in a SLCuNC system, mediated by in situ ligand replacement. 1,6-Hexanedithiol-protected blue emissive discrete Cu nanoclusters (CuNCs) and red emissive CuNC assemblies have been synthesized in one pot. The red emissive CuNC assemblies were characterized and found to be covalently-linked nanocluster superstructures. The blue emissive CuNC was further converted to a green-yellow emissive CuNC over time by a ligand replacement process, which was mediated by the oxidized form of the reducing agent used for synthesizing the blue emissive nanocluster. Steady-state emission results and fluorescence dynamics studies were used to elucidate that the ligand replacement process not only modulates the emission color but also alters the nature of emission from metal-centered intrinsic to ligand-centered extrinsic emission. Moreover, time-dependent blue to green-yellow emission tunability was demonstrated under optimized reaction conditions.

Fluorescence and visual immunoassay of HIV-1 p24 antigen in clinical samples via multiple selective recognitions of CdTe QDs

Human immunodeficiency virus (HIV) infection inflicts significant economic and social burdens on many countries worldwide. Given the substantial morbidity and mortality from HIV infection, there is an urgent need for accurate and early detection of the virus. In this study, immunofluorescence and visual techniques are described that detect the HIV-1 p24 antigen, which relied on selective recognition of Ag⁺/Ag nanoparticles (Ag NPs) and Cu²⁺/Cu⁺ using cadmium telluride quantum dots (CdTe QDs). After the sandwich immunoreactions were accomplished, the alkaline phosphatase (ALP) hydrolyzed L-ascorbic acid 2-phosphate (AAP) to form ascorbic acid (AA) that further reduces Ag⁺ and Cu²⁺ to Ag NPs and Cu⁺, respectively. This method was highly sensitive and selective and could detect as low as 1 pg/mL of p24 antigen by naked eyes and had a good linearity in the concentration range 1-100 pg/mL. When using Ag⁺ and Cu²⁺ as media, the limit of detection (LOD) of the new method was 0.3 pg/mL and 0.2 pg/mL, respectively. Compared with clinical electrochemiluminescence immunoassay (ECLIA) results and clinical data, this method demonstrated good consistency for the quantification of HIV-1 p24 antigen in 34 clinical serum samples. In addition, this method could accurately distinguish HIV from other viruses and infections such as hepatitis B virus, systemic lupus erythematosus, hepatitis C virus, Epstein-Barr virus, cytomegalovirus, lipemia, and hemolysis. Therefore, our dual-mode analysis method may provide additional solutions to identify clinical HIV infection. An immunofluorescence and visualization dual-mode strategy for the detection of p24 antigen was constructed based on immune recognition reaction and a phenomenon that cadmium telluride quantum dots (CdTe QDs) can selectively recognize Ag⁺/Ag nanoparticles (Ag NPs) and Cu²⁺/Cu⁺.

Self-assembly of copper nanoclusters: isomeric ligand effect on morphological evolution

Tailoring the hierarchical self-assembly of metal nanoclusters (NCs) is an emergent area of research owing to their precise structure and flexible surface environment. Herein, the morphological evolution from rods to platelets to ribbon-like structures through self-assembly of Cu₇ NCs is dictated by the positional isomerism of the surface capping ligand, dimethylbenzenethiol (DMBT). Besides cuprophilic interaction, the interplay between π-π stacking and agostic interaction (Cu⋯H-C) directs the inter-NC organization into different ordered architectures. The excited-state relaxation dynamics of the red phosphorescent assembled structures has been correlated with their compactness and the degree of bonding interactions present.

DNA dendrimer-templated copper nanoparticles: self-assembly, aggregation-induced emission enhancement and sensing of lead ions

Copper nanomaterials based on DNA scaffold (DNA-Cu NMs) are becoming a novel fluorescent material, but it is still challenging to obtain highly fluorescent DNA-Cu NMs with excellent stability. In this work, we report a kind of copper nano-assemblies (Cu NASs) with aggregation-induced emission enhancement (AIEE) property using DNA dendrimers with sticky end as template. The sticky end of the DNA dendrimers induced the formation of much bigger Cu NASs with average size ranging from 131 to 264 nm, depending on the length of the DNA dendrimer sticky end from 6 bases to 27 bases. Compared with complete complementary DNA dendrimer, nearly 6-fold fluorescence enhancement was achieved using DNA dendrimer with 27 bases sticky end. Moreover, the DNA dendrimer-Cu NASs demonstrated excellent stability in serum and could be rapidly quenched by Pb²⁺ ions. Based on the above property, highly sensitive and selective fluorescent detection of Pb²⁺ ions was possible with a linear range of 2.0-100 nM and a detection limit of 0.75 nM. Due to the sensitive and rapid response to Pb²⁺ as well as excellent stability in complex matrix, the proposed fluorescent Cu NASs demonstrated high potential as an excellent fluorescent probe for Pb²⁺ in complex matrix.

Facile preparation of silver nanocluster self-assemblies with aggregation-induced emission by equilibrium shifting

Aggregation-induced emission is a promising pathway to get high photoluminescence from metal nanocluster assemblies. The self-assembly of metal nanoclusters with regular morphologies can restrict the rotation and vibration modes of capping ligands, reduce nanoclusters' non-radiative decay, and finally result in an aggregation-induced strong emission. In this study, silver nanocluster self-assemblies stabilized by thiosalicylic acid (TSA) were prepared in water by equilibrium shifting, which exhibit nanofiber-like morphologies. The resulting silver nanocluster self-assemblies exhibit aggregation-induced emission in solid or aggregated state with a decent quantum yield i.e., 13.05%. The obtained silver nanocluster self-assemblies were thoroughly characterized by fluorescence spectroscopy, UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), matrix assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF), powder X-ray diffraction (PXRD) and high-resolution transmission electron microscopy (HRTEM). These silver nanocluster self-assemblies with high photoluminescence in aggregated state may have potential use in light emitting devices and bioapplications.

DNA Based and Stimuli-Responsive Smart Nanocarrier for Diagnosis and Treatment of Cancer: Applications and Challenges

The rapid development of multidrug co-delivery and nano-medicines has made spontaneous progress in tumor treatment and diagnosis. DNA is a unique biological molecule that can be tailored and molded into various nanostructures. The addition of ligands or stimuli-responsive elements enables DNA nanostructures to mediate highly targeted drug delivery to the cancer cells. Smart DNA nanostructures, owing to their various shapes, sizes, geometry, sequences, and characteristics, have various modes of cellular internalization and final disposition. On the other hand, functionalized DNA nanocarriers have specific receptor-mediated uptake, and most of these ligand anchored nanostructures able to escape lysosomal degradation. DNA-based and stimuli responsive nano-carrier systems are the latest advancement in cancer targeting. The data exploration from various studies demonstrated that the DNA nanostructure and stimuli responsive drug delivery systems are perfect tools to overcome the problems existing in the cancer treatment including toxicity and compromised drug efficacy. In this light, the review summarized the insights about various types of DNA nanostructures and stimuli responsive nanocarrier systems applications for diagnosis and treatment of cancer.

Self-Assembly of Precision Noble Metal Nanoclusters: Hierarchical Structural Complexity, Colloidal Superstructures, and Applications

Ligand protected noble metal nanoparticles are excellent building blocks for colloidal self-assembly. Metal nanoparticle self-assembly offers routes for a wide range of multifunctional nanomaterials with enhanced optoelectronic properties. The emergence of atomically precise monolayer thiol-protected noble metal nanoclusters has overcome numerous challenges such as uncontrolled aggregation, polydispersity, and directionalities faced in plasmonic nanoparticle self-assemblies. Because of their well-defined molecular compositions, enhanced stability, and diverse surface functionalities, nanoclusters offer an excellent platform for developing colloidal superstructures via the self-assembly driven by surface ligands and metal cores. More importantly, recent reports have also revealed the hierarchical structural complexity of several nanoclusters. In this review, the formulation and periodic self-assembly of different noble metal nanoclusters are focused upon. Further, self-assembly induced amplification of physicochemical properties, and their potential applications in molecular recognition, sensing, gas storage, device fabrication, bioimaging, therapeutics, and catalysis are discussed. The topics covered in this review are extensively associated with state-of-the-art achievements in the field of precision noble metal nanoclusters.

Bottom-Up Fabrication of DNA-Templated Electronic Nanomaterials and Their Characterization

Bottom-up fabrication using DNA is a promising approach for the creation of nanoarchitectures. Accordingly, nanomaterials with specific electronic, photonic, or other functions are precisely and programmably positioned on DNA nanostructures from a disordered collection of smaller parts. These self-assembled structures offer significant potential in many domains such as sensing, drug delivery, and electronic device manufacturing. This review describes recent progress in organizing nanoscale morphologies of metals, semiconductors, and carbon nanotubes using DNA templates. We describe common substrates, DNA templates, seeding, plating, nanomaterial placement, and methods for structural and electrical characterization. Finally, our outlook for DNA-enabled bottom-up nanofabrication of materials is presented.

Homogeneous Visual and Fluorescence Detection of Circulating Tumor Cells in Clinical Samples via Selective Recognition Reaction and Enzyme-Free Amplification

Here we report a simple all-nucleic-acid enzyme-free catalyzed hairpin assembly assisted amplification strategy with quantum dots (QDs) as the nanoscale signal reporter for homogeneous visual and fluorescent detection of A549 lung cancer cells from clinical blood samples. This work was based on the phenomenon that CdTe QDs can selectively recognize Ag⁺ and C-Ag⁺-C and by using mucin 1 as the circulating tumor cells (CTCs) marker and aptamer as the recognition probe. Under optimized conditions, the limits of detections as low as 0.15 fg/mL of mucin 1 and 3 cells/mL of A549 cells were achieved with fluorescence signals. A 1 fg/mL concentration of mucin 1 and 100 cells/mL of A549 can be distinguished by the naked eye. This method was used to quantitatively analyze CTCs in 51 clinical whole blood samples of patients with lung cancer. The levels of CTCs detected in clinical samples by this method were consistent with those obtained using the folate receptor-polymerase chain reaction clinical test kit and correlated with radiologic and pathological findings.

Highly luminescent and catalytically active suprastructures of magic-sized semiconductor nanoclusters

Metal chalcogenide magic-sized nanoclusters have shown intriguing photophysical and chemical properties, yet ambient instability has hampered their extensive applications. Here we explore the periodic assembly of these nanoscale building blocks through organic linkers to overcome such limitations and further boost their properties. We designed a diamine-based heat-up self-assembly process to assemble Mn²⁺:(CdSe)₁₃ and Mn²⁺:(ZnSe)₁₃ magic-sized nanoclusters into three- and two-dimensional suprastructures, respectively, obtaining enhanced stability and solid-state photoluminescence quantum yields (from <1% for monoamine-based systems to ~72% for diamine-based suprastructures). We also exploited the atomic-level miscibility of Cd and Zn to synthesize Mn²⁺:(Cd_1-xZn_xSe)₁₃ alloy suprastructures with tunable metal synergy: Mn²⁺:(Cd_0.5Zn_0.5Se)₁₃ suprastructures demonstrated high catalytic activity (turnover number, 17,964 per cluster in 6 h; turnover frequency, 2,994 per cluster per hour) for converting CO₂ to organic cyclic carbonates under mild reaction conditions. The enhanced stability, photoluminescence and catalytic activity through combined cluster-assembly and metal synergy advance the usability of inorganic semiconductor nanoclusters.

Development of General Methods for Detection of Virus by Engineering Fluorescent Silver Nanoclusters

Viruses have caused significant damage to the world. Effective detection is required to relieve the impact of viral infections. A biomolecule can be used as a template such as deoxyribonucleic acid (DNA), peptide, or protein, for the growth of silver nanoclusters (AgNCs) and for recognizing a virus. Both the AgNCs and the recognition elements are tunable, which is promising for the analysis of new viruses. Considering that a new virus such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) urgently requires a facile sensing strategy, various virus detection strategies based on AgNCs including fluorescence enhancement, color change, quenching, and recovery are summarized. Particular emphasis is placed on the molecular analysis of viruses using DNA stabilized AgNCs (DNA-AgNCs), which detect the virus's genetic material. The more widespread applications of AgNCs for general virus detection are also discussed. Further development of these technologies may address the challenge for facile detection of SARS-CoV-2.

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.

Visual and dual-fluorescence homogeneous sensor for the detection of pyrophosphatase in clinical hyperthyroidism samples based on selective recognition of CdTe QDs and coordination polymerization of Ce3+

A visual / dual fluorescent strategy based on selective recognition of QDs and coordination polymerization of Ce³⁺ was developed for pyrophosphatase detection.

Highly Stable Pyrimidine Based Luminescent Copper Nanoclusters with Superoxide Dismutase Mimetic and Nitric Oxide Releasing Activity

Copper nanoclusters (CuNCs) are emerging as an interesting class of materials for various biomedical applications. In this work, we have designed highly stable nucleobase-capped luminescent CuNCs and studied the effect of substituents on the cluster composition and photophysical properties. The NCs exhibit exceptional stability in ambient atmosphere and show significant variation in the emission properties with a change in position of substituents on the ligand, thiouracil. This study represents the first example of a nanocluster that functionally mimics the activity of a major antioxidant enzyme, superoxide dismutase (SOD). In addition to their enzyme-mimetic activity, the CuNCs evince controlled release of nitric oxide (NO), a key gaseous molecule of endothelial system from S-nitrosothiol, S-nitrosoglutathione (GSNO). Further, to a greater significance, these luminescent CuNCs are readily taken up by the mammalian cells and exhibit low toxicity. The superoxide dismutase and NO releasing activity of the fluorescent, biocompatible copper nanoclusters suggest their potential application in both therapeutics and bioimaging.

Chiroptical property enhancement of chiral Eu(III) complex upon association with DNA-CTMA

DNA-based materials have attracted much attention due to their unique photo-functional properties and potential applications in various fields such as luminescent and biological systems, nanodevices, etc. In this study, the photophysical properties of a chiral Eu(III) complex, namely (Eu(D-facam)₃), within DNA films were extensively investigated. The enhancement of photoluminescence (more than 25-folds increase of luminescence quantum yield) and degree of circularly polarization in luminescence (g_lum = − 0.6) was observed upon interaction with DNA. Various photophysical analyses suggested that the emission enhancement was mainly due to an increase of the sensitization efficiency (high η_sens) from the ligands to Eu(III) and suppression of the vibrational deactivation upon immobilization onto the DNA molecule. From CD and VCD measurements, it was suggested that the coordination structure of Eu(D-facam)₃ was affected by the interaction with DNA, suggesting that the structural change of Eu(D-facam)₃ contributed to the improvement of its luminescent properties.

Facile Synthesis of Ultrastable Fluorescent Copper Nanoclusters and Their Cellular Imaging Application

Copper nanoclusters (Cu NCs) are generally formed by several to dozens of atoms. Because of wide range of raw materials and cheap prices, Cu NCs have attracted scientists’ special attention. However, Cu NCs tend to undergo oxidation easily. Thus, there is a dire need to develop a synthetic protocol for preparing fluorescent Cu NCs with high QY and better stability. Herein, we report a one-step method for preparing stable blue-green fluorescent copper nanoclusters using glutathione (GSH) as both a reducing agent and a stabilizing agent. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrospray ionization mass spectrometer (ESI-MS) were used to characterize the resulting Cu NCs. The as-prepared Cu NCs@GSH possess an ultrasmall size (2.3 ± 0.4 nm), blue-green fluorescence with decent quantum yield (6.2%) and good stability. MTT results clearly suggest that the Cu NCs@GSH are biocompatible. After incubated with EB-labeled HEK293T cells, the Cu NCs mainly accumulated in nuclei of the cells, suggesting that the as-prepared Cu NCs could potentially be used as the fluorescent probe for applications in cellular imaging.

Highly Luminescent Copper Nanoclusters Stabilized by Ascorbic Acid for the Quantitative Detection of 4-Aminoazobenzene

As one of the widely studied metal nanoclusters, the preparation of copper nanoclusters (Cu NCs) by a facile method with high fluorescence performance has been the interest of researchers. In this paper, a simple, green, clean, and time-saving chemical etching method was used to synthesize water-soluble Cu NCs using ascorbic acid (AA) as the reducing agent. The as-prepared Cu NCs showed strong green fluorescence (with a quantum yield as high as 33.6%) and high ion stability, and good antioxidant activity as well. The resultant Cu NCs were used for the detection of 4-aminoazobenzene (one of 24 kinds of prohibited textile compounds) in water with a minimum detection limit of 1.44 μM, which has good potential for fabric safety monitoring.