DNA Templated Metal Nanoclusters: From Emergent Properties to Unique Applications

DNA-based FeCuAg nanoclusters with peroxidase-like and GSH depletion activities for toxicity of in vitro cancer cells

Developing the efficient nanozymes for reactive oxygen species (ROS)-mediated highly potent tumor catalytic therapy has become a great challenge. In this study, we prepared the DNA-Fe, -FeAg, and -FeCuAg nanocluster (NCs) using the G-/C-rich single-stranded DNA (ssDNA) templates. The steady-state kinetic and the catalytic performances and mechanisms of DNA-metal NCs were first systematically investigated. The results indicated that c-kit-TBA-Fe, c-kit-TBA-FeAg, and c-kit-TBA-FeCuAg NCs exhibited the high peroxidase-like activity. All of three types of NCs presented the higher affinity to the substrate TMB and better storage stability at 4 °C than horseradish peroxidase (HRP). Moreover, c-kit-TBA-FeAg and c-kit-TBA-FeCuAg NCs presented the 6.7- and 4.7-fold stronger affinity to TMB than c-kit-TBA-Fe, respectively. However, the maximum reaction rate (Vmax) of c-kit-TBA-FeCuAg NCs with H2O2 was the largest, which promoted the generation of much more •OH in the reaction system. More importantly, c-kit-TBA-FeCuAg NCs were able to deplete largely the intracellular GSH and thus generate lots of endogenous ROS in HeLa cells, thereby exhibiting the significant and specific in vitro cancer cells toxicity. Therefore, c-kit-TBA-FeCuAg NCs, with peroxidase-like activity and glutathione (GSH) consumption ability, hold the ROS-based promising therapeutic effects for cancer.

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.

Synthesis of novel phenylalanine-coated copper nanoclusters for fluorescent probes to determine the interactions of cancer drugs with DNA

Abiraterone acetate (ATA) is an FDA-approved prodrug that exerts its effects by irreversibly inhibiting the enzymatic activities of 17α-hydroxylase and C17,20-lyase, which are responsible for testosterone production, particularly. Drug-DNA interaction studies are conducted using various methods. In this study, CuNCs were used as a fluorescent probe for the first time to investigate drug-DNA interactions. Additionally, a new synthesis was developed for copper nanoclusters coated with phenylalanine (Phe). Ascorbic acid served as the reducing agent, while Phe was used as a surface functionalizing and stabilizing agent. Phe/CuNCs were characterized using various techniques including TEM, DLS, XPS, UV-Vis spectroscopy, and fluorescence spectroscopy. Optimization studies were conducted for synthesis parameters such as ascorbic acid concentration, Phe concentration, incubation time, and incubation temperature. This new synthesis method offers various advantages such as easy synthesis procedure, short synthesis time, and compatibility with green chemistry principles. Phe/CuNCs were used as a fluorescent probe for ATA-DNA interactions. The binding constant (Ka) between ATA and DNA was calculated as 1.03 × 104. Furthermore, thermodynamic studies indicated that the effective forces involved in ATA-DNA interaction are Van der Waals and hydrogen bonding.

Simulating the Lyotropic Phase Behavior of a Partially Self-Complementary DNA Tetramer

DNA oligomers in solution have been found to develop liquid crystal phases via a hierarchical process that involves Watson-Crick base pairing, supramolecular assembly into columns of duplexes, and long-range ordering. The multiscale nature of this phenomenon makes it difficult to quantitatively describe and assess the importance of the various contributions, particularly for very short strands. We performed molecular dynamics simulations based on the coarse-grained oxDNA model, aiming to depict all of the assembly processes involved and the phase behavior of solutions of the DNA GCCG tetramers. We find good quantitative matching to experimental data at both levels of molecular association (thermal melting) and collective ordering (phase diagram). We characterize the isotropic state and the low-density nematic and high-density columnar liquid crystal phases in terms of molecular order, size of aggregates, and structure, together with their effects on diffusivity processes. We observe a cooperative aggregation mechanism in which the formation of dimers is less thermodynamically favored than the formation of longer aggregates.

Strategic framework for harnessing luminescent metal nanocluster assemblies in biosensing applications

The distinctive physicochemical attributes of ultra-small metal nanoclusters (MNCs) resembling those of molecules make them versatile constituents for self-assembled frameworks. This critical review scrutinizes the influence of assembly on the photoluminescence (PL) properties of MNCs and investigates their utility in biosensing applications. The investigation is initiated with an assessment of the shift from individual MNCs to assemblies and its repercussions on PL efficacy. Subsequently, two distinct biosensing modalities are explored: assembly-driven detection mechanisms and detection predicated on structural modifications in assembled MNCs. Through meticulous examination, we underscore the potential of self-assembly methodologies in tailoring the PL behavior of MNCs for the detection of diverse biological analytes and diseases.

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.

Protector-free, non-plasmonic silver quantum clusters by femtosecond pulse laser irradiation: in situ binding on nanocellulose filaments for improved catalytic activity and cycling performance

This study introduces a new, facile method to synthesize silver clusters from aqueous silver ion solution by using high intensity femtosecond pulse laser irradiation. The particles obtained in the absence of reducing or capping agents are 1-17 nm in size and presented quantum properties, as characterized by fluorescence, but did not exhibit plasmon signals, which is not a common characteristic of conventional silver nanoparticles. In a further development, small silver quantum clusters (∼1 nm) were bound in situ to wet-spun filaments of cellulose nanofibrils by pulsed laser irradiation. The obtained hybrid filaments as well as free silver quantum clusters revealed a catalytic activity remarkably higher than that of free gold quantum clusters; moreover, the hybrid filaments were found to show improved stability and cycling performance for silver-based catalysis. The present results indicate the potential of femtosecond laser irradiation to generate clusters as well as hybrid systems with excellent performance and reactivity.

Recent Advances in Fluorescent Nanoparticles for Stimulated Emission Depletion Imaging

Stimulated emission depletion (STED) microscopy, as a popular super-resolution imaging technique, has been widely used in bio-structure analysis and resolving the dynamics of biological processes beyond the diffraction limit. The performance of STED critically depends on the optical properties of the fluorescent probes. Ideally, the probe should process high brightness and good photostability, and exhibit a sensitive response to the depletion beam. Organic dyes and fluorescent proteins, as the most widely used STED probes, suffer from low brightness and exhibit rapid photobleaching under a high excitation power. Recently, luminescent nanoparticles (NPs) have emerged as promising fluorescent probes in biological imaging due to their high brightness and good photostability. STED imaging using various kinds of NPs, including quantum dots, polymer dots, carbon dots, aggregation-induced emission dots, etc., has been demonstrated. This review will comprehensively review recent advances in fluorescent NP-based STED probes, discuss their advantages and pitfalls, and outline the directions for future development.

Bonding states of gold/silver plasmonic nanostructures and sulfur-containing active biological ingredients in biomedical applications: a review

As one of the most instrumental components in the architecture of advanced nanomedicines, plasmonic nanostructures (mainly gold and silver nanomaterials) have been paid a lot of attention. This type of nanomaterial can absorb light photons with a specific wavelength and generate heat or excited electrons through surface resonance, which is a unique physical property. In innovative biomaterials, a significant number of theranostic (therapeutic and diagnostic) materials are produced through the conjugation of thiol-containing ingredients with gold and silver nanoparticles (Au and Ag NPs). Hence, it is essential to investigate Au/Ag-S interfaces precisely and determine the exact bonding states in the active nanobiomaterials. This study intends to provide useful insights into the interactions between Au/Ag NPs and thiol groups that exist in the structure of biomaterials. In this regard, the modeling of Au/Ag-S bonding in active biological ingredients is precisely reviewed. Then, the physiological stability of Au/Ag-based plasmonic nanobioconjugates in real physiological environments (pharmacokinetics) is discussed. Recent experimental validation and achievements of plasmonic theranostics and radiolabelled nanomaterials based on Au/Ag-S conjugation are also profoundly reviewed. This study will also help researchers working on biosensors in which plasmonic devices deal with the thiol-containing biomaterials (e.g., antibodies) inside blood serum and living cells.

Upgraded and Light-Up Biosensing Platform: Entropy-Driven Catalysis Circuit Manipulates the Configuration Transformation of Novel DNA Silver Nanoclusters on the Graphene Oxide Surface

To tackle the predicament of the traditional turn-off mechanism, exploring an activated turn-on system remains an intriguing and crucial objective in biosensing fields. Herein, a dark DNA Ag nanocluster (NC) with hairpin-structured DNA containing a six-base cytosine loop (6C loop) as a template is atypically synthesized. Intriguingly, the dark DNA Ag NCs can be lit to display strong red-emission nanoclusters. Building upon these exciting findings, an unprecedented and upgraded turn-on biosensing system [entropy-driven catalysis circuit (EDCC)-Ag NCs/graphene oxide (GO)] has been created, which employs an EDCC to precisely manipulate the conformational transition of DNA Ag NCs on the GO surface from adsorption to desorption. Benefiting from the effective quenching of GO and signal amplification capability of the EDCC, the newly developed EDCC-Ag NCs/GO biosensing system displays a high signal-to-background (S/B) ratio (26-fold) and sensitivity (limit of detection as low as 0.4 pM). Meanwhile, it has good specificity, excellent stability, and reliability in both buffer and biological samples. To the best of our knowledge, it is the first example that adopts an EDCC to precisely modulate the configuration transformation of DNA Ag NCs on the GO surface to obtain a biosensor with low background, strong fluorescence, high contrast, and sensitivity. This exciting finding may provide a new route to fabricate a novel turn-on biosensor based on hairpin-templated DNA Ag NCs in the optical imaging and bioanalytical fields.

Fluorescent DNA-Silver nanoclusters in food safety detection: From synthesis to application

In recent years, the conventional preparation of silver nanoclusters (AgNCs) has attracted much attention due to their ultra-small size, tunable fluorescence, easy-to-engineer, as well as biocompatible material. Moreover, its great affinity towards cytosine bases on single-stranded DNA has led to the construction of biosensors, especially aptamers, for a broad variety of applications in food safety and environmental protection. In past years, numerous researchers paid attention to the construction of AgNCs aptasensor. Therefore, this review will be an effort to summarize the synthetic strategy along with the influences of factors on synthesis, categorize the sensing mechanism of aptamer-functionalized AgNCs biosensors, as well as their specific applications in food safety detection including heavy metal, toxin, and foodborne pathogenic bacteria. Furthermore, a brief conclusion and outlook regarding the prospects and challenges of their applications in food safety were drawn in line with the developments in DNA-AgNCs.

Recent Advances of DNA-Templated Metal Nanoclusters for Food Safety Detection: From Synthesis, Applications, Challenges, and Beyond

Food safety concerns have become a significant threat to human health and well-being, catching global attention in recent years. As a result, it is imperative to research conceptually novel biosensing and effective techniques for food matrices detection. Currently, DNA-templated metal nanoclusters (DNA-MNCs) are considered as one of the most promising nanomaterials due to their excellent properties in biosensing. While DNA-MNCs have garnered increasing interest, the reviews of design strategies, applications, and futuristic prospects for biosensing have been hardly found especially in food safety. The synthesis of DNA-MNCs and their use as biosensing materials in food contamination detection, including pathogenic bacteria, toxins, heavy metals, residues of pesticides, and others were comprehensively reviewed. In addition, we summarize the properties of DNA-MNCs briefly and discuss the challenges and future trends. The application of DNA-MNCs powered biosensing has been demonstrated and actively studied, which is a promising paradigm for food safety testing that can supplement or even replace current existing methods. Despite the challenges of difficulty regulating accurately, poor stability, low quantum yield, and difficult commercial transformation, the application prospects of DNA-MNCs biosensors are promising. This review aims to provide insights and directions for the future development of DNA-MNCs based food detection technology.

Water-ultrastable perovskite CsPbBr3 nanocrystals tailored by surface-confined strategy for amaranth sensing in food samples

A vital challenge is to develop water-stable perovskite nanocrystals owing to the easy attack of its surface vacancy defects by water-molecule. Here, a facile surface-passivated strategy to dramatically improve the chem-stability and luminescent efficiency (LE) of the CsPbBr3 nanocrystals (CPB) is proposed, where sodium dodecyl sulfate (SDS) encapsulate on CPB, generating confined environment (named SDS@CPB). The flexible long carbon-chain of SDS can confine the movement of CPB to form an externally hydrophobic closed-shell and internally structural rigidity through the hydrophobic association between surface hydrophobic groups, improving the LE and maintaining long-term composition of CPB. While the sulfate group in SDS can reduce the surface-defects exposure of CPB through the coordination with Pb2+, inhibiting the invasion of water-molecule. Importantly, an SDS@CPB-based sensor was fabricated to detect amaranth in food samples with a lower detection limit (5.43 nM), which opens a new avenue for food sensing based on high-efficiency perovskite nanocrystals.

Challenges and Opportunities of Using Fluorescent Metal Nanocluster-Based Colorimetric Assays in Medicine

Development of rapid colorimetric methods based on novel optical-active metal nanomaterials has provided methods for the detection of ions, biomarkers, cancers, etc. Fluorescent metal nanoclusters (FMNCs) have gained a lot of attention due to their unique physical, chemical, and optical properties providing numerous applications from rapid and sensitive detection to cellular imaging. However, because of very small color changes, their colorimetric applications for developing rapid tests based on the naked eye or simple UV-vis absorption spectrophotometry are still limited. FMNCs with peroxidase-like activity have significant potential in a wide variety of applications, especially for point-of-care diagnostics. In this review, the effect of using various capping agents and metals for the preparation of nanoclusters in their colorimetric sensing properties is explored, and the synthesis and detection mechanisms and the recent advances in their application for ultrasensitive chemical and biological analysis regarding human health are highlighted. Finally, the challenges that remain as well as the future perspectives are briefly discussed. Overcoming these limitations will allow us to expand the nanocluster's application for colorimetric diagnostic purposes in medical practice.

Electrochemical aptasensor based on DNA-templated copper nanoparticles and RecJf exonuclease-assisted target recycling for lipopolysaccharide detection

An electrochemical aptasensor for detecting lipopolysaccharides (LPS) was fabricated based on DNA-templated copper nanoparticles (DNA-CuNPs) and RecJf exonuclease-assisted target recycling. The DNA-CuNPs were synthesized on a double-stranded DNA template generated through the hybridization of the LPS aptamer and its complementary chain (cDNA). In the absence of LPS, the CuNPs were synthesized on DNA double-strands, and a strong readout corresponding to the CuNPs was achieved at 0.10 V (vs. SCE). In the presence of LPS, the fabricated aptamer could detach from the DNA double-strand to form a complex with LPS, disrupting the template for the synthesis of CuNPs on the electrode. Meanwhile, RecJf exonuclease could hydrolyze the cDNA together with this single-stranded aptamer, releasing the LPS for the next round of aptamer binding, thereby enabling target recycling amplification. As a result, the electrochemical signal decreased and could be used to indicate the LPS content. The fabricated electrochemical aptasensor exhibited an extensive dynamic working range of 0.01 pg mL-1 to 100 ng mL-1, and its detection limit was 6.8 fg mL-1. The aptasensor also exhibited high selectivity and excellent reproducibility. Moreover, the proposed aptasensor could be used in practical applications for the detection of LPS in human serum samples.

Optical nanosensors based on noble metal nanoclusters for detecting food contaminants: A review

Food contaminants present a significant threat to public health. In response to escalating global concerns regarding food safety, there is a growing demand for straightforward, rapid, and sensitive detection technologies. Noble metal nanoclusters (NMNCs) have garnered considerable attention due to their superior attributes compared to other optical materials. These attributes include high catalytic activity, excellent biocompatibility, and outstanding photoluminescence properties. These features render NMNCs promising candidates for crafting nanosensors for food contaminant detection, offering the potential for the development of uncomplicated, swift, sensitive, user-friendly, and cost-effective detection approaches. This review investigates optical nanosensors based on NMNCs, including the synthesis methodologies of NMNCs, sensing strategies, and their applications in detecting food contaminants. Furthermore, it involves a comparative assessment of the applications of NMNCs in optical sensing and their performance. Ultimately, this paper imparts fresh perspectives on the forthcoming challenges. Hitherto, optical (particularly fluorescent) nanosensors founded on NMNCs have demonstrated exceptional sensing capabilities in the realm of food contaminant detection. To enhance sensing performance, future research should prioritize atomically precise NMNCs synthesis, augmentation of catalytic activity and optical properties, development of high-throughput and multimode sensing, integration of NMNCs with microfluidic devices, and the optimization of NMNCs storage, shelf life, and transportation conditions.

Ratiometric Fluorescence Biosensing of Tandem Biemissive Ag Clusters Boosted by Confined Catalytic DNA Assembly

The reaction kinetics and yield of traditional DNA assembly with a low local concentration in homogeneous solution remain challenging. Exploring confined catalytic DNA assembly (CCDA) is intriguing to boost the reaction rate and efficacy for creating rapid and sensitive biosensing platforms. A rolling circle amplification (RCA) product containing multiple tandem repeats is a natural scaffold capable of guiding the periodic assembly of customized functional probes at precise sites. Here, we present a RCA-confined CCDA strategy to speed up amplifiable conversion for ratiometric fluorescent sensing of a sequence-specific inducer (I*) by using string green-/red-Ag clusters (sgAgCs and srAgCs) as two counterbalance emitters. Upon recognition of I*, CCDA events are operated by two toehold-mediated strand displacements and localized in repetitive units, thereby releasing I* for recycled signal amplification in the as-grown RCA concatemer. The local concentration of reactive species is increased to facilitate rapider dsDNA complex assembly and more efficient input-output conversion, on which the clustering template sequences of sgAgCs and srAgCs are blocked and opened, enabling srAgCs synthesis but opposite to sgAgCs. Thus, the fluorescence emission of srAgCs goes up, while sgAgCs go down. With the resultant ratio featuring inherent built-in correction, rapid, sensitive, and accurate quantification of I* at the picomolar level is achieved. Benefiting from efficient RCA confinement to enhance reaction kinetics and conversion yield, this CCDA-based strategy provides a new paradigm for developing simple and diverse biosensing methodologies.

Synthesis of copper nanoclusters from Bacopa monnieri leaves for fluorescence sensing of dichlorvos

In this work, a facile one-step green synthesis was developed for the fabrication of blue fluorescent copper nanocluster (Brahmi-CuNCs) from the extract of Bacopa monnieri (common name is Brahmi) via a microwave method. The as-prepared Brahmi-CuNCs emitted blue fluorescence at 452 nm when excited at 352 nm and showed a quantum yield of 31.32%. Brahmi-derived blue fluorescent CuNCs acted as a probe for fluorescence sensing of dichlorvos. Upon the addition of dichlorvos, the blue emission for Brahmi-CuNCs was gradually turned off, favouring establishment of a calibration graph in the range 0.5-100 μM with a detection limit of 0.23 μM. The as-synthesized Brahmi-CuNCs exhibited marked sensitivity and selectivity towards dichlorvos, favourable for assaying dichlorvos in various samples (cabbage, apple juice, and rice).

Electron count and ligand composition influence the optical and chiroptical signatures of far-red and NIR-emissive DNA-stabilized silver nanoclusters

Near-infrared (NIR) emissive DNA-stabilized silver nanoclusters (AgN-DNAs) are promising fluorophores in the biological tissue transparency windows. Hundreds of NIR-emissive AgN-DNAs have recently been discovered, but their structure-property relationships remain poorly understood. Here, we investigate 19 different far-red and NIR emissive AgN-DNA species stabilized by 10-base DNA templates, including well-studied emitters whose compositions and chiroptical properties have never been reported before. The molecular formula of each purified species is determined by high-resolution mass spectrometry and correlated to its optical absorbance, emission, and circular dichroism (CD) spectra. We find that there are four distinct compositions for AgN-DNAs emissive at the far red/NIR spectral border. These emitters are either 8-electron clusters stabilized by two DNA oligomer copies or 6-electron clusters with one of three different ligand compositions: two oligomer copies, three oligomer copies, or two oligomer copies with additional chlorido ligands. Distinct optical and chiroptical signatures of 6-electron AgN-DNAs correlate with each ligand composition. AgN-DNAs with three oligomer ligands exhibit shorter Stokes shifts than AgN-DNAs with two oligomers, and AgN-DNAs with chlorido ligands have increased Stokes shifts and significantly suppressed visible CD transitions. Nanocluster electron count also significantly influences electronic structure and optical properties, with 6-electron and 8-electron AgN-DNAs exhibiting distinct absorbance and CD spectral features. This study shows that the optical and chiroptical properties of NIR-emissive AgN-DNAs are highly sensitive to nanocluster composition and illustrates the diversity of structure-property relationships for NIR-emissive AgN-DNAs, which could be harnessed to precisely tune these emitters for bioimaging applications.

Untapped Potential of Deep Eutectic Solvents for the Synthesis of Bioinspired Inorganic-Organic Materials

Since the discovery of deep eutectic solvents (DESs) in 2003, significant progress has been made in the field, specifically advancing aspects of their preparation and physicochemical characterization. Their low-cost and unique tailored properties are reasons for their growing importance as a sustainable medium for the resource-efficient processing and synthesis of advanced materials. In this paper, the significance of these designer solvents and their beneficial features, in particular with respect to biomimetic materials chemistry, is discussed. Finally, this article explores the unrealized potential and advantageous aspects of DESs, focusing on the development of biomineralization-inspired hybrid materials. It is anticipated that this article can stimulate new concepts and advances providing a reference for breaking down the multidisciplinary borders in the field of bioinspired materials chemistry, especially at the nexus of computation and experiment, and to develop a rigorous materials-by-design paradigm.

A Sensitive Fluorescence Sensor for Tetracycline Determination Based on Adenine Thymine-Rich Single-Stranded DNA-Templated Copper Nanoclusters

A sensitive fluorescent sensor has been developed for the determination of tetracycline (TC) using adenine thymine (AT)-rich single-stranded DNA (ssDNA) templated copper nanoclusters (CuNCs) as a fluorescent probe. Fluorescent ssDNA-CuNCs were synthesized by employing AT-rich ssDNA as templates and ascorbic acid as reducing agents through a facile one-step method. The as-prepared ssDNA-CuNCs exhibited strong fluorescence with a large Stokes shift (240 nm) and stable fluorescence emission. In the presence of TC, the fluorescent intensity of ssDNA-CuNCs was obviously decreased through the inner filter effect, due to the spectral overlapping between ssDNA-CuNCs and TC. Under the optimal conditions, the strategy exhibited sensitive detection of TC with a linear range from 2 nM to 30 μM and with a limit of detection of 0.5 nM. Furthermore, the sensor was successfully applied for the detection of TC in milk samples. Therefore, it provided a simple, rapid, and label-free fluorescent method for TC detection.

pH-Switchable phenylalanine-templated copper nanoclusters: CO2 probing and efficient peroxidase mimicking activity

Inter-cluster conversion through the strategic tuning of external stimuli and thereby modulation of the optical properties of metal nanoclusters (MNCs) is an emerging domain for exploration. Herein, we report the preparation of blue-emitting CuNCs using phenylalanine (Phe) as a template under acidic conditions (pH ∼ 4). The as-prepared CuNCs exhibit a sequential tuning of the photophysical properties upon varying the pH of the solution from pH ∼4 to pH ∼12. Blue-emitting CuNCs (B-CuNCs, λem = 410 nm) are systematically converted to cyan-emitting CuNCs (C-CuNCs, λem = 490 nm) with a large red-shifted emission maximum by 80 nm as a function of pH. Our present investigation delineates an unprecedented switchability of the photoluminescence (PL) properties of the CuNCs with the variations of the pH from pH ∼4 to pH ∼12. Both the Phe-templated CuNCs (B-CuNCs and C-CuNCs) were broadly characterized by various spectroscopic and morphological techniques. The X-ray photoelectron spectroscopy (XPS) studies reveal the presence of different oxidation states in the metallic core of B-CuNCs and C-CuNCs. These results in turn substantiate the pH-induced intercluster conversion of CuNCs through the substantial change in their core composition as well as valence states. Owing to the pH sensitivity, the CuNCs act as an efficient and highly sensitive probe for CO2, and quantitative estimation of the dissolved CO2 in the form of bicarbonate ions has been achieved through the enhancement of the PL intensity, wherein a very low value of the limit of detection (LOD) of ∼60 μM was obtained. Furthermore, we demonstrated that the CuNCs act as an efficient bio-catalyst with peroxidase mimicking enzymatic activity which has been investigated using OPD as a substrate under physiological conditions (pH ∼7.4 and temperature ∼37 °C). The mechanistic investigations confirmed that the oxidation of OPD mainly proceeds through the generation of hydroxyl radicals (˙OH). We hope the present investigations shed light on a multidimensional aspect of MNCs and uncover an upsurging recent interest in MNCs to act as an artificial enzyme.

Heat, pH, and salt: synthesis strategies to favor formation of near-infrared emissive DNA-stabilized silver nanoclusters

We present chemical synthesis strategies for DNA-stabilized silver nanoclusters (AgN-DNAs) with near-infrared (NIR) emission in the biological tissue transparency windows. Elevated temperatures can significantly increase chemical yield of near-infrared nanoclusters. In most cases, basic pH favors near-infrared nanoclusters while micromolar amounts of NaCl inhibit their formation.

Dual-functional cellulase-mediated gold nanoclusters for ascorbic acid detection and fluorescence bacterial imaging

Protein-protected metal nanomaterials are becoming the most promising fluorescent nanomaterials for biosensing, bioimaging, and therapeutic applications due to their obvious fluorescent molecular properties, favorable biocompatibility and excellent physicochemical properties. Herein, we pioneeringly prepared a cellulase protected fluorescent gold nanoclusters (Cel-Au NCs) exhibiting red fluorescence under the excitation wavelength of 560 nm via a facile and green one-step method. Based on the fluorescence turn-off mechanism, the Cel-Au NCs were used as a biosensor for specificity determination of ascorbic acid (AA) at the emission of 680 nm, which exhibited satisfactory linearity over the range of 10-400 µM and the detection limit of 2.5 µM. Further, the actual sample application of the Au NCs was successfully established by evaluating AA in serum with good recoveries of 98.76%-104.83%. Additionally, the bacteria, including gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and gram-negative bacteria (Escherichia coli), were obviously stained by Cel-Au NCs with strong red emission. Thereby, as dual-functional nanoclusters, the prepared Cel-Au NCs have been proven to be an excellent fluorescent bioprobe for the detection of AA and bacterial labeling in medical diagnosis and human health maintenance.

Beyond nature's base pairs: machine learning-enabled design of DNA-stabilized silver nanoclusters

Sequence-encoded biomolecules such as DNA and peptides are powerful programmable building blocks for nanomaterials. This paradigm is enabled by decades of prior research into how nucleic acid and amino acid sequences dictate biomolecular interactions. The properties of biomolecular materials can be significantly expanded with non-natural interactions, including metal ion coordination of nucleic acids and amino acids. However, these approaches present design challenges because it is often not well-understood how biomolecular sequence dictates such non-natural interactions. This Feature Article presents a case study in overcoming challenges in biomolecular materials with emerging approaches in data mining and machine learning for chemical design. We review progress in this area for a specific class of DNA-templated metal nanomaterials with complex sequence-to-property relationships: DNA-stabilized silver nanoclusters (AgN-DNAs) with bright, sequence-tuned fluorescence colors and promise for biophotonics applications. A brief overview of machine learning concepts is presented, and high-throughput experimental synthesis and characterization of AgN-DNAs are discussed. Then, recent progress in machine learning-guided design of DNA sequences that select for specific AgN-DNA fluorescence properties is reviewed. We conclude with emerging opportunities in machine learning-guided design and discovery of AgN-DNAs and other sequence-encoded biomolecular nanomaterials.

Label-Free, High-Throughput, Sensitive, and Logical Analysis Using Biomimetic Array Based on Stable Luminescent Copper Nanoclusters and Entropy-Driven Nanomachine

The development of an array for high-throughput and logical analysis of biomarkers is significant for disease diagnosis. DNA-templated copper nanoclusters (CuNCs) have a strong potential to serve as a label-free photoluminescence source in array platforms, but their luminescent stability and sensitivity need to be improved. Herein, we report a facile, sensitive, and robust biomimetic array assay by integrating with stable luminescent CuNCs and entropy-driven nanomachine (EDN). In this strategy, the luminescent stability of CuNCs was improved by adding fructose in CuNCs synthesis to offer a reliable label-free signal. Meanwhile, the DNA template for CuNCs synthesis was introduced into EDN with excellent signal amplification ability, in which the reaction triggered by target miRNA would cause the blunt/protruding conformation change of 3'-terminus accompanied by the production or loss of luminescence. In addition, a biomimetic array fabricated by photonic crystals (PCs) physically enhanced the emitted luminescent signal of CuNCs and achieved high-throughput signal readout by a microplate reader. The proposed assay can isothermally detect as low as 4.5 pM of miR-21. Moreover, the logical EDN was constructed to achieve logical analysis of multiple miRNAs by "AND" or "OR" logic gate operation. Therefore, the proposed assay has the advantages of label-free property, high sensitivity, flexible design, and high-throughput analysis, which provides ideas for developing a new generation of facile and smart platforms in the fields of biological analysis and clinical application.

Simultaneous screening of multiple diarrhetic shellfish poisons with group-specific split aptamers and silver nanocluster beacon

Poisoning events concerning diarrhetic shellfish poisons (DSPs) are increasing continually. It is extremely necessary to develop simple analysis methods for screening simultaneously different types of DSPs from food-related samples. Okadaic acid (OA) and its analogues, i.e., dinophysistoxin-1 (DTX-1) and dinophysistoxin-2 (DTX-2), are the prevalent DSPs. Herein, a facile and label-free fluorescent aptasensor targeting the three DSPs was constructed with a pair of group-specific split aptamers and silver nanocluster beacon. In presence of the targets, the DNA templates attached at the ends of the split aptamers would be dragged close to trigger enhanced fluorescence signals from silver nanoclusters. The aptasensor offered high sensitivity and good selectivity, with limit of detection of 2.282 nmolL^-1, 19.38 nmolL^-1, and 13.61 nmolL^-1 for OA, DTX-1, and DTX-2, respectively. Moreover, the applicability of aptasensor was well verified with shellfish and seawater samples. This study provides good reference for further exploration on analysis methods for food-related molecules.

Facile preparation of bimetallic Au-Cu nanoclusters as fluorescent nanoprobes for sensitive detection of Cr3+ and S2O82- ions

Metallic nanoclusters (NCs) have attracted special attention from researchers due to their interesting optical properties. In this experiment, we proposed a facile one-step method for the synthesis of bimetallic gold-copper nanoclusters (AuCuNCs). The prepared AuCuNCs were characterized by fluorescence spectroscopy (FL), UV-vis absorption spectrum, transmission electron microscopy (TEM), etc. The emission peak of the prepared AuCuNCs was located at 455 nm and showed blue luminescence under the excitation of 365 nm UV light. Furthermore, after the addition of Cr³⁺ and S₂O₈^2- ions, the FL emission intensity of AuCuNCs was significantly reduced at 455 nm and there was a color change of diminished blue luminescence under UV lamp. The AuCuNCs exhibited excellent linearity and sensitivity for the detection of Cr³⁺ and S₂O₈^2- ions. The limits of detection (LOD) for the Cr³⁺ and S₂O₈^2- ions were calculated to be 1.5 and 0.037 μM, respectively. Finally, the recoveries of Cr³⁺ and S₂O₈^2- ions in Runxi Lake and tap water were measured by standard addition recovery test and were 96.66 ∼ 116.29 %, 95.75 ∼ 119.4 %.

Chloride Ligands on DNA-Stabilized Silver Nanoclusters

DNA-stabilized silver nanoclusters (Ag_N-DNAs) are known to have one or two DNA oligomer ligands per nanocluster. Here, we present the first evidence that Ag_N-DNA species can possess additional chloride ligands that lead to increased stability in biologically relevant concentrations of chloride. Mass spectrometry of five chromatographically isolated near-infrared (NIR)-emissive Ag_N-DNA species with previously reported X-ray crystal structures determines their molecular formulas to be (DNA)₂[Ag₁₆Cl₂]⁸⁺. Chloride ligands can be exchanged for bromides, which red-shift the optical spectra of these emitters. Density functional theory (DFT) calculations of the 6-electron nanocluster show that the two newly identified chloride ligands were previously assigned as low-occupancy silvers by X-ray crystallography. DFT also confirms the stability of chloride in the crystallographic structure, yields qualitative agreement between computed and measured UV-vis absorption spectra, and provides interpretation of the ³⁵Cl-nuclear magnetic resonance spectrum of (DNA)₂[Ag₁₆Cl₂]⁸⁺. A reanalysis of the X-ray crystal structure confirms that the two previously assigned low-occupancy silvers are, in fact, chlorides, yielding (DNA)₂[Ag₁₆Cl₂]⁸⁺. Using the unusual stability of (DNA)₂[Ag₁₆Cl₂]⁸⁺ in biologically relevant saline solutions as a possible indicator of other chloride-containing Ag_N-DNAs, we identified an additional Ag_N-DNA with a chloride ligand by high-throughput screening. Inclusion of chlorides on Ag_N-DNAs presents a promising new route to expand the diversity of Ag_N-DNA structure-property relationships and to imbue these emitters with favorable stability for biophotonics applications.

An amplified logic gate driven by in situ synthesis of silver nanoclusters for identification of biomarkers

An amplified DNA logic sensor was constructed for the identification of multiple biomarkers, in which the inputs of targets triggered the disassembly of a V-shaped probe (VSP) structure by a strand displacement reaction, leading to the synthesis of silver nanoclusters (AgNCs) for electrocatalytic reduction of H₂O₂. The sensing platform achieved sensitive detection of methylated DNA and microRNA 122 with detection limits down to 3.4 and 4.1 fM, respectively, and can be used for the assay of clinical serum samples from healthy volunteers and liver injury patients with satisfactory results. The DNA logic sensor exhibited the advantages of convenience, low cost, and versatility without the involvement of electroactive label modification, which is helpful for disease diagnosis as well as the fundamental investigation of interfacial electrochemistry and molecular biology.

Fluorescent detection of emerging virus based on nanoparticles: From synthesis to application

The spread of COVID-19 has caused huge economic losses and irreversible social impact. Therefore, to successfully prevent the spread of the virus and solve public health problems, it is urgent to develop detection methods with high sensitivity and accuracy. However, existing detection methods are time-consuming, rely on instruments, and require skilled operators, making rapid detection challenging to implement. Biosensors based on fluorescent nanoparticles have attracted interest in the field of detection because of their advantages, such as high sensitivity, low detection limit, and simple result readout. In this review, we systematically describe the synthesis, intrinsic advantages, and applications of organic dye-doped fluorescent nanoparticles, metal nanoclusters, up-conversion particles, quantum dots, carbon dots, and others for virus detection. Furthermore, future research initiatives are highlighted, including green production of fluorescent nanoparticles with high quantum yield, speedy signal reading by integrating with intelligent information, and error reduction by coupling with numerous fluorescent nanoparticles.

Glutathione-ascorbic acid-functionalized molybdenum oxide quantum dots-based fluorescent sensor for the detection of isoniazid drug in pharmaceutical samples

Herein, glutathione-ascorbic acid-functionalized molybdenum oxide quantum dots (GSH-AA-MoO_x QDs) are synthesized by the conventional method and used as a fluorescent probe for the rapid detection of isoniazid drug in pharmaceutical samples. Ascorbic acid and glutathione are used as surface ligands for the modification of MoO_x QDs. The as-synthesized GSH-AA-MoO_x QDs display λ_Em at 416 nm when applied λ_Ex at 330 nm. The introduction of isoniazid drug into GSH-AA-MoO_x QDs solution results the assembly of GSH-AA-MoO_x QDs-isoniazid nanoarchitectures, leading to quench λ_Em at 416 nm. Thus, GSH-AA-MoO_x QDs can work as a fluorescent sensor for the rapid identification of isoniazid in real samples. The as-prepared GSH-AA-MoO_x QDs not only allows superior analytical features (rapidity, and selectivity) toward isoniazid with the detection limit of 94 nM, but also displays fluorescence "turn-off" response for assaying of isoniazid in real samples (pharmaceutical and biofluids). Finally, GSH-AA-MoO_x QDs are highly promising fluorescent probe for the rapid detection of isoniazid in real samples.

In-situ bio-assembled specific Au NCs-Aptamer-Pyro conjugates nanoprobe for tumor imaging and mitochondria-targeted photodynamic therapy

Mitochondrion has emerged as a promising drug target for photodynamic therapy (PDT), due to its significant role in supporting life activities and being reactive oxygen species (ROS)-sensitive. Herein, we establish a new strategy that in-situ bio-synthesized Au NCs combine with mitochondria-targeted aptamer-Pyro conjugates (ApPCs) for specific tumor imaging and PDT. The prepared ApPCs can serve as template for the in-situ bio-synthesis of Au NCs, thereby facilitating the generation of Au NCs-ApPCs assemblies in unique tumor microenvironment. Compared with highly negatively charged ApPCs, bio-synthesized nanoscale Au NCs-ApPCs assemblies are conducive to cell uptake, which consequently benefits the delivery of ApPCs. After dissociated from Au NCs-ApPCs, internalized ApPCs can selectively accumulate in mitochondria and generate excess ROS to disrupt the mitochondrial membrane upon irradiation, thus inducing efficient cell killing. In vitro assays demonstrated that the fluorescent Au NCs-ApPCs assemblies could be specifically produced in cancerous cells, indicating the specific tumor imaging ability, while intracellular ApPCs co-localized well with mitochondria. CCK-8 results revealed over 80% cell death after PDT. In vivo study showed that fluorescent Au NCs-ApPCs assemblies were exclusively generated in tumor and achieved long-term retention; tumor growth was significantly inhibited after 15-day PDT treatment. All these evidences suggest that in-situ bio-synthesized Au NCs-ApPCs assembly is a potent mitochondria-targeted nanoprobe to boost the PDT efficacy of cancers.

Chemistry-Informed Machine Learning Enables Discovery of DNA-Stabilized Silver Nanoclusters with Near-Infrared Fluorescence

DNA can stabilize silver nanoclusters (Ag_N-DNAs) whose atomic sizes and diverse fluorescence colors are selected by nucleobase sequence. These programmable nanoclusters hold promise for sensing, bioimaging, and nanophononics. However, DNA's vast sequence space challenges the design and discovery of Ag_N-DNAs with tailored properties. In particular, Ag_N-DNAs with bright near-infrared luminescence above 800 nm remain rare, placing limits on their applications for bioimaging in the tissue transparency windows. Here, we present a design method for near-infrared emissive Ag_N-DNAs. By combining high-throughput experimentation and machine learning with fundamental information from Ag_N-DNA crystal structures, we distill the salient DNA sequence features that determine Ag_N-DNA color, for the entire known spectral range of these nanoclusters. A succinct set of nucleobase staple features are predictive of Ag_N-DNA color. By representing DNA sequences in terms of these motifs, our machine learning models increase the design success for near-infrared emissive Ag_N-DNAs by 12.3 times as compared to training data, nearly doubling the number of known Ag_N-DNAs with bright near-infrared luminescence above 800 nm. These results demonstrate how incorporating known structure-property relationships into machine learning models can enhance materials study and design, even for sparse and imbalanced training data.

Metal Cluster Triggered-Assembling Heterogeneous Au-Ag Nanoclusters with Highly Loading Performance and Biocompatible Capability

In this work, we firstly report the preparation of heterogeneously assembled structures Au-Ag nanoclusters (NCs) as good drug carriers with high loading performance and biocompatible capability. As glutathione-protected Au and Ag clusters self-assembled into porous Au-Ag NCs, the size value is about 1.358 (±0.05) nm. The morphology characterization revealed that the diameter of Au-Ag NCs is approximately 120 nm, as well as the corresponding potential ability in loading performance of the metal cluster triggered-assembling process. Compared with individual components, the stability and loading performance of heterogeneous Au-Ag NCs were improved and exhibit that the relative biocompatibility was enhanced. The exact information about this is that cell viability was approximately to 98% when cells were incubated with 100 µg mL−1 particle solution for 3 days. The drug release of Adriamycin from Au-Ag NCs was carried out in PBS at pH = 7.4 and 5.8, respectively. By simulating in vivo and tumor microenvironment, the release efficiency could reach over 65% at pH = 5.8 but less than 30% at pH = 7.2. Using an ultrasound field as external environment can accelerate the assembling process while metal clusters triggered assembling Au-Ag NCs. The size and morphology of the assembled Au-Ag NCs can be controlled by using different power parameters (8 W, 13 W, 18 W) under ambient atmosphere. Overall, a novel approach is exhibited, which conveys assembling work for metal clusters triggers into heterogeneous structures with porous characteristic. Its existing properties such as water-solubility, stability, low toxicity and capsulation can be considered as dependable agents in various biomedical applications and drug carriers in immunotherapies.

Inhibition of Bacteria In Vitro and In Vivo by Self-Assembled DNA-Silver Nanocluster Structures

Antimicrobial nanomaterials hold great promise for bacteria-infected wound healing. However, it remains a challenge to balance antimicrobial efficacy and biocompatibility for these artificial antimicrobials. Here we employed biocompatible genetic molecule DNA as a building material to fabricate antimicrobial materials, including self-assembled Y-shaped DNA-silver nanocluster composite (Y-Ag) and Y-Ag hydrogel (Y-Ag-gel). We demonstrate that macroscopic and microcosmic DNA-Ag composites can effectively inhibit bacterial growth but do not affect cell proliferation in vitro. In particular, Y-Ag spray can speed up the process of wound healing in vivo. Considering the efficacy and advantages of DNA-based materials, our findings provide a promising route to fabricate a novel wound dressing such as spray and hydrogel for therapeutic wound healing.

DNA Stabilizes Eight-Electron Superatom Silver Nanoclusters with Broadband Downconversion and Microsecond-Lived Luminescence

DNA oligomers are known to serve as stabilizing ligands for silver nanoclusters (Ag_N-DNAs) with rod-like nanocluster geometries and nanosecond-lived fluorescence. Here, we report two Ag_N-DNAs that possess distinctly different structural properties and are the first to exhibit only microsecond-lived luminescence. These emitters are characterized by significant broadband downconversion from the ultraviolet/visible to the near-infrared region. Circular dichroism spectroscopy shows that the structures of these two Ag_N-DNAs differ significantly from previously reported Ag_N-DNAs. We find that these nanoclusters contain eight valence electrons, making them the first reported DNA-stabilized luminescent quasi-spherical superatoms. This work demonstrates the important role that nanocluster composition and geometry play in dictating luminescence properties of Ag_N-DNAs and significantly expands the space of structure-property relations that can be achieved for Ag_N-DNAs.

Sperm-like nanocarriers for ultrafast delivery of antisense DNA

Although various nanomaterials have been designed as intracellular delivery tools, the following aspects have become obstacles to limit their development, like a complex and time-consuming synthesis process, as well as relatively limited application areas (i.e. biosensing or cell imaging). Here, we developed a novel nano-delivery system called "nano-sperm" with low cytotoxicity and high biocompatibility. In this system, we used DNA oligonucleotides as a backbone to synthesize a nanostructure with silver nanoclusters in the head and functional fragments in the tail, which is shaped like a sperm, to achieve dual functions of ultrafast delivery and imaging/therapy. As a model, we analyzed the possibility of the "nano-sperm" carrying DNA with different structures for imaging or survivin-asDNA for tumor therapy. Therefore, this work reports a novel bifunctional high-speed delivery vehicle, which successfully fills the gap in the field of tumor therapy using DNA-templated nanoclusters as a delivery vehicle.

An Overview on Coinage Metal Nanocluster-Based Luminescent Biosensors via Etching Chemistry

The findings from the synthetic mechanism of metal nanoclusters yield the etching chemistry based on coinage metal nanoclusters. The utilization of such chemistry as a tool that can alter the optical properties of metal nanoclusters has inspired the development of a series of emerging luminescent biosensors. Compared with other sensors, the luminescent biosensors have the advantages of being more sensitive, saving time and saving cost. We reviewed topics on the luminescent sensors based on the etching of emissive coinage metal nanoclusters. The molecules possessing varied etching ability towards metal nanoclusters were categorized with discussions of corresponding etching mechanisms. The understanding of etching mechanisms favored the discussions of how to use etching methods to detecting biochemical molecules. The emerging luminescent biosensors via etching chemistry also provided challenges and new opportunities for analytical chemistry and sensors.

Detection of Pyrophosphate and Alkaline Phosphatase Activity Based on PolyT Single Stranded DNA - Copper Nanoclusters

The determination of pyrophosphate and alkaline phosphatase activity plays a significant role in medical diagnosis. In this work, a label-free "ON-OFF-ON" fluorescence strategy is developed for the analysis of pyrophosphate and alkaline phosphatase activity. Using PolyT single strand DNA as templates to synthesize fluorescent copper nanoparticles, the coordination effect of pyrophosphoric acid on Cu²⁺ inhibited the generation of fluorescence. Afterwards, the addition of alkaline phosphatase into hydrolyze pyrophosphoric acid resulted in the release of Cu^2+, whereby the fluorescence intensity could be recovered. Thereupon enhanced-sensitivity for alkaline phosphatase was obtained (0.1 mU/L), much better than previously reported methods. Meanwhile, it could be performed directly in homogeneous solution, which was very close to the actual activity level of alkaline phosphatase under physiological conditions. Likewise, satisfactory results were also obtained in specificity assessment, which demonstrated its potential application in clinical diagnosis. Notably, a new, sensitive, low-cost, short-time, and high-sensitivity platform for alkaline phosphatase detection was constructed, and the design of biosensor using DNA-templated Copper nanoclusters (CuNCs) was instructed in this study.

Combining metal nanoclusters and carbon nanomaterials: Opportunities and challenges in advanced nanohybrids

The development of functional materials with uniquely advanced properties lies at the core of nanoscience and nanotechnology. From the myriad possible combinations of organic and/or inorganic blocks, hybrids combining metal nanoclusters and carbon nanomaterials have emerged as highly attractive colloidal materials for imaging, sensing (optical and electrochemical) and catalysis, among other applications. While the metal nanoclusters provide extraordinary luminescent and electronic properties, the carbon nanomaterials (of zero, one or two dimensions) convey versatility, as well as unique interfacial, electronic, thermal, optical, and mechanical properties, which altogether can be put to use for the desired application. Herein, we present an overview of the field, for experts and non-experts, encompassing the basic properties of the building blocks, a systematic view of the chemical preparation routes and physicochemical properties of the hybrids, and a critical analysis of their ongoing and emerging applications. Challenges and opportunities, including directions towards green chemistry approaches, are also discussed.

Interactions of Metal Nanoclusters with Light: Fundamentals and Applications

The interactions of materials with light determine their applications in various fields. In the past decade, ultrasmall metal nanoclusters (NCs) have emerged as a promising class of optical materials due to their unique molecular-like properties. Herein, the basic principles of optical absorption and photoluminescence of metal NCs, their interactions with polarized light, and light-induced chemical reactions, are discussed, highlighting the roles of the core and protecting ligands/motifs of metal NCs in their interactions with light. The metal core and protecting ligands/motifs determine the electronic structures of metal NCs, which are closely related to their optical properties. In addition, the protecting ligands/motifs of metal NCs contribute to their photoluminescence and chiral origin, further promoting the interactions of metal NCs with light through various pathways. The fundamentals of light-NC interactions provide guidance for the design of metal NCs in optical applications, which are discussed in the second part. In the last section, some strategies are proposed to further understand light-NC interactions, highlighting the challenges and opportunities. It is hoped that this work will stimulate more research on the optical properties of metal NCs and their applications in various fields.