A photo zipper locked DNA nanomachine with an internal standard for precise miRNA imaging in living cells

Construction of an exogenously and endogenously Co-activated DNA logic amplifier for highly reliable intracellular MicroRNA imaging

DNA-based molecular amplifiers offer significant promise for molecular-level disease diagnosis and treatment, yet tailoring their activation for precise timing and localization remains a challenge. Herein, we've pioneered a dual activation strategy harnessing external light and internal ATP to create a highly controlled DNA logic amplifier (FDLA) for accurate miRNA monitoring in cancer cells. The FDLA was constructed by tethered the two functionalized catalytic hairpin assembly (CHA) hairpin modules (ATP aptamer sealed hairpin aH1 and photocleavable (PC-linker) sites modified hairpin pH2) to DNA tetrahedron (DTN). The FDLA system incorporates ATP aptamers and PC-linkers as logic control units, allowing them to respond to both exogenous UV light and endogenous ATP present within cancer cells. This response triggers the release of CHA hairpin modules, enabling amplified FRET miRNA imaging through an AND-AND gate. The DTN structure could improve the stability of FDLA and accelerate the kinetics of the strand displacement reaction. It is noteworthy that the UV and ATP co-gated DNA circuit can control the DNA bio-computing at specific time and location, offering spatial and temporal capabilities that can be harnessed for miRNA imaging. Furthermore, the miRNA-sensing FDLA amplifier demonstrates reliable imaging of intracellular miRNA with minimal background noise and false-positive signals. This highlights the feasibility of utilizing both exogenous and endogenous regulatory strategies to achieve spatial and temporal control of DNA molecular circuits within living cancer cells. Such advancements hold immense potential for unraveling the correlation between miRNA and associated diseases.

Phototriggered Equilibrated and Transient Orthogonally Operating Constitutional Dynamic Networks Guiding Biocatalytic Cascades

The photochemical deprotection of structurally engineered o-nitrobenzylphosphate-caged hairpin nucleic acids is introduced as a versatile method to evolve constitutional dynamic networks, CDNs. The photogenerated CDNs, in the presence of fuel strands, interact with auxiliary CDNs, resulting in their dynamically equilibrated reconfiguration. By modification of the constituents associated with the auxiliary CDNs with glucose oxidase (GOx)/horseradish peroxidase (HRP) or the lactate dehydrogenase (LDH)/nicotinamide adenine dinucleotide (NAD+) cofactor, the photogenerated CDN drives the orthogonal operation upregulated/downregulated operation of the GOx/HRP and LDH/NAD+ biocatalytic cascade in the conjugate mixture of auxiliary CDNs. Also, the photogenerated CDN was applied to control the reconfiguration of coupled CDNs, leading to upregulated/downregulated formation of the antithrombin aptamer units, resulting in the dictated inhibition of thrombin activity (fibrinogen coagulation). Moreover, a reaction module consisting of GOx/HRP-modified o-nitrobenzyl phosphate-caged DNA hairpins, photoresponsive caged auxiliary duplexes, and nickase leads upon irradiation to the emergence of a transient, dissipative CDN activating in the presence of two alternate auxiliary triggers, achieving transient operation of up- and downregulated GOx/HRP biocatalytic cascades.

Target-Responsive DNA Nanoclaw for the On-Site Identification of Chinese Medicines with Naked Eye

The identification of Chinese medicinal herbs occupies a crucial part in the development of the food and drug market. Although molecular identification based on real-time PCR offers good versatility and uniform digital standards compared with traditional methods, such as morphology, the dependence on large-scale equipment hinders spot detection and marketable applications. In this study, we developed a DNA nanoclaw for colorimetric detection and visible on-site identification of Chinese medicines. When specific miRNA is present, the DNAzyme is activated and cleaves the substrate strand, triggering the catalytic hairpin assembly (CHA) reaction and forming branched DNA junctions on AuNP-I. This can then capture AuNP-II through hybridization and facilitate their aggregation, resulting in a noticeable color change that is observable to the naked eye. By harnessing the dual amplification of DNAzyme and CHA, this highly sensitive nanoprobe successfully achieved specific identification of Chinese medicines. This offers a new perspective for on-site testing in the herbal market.

Photoresponsive CHA-Integrated Self-Propelling 3D DNA Walking Amplifier within the Concentration Localization Effect of DNA Molecular Framework Enables Highly Efficient Fluorescence Bioimaging

While three-dimensional (3D) DNA walking amplifiers hold considerable promise in the construction of advanced DNA-based fluorescent biosensors for bioimaging, they encounter certain difficulties such as inadequate sensitivity, premature activation, the need for exogenous propelling forces, and low reaction rates. In this contribution, a variety of profitable solutions have been explored. First, a catalytic hairpin assembly (CHA)-achieved nonenzymatic isothermal nucleic acid amplification is integrated to enhance sensitivity. Subsequently, one DNA component is simply functionalized with a photocleavage-bond to conduct a photoresponsive manner, whereby the target recognition occurs only when the biosensor is exposed to an external ultraviolet light source, overcoming premature activation during biodelivery. Furthermore, a special self-propelling walking mechanism is implemented by reducing biothiols to MnO2 nanosheets, thereby propelling forces that are self-supplied to a Mn2+-reliant DNAzyme. By carrying the biosensing system with a DNA molecular framework to induce a unique concentration localization effect, the nucleic acid contact reaction rate is notably elevated by 6 times. Following these, an ultrasensitive in vitro detection performance with a limit of detection down to 2.89 fM is verified for a cancer-correlated microRNA biomarker (miRNA-21). Of particular importance, our multiple concepts combined 3D DNA walking amplifier that enables highly efficient fluorescence bioimaging in live cells and even bodies, exhibiting a favorable application prospect in disease analysis.

Dual-Signal Amplification Strategy Based on Catalytic Hairpin Assembly and APE1-Assisted Amplification for High-Contrast miRNA Imaging in Living Cells

Early tumor diagnosis is crucial to successful treatment. Earlier studies have shown that microRNA is a biomarker for early tumor diagnosis. The development of highly sensitive miRNA detection methods, especially in living cells, plays an indispensable role for early diagnosis and treatment of tumor. Although the catalytic hairpin assembly (CHA)-based miRNA analysis strategy is commonly used for disease diagnosis, further application of CHA is hindered due to its low amplification efficiency and low tumor recognition contrast. To address these limitations, we propose a dual-signal amplification strategy based on CHA and APE1-assisted amplification, enabling highly sensitive and high-contrast miRNA imaging. The miR-221 was selected as a target model. This dual-signal amplification strategy has exhibited high amplification efficiency, which could analyze miRNA as low as 21 fM. This strategy also exhibited high specificity, which could distinguish target miRNA and nontarget with single-base differences. Moreover, this method showed significant potential for practical application, as it could successfully distinguish the expression difference of miR-221 in the plasma samples of normal people and patients. Most importantly, the expression level of the APE1 enzyme in tumor cells is higher than that in normal cells, allowing this strategy to sensitively and specifically image miRNA within tumor cells. This proposed method has also been successfully used to indicate fluctuations of intracellular miRNA and to distinguish miRNA expression between normal cells and cancer cells with high contrast. We anticipate that this method will provide fresh insights and can be a powerful tool for tumor diagnosis and treatment based on miRNA analysis.

Remotely Activated DNA Probe System for the Detection and Imaging of Dual miRNAs

Cancers remain the leading cause of mortality worldwide. It is crucial to detect cancer at an early stage for improving survival rates. Biomarkers have precise implications for cancer progression. Here, we built a straightforward DNA probe system that could be activated by near-infrared light to detect dual miRNAs with a high specificity. This probe is built on the basis of upconversion nanoparticles, which could emit ultraviolet light and activate DNA probes adsorbed on the outer layer. The DNA probe system is remotely controlled through manipulation of the near-infrared (NIR) light, enabling simultaneous detection of dual miRNAs. The DNA nanosystem could be effectively endocytosed by cancer cells and reflect expression levels of dual miRNAs. Overall, this study demonstrates a promising remote-controlled DNA nanoplatform for the simultaneous detection of dual miRNAs, which has tremendous potential for precise cancer diagnostics and therapies.

A NIR Programmable In Vivo miRNA Magnifier for NIR-II Imaging of Early Stage Cancer

Aberrant expressions of biomolecules occur much earlier than tumor visualized size and morphology change, but their common measurement strategies such as biopsy suffer from invasive sampling process. In vivo imaging of slight biomolecule expression difference is urgently needed for early cancer detection. Fluorescence of rare earth nanoparticles (RENPs) in second near-infrared (NIR-II) region makes them appropriate tool for in vivo imaging. However, the incapacity to couple with signal amplification strategies, especially programmable signal amplification strategies, limited their application in lowly expressed biomarkers imaging. Here we develop a 980/808 nm NIR programmed in vivo microRNAs (miRNAs) magnifier by conjugating activatable DNAzyme walker set to RENPs, which achieves more effective NIR-II imaging of early stage tumor than size monitoring imaging technique. Dye FD1080 (FD1080) modified substrate DNA quenches NIR-II downconversion emission of RENPs under 808 nm excitation. The miRNA recognition region in DNAzyme walker is sealed by a photo-cleavable strand to avoid "false positive" signal in systemic circulation. Upconversion emission of RENPs under 980 nm irradiation activates DNAzyme walker for miRNA recognition and amplifies NIR-II fluorescence recovery of RENPs via DNAzyme catalytic reaction to achieve in vivo miRNA imaging. This strategy demonstrates good application potential in the field of early cancer detection.

Construction of a Near-Infrared Photoswitched Nanomachine Powered by an Endogenous Trigger for Activatable Imaging of Intracellular MicroRNA and Amplified Photodynamic Therapy for Cancer Cells

DNA nanomachines could initiate the cascade reaction in an autonomous mode under the drive of triggers, which achieve the signal amplification for the bioimaging of intracellular biomarkers. Compared with the "always-on" nanomachine that possibly produces false-positive signals, a controllable nanomachine with the on-site activation could be better for accurate tumor imaging and precise tumor therapy. Till now, the endogenous and exogenous triggers have been developed to design the controllable nanosensors. However, their combinations to develop feasible DNA nanomachines have been rarely studied. Herein, we constructed a near-infrared (NIR)-light-controlled DNA nanomachine that was first activated by the NIR light and then induced a target-triggered amplification process under the drive of an endogenous stimulus. Owing to adenosine-5'-triphosphate (ATP) having much higher concentration in cancer cells than that in healthy cells and the extracellular fluid, the obtained DNA nanomachine was selectively activated in cancer cells with inhibited interference signals from the surrounding healthy tissues. With obvious advantages including the exogenous NIR light initiation, the selective activation by the target microRNA, and the sensitive acceleration by the ATP-induced strand recycling reaction, the constructed nanomachine could be used to image the intracellular microRNA with increased sensitivity. Besides, after modifying the DNA sequence with the photosensitizer molecules, the obtained nanomachine could perform the selective photodynamic therapy on the tumor sections with the outstandingly decreased side effects. Thus, we hope the designed nanomachine could provide some important hints to design feasible nanomachines for accurate tumor diagnosis and precise tumor therapy.

Stimuli-responsive probes for amplification-based imaging of miRNAs in living cells

MicroRNAs (miRNAs) have emerged as important biomarkers in biomedicine and bioimaging due to their roles in various physiological and pathological processes. Real-time and in situ monitoring of dynamic fluctuation of miRNAs in living cells is crucial for understanding these processes. However, current miRNA imaging probes still have some limitations, including the lack of effective amplification methods for low abundance miRNAs bioanalysis and uncontrollable activation, leading to background signals and potential false-positive results. Therefore, researchers have been integrating activatable devices with miRNA amplification techniques to design stimuli-responsive nanoprobes for "on-demand" and precise imaging of miRNAs in living cells. In this review, we summarize recent advances of stimuli-responsive probes for the amplification-based imaging of miRNAs in living cells and discuss the future challenges and opportunities in this field, aiming to provide valuable insights for accurate disease diagnosis and monitoring.

On-Site-Activated Transmembrane Logic DNA Nanodevice Enables Highly Specific Imaging of Cancer Cells by Targeting Tumor-Related Nucleolin and Intracellular MicroRNA

The ability to specifically image cancer cells is essential for cancer diagnosis; however, this ability is limited by the false positive associated with single-biomarker sensors and off-site activation of "always active" nucleic acid probes. Herein, we propose an on-site, activatable, transmembrane logic DNA (TLD) nanodevice that enables dual-biomarker sensing of tumor-related nucleolin and intracellular microRNA for highly specific cancer cell imaging. The TLD nanodevice is constructed by assembling a tetrahedral DNA nanostructure containing a linker (L)-blocker (B)-DNAzyme (D)-substrate (S) unit. AS-apt, a DNA strand containing an elongated segment and the AS1411 aptamer, is pre-anchored to nucleolin protein, which is specifically expressed on the membrane of cancer cells. Initially, the TLD nanodevice is firmly sealed by the blocker containing an AS-apt recognition zone, which prevents off-site activation. When the nanodevice encounters a target cancer cell, AS-apt (input 1) binds to the blocker and unlocks the sensing ability of the nanodevice for miR-21 (input 2). The TLD nanodevice achieves dual-biomarker sensing from the cell membrane to the cytoplasm, thereby ensuring cancer cell-specific imaging. This TLD nanodevice represents a promising strategy for the highly reliable analysis of intracellular biomarkers and a promising platform for cancer diagnosis and related biomedical applications.

Near-Infrared-Driven Nanorocket for Rapid and Ultrasensitive Detection of MicroRNA

Herein, by introducing gold nanostars (AuNSs) as fuel core, a near-infrared-driven nanorocket (NIDNR) with pretty fast walking was exploited for ultrasensitive miRNA detection. Compared with traditional nanomaterials-comprised nanomachines (NMs), the NIDNR possesses much better kinetic and thermodynamic performance owing to the extra photothermal driving force from localized surface plasmon (LSP). Impressively, the whole reaction time of NIDNR down to 15 min was realized, which is almost more than 8 times beyond those of conventional DNA-based NMs. This way, the inherent obstacle of traditional NMs, including long reaction time and low efficiency, could be easily addressed. As a proof of concept, the NIDNR was successfully applied to develop an electrochemical biosensing platform for rapid and sensitive detection of miRNA with an LOD down to 2.95 aM and achieved the real-time assay of real biological samples from human hepatocellular carcinoma cells (MHCC97L) and HeLa, thus providing an innovative insight to design more versatile DNA nanomachines for ultimate application in biosensing platform construction and clinical sample detection.

Advances and Trends in miRNA Analysis Using DNAzyme-Based Biosensors

miRNAs are endogenous small, non-coding RNA molecules that function in post-transcriptional regulation of gene expression. Because miRNA plays a pivotal role in maintaining the intracellular environment, and abnormal expression has been found in many cancer diseases, detection of miRNA as a biomarker is important for early diagnosis of disease and study of miRNA function. However, because miRNA is present in extremely low concentrations in cells and many types of miRNAs with similar sequences are mixed, traditional gene detection methods are not suitable for miRNA detection. Therefore, in order to overcome this limitation, a signal amplification process is essential for high sensitivity. In particular, enzyme-free signal amplification systems such as DNAzyme systems have been developed for miRNA analysis with high specificity. DNAzymes have the advantage of being more stable in the physiological environment than enzymes, easy to chemically synthesize, and biocompatible. In this review, we summarize and introduce the methods using DNAzyme-based biosensors, especially with regard to various signal amplification methods for high sensitivity and strategies for improving detection specificity. We also discuss the current challenges and trends of these DNAzyme-based biosensors.

The rate-limiting procedure of 3D DNA walkers and their applications in tandem technology

DNA walkers, artificial dynamic DNA nanomachines, can mimic actin to move rapidly along a predefined nucleic acid track. They can generally be classified as one- (1D), two- (2D), and three-dimensional (3D) DNA walkers. In particular, 3D DNA walkers demonstrate amazing sustainable walking ability, strong enrichment ability, and fantastic signal amplification ability. In light of these, 3D DNA walkers have been widely used in fields such as biosensors, bioanalysis and cell imaging. Most notably, the strong compatibility of 3D DNA walkers allows their integration with a range of amplification strategies, effectively enhancing signal transduction and amplifying biosensor sensing signals. Herein, we first systematically expound the walking principle of the 3D walkers in this review. Then, by presenting representative examples, the research direction of 3D walkers in recent years is discussed. Furthermore, we also categorize and evaluate diverse tandem signal amplification strategies in 3D walkers. Finally, the challenges and development trends of 3D DNA walkers in the emerging field of analysis are carefully discussed. It is believed that this work can provide new ideas for researchers to quickly understand 3D DNA walkers and their applications in diverse biosensors.

Dynamic Fusion of Nucleic Acid Functionalized Nano-/Micro-Cell-Like Containments: From Basic Concepts to Applications

Membrane fusion processes play key roles in biological transformations, such as endocytosis/exocytosis, signal transduction, neurotransmission, or viral infections, and substantial research efforts have been directed to emulate these functions by artificial means. The recognition and dynamic reconfiguration properties of nucleic acids provide a versatile means to induce membrane fusion. Here we address recent advances in the functionalization of liposomes or membranes with structurally engineered lipidated nucleic acids guiding the fusion of cell-like containments, and the biophysical and chemical parameters controlling the fusion of the liposomes will be discussed. Intermembrane bridging by duplex or triplex nucleic acids and light-induced activation of membrane-associated nucleic acid constituents provide the means for spatiotemporal fusion of liposomes or nucleic acid modified liposome fusion with native cell membranes. The membrane fusion processes lead to exchange of loads in the fused containments and are a means to integrate functional assemblies. This is exemplified with the operation of biocatalytic cascades and dynamic DNA polymerization/nicking or transcription machineries in fused protocell systems. Membrane fusion processes of protocell assemblies are found to have important drug-delivery, therapeutic, sensing, and biocatalytic applications. The future challenges and perspectives of DNA-guided fused containments and membranes are addressed.

DNA tetrahedral scaffold-corbelled 3D DNAzyme walker for electrochemiluminescent aflatoxin B1 detection

The reaction efficiency of surface-based DNA walker can directly affect the properties of a biosensor. Herein, three-dimensional (3D) DNAzyme walker were first fixed on the top of DNA tetrahedral scaffold to improve the immobilization efficiency. Ferrocene (Fc) that labeled at substrate strand ends effectively quenched the electrochemiluminescence (ECL) signal of Ru(bpy)₂(cpaphen)²⁺, yielding the sensor in a "signal-off" state. Upon the addition of aflatoxin B₁ (AFB₁), 3D DNAzyme walker was activated and fueled by Na⁺, accordingly releasing Fc and recovering the ECL signal of Ru(bpy)₂(cpaphen)²⁺. Due to the high movement efficiency of such 3D DNAzyme walker, ultrasensitive detection of AFB₁ was achieved in the range of 1.0 fg mL^-1-10 ng mL^-1, with a detection limit of 0.58 fg mL^-1. Moreover, satisfactory results were obtained while detecting AFB₁ in corn and peanut samples, suggesting it has a potential application in food safety analysis.

Self-Powered DNAzyme Walker Enables Dual-Mode Biosensor Construction for Electrochemiluminescence and Electrochemical Detection of MicroRNA

Herein, an electrochemiluminescence (ECL) and electrochemical (EC) dual-mode biosensor platform with a self-powered DNAzyme walking machine was established for accurate and sensitive detection of miRNA-21. By employing a magnesium ion (Mn²⁺)-dependent DNAzyme cleavage cycling reaction, the walking machine was built by assembling DNAzyme walking strands and ferrocene (Fc)-labeled substrate strands on the Au nanoparticles and graphitic carbon nitride nanosheet (g-C₃N₄ NS)-covered electrode. The DNAzyme walking strand was first prohibited by a blocker strand. After the addition of target miRNA-21 and Mn²⁺, the DNAzyme walker could be activated and produce autonomous movements along the electrode track fueled by Mn²⁺-dependent DNAzyme-catalyzed substrate cleavage without additional energy supply. Notably, each walking step resulted in the cleavage of a substrate strand and the release of a Fc-labeled DNA strand fragment, allowing us to acquire an extreme ECL signal recovery of g-C₃N₄ inhibited by Fc. Meanwhile, numerous Fc-labeled DNA fragments escaped from the surface of the electrode, directly producing an obvious decrease in the square wave voltammetry (SWV) signal from Fc on the same sensing platform. This work not only avoided difficultly assembling various signal indicators but also significantly improved the sensitivity through using self-powered DNAzyme-walker amplification. Moreover, the proposed design employed the same reaction to produce two signal output modes, which could eliminate the interference from diverse reactive pathways on the outcome to mutually improve the accuracy. Therefore, the dual-mode miRNA-21 biosensor exhibited wide detection ranges of 100 aM to 100 nM with low detection limits of 54.3 and 78.6 aM by ECL and SWV modes, respectively, which provided an efficient and universal biosensing approach with extensive applications in early disease diagnosis and bioanalysis.

Target-catalyzed self-assembled spherical G-quadruplex/hemin DNAzymes for highly sensitive colorimetric detection of microRNA in serum

The accurate and visual detection of circulating microRNA (miRNA) has attracted increasing interest due to its pivotal role in clinical disease diagnosis. Taking advantages of nucleic acid isothermal amplification and enzyme-catalyzed chromogenic reaction, here, a colorimetric sensing strategy was proposed for sensitive miRNA analysis. When the target miRNA was present, local catalytic hairpin assembly (CHA) would be triggered and proceed continuously to form dozens of double-stranded oligonucleotides with G-rich sticky ends on the gold nanoparticle, which could self-assemble into a spherical G-quadruplex (GQ)/hemin DNAzyme by binding with hemin and potassium ions. As a horseradish peroxidase-mimic, GQ/hemin DNAzyme could catalyze the redox reaction and color change of the substrates. Taking miRNA-21 as an example, the developed method exhibited satisfactory specificity as well as high sensitivity with a detection limit of 90.3 fM. Furthermore, the sensing platform has been successfully employed to detect miRNA-21 in spiked serum, providing a promising tool for early diagnosis of cancers.

Dual factor coactivatable fluorescent nanosensor with boosted cytoplasmic biomarker accessibility toward selective tumor imaging

Fluorescent nanosensor-based tumor imaging holds great promise in cancer diagnosis and treatment assistance, yet the signal contrast is heavily hampered by the unspecific/unwanted activation at microscopic regions with a highly restricted local abundance of biomarkers. Herein, we developed an activation boosting strategy by the integration and manipulation of dual-factor coactivation of sensing and lysosome escape facilitated the rise of cytosolic biomarker accessibility. By employing hybrid DNA probes on gold nanoquenchers, ATP sensing initiated conformation switch of the corresponding aptamer units triggered the exposure of a hidden toehold in a loop structure. Sequentially, miRNA-21 sensing was triggered by toehold-mediated strand displacement and detachment of the binding complexes. The application of lysosomotropic agent chloroquine at optimized time interval facilitated the release of nanosensors into the cytosol and a ∼10.5-fold increment of intracellular fluorescence in vitro, while coactivation improved the cancer-to-normal cell signal ratio by ∼5.9 times. The synergy effects led to a high tumor-to-normal tissue ratio value of ∼7.9 in the in vivo imaging results. This strategy establishes a new paradigm of fluorescent nanosensors for selective and specific tumor imaging.

A novel ADA-coated UCNPs@NB sensing platform combined with nucleic acid amplification for rapid detection of Escherichia coli

In this study, we reported a novel sensing platform based on fluorescence quenching composed of alendronic acid (ADA) coated upconversion nanoparticles (UCNPs) and Nile Blue (NB) combined with polymerase chain reaction (PCR) for rapid, sensitive, and specific detection of Escherichia coli (E. coli). As a fluorescence acceptor, NB has a broad absorption band and can quench upconversion fluorescence intensity at 544 nm and 658 nm based on IFE. PCR is a double-stranded DNA (dsDNA) amplification technique with high specificity. The NB-dsDNA complex can be formed by intercalation of NB between base pairs and groove of dsDNA, leading to upconversion fluorescence recovery. The ADA-coated UCNPs@NB sensing platform achieved to detect E. coli in 1.5 h, with a lower limit of detection (33 CFU mL^-1). In addition, the sensitivity of the ADA@UCNPs-NB fluorescence sensor under different PCR cycle numbers was discussed. The results showed that the proposed sensor could effectively shorten the assay time (1.0 h) while maintaining excellent sensitivity. This study demonstrated a rapid and sensitive analytical method for detecting E. coli in chicken, providing a reference for constructing PCR fluorescence sensors.

A Lanthanide Upconversion Nanothermometer for Precise Temperature Mapping on Immune Cell Membrane

Cell temperature monitoring is of great importance to uncover temperature-dependent intracellular events and regulate cellular functions. However, it remains a great challenge to precisely probe the localized temperature status in living cells. Herein, we report a strategy for in situ temperature mapping on an immune cell membrane for the first time, which was achieved by using the lanthanide-doped upconversion nanoparticles. The nanothermometer was designed to label the cell membrane by combining metabolic labeling and click chemistry and can leverage ratiometric upconversion luminescence signals to in situ sensitively monitor temperature variation (1.4% K^-1). Moreover, a purpose-built upconversion hyperspectral microscope was utilized to synchronously map temperature changes on T cell membrane and visualize intracellular Ca²⁺ influx. This strategy was able to identify a suitable temperature status for facilitating thermally stimulated calcium influx in T cells, thus enabling high-efficiency activation of immune cells. Such findings might advance understandings on thermally dependent biological processes and their regulation methodology.

Upconverting nanoparticles based nanodevice for DNAzymes amplified miRNAs detection and artificially controlled chemo-gene therapy

Despite the great promise of cancer theranostic platforms, accurate diagnosis and effective treatment are still highly challenging. In this work, nanodevice for intracellular miRNAs detection and artificially controlled drug releasement was developed based on upconverting nanoparticles (UCNPs). For analysis aspect, DNAzymes amplified miRNA-21 detection was carried out, giving excellent sensitivity with detection limits of 1.8 × 10^-11 M. Moreover, intracellular fluorescence imaging permitted in situ diagnoses of miRNA-21 expression in living cells. Once the test identifies tumor markers, treatment can be performed. Here, artificially controlled chemo-gene synergetic therapy nanodevice was obtained by integrating UCNPs with photocleavable linkers (PC-linkers). In vitro and in vivo experiments verified the potential application of prepared nanodevice in cancer theranostics.

Nucleic acid nanoassembly-enhanced RNA therapeutics and diagnosis

RNAs are involved in the crucial processes of disease progression and have emerged as powerful therapeutic targets and diagnostic biomarkers. However, efficient delivery of therapeutic RNA to the targeted location and precise detection of RNA markers remains challenging. Recently, more and more attention has been paid to applying nucleic acid nanoassemblies in diagnosing and treating. Due to the flexibility and deformability of nucleic acids, the nanoassemblies could be fabricated with different shapes and structures. With hybridization, nucleic acid nanoassemblies, including DNA and RNA nanostructures, can be applied to enhance RNA therapeutics and diagnosis. This review briefly introduces the construction and properties of different nucleic acid nanoassemblies and their applications for RNA therapy and diagnosis and makes further prospects for their development.

Intelligent Programmable DNA Nanomachines for the Spatially Controllable Imaging of Intracellular MicroRNA

The high programmability of DNA molecules makes them particularly suitable for constructing artificial molecular machines to perform sophisticated functions by simulating complex living systems. However, intelligent DNA nanomachines which can perform precise tasks logically in complex environments still remain challenging. Herein, we develop a general strategy to design a pH-responsive programmable DNA (PRPD) nanomachine to perform multilayer DNA cascades, enabling precise sensing and calculation of intracellular biomolecules. The PRPD nanomachine is built on a four-stranded DNAzyme walker precursor with a DNA switch on the surface of an Au nanoparticle, which is capable of precisely responding to pH variations in living cells by sequence tuning. This multilayer DNA cascade networks have been applicated in spatially controlled imaging of intracellular microRNA, which efficiently avoided the DNA nanomachine activated by nonspecific extracellular molecules and achieved apparent signal amplification. Our strategy enables the sensing-computing-output functional integration of DNA nanomachines, facilitating the application of programmable and complex nanomachines in nanoengineering, chemistry, and biomedicine.

Sense and Validate: Fluorophore/Mass Dual-Encoded Nanoprobes for Fluorescence Imaging and MS Quantification of Intracellular Multiple MicroRNAs

Simultaneously monitoring and quantifying intracellular multiple microRNAs (miRNAs) is highly essential to clinical diagnosis and pathological research. However, revealing the intracellular distribution of multiple miRNAs while determining their content in a multiplex and quantitative format remains challenging. Considering the respective technical merit of fluorescence imaging and mass spectrometry (MS) in in situ detection and multiplex assaying, we herein propose fluorophore/mass dual-encoded nanoprobes (FMNPs) that can execute target-triggered hairpin self-assembly to enable in situ amplified imaging and follow-up MS quantification of intracellular multiple miRNAs. The FMNPs responsive to the target miRNA were constructed by codecorating gold nanoparticles (AuNPs) with locked hairpin DNA probes (LH1) and corresponding mass tags (MTs) for fluorescent and mass spectrometric dual-modal readout. Cellular miRNAs can separately trigger recycled hairpin self-assembly, leading to the continuous liberation of fluorophore-labeled bolt DNA (bDNA) for fluorescence imaging in cells. Moreover, the postreaction FMNPs afford an extra chance to validate the fluorescence output of miRNA-21 and miRNA-141 by accurate MS quantification relying on the ion signal of the barcoded MTs. Fluorescence imaging and MS quantification of miRNA-21 and miRNA-141 have also been successfully accomplished in different cell lines, highlighting its potential in cell subtyping. This "sense-and-validate" strategy creates a new modality for assaying multiple intracellular miRNAs and holds great promise in unveiling multicomponent-involved events in cellular processes and determining multiple biomarkers in accurate clinical diagnosis.

Biologically stable threose nucleic acid-based probes for real-time microRNA detection and imaging in living cells

We successfully fabricated threose nucleic acid (TNA)-based probes for real-time monitoring of target miRNA levels in cells. Our TNA probe is comprised of a fluorophore-labeled TNA reporter strand by partially hybridizing to a quencher-labeled TNA that is designed to be antisense to a target RNA transcript; this results in effective quenching of its fluorescence. In the presence of RNA targets, the antisense capture sequence of the TNA binds to targeted transcripts to form longer, thermodynamic stable duplexes. This binding event displaces the reporter strand from the quencher resulting in a discrete “turning-on” of the fluorescence. Our TNA probe is highly specific and selective toward target miRNA and is able to distinguish one to two base mismatches in the target RNA. Compared with DNA probes, our TNA probes exhibited favorable nuclease stability, thermal stability, and exceptional storage ability for long-term cellular studies. Our TNA probes are efficiently taken up by cells with negligible cytotoxicity for dynamic detection of target miRNAs and can also differentiate the distinct target miRNA expression levels in different cell lines. This work illuminates for using TNA as a building component to construct a biocompatible probe for miRNA detection that offers alternative molecular reagents for miRNA-related diagnostics.

A DNA–Au nanomachine activated by dual types of biomarkers for multi-site imaging and gene silencing

A programmed DNA–Au nanomachine was constructed to achieve in situ imaging of the transmembrane glycoprotein MUC1 and cytoplasmic miRNA-21 and trigger precise gene silencing therapy for breast cancer.

Multivalent self-assembled nano string lights for tumor-targeted delivery and accelerated biomarker imaging in living cells and in vivo

Multivalent self-assembled nano string lights for tumor-targeted delivery with high efficiency and accelerated biomarker imaging in living cells and in vivo.

A core-brush 3D DNA nanostructure: the next generation of DNA nanomachine for ultrasensitive sensing and imaging of intracellular microRNA with rapid kinetics

A highly loaded and integrated core–brush three-dimensional (3D) DNA nanostructure is constructed by programmatically assembling a locked DNA walking arm (DA) and hairpin substrate (HS) into a repetitive array along a well-designed DNA track generated by rolling circle amplification (RCA) and is applied as a 3D DNA nanomachine for rapid and sensitive intracellular microRNA (miRNA) imaging and sensing. Impressively, the homogeneous distribution of the DA and HS at a ratio of 1 : 3 on the DNA track provides a specific walking range for the DA to avoid invalid and random self-walking and notably improve the executive ability of the core–brush 3D DNA nanomachine, which easily solves the major technical challenges of traditional Au-based 3D DNA nanomachines: low loading capacity and low executive efficiency. As a proof of concept, the interaction of miRNA with the 3D DNA nanomachine could initiate the autonomous and progressive operation of the DA to cleave the HS for ultrasensitive ECL detection of target miRNA-21 with a detection limit as low as 3.57 aM and rapid imaging in living cells within 15 min. Therefore, the proposed core–brush 3D DNA nanomachine could not only provide convincing evidence for sensitive detection and rapid visual imaging of biomarkers with tiny change, but also assist researchers in investigating the formation mechanism of tumors, improving their recovery rates and reducing correlative complications. This strategy might enrich the method to design a new generation of 3D DNA nanomachine and promote the development of clinical diagnosis, targeted therapy and prognosis monitoring.

This study designed a highly loaded and integrated core–brush 3D DNA nanomachine for miRNA imaging and sensing, which easily solves the major technical challenges of traditional Au-based 3D nanomachines: low loading capacity and low executive efficiency.

Rational Utilization of Photoelectrochemistry of Photosystem II for Self-Powered Photocathodic Detection of MicroRNA in Cells

The photoanode, photosystem II (PSII)/hierarchical inverse opal (IO) TiO₂, is coupled to the complementary photocathode, PbS quantum dots (QDs)/DNA probes, which is then integrated into a two-compartment photoelectrochemical (PEC) cell to achieve a self-powered system to enable photocathodic detection of microRNA-10b from HeLa cells. In such a system, all of the PSII catalytic products, i.e., electrons, protons, and O₂, were rationally utilized and could overcome the general issue of varied O₂ levels in photocathodic detection. The correlation between the target-triggered formation of the DNA complexes and the catalytic reduction of the dissolved O₂ makes possible the steady microRNA-10b detection with good sensitivity and selectivity. This work has unveiled the ability of PSII to construct self-powered detecting devices and shed light on its application in new arenas.

miR122-controlled all-in-one nanoplatform for in situ theranostic of drug-induced liver injury by visualization imaging guided on-demand drug release

Drug-induced liver injury (DILI) is a challenging clinical problem with respect to both diagnosis and management. As a newly emerging biomarker of liver injury, miR122 shows great potential in early and sensitive in situ detection of DILI. Glycyrrhetinic acid (GA) possesses desirable therapeutic effect on DILI, but its certain dose-dependent side effects after long-term and/or high-dose administration limit its clinical application. In this study, in order to improve the precise diagnosis and effective treatment of DILI, GA loaded all-in-one theranostic nanoplatform was designed by assembling of upconversion nanoparticles and gold nanocages. As a proof of concept, we demonstrated the applicability of this single-wavelength laser-triggered theranostic nanoplatform for the spatiotemporally controllable in situ imaging of DILI and miR122-controlled on-demand drug release in vitro and in vivo. This novel nanoplatform opens a promising avenue for the clinical diagnosis and treatment of DILI.

Spatiotemporally Controlled DNA Nanoclamps: Single-Molecule Imaging of Receptor Protein Oligomerization

Cell membrane surface receptor proteins play an important role in cellular biological processes. There are numerous methods to detect receptors, yet developing an artificially controlled and specific detection and treatment strategy remains a challenge. Herein, we develop such a strategy based on upconversion nanoparticles (UCNPs) loaded DNA probes that enable two-color ratiometric imaging excitated by a 980 nm laser. The light response controllable signal opening strategy avoids waste during probe transportation and improves sensitivity. Thereby the number of receptors on individual DU145 cell membranes is counted by single-molecule detection. Due to the different expression of specific receptor proteins, the number of single fluorescent dots counted can be used as a basis for distinguishing DU145 from other cells. This work is highly controllable to increase sensitivity, providing a platform for cancer diagnosis and treatment.

A mismatch-suppressed, duplex-specific nuclease powered nanowalker for multiplexed sensing of microRNA

DNA molecular machines have attracted immense interest for their potential in biosensing, drug delivery, and cellular imaging. Herein, we report a duplex-specific nuclease (DSN) powered nanowalker that can autonomously and progressively move on a spherical three-dimensional track, which is constructed by functionalizing a 13 nm diameter gold nanoparticle (AuNP) with densely mismatched DNA duplexes. The motion is initiated by an RNA walking strand, and in its absence, the walker is suppressed because the DSN is inactive toward the mismatched DNA duplexes. Once the walking strand is added, perfectly matched DNA-RNA hybrid is formed via a toehold-mediated displacement reaction between the walking strand and mismatched duplex. Thereafter, the DNA-RNA hybrid is simultaneously cleaved by DSN, by releasing the walking strand, which autonomously moves on the track with the aid of DSN. The present study provides a novel energy input and power mechanism for the operation of 3-D nanowalker with high efficiency. Moreover, the proposed nanowalker can be designed in a target microRNA (miRNA)-specific manner by altering the mismatched duplexes, and it exhibits femtomole level sensitivity in both singleplexed and multiplexed sensing of three miRNA targets. In addition, multiplexed quantification of the three miRNAs in biological samples is achieved, further suggesting that the proposed nanowalker has immense potential in biomedical research and early diagnosis of clinical disorders.

Multicolor fluorescence encoding of different microRNAs in lung cancer tissues at the single-molecule level

The simultaneous detection of multiple microRNAs (miRNAs) will facilitate early clinical diagnosis. Herein, we demonstrate the integration of multicolor fluorophore-encoded cascade signal amplification with single-molecule detection for simultaneous measurement of different miRNAs in lung cancer tissues. This assay involves two linear templates and two circular templates without the requirement of any fluorescent-labeled probes. The binding of target miRNAs to their corresponding linear templates initiates the cyclic strand displacement amplification, generating many triggers which can specifically hybridize with the corresponding biotin-labeled AP probes to initiate the apurinic/apyrimidic endonuclease 1-assisted cyclic cleavage reaction for the production of more biotin-labeled primers for each miRNA. The resultant two primers can react with their corresponding circular templates to initiate rolling circle amplification which enables the incorporation of Cy5-dCTP/Cy3-dGTP nucleotides, resulting in the simultaneous production of abundant biotin-/multiple Cy5/Cy3-labeled DNA products. After magnetic separation and exonuclease cleavage, the amplified products release abundant Cy5 and Cy3 fluorescent molecules which can be simply monitored by single-molecule detection, with Cy3 indicating miR-21 and Cy5 indicating miR-155. This assay involves three consecutive amplification reactions, enabling the conversion of extremely low abundant target miRNAs into large numbers of Cy5/Cy3 fluorophore-encoded DNA products which can release abundant fluorescent molecules for the generation of amplified signals. This assay exhibits high sensitivity, good selectivity, and the capability of multiplexed assay. This method can simultaneously quantify miR-155 and miR-21 in living cells and in lung cancer tissues, and it can distinguish the expression of miRNAs between non-small cell lung cancer patients and healthy persons. The accuracy and reliability of the proposed method are further validated by quantitative reverse transcription polymerase chain reaction.

Near-Infrared Light Controllable DNA Walker Driven by Endogenous Adenosine Triphosphate for in Situ Spatiotemporal Imaging of Intracellular MicroRNA

As a powerful signal amplification tool, the DNA walker has been widely applied to detect rare microRNA (miRNA) in vivo. Despite the significant advances, a near-infrared (NIR) light controllable DNA walker for signal amplification powered by an endogenous initiator has not been realized, which is crucial for spatiotemporal imaging of miRNA in living cells with high sensitivity. Herein, we constructed a NIR-photoactivatable DNA walker system, which was powered by endogenous adenosine triphosphate (ATP) for in situ miRNA imaging with spatial and temporal resolution. The system was very stable with an extremely low fluorescent background for the bioimaging in living cells. We employed upconversion nanoparticles (UCNPs) as the carriers of the DNA probe and transducers of converting NIR to UV light. Coupled with the DNA walker fueled by intracellular ATP, a smart system based on the NIR light initiated DNA walker was successfully developed for precise spatiotemporal control in living cells. Triggered by NIR light, the DNA walker could autonomously and progressively travel along the track with the assistance of intracellular ATP. The system has been successfully applied for in situ miRNA imaging in different cell lines with highly spatial and temporal resolution. This strategy can expand NIR photocontrol the DNA walker for precise imaging in a biological system.

Activating a DNA Nanomachine via Computation across Cancer Cell Membranes for Precise Therapy of Solid Tumors

Taking advantage of cancer cells' endogenous characters, the responsive activation of DNA nanomachines has achieved great success in tumor therapy. Combining with extra stimuli such as external light irradiation provided spatiotemporal control of DNA nanomachine activation. However, specific activation at the cellular level is still challenging considering the macroscopic-scale exposure area of usual light sources. DNA logic gates located at the cell membrane contributed to cellular specificity, but the free diffusion of input DNA strands during the operation process would impair efficiency and result in side effects to circumjacent normal cells in solid tumors. Here we design a transmembrane DNA logical computation strategy to activate a DNA nanomachine only in cancer cells from a complex solid tumor microenvironment. The DNA nanomachine multishell UCNPs-DNA is prepared by modifying DNA strands on upconversion nanoparticles. LA-apt, a DNA strand anchoring to a cancer cell membrane overexpressed receptor, and intracellular miRNA-21 served as inputs 1 and 2, respectively. Hybridization with input 1 at the cell membrane not only exposes the miRNA-21 recognition region at the DNA nanomachine, but also delivers it into cancer cells. The cascade hybridization with intracellular input 2 completes the "AND" gate operation and releases a DNA strand L2 as output. L2 acts as the trigger to operate the DNA nanomachine and correspondingly activates the photosensitizer Rose Bengal for reactive oxygen species generation. Through the "AND" gate operation of the DNA nanomachine across the cancer cell membrane, highly precise therapy only to cancer cells is achieved in a complex solid tumor microenvironment, which could become a promising modality for precise therapy of solid tumors.

From Passive Signal Output to Intelligent Response: "On-Demand" Precise Imaging Controlled by Near-Infrared Light

"On-demand" accurate imaging of multiple intracellular miRNAs will significantly improve the detection reliability and accuracy. However, the "always-active" design of traditional multicomponent detection probes enables them to passively recognize and output signals as soon as they encounter targets, which will inevitably impair the detection accuracy and, inevitably, result in false-positive signals. To address this scientific problem, in this work, we developed a near-infrared (NIR) light-activated multicomponent detection intelligent nanoprobe for spatially and temporally controlled on-demand accurate imaging of multiple intracellular miRNAs. The proposed intelligent nanoprobe is composed of a rationally designed UV light-responsive triangular DNA nano sucker (TDS) and upconversion nanoparticles (UCNPs), named UCNPs@TDS (UTDS), which can enter cells autonomously through endocytosis and enable remote regulation of on-demand accurate imaging for multiple intracellular miRNAs using NIR light illumination at a chosen time and place. It is worth noting that the most important highlight of the UTDS we designed in this work is that it can resist nonspecific activation as well as effectively avoid false-positive signals and improve the accuracy of imaging of multiple intracellular miRNAs. Moreover, distinguishing different kinds of cell lines with different miRNA expressions levels can be also achieved through this NIR light-activated intelligent UTDS, showing feasible prospects in precise imaging and disease diagnosis.

Intraparticle and Interparticle Transferable DNA Walker Supported by DNA Micelles for Rapid Detection of MicroRNA

Synthetic DNA walkers are artificially designed DNA self-assemblies with the capability of performing quasi-mechanical movement at the micro/nanoscale and have shown extensive promise in biosensing, intracellular imaging, and drug delivery. However, DNA walkers are usually constructed by covalently or coordinately binding DNA strands specifically to hard surfaces, thereby greatly limiting their movement efficiency. Herein, we report an intraparticle and interparticle transferable DNA walker (dynamic micelle-supported DNA walker, DM-walker) constructed by immobilizing walking tracks and walking arms onto the corona of DNA micelles according to the principle of Watson-Crick base pairing. The DNAzyme-powered walking arm can drive the intraparticle and interparticle movements of the DM-walker due to the fact that the dynamic structure of the DNA micelle helps overcome the spatial barrier between the arms and tracks in the system, resulting in high walking efficiency. Moreover, the whole DM-walker can be constructed by self-assembly, getting rid of the tedious process and low efficiency of fixing DNA strands on hard surfaces. Taking miRNA-10b as a model target, the DM-walker demonstrates high walking efficiency (reaction duration of 20 min) and high sensitivity (LOD of 87 pM). The proposed DM-walker provides an avenue to develop novel DNA walkers on dynamic interfaces and holds great potential in clinical diagnosis.

Antibody-powered DNA switches to initiate the hybridization chain reaction for the amplified fluorescence immunoassay

Designing antibody-powered DNA nanodevice switches is crucial and fascinating to perform a variety of functions in response to specific antibodies as regulatory inputs, achieving highly sensitive detection by integration with simple amplified methods. In this work, we report a unique DNA-based conformational switch, powered by a targeted anti-digoxin mouse monoclonal antibody (anti-Dig) as a model, to rationally initiate the hybridization chain reaction (HCR) for enzyme-free signal amplification. As a proof-of-concept, both a fluorophore Cy3-labeled reporter hairpin (RH) in the 3' terminus and a single-stranded helper DNA (HS) were individually hybridized with a recognition single-stranded DNA (RS) modified with Dig hapten, while the unpaired loop of RH was hybridized with the exposed 3'-toehold of HS, isothermally self-assembling an intermediate metastable DNA structure. The introduction of target anti-Dig drove the concurrent conjugation with two tethered Dig haptens, powering the directional switch of this DNA structure into a stable conformation. In this case, the unlocked 3'-stem of RH was implemented to unfold the 5'-stem of the BHQ-2-labeled quench hairpin (QH), rationally initiating the HCR between them by the overlapping complementary hybridization. As a result, numerous pairs of Cy3 and BHQ-2 in the formed long double helix were located in spatial proximity. In response to this, the significant quenching of the fluorescence intensity of Cy3 by BHQ-2 was dependent on the variable concentration of anti-Dig, achieving a highly sensitive quantification down to the picomolar level based on a simplified protocol integrated with enzyme-free amplification.

Photo-gated and self-powered three-dimensional DNA motors with boosted biostability for exceptionally precise and efficient tracing of intracellular survivin mRNA

Benefiting from the outstanding signal amplification effect and the admirable construction flexibility, the currently proposed DNA motors (particularly DNA walkers) based biosensing concepts have provided a forceful fluorescence imaging tool for intracellular detection. Even so, this promising sensing means is not only subject to poor controllability and prone to produce false signals but also requires exogenous powering forces owing to the common employment of DNAzyme. In response to these challenges, we are herein motivated to present some meaningful solving strategies. For one thing, the surfaces of gold nanoparticles are conducted with a photo-gated walking behavior by introducing a photocleave mode, under which the light-switchable DNA walkers are capable of being selectively activated via an external ultraviolet source to faultlessly prevent the sensing frame from being pre-initiated during cellular uptake and intracellular delivery. For another, the intracellular biothiols are consumed by MnO₂ nanosheets to effectively avoid the competitions to Au-S bonds to eliminate potential false outputs and also self-supply sufficient cofactors (Mn²⁺) to actualize a self-powered operation pattern as well as facilitate the endocytosis process. Following these breakthroughs, a favorable analysis performance towards a model tumor biomarker (survivin mRNA) is endowed with the newly raised biosensor, whose sensitivity is low to pM level with a sound specificity for identifying single base mismatching. Moreover, the significantly improved autonomous three-dimensional DNA walkers can be used to determine and dynamically trace the targets in live cancer cells with an exceptional precise and efficient manner, commendably impelling the sensing ability of DNA motors in biological specimens.

Dual-Mode SERS and Electrochemical Detection of miRNA Based on Popcorn-like Gold Nanofilms and Toehold-Mediated Strand Displacement Amplification Reaction

MicroRNA (miRNA) has emerged as one of the ideal target biomarker analytes for cancer detection because its abnormal expression is closely related to the occurrence of many cancers. In this work, we combined three-dimensional (3D) popcorn-like gold nanofilms as novel surface-enhanced Raman scattering (SERS)-electrochemistry active substrates with toehold-mediated strand displacement reactions (TSDRs) to construct a DNA molecular machine for SERS-electrochemistry dual-mode detection of miRNA. 3D popcorn-like spatial structures generated more active "hot spots" and thus enhanced the sensitivity of SERS and electrochemical signals. Besides, the TSDRs showed high sequence-dependence and high specificity. The addition of target miRNA will trigger the molecular machine to perform two TSDRs in the presence of signal DNA strands modified by R6G (R6G-DNA), thus achieving an enzyme-free amplification detection of miRNA with a low limit of detection of 0.12 fM (for the SERS method) and 2.2 fM (for the electrochemical method). This biosensor can also serve as a universally amplified and sensitive detection platform for monitoring different biomarkers, such as cancer-related DNA, messenger RNA, or miRNA molecules, with high selectivity by changing the corresponding probe sequence.

Swing Arm Location-Controllable DNA Walker for Electrochemiluminescence Biosensing

Here, we described a novel swing arm location-controllable DNA walker based on the DNA tetrahedral nanostructures (DTNs) for nucleic acid detection using the polycyclic aromatic hydrocarbon (PAH) microcrystals (TAPE-Pe MCs) consisting of the nonplanar molecular tetrakis(4-aminophenyl)ethene (TAPE) and planar molecular perylene (Pe) as electrochemiluminescence (ECL) luminophores. Specifically, the swing arm strands and track strands were fixed simultaneously on the DTNs to obtain the location-controllable DNA walker, which possessed an improved reaction efficiency compared to that of a fixed swing arm-based DNA walker due to the quantitative and orderly swing arm on the DTNs. On the other hand, the Pe microcrystals doped by TAPE molecules could decrease the π-π stacking of Pe molecules for the ECL efficiency enhancement, achieving a blue-shifted and intense ECL emission. Therefore, we defined this enhanced and blue-shifted ECL phenomenon as "inhibition of conjugation-driven ECL (IC-ECL)". To prove these principles, a location-controllable DNA walker-based ECL biosensor was developed with microRNA let-7a as target molecules. The ECL biosensor achieved a low detection limit of 4.92 fM within a wide linear range from 10 fM to 100 nM. This approach offers a new insight for ECL efficiency increase and location-controllable strategies with improved reaction efficiency, demonstrating potential in diagnostic analysis.

Microfluidic synthesis of high-valence programmable atom-like nanoparticles for reliable sensing

Synthesis of programmable atom-like nanoparticles (PANs) with high valences and high yields remains a grand challenge. Here, a novel synthetic strategy of microfluidic galvanic displacement (μ-GD) coupled with microfluidic DNA nanoassembly is advanced for synthesis of single-stranded DNA encoder (SSE)-encoded PANs for reliable surface-enhanced Raman scattering (SERS) sensing. Notably, PANs with high valences (e.g., n-valence, n = 12) are synthesized with high yields (e.g., >80%) owing to the effective control of interfacial reactions sequentially occurring in the microfluidic system. On the basis of this, we present the first demonstration of a PAN-based automatic analytical platform, in which sensor construction, sample loading and on-line monitoring are carried out in the microfluidic system, thus guaranteeing reliable quantitative measurement. In the proof-of-concept demonstration, accurate determination of tetracycline (TET) in serum and milk samples with a high recovery close to 100% and a low relative standard deviation (RSD) less than 5.0% is achieved by using this integrated analytical platform.