DNA Nanowire Guided-Catalyzed Hairpin Assembly Nanoprobe for In Situ Profiling of Circulating Extracellular Vesicle-Associated MicroRNAs

Profiling the Ocular Landscape of sEVs miRNAs: Mechanisms and Applications

In this review, we comprehensively discuss the application of sEVs miRNAs in ophthalmic diseases by examining their basic characteristics and clinical application potential. Initially, we provide an overview of sEVs, including their definition, source, and functions, while particularly highlighting the importance of miRNAs contained in sEVs and its prospects in the treatment of ocular diseases. Subsequently, the structure and composition of sEVs as well as the biological functions of their encapsulated miRNAs, which expands the current knowledge about their roles in ophthalmic physiology and pathology. In addition, the functions of sEVs miRNAs in the growth of ocular tissues, ocular tissue homeostasis, and common eye diseases such as glaucoma, age-related macular degeneration, and diabetic retinopathy, are discussed. The application potential of sEVs miRNAs as diagnostic biomarkers and drug delivery systems for ophthalmic conditions and therapeutic value in diverse eye diseases are explored. Finally, the current challenges affecting research in this field are outlined to provide a basis that guide future utilization of sEVs miRNAs in ophthalmic disease research and clinical management of diverse ophthalmological conditions.

Self-Assembled DNA/SG-I Nanoflower: Versatile Photocatalytic Biosensors for Disease-Related Markers

DNA nanostructures have recently attracted more attention with functionalities, programmability, and biocompatibility. Herein, a novel self-assembled photocatalytic DNA/SYBR Green I (SG-I) nanoflower (DSNF) was successfully synthesized by rolling circle amplification. DSNF was self-assembled through liquid crystallization of a high concentration of DNA in the RCA products, without relying on the Watson-Crick base-pairing principle. Interestingly, DSNF not only possessed a larger specific surface area and good stability but also exhibited excellent photocatalytic activity that generates singlet oxygen and superoxide anion to oxidate 3,3',5,5'-tetramethylbenzidine. Meanwhile, the photocatalytic DSNF combined with an enzyme-linked immunosorbent assay to develop a new colorimetric sensor for highly specific, sensitive, and visual detection of carcinoembryonic antigens (CEAs). The colorimetric sensor achieved sensitive and low-cost quantitative detection of CEA in the linear range of 0.5-80.0 ng/mL, and the LOD was 0.5 ng/mL. In addition, three negative and seven positive clinical serum samples of CEA were obtained with 100% accuracy using the proposed colorimetric sensor, showing great potential in the clinical application of cancer diagnosis. We envision that this photocatalytic DSNF is expected to provide important perspectives in fluorescence imaging, photosensitizing cancer therapy, and clinical diagnosis fields.

Combinatorial Nanoparticle-Bound ssDNA Oligonucleotide Library Synthesized by Split-and-Pool Synthesis

Synthetic ssDNA oligonucleotides hold great potential for various applications, including DNA aptamers, DNA digital data storage, DNA origami, and synthetic genomes. In these contexts, precise control over the synthesis of the ssDNA strands is essential for generating combinatorial sequences with user-defined parameters. Desired features for creating synthetic DNA oligonucleotides include easy manipulation of DNA strands, effective detection of unique DNA sequences, and a straightforward mechanism for strand elongation and termination. In this study, we present a split-and-pool method for generating synthetic DNA oligonucleotides on nanoparticles, enabling the creation of scalable combinatorial libraries. Our approach involves coupling DNA to nanoparticles, ligating double-digested fragments for orientation-specific synthesis, and attaching a final single-digested fragment to ensure strand termination. We assess the quality of our method by characterizing both the DNA and the nanoparticles used as solid supports, confirming that our method produces scalable, combinatorial nanoparticle-bound ssDNA libraries with controllable strand lengths.

Circulating Extracellular Vesicles as Promising Biomarkers for Precession Diagnostics: A Perspective on Lung Cancer

Extracellular vesicles (EVs) have emerged as promising biomarkers in liquid biopsy, owing to their ubiquitous presence in bodily fluids and their ability to carry disease-related cargo. Recognizing their significance in disease diagnosis and treatment, substantial efforts have been dedicated to developing efficient methods for EV isolation, detection, and analysis. EVs, heterogeneous membrane-encapsulated vesicles secreted by all cells, contain bioactive substances capable of modulating recipient cell biology upon internalization, including proteins, lipids, DNA, and various RNAs. Their prevalence across bodily fluids has positioned them as pivotal mediators in physiological and pathological processes, notably in cancer, where they hold potential as straightforward tumor biomarkers. This review offers a comprehensive examination of advanced nanotechnology-based techniques for detecting lung cancer through EV analysis. It begins by providing a brief overview of exosomes and their role in lung cancer progression. Furthermore, this review explores the evolving landscape of EV isolation and cargo analysis, highlighting the importance of characterizing specific biomolecular signatures within EVs for improved diagnostic accuracy in lung cancer patients. Innovative strategies for enhancing the sensitivity and specificity of EV isolation and detection, including the integration of microfluidic platforms and multiplexed biosensing technologies are summarized. The discussion then extends to key challenges associated with EV-based liquid biopsies, such as the standardization of isolation and detection protocols and the establishment of robust analytical platforms for clinical translation. This review highlights the transformative impact of EV-based liquid biopsy in lung cancer diagnosis, heralding a new era of personalized medicine and improved patient care.

Proximity hybridization-triggered cascade amplification for label-free SERS detection of Alzheimer's amyloid-β oligomers

Most of the existing SERS systems failed to achieve satisfactory results in early diagnosis of Alzheimer's disease owing to a lack of effective signal transduction. Herein, we developed a dual signal amplification strategy for SERS detection of amyloid-β oligomers based on proximity hybridization-triggered catalyzed hairpin assembly (CHA) and hybridization chain reaction (HCR). In the presence of the target protein and two DNA-labeled antibodies, a proximate complex formed in a homogeneous solution. Each of the AβO-DNA complexes served as a catalyst to trigger and accelerate numerous hybridization processes between MB1 and MB2. Subsequently, the single-strand fragment on the electrode surface initiated HCR, resulting in the hybridization reaction to form double-strand DNA concatemers on the substrate surface. The surface became negatively charged and allowed the absorption of silver ions on the DNA skeleton. After chemical reduction by hydroquinone, the formed silver nanoparticles could be further grown with a silver enhancement step to amplify the detectable SERS signal by absorbing rhodamine 6G as a SERS reporter on the silver nanoparticle surface. This biosensing platform had potential applications in molecular diagnostics of AD serum samples.

Precision detection of hepatocellular carcinoma-associated telomerase RNA with SA@Comb-HCR nanosystem

Accurate intracellular visualization of human telomerase RNA (hTR) is imperative for early diagnosis and treatment monitoring of hepatocellular carcinoma (HCC). While isothermal amplification-based DNA cascade strategies are promising, challenges persist in achieving great intake efficiency of detection probes within tumor cells and enhancing intracellular reaction efficiency. This study introduces a SA@Comb-HCR nanosystem, a highly effective approach for in situ hTR detection in HCC cells. Sodium alginate-coated liposomes ensures efficient nanoprobe delivery, which are then combined with proximity effect-inspired signal amplification. The coating of sodium alginate facilitates receptor-mediated endocytosis, prevents serum protein adhesion, and mitigates cationic liposome cytotoxicity. The designed Comb-like consolidated hairpin probe enhances the concentration of the local reactant, resulting in cascade amplification upon hTR activation. This technique achieves precision detection of intracellularly overexpressed hTR in HCC cells with a remarkable detection limit of 0.7 pM. This approach holds great promise for advancing targeted and sensitive early clinical diagnosis of HCC.

All-in-One Fusogenic Nanoreactor for the Rapid Detection of Exosomal MicroRNAs for Breast Cancer Diagnosis

Molecular-profiling-based cancer diagnosis has significant implications for predicting disease prognosis and selecting targeted therapeutic interventions. The analysis of cancer-derived extracellular vesicles (EVs) provides a noninvasive and sequential method to assess the molecular landscape of cancer. Here, we developed an all-in-one fusogenic nanoreactor (FNR) encapsulating DNA-fueled molecular machines (DMMs) for the rapid and direct detection of EV-associated microRNAs (EV miRNAs) in a single step. This platform was strategically designed to interact selectively with EVs and induce membrane fusion under a specific trigger. After fusion, the DMMs recognized the target miRNA and initiated nonenzymatic signal amplification within a well-defined reaction volume, thus producing an amplified fluorescent signal within 30 min. We used the FNRs to analyze the unique expression levels of three EV miRNAs in various biofluids, including cell culture, urine, and plasma, and obtained an accuracy of 86.7% in the classification of three major breast cancer (BC) cell lines and a diagnostic accuracy of 86.4% in the distinction between patients with cancer and healthy donors. Notably, a linear discriminant analysis revealed that increasing the number of miRNAs from one to three improved the accuracy of BC patient discrimination from 78.8 to 95.4%. Therefore, this all-in-one diagnostic platform performs nondestructive EV processing and signal amplification in one step, providing a straightforward, accurate, and effective individual EV miRNA analysis strategy for personalized BC treatment.

Intelligent near-infrared light-activatable DNA machine with DNA wire nano-scaffold-integrated fast domino-like driving amplification for high-performance imaging in live biological samples

While there is significant potential for DNA machine-built enzyme-free fluorescence biosensors in the imaging analysis of live biological samples, they persist certain shortcomings. These encompass a deficiency of signal enrichment within a singular interface, uncontrolled premature activation during bio-delivery, and a slow reaction rate due to free nucleic acid collisions. In this contribution, we are committed to resolving the above challenges. Firstly, a single-interface-integrated domino-like driving amplification is constructed. In this conception, a specific target acts as the domino promotor (namely the energy source), initiating a cascading chain reaction that grafts onto a singular interface. Next, an 808 nm near-infrared (NIR) light-excited up-converting luminescence-induced light-activatable biosensing technique is introduced. By locking the target-specific identification segment with a photo-cleavage connector, the up-converted ultraviolet emission can activate target binding in a completely controlled manner. Moreover, a fast reaction rate is achieved by confining nucleic acid collisions within the surface of a DNA wire nano-scaffold, leading to a substantial enhancement in local contact concentration (30.8-fold increase, alongside a 15 times elevation in rate). When a non-coding microRNA (miRNA-221) is positioned as the model low-abundance target for proof-of-concept validation, our intelligent DNA machine demonstrates ultra-high sensitivity (with a limit of detection down to 62.65 fM) and good specificity for this hepatic malignant tumor-associated biomarker in solution detection. Going further, it is worth highlighting that the biosensing system can be employed to carry out high-performance imaging analysis in live bio-samples (ranging from the cellular level to the nude mouse body), thereby propelling the field of DNA machines in disease diagnosis.

Aptamer-Loop DNA Nanoflower Recognition and Multicolor Fluorescent Carbon Quantum Dots Labeling System for Multitarget Living Cell Imaging

Visualization of multiple targets in living cells is important for understanding complex biological processes, but it still faces difficulties, such as complex operation, difficulty in multiplexing, and expensive equipment. Here, we developed a nanoplatform integrating a nucleic acid aptamer and DNA nanotechnology for living cell imaging. Aptamer-based recognition probes (RPs) were synthesized through rolling circle amplification, which were further self-assembled into DNA nanoflowers encapsulated by an aptamer loop. The signal probes (SPs) were obtained by conjugation of multicolor emission carbon quantum dots with oligonucleotides complementary to RPs. Through base pairing, RPs and SPs were hybridized to generate aptamer sgc8-, AS1411-, and Apt-based imaging systems. They were used for individual/simultaneous imaging of cellular membrane protein PTK7, nucleolin, and adenosine triphosphate (ATP) molecules. Fluorescence imaging and intensity analysis showed that the living cell imaging system can not only specifically recognize and efficiently bind their respective targets but also provide a 5-10-fold signal amplification. Cell-cycle-dependent distribution of nucleolin and concentration-dependent fluorescence intensity of ATP demonstrated the utility of the system for tracking changes in cellular status. Overall, this system shows the potential to be a simple, low-cost, highly selective, and sensitive living cell imaging platform.

An Oxidative Cleavage-Based Cruciform DNA Nanostructure for In Vivo Hypochlorous Acid Visualization to Monitor Intestinal Inflammation

Ulcerative colitis is a persistent inflammatory bowel disease characterized by inflammation and ulceration in the colon and gastrointestinal tract. It was indicated that the generation of hypochlorous acid (HClO) through the enzymatic activity of myeloperoxidase is significantly linked to ulcerative colitis. In this study, by assembling two hairpins (Hpa and Hpb) onto a quadrivalent cruciform DNA nanostructure, a novel HClO-activatable fluorescent probe was developed based on DNA nanomaterials (denoted MHDNA), which is sensitive, economic, simple, and stable. In the presence of HClO, the Trigger (T) was liberated from the MHDNA probe through a hydrolysis reaction between HClO and phosphorothioate (PS), which is modified on the MHDNA probe and has proved to exhibit particular susceptibility to the HClO. The liberated T subsequently initiated the opening of Hpa and Hpb to facilitate the catalyzed hairpin assembly (CHA) reaction, resulting in the changes of fluorescence and releasing T for recycled signal amplification to achieve sensitive detection of HClO (with a limit of detection 9.83 nM). Additionally, the MHDNA-based spatial-confinement effect shortens the physical distance between Hpa and Hpb and yields a high local concentration of the two reactive hairpins, achieving more rapid reaction kinetics in comparison to conventional CHA methods. Inspirationally, the MHDNA probe was effectively utilized for imaging HClO in ulcerative colitis mice, yielding valuable diagnostic insights for ulcerative colitis.

Endogenous AND Logic DNA Nanomachine for Highly Specific Cancer Cell Imaging

Intracellular cancer-related biomarker imaging strategy has been used for specific identification of cancer cells, which was of great importance to accurate cancer clinical diagnosis and prognosis studies. Localized DNA circuits with improved sensitivity showed great potential for intracellular biomarkers imaging. However, the ability of localized DNA circuits to specifically image cancer cells is limited by off-site signal leakage associated with a single-biomarker sensing strategy. Herein, we integrated the endogenous enzyme-powered strategy with logic-responsive and localized signal amplifying capability to construct a self-assembled endogenously AND logic DNA nanomachine (EDN) for highly specific cancer cell imaging. When the EDN encountered a cancer cell, the overexpressed DNA repairing enzyme apurinic/apyrimidinic endonuclease 1 (APE1) and miR-21 could synergistically activate a DNA circuit via cascaded localized toehold-mediated strand displacement (TMSD) reactions, resulting in amplified fluorescence resonance energy transfer (FRET) signal. In this strategy, both endogenous APE1 and miR-21, served as two "keys" to activate the AND logic operation in cancer cells to reduce off-tumor signal leakage. Such a multiplied molecular recognition/activation nanomachine as a powerful toolbox realized specific capture and reliable imaging of biomolecules in living cancer cells.

DNA-Based Nanomaterials for Analysis of Extracellular Vesicles

Extracellular vesicles (EVs) are cell-derived nanovesicles comprising a myriad of molecular cargo such as proteins and nucleic acids, playing essential roles in intercellular communication and physiological and pathological processes. EVs have received substantial attention as noninvasive biomarkers for disease diagnosis and prognosis. Owing to their ability to recognize protein and nucleic acid targets, DNA-based nanomaterials with excellent programmability and modifiability provide a promising tool for the sensitive and accurate detection of molecular cargo carried by EVs. In this perspective, recent advancements in EV analysis using a variety of DNA-based nanomaterials are summarized, which can be broadly classified into three categories: linear DNA probes, DNA nanostructures, and hybrid DNA nanomaterials. The design, construction, advantages, and disadvantages of different types of DNA nanomaterials, as well as their performance for detecting EVs are reviewed. The challenges and opportunities in the field of EV analysis by DNA nanomaterials are also discussed.

DNA nanotechnology-based nucleic acid delivery systems for bioimaging and disease treatment

Nucleic acids, including DNA and RNA, have been considered as powerful and functional biomaterials owing to their programmable structure, good biocompatibility, and ease of synthesis. However, traditional nucleic acid-based probes have always suffered from inherent limitations, including restricted cell internalization efficiency and structural instability. In recent years, DNA nanotechnology has shown great promise for the applications of bioimaging and drug delivery. The attractive superiorities of DNA nanostructures, such as precise geometries, spatial addressability, and improved biostability, have enabled them to be a novel category of nucleic acid delivery systems for biomedical applications. In this review, we introduce the development of DNA nanotechnology, and highlight recent advances of DNA nanostructure-based delivery systems for cellular imaging and therapeutic applications. Finally, we propose the challenges as well as opportunities for the future development of DNA nanotechnology in biomedical research.

DNAzyme-Amplified Cascade Catalytic Hairpin Assembly Nanosystem for Sensitive MicroRNA Imaging in Living Cells

Sensitive imaging of microRNAs (miRNAs) in living cells is significant for accurate cancer clinical diagnosis and prognosis research studies, but it is challenged by inefficient intracellular delivery, instability of nucleic acid probes, and limited amplification efficiency. Herein, we engineered a DNAzyme-amplified cascade catalytic hairpin assembly (CHA)-based nanosystem (DCC) that overcomes these challenges and improves the imaging sensitivity. This enzyme-free amplification nanosystem is based on the sequential activation of DNAzyme amplification and CHA. MnO2 nanosheets were used as nanocarriers for the delivery of nucleic acid probes, which can resist the degradation by nucleases and supply Mn2+ for the DNAzyme reaction. After entering into living cells, the MnO2 nanosheets can be decomposed by intracellular glutathione (GSH) and release the loaded nucleic acid probes. In the presence of target miRNA, the locking strand (L) was hybridized with target miRNA, and the DNAzyme was released, which then cleaved the substrate hairpin (H1). This cleavage reaction resulted in the formation of a trigger sequence (TS) that can activate CHA and recover the fluorescence readout. Meanwhile, the DNAzyme was released from the cleaved H1 and bound to other H1 for new rounds of DNAzyme-based amplification. The TS was also released from CHA and involved in the new cycle of CHA. By this DCC nanosystem, low-abundance target miRNA can activate many DNAzyme and generate numerous TS for CHA, resulting in sensitive and selective analysis of miRNAs with a limit of detection of 5.4 pM, which is 18-fold lower than that of the traditional CHA system. This stable, sensitive, and selective nanosystem holds great potential for miRNA analysis, clinical diagnosis, and other related biomedical applications.

Assembly of DNA triangular pyramid frustum for ultrasensitive quantification of exosomal miRNA

Early screening of biomarkers benefits therapy and prognosis of cancers. MiRNAs encapsulated in tumor-derived exosomes are emerging biomarkers for early diagnosis of cancers. Nevertheless, traditional methods suffer certain drawbacks, which hamper their wide applications. In this contribution, we have developed a convenient electrochemical approach for quantification of exosomal miRNA based on the assembly of DNA triangular pyramid frustum (TPF) and strand displacement amplification. Four single-stranded DNA helps the formation of primary DNA triangle with three thiols for gold electrode immobilization at the bottom and three amino groups on overhangs for the capture of silver nanoparticles. On the other hand, target miRNA induced strand displacement reaction produces abundant specific DNA strands, which help the DNA structural transition from triangle to TPF. Amino groups are thus hidden and the declined silver stripping current can be used for the evaluation of target miRNA concentration. This biosensor exhibits excellent analytical performances and successfully achieves analysis of exosomal miRNAs from cells and clinical serum samples.

A review of sensors for classification and subtype discrimination of cancer: Insights into circulating tumor cells and tumor-derived extracellular vesicles

Liquid biopsy can reflect the state of tumors in vivo non-invasively, thus providing a strong basis for the early diagnosis, individualized treatment monitoring and prognosis of tumors. Circulating tumor cells (CTCs) and tumor-derived extracellular vesicles (tdEVs) contain information-rich components, such as nucleic acids and proteins, and they are essential markers for liquid biopsies. Their capture and analysis are of great importance for the study of disease occurrence and development and, consequently, have been the subject of many reviews. However, both CTCs and tdEVs carry the biological characteristics of their original tissue, and few reviews have focused on their function in the staging and classification of cancer. In this review, we focus on state-of-the-art sensors based on the simultaneous detection of multiple biomarkers within CTCs and tdEVs, with clinical applications centered on cancer classification and subtyping. We also provide a thorough discussion of the current challenges and prospects for novel sensors with the ultimate goal of cancer classification and staging. It is hoped that these most advanced technologies will bring new insights into the clinical practice of cancer screening and diagnosis.

An in situ exosomal miRNA sensing biochip based on multi-branched localized catalytic hairpin assembly and photonic crystals

Exosomal microRNAs (miRNAs) are emerging as attractive non-invasive and reliable biomarkers for disease diagnosis. In situ exosomal miRNA detection can avoid laborious and time-consuming exosome lysis, RNA extraction and effectively improve the accuracy. However, in situ exosomal miRNA detection is hampered by the low abundance of the targets and low permeability of the probes. Herein, an in situ exosomal miRNA sensing biochip based on multi-branched localized catalytic hairpin assembly (MLCHA) and photonic crystals (PCs) was proposed. The MLCHA probes could penetrate into the exosomes nondestructively due to its rigidity and generate amplified fluorescence signal upon recognizing the target miRNA. And then, the fluorescence signal was further enhanced by PCs to improve the sensitivity. The developed biosensor can not only detect exosomal miRNA in a concentration-dependent manner but also distinguish samples from cancer state and healthy state, which is potential for non-invasive clinical diagnostics.

A programmable catalytic molecular nanomachine for highly sensitive protein and small molecule detection

Herein, we report the construction of a programmable catalytic molecular nanomachine based on a cross-linked catalytic hairpin assembly (CCHA) reaction for the one-step highly sensitive detection of proteins and small molecules. In this system, when the recognition elements attached on split initiators bind to the target proteins, it can trigger the cascade of the CCHA reaction, resulting in the formation of many macromolecular fluorescent products for signaling. This platform couples the advantages of highly efficient DNA-based nanotechnology with specific protein-small molecule interactions. We demonstrated the sensitive detection of streptavidin and anti-digoxigenin antibody with detection limits as low as 48.8 pM and 0.85 nM, respectively. This nanomachine also demonstrated its flexibility in the nanomolar detection of corresponding small molecules, such as biotin and digoxigenin, using a competitive method. In addition, the nanomachine was robust enough to perform well with human serum samples. Overall, this programmable catalytic molecular nanomachine provides a versatile platform for the detection of proteins and small molecules by replacing the recognition elements, which can promote the development of DNA nanotechnology in disease diagnosis and therapeutic drug monitoring.

In situ detection of exosomal RNAs for cancer diagnosis

Exosomes are considered as biomarkers reflecting the physiological state of the human body. Studies have revealed that the expression levels of specific exosomal RNAs are closely associated with certain cancers. Thus, detection of exosomal RNA offers a new avenue for liquid biopsy of cancers. Many exosomal RNA detection methods based on various principles have been developed, and most of the methods detect the extracted RNAs after lysing exosomes. Besides complex and time-consuming extraction steps, a major drawback of this approach is the degradation of the extracted RNAs in the absence of plasma membrane and cytosol. In addition, there is considerable loss of RNAs during their extraction. In situ detection of exosomal RNAs can avoid these drawbacks, thus allowing higher diagnostic reliability. In this paper, in situ detection of exosomal RNAs was systematically reviewed from the perspectives of detection methods, transport methods of the probe systems, probe structures, signal amplification strategies, and involved functional materials. Furthermore, the limitations and possible improvements of the current in situ detection methods for exosomal RNAs towards the clinical diagnostic application are discussed. This review aims to provide a valuable reference for the development of in situ exosomal RNA detection strategies for non-invasive diagnosis of cancers. STATEMENT OF SIGNIFICANCE: Certain RNAs have been identified as valuable biomarkers for some cancers, and sensitive detection of cancer-related RNAs is expected to achieve better diagnostic efficacy. Currently, the detection of exosomal RNAs is receiving increasing attention due to their high stability and significant concentration differences between patients and healthy individuals. In situ detection of exosomal RNAs has greater diagnostic reliability due to the avoidance of RNA degradation and loss. However, this mode is still limited by some factors such as detection methods, transport methods of the probe systems, probe structures, signal amplification strategies, etc. This review focuses on the progress of in situ detection of exosomal RNAs and aims to promote the development of this field.

A domino-like localized cascade toehold assembly amplification-based DNA nanowire for microRNA imaging in living cells

High sensitivity and specificity imaging of miRNA in living cells plays an important role in understanding miRNA-related regulation and pathological research. Localized DNA circuits have shown good performance in reaction rate and sensitivity and have been proposed for sensitive imaging of miRNA in living cells. However, most reported localized DNA circuits have a high risk of derailment or a limited loading rate capacity, which hinder their further application. To solve these issues, we herein developed a domino-like localized cascade toehold assembly (LCTA) amplification-based DNA nanowire to achieve highly sensitive and highly specific imaging of miRNAs in living cells by using DNA nanowires as reactant delivery vehicles and confining both reactant probes in a compact space. The LCTA is constructed by interval hybridization of DNA double-stranded probe pairs to a DNA nanowire with multiplex footholds generated by alternating chain hybridization. Due to the localized effect, the LCTA showed high reaction kinetics and sensitivity, and the method could detect miRNAs as low as 51 pM. The LCTA was proven to be able to accurately distinguish the miRNA expression difference between normal cells and cancer cells. In particular, the developed LCTA could be used to construct an OR logic gate to simultaneously image the total amount of multiple miRNAs in living cells. We believe that the developed LCTA can be an effective intracellular nucleic acid imaging tool and can promote the development of nucleic acid-related clinical disease diagnosis and DNA logical sensors.

A functional RNA/DNA circuit for one-pot detection of SARS-CoV-2 RNA

A simple method is proposed in this work for the detection of SARS-CoV-2 RNA based on a functional RNA/DNA circuit. By ingeniously integrating the nucleic acid circuit technology and CRISPR/cas12a system, this method can achieve femtomolar detection of the target RNA in one step and successfully distinguish COVID-19 positive cases from clinical samples, proving its great potential for clinical application.

Nonenzymatic Multiamplified Electrochemical Detection of Medulloblastoma-Relevant MicroRNAs from Cerebrospinal Fluid

The sensitive analysis of microRNAs (miRNAs) in cerebrospinal fluid (CSF) holds promise for the minimally invasive early diagnosis of brain cancers such as pediatric medulloblastoma but remains challenging due partially to a lack of facile yet sensitive sensing methods. Herein, an enzyme-free triple-signal amplification electrochemical assay for miRNA was developed by integrating the target-triggered cyclic strand-displacement reaction (TCSDR), hybridization chain reaction (HCR), and methylene blue (MB) intercalation. In this assay, the presence of target miRNA (miR-9) initiated the TCSDR and produced primers that triggered the subsequent HCR amplification to generate copious double-stranded DNAs (dsDNAs) on the electrode surface. Intercalation of a large number of MB reporters into the long nicked double helixes of dsDNAs yielded a more enhanced signal of differential pulse voltammetry. The enzyme-free multiple-amplification approach allowed for highly sensitive (detection limit: 6.5 fM) and sequence-specific (single-base mismatch resolution) detection of miR-9 from tumor cells and human CSF with minimal sample consumption (10 μL). Moreover, the clinical utilization of this method was documented by accurate discrimination of five medulloblastoma patients from the nontumoral controls. In light of its sensitivity, specificity, and convenience of use, this electrochemical method was expected to facilitate the early detection of malignant brain tumors.