Multiple amplified microRNAs monitoring in living cells based on fluorescence quenching of Mo2B and hybridization chain reaction

Recent Developments and Future Perspectives of Molybdenum Borides and MBenes

Metal borides have received a lot of attention recently as a potentially useful material for a wide range of applications. In particular, molybdenum-based borides and MBenes are of great significance, due to their remarkable properties like good electronic conductivity, considerable stability, high surface area, and environmental harmlessness. Therefore, in this article, the progress made in molybdenum-based borides and MBenes in recent years is reviewed. The first step in understanding these materials is to begin with an overview of their structural and electronic properties. Then synthetic technologies for the production of molybdenum borides, such as high-temperature/pressure methods, physical vapor deposition (PVD), chemical vapor deposition (CVD), element reaction route, molten salt-assisted, and selective etching methods are surveyed. Then, the critical performance of these materials in numerous applications like energy storage, catalysis, biosensors, biomedical devices, surface-enhanced Raman spectroscopy (SERS), and tribology and lubrication are summarized. The review concludes with an analysis of the current progress of these materials and provides perspectives for future research. Overall, this review will offer an insightful reference for the understanding molybdenum-based borides and their development in the future.

Deoxynivalenol (DON)-Triggered Dual-Color Composite Probe Based on Gold Nanoclusters for Simultaneous Imaging of DON and miR-34a in Living Cells

Deoxynivalenol (DON) is a mycotoxin secreted by Fusarium species, posing great harm to food safety and human health. Therefore, it is of great significance to study its toxic effects and mechanism. miR-34a is a representative biomarker during the process of DON-induced apoptosis. Herein, a DON-triggered dual-color composite probe was constructed for simultaneous imaging of DON and miR-34a in living cells. The aptamer blocks the recognition sequence of miR-34a to realize DON-triggered cell imaging. The specific binding of DON with its aptamer and HCR induced by miR-34a resulted in the recovery of fluorescence of the dual-color Au NCs. Under the optimal conditions, the correlation between the relative fluorescence intensities of dual-color Au NCs showed good linear relationships with the logarithm of DON and miR-34a concentration, respectively. With the increase in DON concentration (0-20 μg/mL) and stimulation time (0-12 h), the fluorescence of dual-color Au NCs gradually recovered. This dual-color Au NCs composite probe can realize simultaneous detection of DON and miR-34a induced by DON, which is significant for verifying the cytotoxic mechanism of DON.

An intelligent DNA nanomachine for amplified MicroRNA imaging and MicroRNA-Guided efficient gene silencing

The DNA nanomachines as excellent synthetic biological tools have been widely used for the sensitive detection of intracellular microRNA (miRNA) and DNAzyme-involved gene silencing. However, intelligent DNA nanomachines which have the ability to sense intracellular specific biomolecules and respond to external information in complex environments still remain challenging. Herein, we develop a miRNA-responsive DNAzyme cascaded catalytic (MDCC) nanomachine to perform multilayer cascade reactions, enabling the amplified intracellular miRNA imaging and miRNA-guided efficient gene silencing. The intelligent MDCC nanomachine is designed based on multiple DNAzyme subunit-encoded catalyzed hairpin assembly (CHA) reactants sustained by the pH-responsive Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles. After cellular uptake, the MDCC nanomachine degrades in acidic endosome and releases three hairpin DNA reactants and Zn2+, and the latter can act as an effective cofactor for DNAzyme. In the presence of miRNA-21, a catalytic hairpin assembly (CHA) reaction is triggered, which produces a large number of Y-shaped fluorescent DNA constructs containing three DNAzyme modules for gene silencing. The construction of Y-shaped DNA modified with multisite fluorescence and the circular reaction realizes ultrasensitive miRNA-21 imaging of cancer cells. Moreover, miRNA-guided gene silencing inhibits the cancer cell proliferation through the DNAzyme-specific recognition and cleavage of target EGR-1 (Early Growth Response-1) mRNA, which is one key tumor-involved mRNA. The strategy may provide a promising platform for highly sensitive determination of biomolecules and accurate gene therapy of cancer cells.

Current research status of tumor cell biomarker detection

With the annual increases in the morbidity and mortality rates of tumors, the use of biomarkers for early diagnosis and real-time monitoring of tumor cells is of great importance. Biomarkers used for tumor cell detection in body fluids include circulating tumor cells, nucleic acids, protein markers, and extracellular vesicles. Among them, circulating tumor cells, circulating tumor DNA, and exosomes have high potential for the prediction, diagnosis, and prognosis of tumor diseases due to the large amount of valuable information on tumor characteristics and evolution; in addition, in situ monitoring of telomerase and miRNA in living cells has been the topic of extensive research to understand tumor development in real time. Various techniques, such as enzyme-linked immunosorbent assays, immunoblotting, and mass spectrometry, have been widely used for the detection of these markers. Among them, the detection of tumor cell markers in body fluids based on electrochemical biosensors and fluorescence signal analysis is highly preferred because of its high sensitivity, rapid detection and portable operation. Herein, we summarize recent research progress in the detection of tumor cell biomarkers in body fluids using electrochemical and fluorescence biosensors, outline the current research status of in situ fluorescence monitoring and the analysis of tumor markers in living cells, and discuss the technical challenges for their practical clinical application to provide a reference for the development of new tumor marker detection methods.

Nanoarchitectonics-Assisted Simultaneous Fluorescence Detection of Urinary Dual miRNAs for Noninvasive Diagnosis of Prostate Cancer

Herein, we report a fluorescence strategy for the homogeneous and simultaneous analysis of urine miRNA-375 and miRNA-148a. The target miRNAs in urine bonded the devised dumbbell-shaped "C-Ag⁺-C" and "T-Hg²⁺-T" hairpin structures that could trigger cascade enzyme-free amplification. Then, the fluorescent CdTe quantum dots (QDs) and carbon dots (CDs) could selectively recognize Ag⁺ and Hg²⁺, to quantify the dual miRNAs concurrently. Under optimized conditions, the linear range was from 0.1 to 1000 fM and the limits of detection (LOD) for dual miRNAs reached 30 and 25 aM, respectively. The practicality was further evaluated with 45 clinical urine samples including prostate cancer (PC) and other patients, and the results were consistent with the clinical polymerase chain reaction (PCR) kit and ultrasonic and pathological findings. The receiver operating characteristic (ROC) curve analysis showed that the estimates of the area under the curve (AUC) were 0.739 for the serum prostate-specific antigen (PSA) and 0.941 for miRNA-375 and 0.946 for miRNA-148a. The sensitivity and specificity reached 75 and 100% for miRNA-375 and 71 and 94% for miRNA-148a, respectively, which was better than serum PSA. This strategy constructed a reliable system for dual miRNA detection in urine samples and proposed new insights into the rapid and noninvasive diagnosis of PC.

Signal Amplification-Based Biosensors and Application in RNA Tumor Markers

Tumor markers are important substances for assessing cancer development. In recent years, RNA tumor markers have attracted significant attention, and studies have shown that their abnormal expression of post-transcriptional regulatory genes is associated with tumor progression. Therefore, RNA tumor markers are considered as potential targets in clinical diagnosis and prognosis. Many studies show that biosensors have good application prospects in the field of medical diagnosis. The application of biosensors in RNA tumor markers is developing rapidly. These sensors have the advantages of high sensitivity, excellent selectivity, and convenience. However, the detection abundance of RNA tumor markers is low. In order to improve the detection sensitivity, researchers have developed a variety of signal amplification strategies to enhance the detection signal. In this review, after a brief introduction of the sensing principles and designs of different biosensing platforms, we will summarize the latest research progress of electrochemical, photoelectrochemical, and fluorescent biosensors based on signal amplification strategies for detecting RNA tumor markers. This review provides a high sensitivity and good selectivity sensing platform for early-stage cancer research. It provides a new idea for the development of accurate, sensitive, and convenient biological analysis in the future, which can be used for the early diagnosis and monitoring of cancer and contribute to the reduction in the mortality rate.

Signal differentiation models for multiple microRNA detection: a critical review

MicroRNAs (miRNAs) are a class of small, single-stranded non-coding RNAs which have critical functions in various biological processes. Increasing evidence suggested that abnormal miRNA expression was closely related to many human diseases, and they are projected to be very promising biomarkers for non-invasive diagnosis. Multiplex detection of aberrant miRNAs has great advantages including improved detection efficiency and enhanced diagnostic precision. Traditional miRNA detection methods do not meet the requirements of high sensitivity or multiplexing. Some new techniques have opened novel paths to solve analytical challenges of multiple miRNA detection. Herein, we give a critical overview of the current multiplex strategies for the simultaneous detection of miRNAs from the perspective of two different signal differentiation models, including label differentiation and space differentiation. Meanwhile, recent advances of signal amplification strategies integrated into multiplex miRNA methods are also discussed. We hope this review provides the reader with future perspectives on multiplex miRNA strategies in biochemical research and clinical diagnostics.

Engineered Biosensors for Diagnosing Multidrug Resistance in Microbial and Malignant Cells

To curtail pathogens or tumors, antimicrobial or antineoplastic drugs have been developed. These drugs target microbial/cancer growth and survival, thereby improving the host's health. In attempts to evade the detrimental effects of such drugs, these cells have evolved several mechanisms over time. Some variants of the cells have developed resistances against multiple drugs or antimicrobial agents. Such microorganisms or cancer cells are said to exhibit multidrug resistance (MDR). The drug resistance status of a cell can be determined by analyzing several genotypic and phenotypic changes, which are brought about by significant physiological and biochemical alterations. Owing to their resilient nature, treatment and management of MDR cases in clinics is arduous and requires a meticulous approach. Currently, techniques such as plating and culturing, biopsy, gene sequencing, and magnetic resonance imaging are prevalent in clinical practices for determining drug resistance status. However, the major drawbacks of using these methods lie in their time-consuming nature and the problem of translating them into point-of-care or mass-detection tools. To overcome the shortcomings of conventional techniques, biosensors with a low detection limit have been engineered to provide quick and reliable results conveniently. These devices are highly versatile in terms of analyte range and quantities that can be detected to report drug resistance in a given sample. A brief introduction to MDR, along with a detailed insight into recent biosensor design trends and use for identifying multidrug-resistant microorganisms and tumors, is presented in this review.

State-of-the-Art Fluorescent Probes: Duplex-Specific Nuclease-Based Strategies for Early Disease Diagnostics

Precision healthcare aims to improve patient health by integrating prevention measures with early disease detection for prompt treatments. For the delivery of preventive healthcare, cutting-edge diagnostics that enable early disease detection must be clinically adopted. Duplex-specific nuclease (DSN) is a useful tool for bioanalysis since it can precisely digest DNA contained in duplexes. DSN is commonly used in biomedical and life science applications, including the construction of cDNA libraries, detection of microRNA, and single-nucleotide polymorphism (SNP) recognition. Herein, following the comprehensive introduction to the field, we highlight the clinical applicability, multi-analyte miRNA, and SNP clinical assays for disease diagnosis through large-cohort studies using DSN-based fluorescent methods. In fluorescent platforms, the signal is produced based on the probe (dyes, TaqMan, or molecular beacon) properties in proportion to the target concentration. We outline the reported fluorescent biosensors for SNP detection in the next section. This review aims to capture current knowledge of the overlapping miRNAs and SNPs' detection that have been widely associated with the pathophysiology of cancer, cardiovascular, neural, and viral diseases. We further highlight the proficiency of DSN-based approaches in complex biological matrices or those constructed on novel nano-architectures. The outlooks on the progress in this field are discussed.

Extension of duplex specific nuclease sensing application with RNA aptamer

Duplex specific nuclease (DSN) that can precisely cleave DNA portion in double-stranded DNA or DNA-RNA hybrid has engrossed immense attention owing to its great potential in emerging bioanalytical applications. Here, we present a novel approach to extend DSN sensing application by coupling RNA aptamer. Specially designed RNA ligand sequences are used to capture the target and simultaneously provide complementary sequences of DNA for DSN aided fluorescent signal enhancement. A clotting enzyme, thrombin, has been used as a model analyte. One RNA aptamer combined with the target molecule can generate fluorescent signals through cleavage of hybridized TaqMan DNA probe (P2) by DSN. The proposed assay has achieved the lowest detection limit of 0.039 pM. The assay has been applied for real-time detection of thrombin release from live cells and other biotic media for early disease diagnosis. The developed method is versatile and can detect various other targets by choosing the relevant aptamer and probe sequences. This method is promising to be applied to medical diagnosis, biosensing, food safety, environmental monitoring, and other fields.