Electrochemical biosensor for ultrasensitive exosomal miRNA analysis by cascade primer exchange reaction and MOF@Pt@MOF nanozyme

Two-dimensional nanozyme nanoarchitectonics customized electrochemical bio diagnostics and lab-on-chip devices for biomarker detection

Recent developments in nanomaterials and nanotechnology have advanced biosensing research. Two-dimensional (2D) nanomaterials or nanozymes, such as metal oxides, graphene and its derivatives, transition metal dichalcogenides, metal-organic frameworks, carbon-organic frameworks and MXenes, have garnered substantial attention in recent years owing to their unique properties, including high surface area, excellent electrical conductivity, and mechanical flexibility. Moreover, 2D nanozymes exhibit intrinsic enzyme-mimicking properties, including those of peroxidase, oxidase, catalase, and superoxide dismutase, making them well-suited for detecting biomarkers of interest and developing bio diagnostics at the point-of-care. Since 2D nanosystems offer ultra-high sensitivity, label-free detection, and real-time analysis, point-of-care testing and multiplexed biomarker detection, the demand is growing. Additionally, their biocompatibility and scalable fabrication make them cost-effective for widespread adoption. This review discusses the advantages of 2D nanozymes and their recent advancements in biosensing applications. This review summarizes the latest developments in 2D nanozymes, focusing on their synthesis, biocatalytic capabilities, and advancements in developing bio diagnostics and lab-on-chip devices for detecting cancer and non-cancer biomarkers. In addition, existing challenges and prospects in 2D nanozyme-based biosensors are identified, highlighting their biosensing potential and advocating for their expanded application in bio diagnostics and lab-on-chip devices.

Bifunctional MXene quantum dots-coated bimetallic Prussian blue analogues for sensitive sensing and accurate localization imaging of miRNAs in living cells

MicroRNAs (miRNAs) are involved in multiple cellular processes and play a critical role in clinical diagnosis. In-situ spatiotemporal imaging of miRNAs in living cells is tightly linked to the carcinogenesis and development of malignant tumors. Herein, we proposed a bifunctional nanosystem-based MXene quantum dots-coated bimetallic Prussian blue analogues (Co-Mn PBA@MQDs) to execute in-vitro sensing and intracellular imaging of miRNA in living cells. The 3D nanostructures of Co-Mn PBAs were regulated to slow down the coordination reaction rate by controlling the diffusion of metal clusters and ligand precursors, thereby anchoring MQDs as the carriers of DNA probes. The resulting Co-Mn PBA@MQDs nanoparticles with miRNA recognition ability exhibit excellent electrocatalytic and photoluminescence properties for target miRNA analysis. It reached miRNA detection limit of 0.37 fM (S/N = 3) with a wide linear range of 1 fM to 1 nM, and allowed distinguish family members without additional complex modifications. Meanwhile, DNA probe adsorbed on Co-Mn PBA@MQDs can provide delivery capacity for intracellular miRNA location, resulting in the in-situ monitoring and imaging of miRNA with deregulated expression levels in cancer cells. With these advantages, the developed strategy provides a paradigm for the rational design of the miRNA analysis system, which is expected to be widely applied to disease diagnosis and further theragnostic fields.

Nicking endonuclease-mediated primer exchange reaction for rapid and sensitive miRNA detection

Primer exchange reaction (PER) is a novel and simple nucleic acid-templated extension technique that has recently attracted much attention in the field of biosensing. However, current PER reactions have shown relatively slow rates and low amplification performances, resulting in long assay times and limited detection sensitivities. Here we report a nicking endonuclease-mediated PER reaction (named NEPER) that rapidly releases amplified DNA products by adding a nicking endonuclease to hydrolyze the hybridized double-stranded DNA (dsDNA), and consequently has a maximum speed that is thirty orders of magnitude greater than the maximum for conventional PER. We further combined a CRISPR/Cas12a signal readout technique and developed a cascade NEPER-CRISPR/Cas12a method that can detect miRNA-155 with a limit of detection (LOD) down to 3.1 fM. We also show that the NEPER-CRISPR/Cas12a can be used to detect targets in serum samples.

CRISPR-Cas12a with split crRNA for the direct and sensitive detection of microRNA

microRNAs (miRNAs) have been identified as potential biomarkers. Despite the prevalence of quantitative PCR in the field of miRNA detection, this technology is encumbered by the complexity of its methodology. This study presents a novel CRISPR/Cas12a-based method for the direct and sensitive detection of miRNA-21 using split crRNA. The system comprises Cas12a protein, crRNA-handle, and activator DNA complementary to the target miRNA. In the presence of the target miRNA, it binds to the activator DNA, forming a duplex. The formed duplex, in conjunction with the crRNA-handle, activates Cas12a's trans-cleavage activity. This leads to cleavage of a fluorescent reporter, generating an enhanced signal. The method enables direct RNA detection without reverse transcription or sample amplification, offering simplicity and efficiency. This method demonstrates high sensitivity with a minimum detectable limit of 5 pM. Furthermore, the method's specificity is substantiated by its capacity to discern point mutations in miRNA. This system has been shown to quantitatively analyse miRNA-21 levels present within serum, as evidenced by the recovery experiment. Therefore, the method's simplicity, stability, and cost-effectiveness render it a powerful tool for nucleic acid detection, with potential for clinical applications.

Logic-Measurer: A Multienzyme-Assisted Ultrasensitive Circuit for Logical Detection of Exosomal MicroRNAs

The logic profiling of exosomal microRNAs (miRNAs) offers broad potential applications in the accurate diagnosis and staging of cancer. However, the logical detection of low-abundance exosomal miRNAs in complex clinical samples remains challenging. This study introduces a logic analysis system termed "Measurer" (a multi-enzyme-assisted ultrasensitive circuit) that offers ultrasensitive and versatile method for detecting multiple exosomal miRNAs. The Logic-Measurer comprises three modules: a stem-loop hairpin-enhanced CRISPR/Cas13a, a polymerase-driven primer exchange reaction, and an exonuclease III-mediated fluorescence output. The efficient Logic-Measurer was switched by the faster rate of trans-cleavage activity of Cas13a due to its improved affinity for hairpin RNA structures. The mechanistic model of hairpin-enhanced CRISPR/Cas13a was confirmed by molecular dynamics simulations. The Logic-Measurer accurately detected exosomal miRNA-21 or miRNA-375 down to 2.1 and 4.4 fM, with superior specificity, and enabled in situ detection of miRNA-21 and miRNA-375 in as low as 1.4 × 102 particles/mL exosomes via membrane fusion. In addition, this method demonstrated 87.3 and 82.1% accuracy in the diagnosis and early detection of breast cancer, respectively, among a cohort of 315 individuals. Subsequent subgroup analysis further confirmed the method's ability to accurately differentiate estrogen receptor-positive patients from healthy individuals. Therefore, the Logic-Measurer offers valuable insights into the development of a CRISPR/Cas-based enhanced diagnostic platform and the next generation of diagnostic technology based on enzyme circuits.

Nanozymes in Biomedical Applications: Innovations Originated From Metal-Organic Frameworks

Nanozymes exhibit significant potential in medical theranostics, environmental protection, energy development, and biopharmaceuticals due to their exceptional catalytic performance. Compared with natural enzymes, nanozymes have the advantages of simple preparation and purification, convenient production and low cost. Therefore, it is very important to prepare nanozymes quickly and efficiently, which not only helps to expand their application scope, but also can further exert their great potential in various fields. Metal-organic frameworks (MOF) materials serve as versatile substrates for constructing nanozymes, offering unique advantages like adjustable structure, high specific surface area, and porous channels. MOF coordination nodes constructed from metal ions or metal clusters have unique properties that can be leveraged to tailor nanozyme characteristics for different applications. This review describes and analyzes recent methods for constructing nanozymes using MOF materials, and explores their application prospects in biomedicine. By expounding the preparation techniques and biomedical applications of nanozymes, this review aims to inspire researchers to develop innovative nanozyme materials and explore new application directions.

A Programmable Automatic Cascade Machinery for Single-Molecule Profiling of Multiple Noncoding RNAs in Breast Tissues

Noncoding RNAs (ncRNAs) are identified as critical regulatory molecules in tumorigenesis and progression. Investigating the expression patterns of multiple ncRNAs in living cells and tissues may facilitate the diagnosis of cancers. Herein, we develop a programmable automatic cascade machinery for single-molecule profiling of multiple ncRNAs. This method involves two successive amplification events that can convert extremely low-abundance target ncRNAs into abundant FAM/Cy5 molecules for the generation of amplified fluorescence signals. The subsequent single-molecule detection can identify piR-36026 with the FAM signal and DSCAM-AS1 with the Cy5 signal. Due to the high efficiency of automatic cascade machinery and the high signal-to-noise ratio of single-molecule imaging, this method can achieve sensitive detection of multiple ncRNAs with a detection limit of 44.67 aM for piR-36026 and 45.71 aM for DSCAM-AS1, and it can measure endogenous piR-36026 and DSCAM-AS1 at the single-cell level. Moreover, the profiling of piR-36026 and DSCAM-AS1 in healthy tissues and breast cancer tissues demonstrates the feasibility of the proposed method in cancer diagnostics. By programming the recognition sequences of dumbbell probes, this method can be extended to measure other cancer-related ncRNAs, with great prospects in clinical applications.

Exploring Nucleic Acid Nanozymes: A New Frontier in Biosensor Development

With the growing interest in nucleic acids and nanozymes, nucleic acid nanozymes (NANs) have emerged as a promising alternative to traditional enzyme catalysts, combining the advantages of nucleic acids and nanomaterials, and are widely applied in the field of biosensing. This review provides a comprehensive overview of recent studies on NAN-based biosensors. It classifies NANs based on six distinct enzymatic activities: peroxidase-like, oxidase-like, catalase-like, superoxide dismutase-like, laccase-like, and glucose oxidase-like. This review emphasizes how the catalytic activity of nanozymes is significantly influenced by the properties of nucleic acids and explores the regulatory mechanisms governing the catalytic activity of NANs. Additionally, it systematically reviews important research progress on NANs in colorimetric, fluorescent, electrochemical, SERS, and chemiluminescent sensors, offering insights into the development of the NAN field and biosensor applications.

Ultrasensitive detection of microRNAs based on cascade amplification strategy of RCA-PER and Cas12a

Since microRNAs (miRNAs) serve as markers for early cancer diagnosis, it is crucial to develop a novel biosensor to detect miRNAs quickly, sensitively and selectively. Hence, we developed a fluorescence biosensor based on target miRNA-initiated rolling circle amplification (RCA) to generate RCA products with multiple tandem catalytic hairpin DNA templates that trigger primer exchange reactions (PER) which extend short single-strand DNA (ssDNA) primers into long ssDNA. Subsequently, the long ssDNA activates the trans-cleavage activity of the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a system to cleave a fluorescent reporter chain, enabling ultrasensitive detection of miRNAs through the output fluorescence signal. The biosensor could quantify miRNA-141 concentrations from 100 to 105 pM, with a detection limit of 94 fM. Therefore, the biosensing strategy proposed in this study offers a robust technique for the clinical diagnosis of miRNA-141.

A promising role of noble metal NPs@MOFs in chondrosarcoma management

Chondrosarcoma, a challenging and malignant neoplasm originating from cartilage cells, poses significant diagnostic and therapeutic hurdles due to its resistance to conventional treatments and the complexity of its diagnosis. Noble metal nanoparticle-embedded metal-organic frameworks (NPs@MOFs) stand out as a novel approach for the diagnosis and treatment of chondrosarcoma. This review delves into the properties and applications of NPs@MOFs, focusing on their classification by noble metal type and their role in enhancing photothermal therapy (PTT), photodynamic therapy (PDT), targeted drug delivery and chondrosarcoma diagnosis. Despite promising in vitro and in vivo results, challenges such as understanding the mechanisms of action and clinical translation remain, and the therapeutic effect of PTT and PDT on deep chondrosarcoma seems unsatisfactory. Future exploration, such as combined therapy and multiple MOF therapy, could unlock the full potential of noble metal NPs@MOFs in revolutionizing chondrosarcoma management, offering insights into the prospect of these materials in chondrosarcoma management.

A magnetic dual-aptamer electrochemical sensor with MOF-on-MOF-derived electrocatalyst as a signal amplifier for sensitive detection of cardiac troponin I

Considering the close association between cardiac troponin I (cTnI) level and various cardiovascular diseases, it becomes essential to explore sensitive and accurate detection methods for monitoring their levels in the early stages of disease. In this work, a magnetic dual-aptamer electrochemical sensor for cTnI detection was constructed in the first utilizing MOF-on-MOF-derived electrocatalyst as a signal amplifier in collaboration with high-efficient separation of magnetic beads (MBs). Employing zeolitic imidazolate framework-67 (ZIF-67) with high surface area as host MOF, MOF-on-MOF heterostructure (ZIF-67@PBA) was facilely prepared by in-situ growth of conductive prussian blue analogue (PBA) as guest MOF onto the surface of ZIF-67 with a simple ion-exchange method. After low-temperature calcination, N doped derived electrocatalyst (N-ZIF-67@PBA) was obtained with intact skeletons and pore structures of MOFs. This not only integrated bimetallic active centers with various valence states and diversiform nanostructures of dual MOF, but endowed N-ZIF-67@PBA 8.3-fold increase of electrocatalytic activity for catalytic amplification. Further using aptamer-modified MBs as capture carriers for recognizing and separating cTnI from complex samples with high specificity, the magnetic dual-aptamer sensor successfully achieved the sensitive detection of cTnI with a low detection limit of 0.31 fg/mL. This work provided a new viewpoint on the use of MOF-on-MOF-derived electrocatalyst for ultrasensitive electrochemical sensing analysis.

Endogenous enzyme-activated AND-gate DNA nanomachines for intracellular miRNA detection and cell-selective imaging

The occurrence and development of tumors are accompanied by the abnormal expression of specific microRNAs (miRNAs). Therefore, miRNAs are considered as an important biomarker. The establishment of efficient, simple and sensitive miRNA imaging methods in living cells will contribute to the early diagnosis, treatment and drug development of diseases. In this study, we developed an endogenous enzyme-initiated AND logic circuit using gold nanocubes (AuNCs) as carriers for simultaneous detection of miRNA-21 and miRNA-210 in cells. Apurinic/apyrimidinic endonuclease 1 (APE1) and telomerase (TE), which are overexpressed in cancer cells, act as control switches in a logic circuit that enables sensitive in situ analysis of intracellular miRNAs without additional external intervention. At the same time, due to the lack of necessary enzymes as activation switches, the DNA circuit in normal cells remains in an inactive state. This strategy effectively reduces the risk of false positive signal generation. Our research results show that the logic circuit can not only distinguish between cancer cells and normal cells, and able to distinguish between different types of cancer cells. This finding provides a promising approach to accurately identify cell types.

Nanomaterial-based electrochemical biosensors as tools for detecting the tumor biomarker miR-21

MicroRNAs (miRNAs) are noncoding RNA transcripts with myriad physiologically important regulatory roles in the human body. These miRNAs have also recently emerged as promising biomarkers for the diagnosis of particular cancers. Conventional miRNA detection strategies, however, are characterized by many limitations. As electrochemical biosensors offer advantages including low costs, high levels of sensitivity, and amenability to miniaturization, they hold great promise as an alternative approach to miRNA detection. Nanomaterials are commonly used in the context of electrochemical sensor production, and this review provides an overview of the use of various carbon nanomaterials, metallic nanomaterials, metal-organic frameworks, magnetic nanomaterials, and conductive polymer nanocomposites to modify electrochemical biosensors in order to facilitate the detection of miRNA-21. A range of materials and detection methods for particular cancer types are discussed herein highlighting the superior sensitivity and specificity of these analytical strategies., which allow for the stable and reproducible detection of miRNAs in clinical samples. Ultimately, this review demonstrates the promising clinical prospects of these modified electrochemical biosensors as tools for early cancer diagnosis and the prognostic evaluation of affected patients.

Emerging biosensing platforms based on metal-organic frameworks (MOFs) for detection of exosomes as diagnostic cancer biomarkers: case study for the role of the MOFs

Exosomes, which are considered nanoscale extracellular vesicles (EVs), are secreted by various cell types and widely distributed in different biological fluids. They consist of multifarious bioactive molecules and use systematic circulation for their transfer to adjoining cells. This phenomenon enables exosomes to take part in intercellular and intracellular communications. They serve as novel and important cancer biomarkers due to their ability to be obtained from various biological fluids and the presence of nucleic acids, proteins, glycoconjugates, and lipids in their structure. The advancement of sensitive and selective exosome detection approaches continues to be a critical challenge that must be addressed. Metal-organic frameworks (MOFs) are a class of 2D and 3D synthetic organic and crystalline nanomaterials, forming through the self-assembly of organic linking molecules and metal ions. The exploration of MOF-based molecules in the recognition of exosomes is an essential aspect in the development of cutting-edge sensing platforms due to their tunable pore structures, excellent adsorption capabilities, and high surface area. Their advantages allow for the inclusion of a large number of electroactive molecules and biological elements, thereby enhancing their electrical conductivity and selectivity, respectively. The synergetic effect of nanomaterials and bioreceptors allows for efficient detection probes. In this review, the different roles of MOFs in the biosensing of exosomes are highlighted, providing a comprehensive understanding of biosensing approaches in this area. In addition, probes based on MOFs and different bioreceptors are investigated for detecting these important cancer biomarkers. The current gaps in this field and future perspectives are discussed.

Liquid biopsy technologies: innovations and future directions in breast cancer biomarker detection

Globally, breast cancer is the most frequent type of cancer, and its early diagnosis and screening can significantly improve the probability of survival and quality of life of those affected. Liquid biopsy-based targets such as circulating tumor cells, circulating tumor DNA, and exosomes have been instrumental in the early discovery of cancer, and have been found to be effective in stage therapy, recurrence monitoring, and drug selection. Biosensors based on these target related biomarkers convert the tested substances into quantifiable signals such as electrical and optical signals through signal transduction, which has the advantages of high sensitivity, simple operation, and low invasiveness. This review provides an overview of the latest progress of liquid biopsy biomarkers in the diagnosis, prognosis and treatment of breast cancer, compares the application and advantages of different biosensors based on these biomarkers in the diagnosis of breast cancer, and analyzes the limitations and solutions of biosensor based methods.

Highly Sensitive Flow Cytometry Biosensor with a High Signal-to-Background Ratio for FEN1 Analysis via Solid-Phase Interface-Mediated Primer Exchange Reaction Amplification

Flap endonuclease 1 (FEN1) is a specific enzyme capable of recognizing and cleaving triplex DNA structures and releasing 5'-flap fragments. It plays a crucial role in the DNA metabolism of cells, participating in DNA replication and the repair of damaged DNA. Additionally, FEN1 is overexpressed in various tumor tissues, promoting tumor progression and drug resistance through different regulatory mechanisms. However, few significant advancements have been made in sensitive analytical methods for detecting FEN1. Herein, in this study, we present a highly sensitive flow cytometry biosensor with solid-phase interface-mediated primer exchange reaction amplification (FCsperA) for FEN1 analysis. By comparing homogeneous PER amplification (h-PER), we found that solid-phase interface-mediated PER amplification (s-PER) effectively suppressed background signals, leading to a higher signal-to-background (S/B) ratio exceeding ∼46-fold when FEN1 was at 1 × 10-3 U/μL. Combining the high efficiency of s-PER, the strong suppression of background signals, and the highly precise flow cytometry assay, FCsperA showed high sensitivity, with a limit of detection (LOD) for FEN1 of 2.53 × 10-6 U/μL. Notably, FCsperA exhibited high selectivity and exceptional anti-interference ability, making it applicable for detecting FEN1 in cells and serum samples. The outstanding performance of FCsperA allowed for sensing FEN1 in ∼10 cancer cells. Additionally, FCsperA demonstrated the potential for screening inhibitors of FEN1.

Advanced design of target-driven self-powered sensor assisted by cascade catalytic strategy

In this work, a self-powered microsensor platform based on enzyme biofuel cells (EBFCs) was developed for intelligent monitoring of disease markers miRNA-451. The cascade catalysis system constructed by using the strategy of enzyme-like ZIF-8 nanocapsule incorporation with biological enzymes, which could simultaneously take into account the specificity of biological enzymes and the high activity of nano-enzymes, significantly promoted the electron transfer between glucose and the bio-anode surface, and improved the sensitivity and stability of the sensing system. Meanwhile, the target-triggered hybridization chain reaction (HCR) amplification strategy to achieve exponential signal amplification based on accurate recognition, and jointly improve the detection sensitivity. As expected, the micro-sensor platform has a wide linear range of 0.5-1.0 fmol/L with a low limit of detection (LOD) of 0.13 fmol/L (S/N = 3) and exhibits excellent selectivity, reproducibility and stability in interference assays under optimal detection conditions. The designed self-powered system is simple to construct, easy to transport and the data transmission mode is intelligent and controllable, which is expected to be used in basic biochemical research, clinical diagnosis and environmental monitoring.

Enhancing peroxidase activity of NiCo2O4 nanoenzyme by Mn doping for catalysis of CRISPR/Cas13a-mediated non-coding RNA detection

CRISPR/Cas13a with precise and controllable programming of endonuclease activity has been served as powerful tool for RNA sensing. Although with high sensitivity, existing CRISPR/Cas13a-based biosensors need complex amplification procedure or special equipment that limited quantification capability. Here, Mn-doped NiCo2O4 (Mn/NiCo2O4) nanozyme with enhanced peroxidase activity was synthesized and combined with CRISPR/Cas13a-based reaction to develop a simple, sensitive and universal biosensor for RNA detection, which is achieved through target recognition that activates Cas enzymes to cleave RNA reporter for inhibiting Mn/NiCo2O4 nanozyme to assemble on microplate. The Mn/NiCo2O4 nanozyme assembled on microplate can be monitored through colorimetric and fluorometric approaches. On one hand, Mn/NiCo2O4 nanozyme offers ideal peroxidase activity to catalyze colorimetric reaction, and as low as dozens of amol level of RNA target can be sensitively detected by naked eyes without any amplification procedures. On the other hand, Mn/NiCo2O4 can be also served as a signal amplifier to produce large amount of Co2+, Mn2+and Ni2+ to quench the fluorescence of calcein. The fluorescent approach can achieve higher sensitivity (about 40-fold) than colorimetric method. More importantly, the proposed biosensor can work well for multiple RNA detection in real biological samples, showing a great potential for monitoring non-coding RNA-related diseases.

Nanozymes: a bibliometrics review

As novel multifunctional materials that merge enzyme-like capabilities with the distinctive traits of nanomaterials, nanozymes have made significant strides in interdisciplinary research areas spanning materials science, bioscience, and beyond. This article, for the first time, employed bibliometric methods to conduct an in-depth statistical analysis of the global nanozymes research and demonstrate research progress, hotspots and trends. Drawing on data from the Web of Science Core Collection database, we comprehensively retrieved the publications from 2004 to 2024. The burgeoning interest in nanozymes research across various nations indicated a growing and widespread trend. This article further systematically elaborated the enzyme-like activities, matrix, multifunctional properties, catalytic mechanisms and various applications of nanozymes, and the field encounters challenges. Despite notable progress, and requires deeper exploration guide the future research directions. This field harbors broad potential for future developments, promising to impact various aspects of technology and society.

Recent Advances in Nanozyme Sensors Based on Metal-Organic Frameworks and Covalent-Organic Frameworks

Nanozymes are nanomaterials that exhibit enzyme-like catalytic activity, which have drawn increasing attention on account of their unique superiorities including very high robustness, low cost, and ease of modification. Metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) have emerged as promising candidates for nanozymes due to their abundant catalytic activity centers, inherent porosity, and tunable chemical functionalities. In this review, we first compare the enzyme-mimicking activity centers and catalytic mechanisms between MOF and COF nanozymes, and then summarize the recent research on designing and modifying MOF and COF nanozymes with inherent catalytic activity. Moreover, typical examples of sensing applications based on these nanozymes are presented, as well as the translation of enzyme catalytic activity into a visible signal response. At last, a discussion of current challenges is presented, followed by some future prospects to provide guidance for designing nanozyme sensors based on MOFs and COFs for practical applications.

Application of Nanozymes and its Progress in the Treatment of Ischemic Stroke

Nanozymes are a new kind of material which has been applied since the beginning of this century, and its birth has promoted the development of chemistry, materials science, and biology. Nanozymes can be used as a substitute for natural enzyme and has a wide range of applications; therefore, it has attracted extensive attention from all sectors of the community, and the number of studies has constantly increasing. In this paper, we introduced the outstanding achievements in the field of nanozymes in recent years from the main function, the construction of nanozyme-based biosensors, and the treatment of ischemic stroke, and we also illustrated the internal mechanism and the catalytic principle. In the end, the obstacles and challenges in the future development of nanozymes were proposed.

Nanozymes-Mediated Cascade Reaction System for Tumor-Specific Diagnosis and Targeted Therapy

Cascade reactions are described as efficient and versatile tools, and organized catalytic cascades can significantly improve the efficiency of chemical interworking between nanozymes. They have attracted great interest in many fields such as chromogenic detection, biosensing, tumor diagnosis, and therapy. However, how to selectively kill tumor cells by enzymatic reactions without harming normal cells, as well as exploring two or more enzyme-engineered nanoreactors for cascading catalytic reactions, remain great challenges in the field of targeted and specific cancer diagnostics and therapy. The latest research advances in nanozyme-catalyzed cascade processes for cancer diagnosis and therapy are described in this article. Here, various sensing strategies are summarized, for tumor-specific diagnostics. Targeting mechanisms for tumor treatment using cascade nanozymes are classified and analyzed, "elements" and "dimensions" of cascade nanozymes, types, designs of structure, and assembly modes of highly active and specific cascade nanozymes, as well as a variety of new strategies of tumor targeting based on the cascade reaction of nanozymes. Finally, the integrated application of the cascade nanozymes systems in tumor-targeted and specific diagnostic therapy is summarized, which will lay the foundation for the design of more rational, efficient, and specific tumor diagnostic and therapeutic modalities in the future.

Development of a Novel System Consisting of a Reductase-Like Nanozyme and the Reaction of Resazurin and Ammonia Borane for Sensitive Fluorometric Sensing

We report a novel system consisting of a redox reaction and a highly efficient reductase-like nanozyme, silica-palladium nanoparticles (Pd@SiO2 NPs), as a novel detection platform for fluorometric sensing. In a proof-of-concept demonstration using an oligonucleotide as the detection target, a glass fiber-based sensor is fabricated by covalently conjugating two oligo probes, which are complementary to the adjacent segments of the target oligonucleotide, on Pd@SiO2 NPs and glass fiber, respectively. In the presence of the target oligonucleotide, the two probes are drawn together by the target through sequence-specific hybridization, bringing the Pd@SiO2 NPs to the glass fiber. When the glass fiber is subsequently immersed in a mixture of resazurin and ammonia borane solution, the Pd@SiO2 NPs on the glass fiber trigger the catalytic conversion of resazurin (blue, slightly fluorescent) to resorufin (pink, highly fluorescent) with massive signal amplification, indirectly signaling the presence of the target oligonucleotide. We show that the glass fiber-based fluorometric sensor can detect a target oligonucleotide associated with the BRAF mutation linearly in the concentration range of 20 to 400 pM with a detection limit (LOD) of 15 pM and the specificity to differentiate targets with single-base difference. These results demonstrate a new frontier for the development of a sensitive, specific, and inexpensive nonenzyme-based fluorometric sensing platform as an alternative to conventional enzyme-based assays.

Recent Advances on the Metal-Organic Frameworks-Based Biosensing Methods for Cancer Biomarkers Detection

Sensitive and selective detection of cancer biomarkers is crucial for early diagnosis and treatment of cancer, one of the most dangerous diseases in the world. Metal-organic frameworks (MOFs), a class of hybrid porous materials fabricated through the assembly of metal ions/clusters and organic ligands, have attracted increasing attention in the sensing of cancer biomarkers, due to the advantages of adjustable size, high porosity, large surface area and ease of modification. MOFs have been utilized to not only fabricate active sensing interfaces but also arouse a variety of measurable signals. Several representative analytical technologies have been applied in MOF-based biosensing strategies to ensure high detection sensitivity toward cancer biomarkers, such as fluorescence, electrochemistry, electrochemiluminescence, photochemistry and colorimetric methods. In this review, we summarized recent advances on MOFs-based biosensing strategies for the detection of cancer biomarkers in recent three years based on the categories of metal nodes, and aimed to provide valuable references for the development of innovative biosensing platform for the purpose of clinical diagnosis.

Metal-organic framework (MOF)-based biosensors for miRNA detection

MicroRNAs (miRNAs) play several crucial roles in the physiological and pathological processes of the human body. They are considered as important biomarkers for the diagnosis of various disorders. Thus, rapid, sensitive, selective, and affordable detection of miRNAs is of great importance. However, the small size, low abundance, and highly similar sequences of miRNAs impose major challenges to their accurate detection in biological samples. In recent years, metal-organic frameworks (MOFs) have been applied as promising sensing materials for the fabrication of different biosensors due to their distinctive characteristics, such as high porosity and surface area, tunable pores, outstanding adsorption affinities, and ease of functionalization. In this review, the applications of MOFs and MOF-derived materials in the fabrication of fluorescence, electrochemical, chemiluminescence, electrochemiluminescent, and photoelectrochemical biosensors for the detection of miRNAs and their detection principle and analytical performance are discussed. This paper attempts to provide readers with a comprehensive knowledge of the fabrication and sensing mechanisms of miRNA detection platforms.

A cubic DNA nanocage probe for in situ analysis of miRNA-10b in tumor-derived extracellular vesicles

A cubic DNA nanocage probe is able to enter EVs derived from MDA-MB-231 cells and react with miRNA-10b. The probe-loaded EVs were employed to monitor the process of entry of miRNA-10b into MCF-10A cells, allowing visualization of EV-mediated intercellular communication of miRNA-10b between the cancer cells.

Self-assembly of a AuNPs/Ti3C2 MXene hydrogel for cascade amplification of microRNA-122 biosensing

A three-dimensional (3D) self-assembled AuNPs/Ti3C2 MXene hydrogel (AuNPs/Ti3C2 MXH) nanocomposite was prepared for the fabrication of a novel microRNA-122 electrochemical biosensor. The 3D hydrogel structure was gelated from two-dimensional MXene nanosheets with the assistance of graphite oxide and ethylenediamine. MXene hydrogels supported the in situ formation of Au nanoparticles (AuNPs) that predominantly exploring the (111) facet, and these AuNPs are utilized as carriers for hairpin DNA (hpDNA) probes, facilitating DNA hybridization. MXene acted as both a reductant and stabilizer, significantly improving the electrochemical signal. In addition, the conjugation of PAMAM dendrimer-encapsulated AuNPs and H-DNA worked as an ideal bridge to connect targets and efficient electrochemical tags, providing a high amplification efficiency for the sensing of microRNA-122. A linear relationship between the peak currents and the logarithm of the concentrations of microRNA-122 from 1.0 × 10-2 to 1.0 × 102 fM (I = 1.642 + 0.312 lgc, R2 = 0.9891), is obtained. The detection limit is  0.8 × 10-2 fM (S/N = 3). The average recovery for human serum detection ranged from 97.32 to 101.4% (RSD < 5%).

Nanozyme-Enhanced Electrochemical Biosensors: Mechanisms and Applications

Nanozymes, as innovative materials, have demonstrated remarkable potential in the field of electrochemical biosensors. This article provides an overview of the mechanisms and extensive practical applications of nanozymes in electrochemical biosensors. First, the definition and characteristics of nanozymes are introduced, emphasizing their significant role in constructing efficient sensors. Subsequently, several common categories of nanozyme materials are delved into, including metal-based, carbon-based, metal-organic framework, and layered double hydroxide nanostructures, discussing their applications in electrochemical biosensors. Regarding their mechanisms, two key roles of nanozymes are particularly focused in electrochemical biosensors: selective enhancement and signal amplification, which crucially support the enhancement of sensor performance. In terms of practical applications, the widespread use of nanozyme-based electrochemical biosensors are showcased in various domains. From detecting biomolecules, pollutants, nucleic acids, proteins, to cells, providing robust means for high-sensitivity detection. Furthermore, insights into the future development of nanozyme-based electrochemical biosensors is provided, encompassing improvements and optimizations of nanozyme materials, innovative sensor design and integration, and the expansion of application fields through interdisciplinary collaboration. In conclusion, this article systematically presents the mechanisms and applications of nanozymes in electrochemical biosensors, offering valuable references and prospects for research and development in this field.

Nanomaterials in electrochemical nanobiosensors of miRNAs

Nanomaterial-based biosensors have received significant attention owing to their unique properties, especially enhanced sensitivity. Recent advancements in biomedical diagnosis have highlighted the role of microRNAs (miRNAs) as sensitive prognostic and diagnostic biomarkers for various diseases. Current diagnostics methods, however, need further improvements with regards to their sensitivity, mainly due to the low concentration levels of miRNAs in the body. The low limit of detection of nanomaterial-based biosensors has turned them into powerful tools for detecting and quantifying these biomarkers. Herein, we assemble an overview of recent developments in the application of different nanomaterials and nanostructures as miRNA electrochemical biosensing platforms, along with their pros and cons. The techniques are categorized based on the nanomaterial used.

Highly sensitive SERS platform for pathogen analysis by cyclic DNA nanostructure@AuNP tags and cascade primer exchange reaction

The capacity to identify small amounts of pathogens in real samples is extremely useful. Herein, we proposed a sensitive platform for detecting pathogens using cyclic DNA nanostructure@AuNP tags (CDNA) and a cascade primer exchange reaction (cPER). This platform employs wheat germ agglutinin-modified Fe3O4@Au magnetic nanoparticles (WMRs) to bind the E. coli O157:H7, and then triggers the cPER to generate branched DNA products for CDNA tag hybridization with high stability and amplified SERS signals. It can identify target pathogens as low as 1.91 CFU/mL and discriminate E. coli O157:H7 in complex samples such as water, milk, and serum, demonstrating comparable or greater sensitivity and accuracy than traditional qPCR. Moreover, the developed platform can detect low levels of E. coli O157:H7 in mouse serum, allowing the discrimination of mice with early-stage infection. Thus, this platform holds promise for food analysis and early infection diagnosis.

All-in-one detection of breast cancer-derived exosomal miRNA on a pen-based paper chip

Exosomal microRNAs (miRNAs) play a pivotal role in intercellular communication, regulating gene expression in target cells, and hold significant promise as cancer biomarkers for early detection and screening. However, achieving precise and viable detection of exosomal miRNAs remains a challenge. This paper proposes an all-in-one detection strategy for breast cancer-derived exosomal miRNA-21 on a pen-based paper chip (PPC). The PPC is constructed using a modified automatic pen and lateral flow assay (LFA), which results in a cost-effective fabrication process. The user only needs to add the sample and trigger the top of the self-contained PPC after a period of time to complete the entire detection process. To enhance the sensitivity of exosomal miRNA testing, an enzyme-free catalyzed hairpin assembly (CHA) is further introduced, enabling highly sensitive detection of miRNA-21 with a limit of detection (LOD) of 25 fmol. Additionally, the detection of miRNAs in differentially-expressed cells and clinical samples has also been successfully achieved with high specificity. Overall, the proposed PPC provides an effective tool for detecting early cancer, monitoring diseases, and establishing point of care testing (POCT).

Recent Progress and Prospect of Metal-Organic Framework-Based Nanozymes in Biomedical Application

A nanozyme is a nanoscale material having enzyme-like properties. It exhibits several superior properties, including low preparation cost, robust catalytic activity, and long-term storage at ambient temperatures. Moreover, high stability enables repetitive use in multiple catalytic reactions. Hence, it is considered a potential replacement for natural enzymes. Enormous research interest in nanozymes in the past two decades has made it imperative to look for better enzyme-mimicking materials for biomedical applications. Given this, research on metal-organic frameworks (MOFs) as a potential nanozyme material has gained momentum. MOFs are advanced hybrid materials made of inorganic metal ions and organic ligands. Their distinct composition, adaptable pore size, structural diversity, and ease in the tunability of physicochemical properties enable MOFs to mimic enzyme-like activities and act as promising nanozyme candidates. This review aims to discuss recent advances in the development of MOF-based nanozymes (MOF-NZs) and highlight their applications in the field of biomedicine. Firstly, different enzyme-mimetic activities exhibited by MOFs are discussed, and insights are given into various strategies to achieve them. Modification and functionalization strategies are deliberated to obtain MOF-NZs with enhanced catalytic activity. Subsequently, applications of MOF-NZs in the biosensing and therapeutics domain are discussed. Finally, the review is concluded by giving insights into the challenges encountered with MOF-NZs and possible directions to overcome them in the future. With this review, we aim to encourage consolidated efforts across enzyme engineering, nanotechnology, materials science, and biomedicine disciplines to inspire exciting innovations in this emerging yet promising field.

PER-CRISPR/Cas14a system-based electrochemical biosensor for the detection of ctDNA EGFR L858R

The detection of epidermal growth factor receptor (EGFR) mutation L858R in circulating tumor DNA (ctDNA) is beneficial for the clinical diagnosis and personalized therapy of non-small cell lung cancer (NSCLC). Herein, for the first time, the combination of the primer exchange reaction (PER) and clustered regularly interspaced short palindromic repeats (CRISPR) and its associated nucleases (Cas) 14a was used in electrochemical biosensor construction for the detection of ctDNA EGFR L858R. EGFR L858R, as the target, induced the isothermal amplification of the PER reaction, and then the CRISPR/Cas14a system was activated; subsequently, the substrate ssDNA-MB was cleaved and the electron on the surface of the gold electrode transferred, resulting in the fluctuation of the electrochemical redox signal on the electrode surface, whereas the electrochemical signal will be stable when EGFR L858R is absent. Therefore, the concentration of EGFR L858R can be quantified by electrochemical signal analysis. The low detection limit is 0.34 fM and the dynamic detection range is from 1 fM to 1 μM in this work. The PER-CRISPR/Cas14a electrochemical biosensor greatly improved the analytical sensitivity. In addition, this platform also exhibited excellent specificity, reproducibility, stability and good recovery. This study provides an efficient and novel strategy for the detection of ctDNA EGFR L858R, which has great potential for application in the diagnosis and treatment of NSCLC.

Design strategies and advanced applications of primer exchange reactions in biosensing: A review

Early disease diagnosis relies on the sensitive detection and imaging of biomarkers. Signal amplification is one of the most commonly used methods to improve detection sensitivity. Primer exchange reaction (PER) is a novel signal amplification technique that has garnered attention because of its simple and sensitive features. The classical PER involves a single catalytic hairpin, which enables the attachment of custom sequences to the primer chain, generating a long repeat sequence that can bind numerous signaling molecules and achieve powerful signal amplification. Currently, numerous PER-based signal amplification strategies are available that can improve detection sensitivity and promote the development of the signal amplification field. This review focuses on the mechanism of typical PER, the diversification of PER, and PER-based biosensors for various targets. Finally, the challenges and prospects of PER development are discussed.

A fluorescent sensor based on strand displacement amplification and primer exchange reaction coupling for label-free detection of miRNA

MicroRNAs (miRNAs) are closely associated with human disease occurrence, including cancers, diabetes, inflammation, heart diseases, and viral infections, and their rapid and accurate detection is vital for the diagnosis and treatment of these diseases. Based on one-step reaction of strand displacement amplification (SDA) and primer exchange reaction (PER), a label-free and highly sensitive miRNA-21 detection strategy was developed. In this strategy, the target miRNA-21 binds directly to the hairpin template, triggering the SDA reaction and generating a large number of single strand DNAs as primers for PER amplification. With the help of polymerase, plenty of G-quadruplex fragments of different lengths were accumulated, and the organic dye thioflavin T selectively binds to these G-quadruplex fragments to produce a strong fluorescent signal. There is a wide detection range in this method, miRNA-21 can be detected in the range of 10 fM - 1 nM, the detection limit is low (1.25 fM). This method has good specificity and can effectively distinguish single-base mismatches of miRNA. In addition, the versatility of the method was validated by changing the target recognition site of SDA template.

A programmable DNA nanodevice for colorimetric detection of DNA methyltransferase activity using functionalized hemin/G-quadruplex DNAzyme

The measurement of DNA methyltransferase (MTase) activity and screening of DNA MTase inhibitors holds significant importance for the diagnosis and therapy of methylation-related illness. Herein, we developed a colorimetric biosensor (PER-FHGD nanodevice) to detect DNA MTase activity by integrating the primer exchange reaction (PER) amplification and functionalized hemin/G-quadruplex DNAzyme (FHGD). By replacing the native hemin cofactor into the functionalized cofactor mimics, FHGD has exhibited significantly improved catalytic efficiency, thereby enhancing the detection performance of the FHGD-based system. The proposed PER-FHGD system is capable of detecting Dam MTase with excellent sensitivity, exhibiting a limit of detection (LOD) as low as 0.3 U/mL. Additionally, this assay demonstrates remarkable selectivity and ability for Dam MTase inhibitors screening. Furthermore, using this assay, we successfully detect the Dam MTase activity both in serum and in E. coli cell extracts. Importantly, this system has the potential to serve as a universal strategy for FHGD-based diagnosis in point-of-care (POC) tests, by simply altering the recognition sequence of the substrate for other analytes.

Multiple TMA-aided CRISPR/Cas13a platform for highly sensitive detection of IL-15 to predict immunotherapeutic response in nasopharyngeal carcinoma

BACKGROUND

Immune checkpoint inhibitors (ICIs)-based treatments have been recommended as the first line for refractory recurrent and/or metastatic nasopharyngeal carcinoma (NPC) patients, yet responses vary, and predictive biomarkers are urgently needed. We selected serum interleukin-15 (sIL-15) out of four interleukins as a candidate biomarker, while most patients' sIL-15 levels were too low to be detected by conventional methods, so it was necessary to construct a highly sensitive method to detect sIL-15 in order to select NPC patients who would benefit most or least from ICIs.

METHODS

Combining a primer exchange reaction (PER), transcription-mediated amplification (TMA), and a immuno-PER-TMA-CRISPR/Cas13a system, we developed a novel multiple signal amplification platform with a detection limit of 32 fg/mL, making it 153-fold more sensitive than ELISA.

RESULTS

This platform demonstrated high specificity, repeatability, and versatility. When applied to two independent cohorts of 130 NPC sera, the predictive value of sIL-15 was accurate in both cohorts (area under the curve: training, 0.882; validation, 0.898). Additionally, lower sIL-15 levels were correlated with poorer progression-free survival (training, HR: 0.080, p<0.0001; validation, HR: 0.053, p<0.0001).

CONCLUSION

This work proposes a simple and sensitive approach for sIL-15 detection to provide insights for personalized immunotherapy of NPC patients.

Development of nanozyme based sensors as diagnostic tools in clinic applications: a review

Since 1970, many artificial enzymes that imitate the activity and structure of natural enzymes have been discovered. Nanozymes are a group of nanomaterials with enzyme-mimetic properties capable of catalyzing natural enzyme processes. Nanozymes have attracted great interest in biomedicine due to their excellent stability, rapid reactivity, and affordable cost. The enzyme-mimetic activities of nanozymes may be modulated by numerous parameters, including the oxidative state of metal ions, pH, hydrogen peroxide (H2O2) level, and glutathione (GSH) concentration, indicating the tremendous potential for biological applications. This article delivers a comprehensive overview of the advances in the knowledge of nanozymes and the creation of unique and multifunctional nanozymes, and their biological applications. In addition, a future perspective of employing the as-designed nanozymes in biomedical and diagnostic applications is provided, and we also discuss the barriers and constraints for their further therapeutic use.

Recent advancements in biosensor designs toward the detection of intestine cancer miRNA biomarkers

Cancer diagnosis and treatment have been of broad interest among scientists in the last decades due to the high death rate, widespread occurrence, and recurrence after treatment. The survival rate of cancer patients depends greatly on early detection and appropriate treatments. Therefore developing new technologies applicable to sensitive and specific methods of cancer detection is an inevitable task for cancer researchers. Abnormal miRNA expression is contributed to severe diseases such as cancers and since their expression level and type differ strictly during carcinogenesis and later metastasis and treatments, the improved detection accuracy of these miRNAs would undoubtedly lead to early diagnosis, prognosis, and targeted therapy. Biosensors are accurate and straightforward analytical devices that have had practical applications especially in the last decade. Their domain is still growing through a combination of attractive nanomaterials and amplification methods, leading to innovative biosensing platforms for the efficient detection of miRNAs as diagnostic and prognostic biomarkers. In this review, we will provide the recent developments in biosensors to detect intestine cancer miRNA biomarkers and also discuss the challenges and outcomings of this field.

Nanozyme-Based Colorimetric SARS-CoV-2 Nucleic Acid Detection by Naked Eye

Fluorescence-based PCR and other amplification methods have been used for SARS-CoV-2 diagnostics, however, it requires costly fluorescence detectors and probes limiting deploying large-scale screening. Here, a cut-price colorimetric method for SARS-CoV-2 RNA detection by iron manganese silicate nanozyme (IMSN) is established. IMSN catalyzes the oxidation of chromogenic substrates by its peroxidase (POD)-like activity, which is effectively inhibited by pyrophosphate ions (PPi). Due to the large number of PPi generated by amplification processes, SARS-CoV-2 RNA can be detected by a colorimetric readout visible to the naked eye, with the detection limit of 240 copies mL^-1 . This conceptually new method has been successfully applied to correctly distinguish positive and negative oropharyngeal swab samples of COVID-19. Colorimetric assay provides a low-cost and instrumental-free solution for nucleic acid detection, which holds great potential for facilitating virus surveillance.

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.

Electrochemical signal amplification strategy based on trace metal ion modified WS2 for ultra-sensitive detection of miRNA-21

Previous researches have suggested the potential correlation between the development of breast cancer and the concentration of miRNA-21 in serum. Theoretically the doping of multivalent metal ions in WS₂ could bring higher electron transfer capacity, but this hasn't been proven. To fill this research gap, through one-pot method we prepared seven nanocomposite structures modified with different metal ions (Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺, Fe³⁺, Cr³⁺, La³⁺). Characterization revealed that ammonia produced by hydrothermal urea exfoliated the multilayer graphene oxide (MGO) and provided a nitrogen source for doping reduction to form a 3D flower-like structure (NrGOF) with high specific surface area. Meanwhile, the modification of WS₂ by Fe³⁺ not only enhanced its electrochemical conductivity but also gave the material an additional peroxidase activity centre. In the composite Fe³⁺-WS₂/NrGOF-AgNPs, NrGOF is used as a conductive loading interface for WS₂, while Fe³⁺ served as the catalytic and electron transfer centre for secondary amplification of the electrochemical signal. The experimental results showed that the sensing platform has a low limit of detection (LOD) of 1.18 aM for miRNA-21 in the concentration range of 10^-17-10^-12 M and has been successfully applied to the detection of real serum samples.

miRNAs as Predictors of Barrier Integrity

The human body has several barriers that protect its integrity and shield it from mechanical, chemical, and microbial harm. The various barriers include the skin, intestinal and respiratory epithelia, blood-brain barrier (BBB), and immune system. In the present review, the focus is on the physical barriers that are formed by cell layers. The barrier function is influenced by the molecular microenvironment of the cells forming the barriers. The integrity of the barrier cell layers is maintained by the intricate balance of protein expression that is partly regulated by microRNAs (miRNAs) both in the intracellular space and the extracellular microenvironment. The detection of changes in miRNA patterns has become a major focus of diagnostic, prognostic, and disease progression, as well as therapy-response, markers using a great variety of detection systems in recent years. In the present review, we highlight the importance of liquid biopsies in assessing barrier integrity and challenges in differential miRNA detection.

Nanozymes and nanoflower: Physiochemical properties, mechanism and biomedical applications

Natural enzymes possess several drawbacks which limits their application in industries, wastewater remediation and biomedical field. Therefore, in recent years researchers have developed enzyme mimicking nanomaterials and enzymatic hybrid nanoflower which are alternatives of enzyme. Nanozymes and organic inorganic hybrid nanoflower have been developed which mimics natural enzymes functionalities such as diverse enzyme mimicking activities, enhanced catalytic activities, low cost, ease of preparation, stability and biocompatibility. Nanozymes include metal and metal oxide nanoparticles mimicking oxidases, peroxidases, superoxide dismutase and catalases while enzymatic and non-enzymatic biomolecules were used for preparing hybrid nanoflower. In this review nanozymes and hybrid nanoflower have been compared in terms of physiochemical properties, common synthetic routes, mechanism of action, modification, green synthesis and application in the field of disease diagnosis, imaging, environmental remediation and disease treatment. We also address the current challenges facing nanozyme and hybrid nanoflower research and the possible way to fulfil their potential in future.

Detection of COVID-19-related biomarkers by electrochemical biosensors and potential for diagnosis, prognosis, and prediction of the course of the disease in the context of personalized medicine

As a more efficient and effective way to address disease diagnosis and intervention, cutting-edge technologies, devices, therapeutic approaches, and practices have emerged within the personalized medicine concept depending on the particular patient's biology and the molecular basis of the disease. Personalized medicine is expected to play a pivotal role in assessing disease risk or predicting response to treatment, understanding a person's health status, and, therefore, health care decision-making. This work discusses electrochemical biosensors for monitoring multiparametric biomarkers at different molecular levels and their potential to elucidate the health status of an individual in a personalized manner. In particular, and as an illustration, we discuss several aspects of the infection produced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as a current health care concern worldwide. This includes SARS-CoV-2 structure, mechanism of infection, biomarkers, and electrochemical biosensors most commonly explored for diagnostics, prognostics, and potentially assessing the risk of complications in patients in the context of personalized medicine. Finally, some concluding remarks and perspectives hint at the use of electrochemical biosensors in the frame of other cutting-edge converging/emerging technologies toward the inauguration of a new paradigm of personalized medicine.

Recent progress of metal-organic frameworks as sensors in (bio)analytical fields: towards real-world applications

The deployment of metal-organic frameworks (MOFs) in a plethora of analytical and bioanalytical applications is a growing research area. Their unique properties such as high but tunable porosity, well-defined channels or pores, and ease of post-synthetic modification to incorporate additional functional units make them ideal candidates for sensing applications. This is possible because the interaction of analytes with a MOF often results in a change in its structure, eventually leading to a modification of the intrinsic physicochemical properties of the MOF which is then transduced into a measurable signal. The high porosity allows for the adsorption of analytes very efficiently, while the tunable pore sizes/nature and/or installation of specific recognition groups allow modulating the affinity towards different classes of compounds, which in turn lead to good sensor sensitivity and selectivity, respectively. Some figures are given to illustrate the potential of MOF-based sensors in the most relevant application fields, and future challenges and opportunities to their possible translation from academia (i.e., laboratory testing of MOF sensing properties) to industry (i.e., real-world analytical sensor devices) are critically discussed.

Target recognition assisted-primer exchange reaction (Ta-PER) for sensitive analysis of p53 gene and its application in analyzing amatoxin-treated samples

Sensitive and reliable detection of the p53 gene plays a significant role in precise cancer targeting and in fundamental research. However, the sensitivity of existing p53 gene detection approaches remains to be improved. Herein, we develop a target recognition assisted-primer exchange reaction (Ta-PER) for sensitive analysis of the p53 gene. Ta-PER was initiated by the recognition of a designed dumbbell structure probe by the p53 gene. In Ta-PER, the primer exchange reaction (PER) was combined with molecular beacon-based chain recycling to construct the signal amplification process. Through integrating target recognition with PER-based signal amplification, Ta-PER was established and exhibited a high detection sensitivity, with a limit of detection as low as 56 fM. In addition, the approach was also used to detect the p53 gene in normal HeLa cells and amatoxin-treated HeLa cells. The high level of the p53 gene in amatoxin-treated HeLa cells, which was approximately 1.67 times higher than that in HeLa cell extract, indicated the apoptosis of cells and suggested the promising prospect of the approach.

An ultrasensitive electrochemical immunosensor for carcinoembryonic antigen detection based on two-dimensional PtPd/Cu-TCPP(Fe) nanocomposites

Establishing an effective signal amplification strategy is the key to achieving sensitive detection of analytes by electrochemical immunoassay. In this work, a novel sandwich-type electrochemical immunosensor with dual-signal amplification was successfully constructed using PtPd/Cu-TCPP(Fe) as the sensing platform and mesoporous silicon dioxide as the signal amplifier. Firstly, two-dimensional wrinkled Cu-TCPP(Fe) nanomaterials loaded with PtPd nanoparticles have strong affinity for the immobilization of capture antibodies and can generate excellent electrochemical signals. Meanwhile, the mesoporous silicon dioxide with large steric hindrance was used as signal label to further improve the sensitivity of the immunosensor by increasing the difference of the current response signal. Under optimal experimental conditions, the electrochemical immunosensor exhibited a wide linear detection range from 0.1 pg/mL to 1.0 μg/mL, with a detection limit as low as 0.166 fg/mL. The experimental results showed that the constructed immunosensor has a great application prospect in clinical biomarker detection.