In situ hybridization chain reaction mediated ultrasensitive enzyme-free and conjugation-free electrochemcial genosensor for BRCA-1 gene in complex matrices

Beyond traditional biosensors: Recent advances in gold nanoparticles modified electrodes for biosensing applications

Gold nanoparticles (AuNPs) have emerged as powerful tools in the construction of highly sensitive electrochemical biosensors. Their unique properties, such as the ability to serve as an effective platform for biomolecule immobilization and to facilitate electron transfer between the electrode surface and the immobilized molecules, make them a promising choice for biosensor applications. Utilizing AuNPs modified electrodes can lead to improved sensitivity and lower limits of detection compared to unmodified electrodes. This review provides a comprehensive overview of the recent advancements and applications of AuNPs-based electrochemical biosensors in the biomedical field. The synthesis methods of AuNPs, their key properties, and various strategies employed for electrode modification are discussed. Furthermore, this review highlights the remarkable applications of these nanostructure-integrated electrodes, including immunosensors, enzyme biosensors, and DNA biosensors.

The Application of Hybridization Chain Reaction in the Detection of Foodborne Pathogens

Today, with the globalization of the food trade progressing, food safety continues to warrant widespread attention. Foodborne diseases caused by contaminated food, including foodborne pathogens, seriously threaten public health and the economy. This has led to the development of more sensitive and accurate methods for detecting pathogenic bacteria. Many signal amplification techniques have been used to improve the sensitivity of foodborne pathogen detection. Among them, hybridization chain reaction (HCR), an isothermal nucleic acid hybridization signal amplification technique, has received increasing attention due to its enzyme-free and isothermal characteristics, and pathogenic bacteria detection methods using HCR for signal amplification have experienced rapid development in the last five years. In this review, we first describe the development of detection technologies for food contaminants represented by pathogens and introduce the fundamental principles, classifications, and characteristics of HCR. Furthermore, we highlight the application of various biosensors based on HCR nucleic acid amplification technology in detecting foodborne pathogens. Lastly, we summarize and offer insights into the prospects of HCR technology and its application in pathogen detection.

Advances in novel strategies for isolation, characterization, and analysis of CTCs and ctDNA

Over the past decade, the detection and analysis of liquid biopsy biomarkers such as circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) have advanced significantly. They have received recognition for their clinical usefulness in detecting cancer at an early stage, monitoring disease, and evaluating treatment response. The emergence of liquid biopsy has been a helpful development, as it offers a minimally invasive, rapid, real-time monitoring, and possible alternative to traditional tissue biopsies. In resource-limited settings, the ideal platform for liquid biopsy should not only extract more CTCs or ctDNA from a minimal sample volume but also accurately represent the molecular heterogeneity of the patient's disease. This review covers novel strategies and advancements in CTC and ctDNA-based liquid biopsy platforms, including microfluidic applications and comprehensive analysis of molecular complexity. We discuss these systems' operational principles and performance efficiencies, as well as future opportunities and challenges for their implementation in clinical settings. In addition, we emphasize the importance of integrated platforms that incorporate machine learning and artificial intelligence in accurate liquid biopsy detection systems, which can greatly improve cancer management and enable precision diagnostics.

Primer exchange reaction-amplified protein-nucleic acid interactions for ultrasensitive and specific microRNA detection

Protein-nucleic acid interactions are not only fundamental to genetic regulation and cellular metabolism, but molecular basis to artificial biosensors. However, such interactions are generally weak and dynamic, making their specific and sensitive quantitative detection challenging. By using primer exchange reaction (PER)-amplified protein-nucleic acid interactions, we here design a universal and ultrasensitive electrochemical sensor to quantify microRNAs (miRNAs) in blood. This PER-miR sensor leverages specific recognition between S9.6 antibodies and miRNA/DNA hybrids to couple with PER-derived multi-enzyme catalysis for ultrasensitive miRNA detection. Surface binding kinetic analysis shows a rational K_d (8.9 nM) between the miRNA/DNA heteroduplex and electrode-attached S9.6 antibody. Based on such a favorable affinity, the programmable PER amplification enables the sensor to detect target miRNAs with sensitivity up to 90.5 aM, three orders of magnitude higher than that without PER in routine design, and with specificity of single-base resolution. Furthermore, the PER-miR sensor allows detecting multiple miRNAs in parallel, measuring target miRNA in lysates across four types of cell lines, and differentiating tumor patients from healthy individuals by directly analyzing the human blood samples (n = 40). These advantages make the sensor a promising tool to enable quantitative sensing of biomolecular interactions and precision diagnostics.

Highly Sensitive Multiplex Detection of Molecular Biomarkers Using Hybridization Chain Reaction in an Encoded Particle Microfluidic Platform

In the continuous combat against diseases, there is the need for tools that enable an improved diagnostic efficiency towards higher information density combined with reduced time-to-result and cost. Here, a novel fully integrated microfluidic platform, the Evalution™, is evaluated as a potential solution to this need. Encoded microparticles combined with channel-based microfluidics allow a fast, sensitive and simultaneous detection of several disease-related biomarkers. Since the binary code is represented by physically present holes, 2¹⁰ different codes can be created that will not be altered by light or chemically induced degradation. Exploiting the unique features of this multiplex platform, hybridization chain reaction (HCR) is explored as a generic approach to reach the desired sensitivity. Compared to a non-amplified reference system, the sensitivity was drastically improved by a factor of 10⁴, down to low fM LOD values. Depending on the HCR duration, the assay can be tuned for sensitivity or total assay time, as desired. The huge potential of this strategy was further demonstrated by the successful detection of a multiplex panel of six different nucleic acid targets including viruses and bacteria. The ability to not only discriminate these two categories but, with the same effort, also virus strains (human adenovirus and human bocavirus), virus subtypes (human adenovirus type B and D) and antibiotic-resistant bacteria (Streptococcus pneumonia), exemplifies the specificity of the developed approach. The effective, yet highly simplified, isothermal and protein-enzyme-free signal amplification tool reaches an LOD ranging from as low as 33 ± 4 to 151 ± 12 fM for the different targets. Moreover, direct detection in a clinically relevant sample matrix was verified, resulting in a detection limit of 309 ± 80 fM, approximating the low fM levels detectable with the gold standard analysis method, PCR, without the drawbacks related to protein enzymes, thermal cycling and elaborate sample preparation steps. The reported strategy can be directly transferred as a generic approach for the sensitive and specific detection of various target molecules in multiplex. In combination with the high-throughput capacity and reduced reagent consumption, the Evalution™ demonstrates immense potential in the next generation of diagnostic tools towards more personalized medicine.

Nanotechnology‐based electrochemical biosensors for monitoring breast cancer biomarkers

Breast cancer is categorized as the most widespread cancer type among women globally. On-time diagnosis can decrease the mortality rate by making the right decision in the therapy procedure. These features lead to a reduction in medication time and socioeconomic burden. The current review article provides a comprehensive assessment for breast cancer diagnosis using nanomaterials and related technologies. Growing use of the nano/biotechnology domain in terms of electrochemical nanobiosensor designing was discussed in detail. In this regard, recent advances in nanomaterial applied for amplified biosensing methodologies were assessed for breast cancer diagnosis by focusing on the advantages and disadvantages of these approaches. We also monitored designing methods, advantages, and the necessity of suitable (nano) materials from a statistical standpoint. The main objective of this review is to classify the applicable biosensors based on breast cancer biomarkers. With numerous nano-sized platforms published for breast cancer diagnosis, this review tried to collect the most suitable methodologies for detecting biomarkers and certain breast cancer cell types.

Spectrophotometric Detection of the BRCA1 Gene via Exponential Isothermal Amplification and Hybridization Chain Reaction of Surface-Bound Probes

In this work, we demonstrated an ultrasensitive approach with a dual-amplification strategy for DNA assay based on isothermal exponential amplification (EXPAR) and the hybridization chain reaction (HCR). In the presence of target DNA, the hairpin probe DNA (HP1) recognized and partially hybridized with the target DNA to form double-stranded structures containing the full recognition sequences for nicking endonuclease and then initiated EXPAR. Under the reaction of EXPAR, a large number of single-stranded DNA (ssDNA) was produced in the circle of nicking, polymerization, and strand displacement. The resulting ssDNA can bind to the surface-bound probe on the well of the microplate and trigger the hybridization chain reaction, resulting in the production of numerous double-stranded DNA concatamers with biotin labeling. In the presence of streptavidin-conjugated horseradish peroxidase (HRP), the amplified signal can be detected by a spectrophotometer via HRP-catalyzed substrate 3,3'5,5'-tetramethylbenzidine (TMB). This proposed dual-amplification method provides a detection limit of 74.48 aM, which also exhibits good linearity ranging from 0.1 fM to 100 pM.

Discrimination of Single-Nucleotide Variants Based on an Allele-Specific Hybridization Chain Reaction and Smartphone Detection

Massive DNA testing requires novel technologies to support a sustainable health system. In recent years, DNA superstructures have emerged as alternative probes and transducers. We, herein, report a multiplexed and highly sensitive approach based on an allele-specific hybridization chain reaction (AS-HCR) in the array format to detect single-nucleotide variants. Fast isothermal amplification was developed before activating the HCR process on a chip to work with genomic DNA. The assay principle was demonstrated, and the variables for integrating the AS-HCR process and smartphone-based detection were also studied. The results were compared to a conventional polymerase reaction chain (PCR)-based test. The developed multiplex method enabled higher selectivity against single-base mismatch sequences at concentrations as low as 10³ copies with a limit of detection of 0.7% of the mutant DNA percentage and good reproducibility (relative error: 5% for intra-assay and 17% for interassay). As proof of concept, the AS-HCR method was applied to clinical samples, including human cell cultures and biopsied tissues of cancer patients. Accurate identification of single-nucleotide mutations in KRAS and NRAS genes was validated, considering those obtained from the reference sequencing method. To conclude, AS-HCR is a rapid, simple, accurate, and cost-effective isothermal method that detects clinically relevant genetic variants and has a high potential for point-of-care demands.

Tetrahedral DNA Framework-Programmed Electrochemical Biosenors with Gold Nanoparticles for Ultrasensitive Cell-Free DNA Detection

Tumor-associated cell-free DNA (cfDNA) is a dynamic biomarker for genetic analysis, early diagnosis and clinical treatment of cancers. However, its detection has limitations because of its low abundance in blood or other complex bodily fluids. Herein, we developed an ultrasensitive cfDNA electrochemical biosensor (E-cfDNA sensor) based on tetrahedral DNA framework (TDF)-modified gold nanoparticles (Au NPs) with an interface for cfDNA detection. By accurately controlling the numbers of base pairs on each DNA framework, three types of TDFs were programmed: 26 base pairs of TDF; 17 base pairs of TDF; and 7 base pairs of TDF (TDF-26, TDF-16 and TDF-7, respectively). We also combined the TDF with hybridization chain reaction (HCR) to achieve signal amplification. Under optimal conditions, we detected the breast cancer susceptibility gene 1 (BRCA-1), a representative cfDNA closely related to breast cancer. An ultra-low detection limit of 1 aM with a linear range from 1 aM to 1 pM by TDF-26 was obtained, which was superior to the existing methods. Each type of TDF has excellent discrimination ability, which can distinguish single mismatch. More significantly, we also detected BRCA-1 in mimic serum samples, demonstrating that the E-cfDNA sensor has potential use in clinical research.

Integrating Cycled Enzymatic DNA Amplification and Surface-Enhanced Raman Scattering for Sensitive Detection of Circulating Tumor DNA

Circulating tumor DNA (ctDNA) represents an emerging biomarker of liquid biopsies for the development of precision cancer diagnostics and therapeutics. However, sensitive detection of ctDNA remains challenging, due to their short half-life and low concentrations in blood samples. In this study, we report a new method to address this challenge by integrating cycled enzymatic DNA amplification technique and Au nanoparticle@silicon-assisted surface-enhanced Raman scattering (SERS) technique. We have demonstrated a reproducible identification of a single-base-mutated ctDNA sequence of diffuse intrinsic pontine gliomas (DIPGs), with the limit of detection (LOD) as low as 9.1 fM in the spiked blood samples. This approach can be used to analyze trace amounts of ctDNA in translational medicine for early diagnosis, therapeutic effect monitoring, and prognosis of patients with cancer.

Circulating tumor DNA analysis for tumor diagnosis

Tumor is a kind of abnormal organism generated by the proliferation and differentiation of cells in the body under the action of various initiating and promoting factors, which seriously threatens human life and health. Tumorigenesis is a gradual process that involves multistage reactions and the accumulation of mutations. Gene mutation usually occurs during tumorigenesis, and can be used for tumor diagnosis. Early diagnosis is the most effective way to improve the cure rate and reduce the mortality rate. Among the peripheral blood circulating tumor DNA (ctDNA), gene mutation in keeping with tumor cells can be detected, which can potentially replace tumor tissue section for early diagnosis. It has been considered as a liquid biopsy marker with good clinical application prospect. However, the high fragmentation and low concentration of ctDNA in blood result in the difficulty of tumor stage determination. Therefore, high sensitive and specific mutation detection methods have been developed to detect trace mutant ctDNA. At present, the approaches include digital PCR (dPCR), Bead, Emulsion, Amplification and Magnetic (BEAMing), Next Generation Sequencing (NGS), Amplification Refractory Mutation System (ARMS), etc. In this paper, the principle, characteristics, latest progress and application prospects of these methods are reviewed, which will facilitate researchers to choose appropriate ctDNA detection approaches.

The Recent Development of Hybridization Chain Reaction Strategies in Biosensors

With the continuous development of biosensors, researchers have focused increasing attention on various signal amplification strategies to pursue superior performance for more applications. In comparison with other signal amplification strategies, hybridization chain reaction (HCR) as a powerful signal amplification technique shows its certain charm owing to nonenzymatic and isothermal features. Recently, on the basis of conventional HCR, this technique has been developed and improved rapidly, and a variety of HCR-based biosensors with excellent performance have been reported. Herein, we present a systematic and critical review on the research progress of HCR in biosensors in the last five years, including the newly developed HCR strategies such as multibranched HCR, migration HCR, localized HCR, in situ HCR, netlike HCR, and so on, as well as the combination strategies of HCR with isothermal signal amplification techniques, nanomaterials, and functional DNA molecules. By illustrating some representative works, we also summarize the advantage and challenge of HCR in biosensors, and offer a deep discussion of the latest progress and future development trends of HCR in biosensors.

Nanotechnology Strategies for the Analysis of Circulating Tumor DNA: A Review

Circulating tumor DNA (ctDNA) describes the fragmented DNA released from tumor cells into the blood. The ctDNA may have the same genetic changes as the primary tumor. Currently, ctDNA has become a popular biomarker for diagnosis, treatment, real-time clinical response monitoring, and prognosis, for solid tumors. Detection of ctDNA is minimally invasive, and repeat sampling can easily be performed. However, due to its low quality and short DNA fragment length, ctDNA detection still faces challenges and requires highly sensitive analytical techniques. Recently, liquid biopsies for the analysis of circulating tumor cells (CTCs) and circulating tumor-derived exosomes have been studied, and nanotechnology techniques have rapidly developed. Compared to traditional analytical methods, these nanotechnology-based platforms have the advantages of sensitivity, multiplex detection, simplicity, miniaturization, and automation, which support their potential use in clinical practice. This review aims to discuss the recent nanotechnological strategies for ctDNA analysis and the design of reliable techniques for ctDNA detection and to identify the potential clinical applications.

Dual-amplified strategy for ultrasensitive electrochemical biosensor based on click chemistry-mediated enzyme-assisted target recycling and functionalized fullerene nanoparticles in the detection of microRNA-141

Rapid and efficient detection of tumor marker at the early stages is one of the crucial challenges in cancer diagnostics and therapy. In this study, an ultrasensitive electrochemical biosensor was fabricated by dual-amplified strategy for the detection of ultra-trace microRNA-141 (miRNA-141). Firstly, two split sequences contained G-quadruplex were connected by click chemistry-mediated nucleic acid strands self-assembly and the obtained complete G-quadruplex was complementary with miRNA-141 to formed DNA-RNA hybrid duplexes. Subsequently, the formed DNA-RNA hybrid duplexes were specifically recognized by duplex-specific nuclease (DSN), and the DNA part of the duplexes were cleaved and the miRNA-141 were released to trigger next cycle, which acquired a primal signal amplification by enzyme-assisted target recycling (EATR). Moreover, amino and thiol group multi-labeled functionalized fullerene nanoparticles (FC60) with a larger surface active sites and better biocompatibility, were designed rationally to modify the Au electrodes, which produced multiply-enhanced amplified signal. This dual-amplified sensing system exhibited a remarkable analytical performance for the detection of miRNA-141 in concentrations ranging from 0.1 pM to 100 nM and the detection limit of 7.78 fM was obtained. Compared with the biosensor with single amplification strategy such as EATR, this electrochemical biosensor based on dual-amplified strategy exhibited an excellent discrimination capability and higher analytical performance. Therefore, this electrochemical biosensor might hold a great potential for further applications in biomedical research and early clinical diagnosis.

Opportunities, Challenges, and Prospects in Electrochemical Biosensing of Circulating Tumor DNA and its Specific Features

Nowadays, analyzing circulating tumor DNA (ctDNA), a very small part of circulating free DNA (cfDNA) carried by blood, is considered to be an interesting alternative to conventional single-site tumor tissue biopsies, both to assess tumor burden and provide a more comprehensive snapshot of the time-related and spatial heterogeneity of cancer genetic/epigenetic scenery. The determination of ctDNA and/or mapping its characteristic features, including tumor-specific mutations, chromosomal aberrations, microsatellite alterations, and epigenetic changes, are minimally invasive, powerful and credible biomarkers for early diagnosis, follow-up, prediction of therapy response/resistance, relapse monitoring, and tracking the rise of new mutant subclones, leading to improved cancer outcomes This review provides an outline of advances published in the last five years in electrochemical biosensing of ctDNA and surrogate markers. It emphasizes those strategies that have been successfully applied to real clinical samples. It highlights the unique opportunities they offer to shift the focus of cancer patient management methods from actual decision making, based on clinic-pathological features, to biomarker-driven treatment strategies, based on genotypes and customized targeted therapies. Also highlighted are the unmet hurdles and future key points to guide these devices in the development of liquid biopsy cornerstone tools in routine clinical practice for the diagnosis, prognosis, and therapy response monitoring in cancer patients.

Double signal amplification strategy for ultrasensitive electrochemical biosensor based on nuclease and quantum dot-DNA nanocomposites in the detection of breast cancer 1 gene mutation

Rapid and efficient detection of microRNA (miRNA) of breast cancer 1 gene mutation (BRCA1) at their earliest stages is one of the crucial challenges in cancer diagnostics. In this study, a highly-sensitive electrochemical DNA biosensor was fabricated by double signal amplification (DSA) strategy for the detection of ultra-trace miRNA of BRCA1. In the presence of target miRNA of BRCA1, the well-matched RNA-DNA duplexes were specifically recognized by double-strand specific nuclease (DSN), and the DNA part of the duplexes were then cleaved and miRNAs were released to trigger another following cycle, which produced a primarily amplified signal by such a cyclic enzymatic signal amplification (CESA). Then triple-CdTe quantum dot labelled DNA nanocomposites (3-QD@DNA NC) was selectively hybridized with the cleaved DNA probe on the electrode and produced multiply amplified signals. The biosensor exhibited a high sensitivity for the detection of miRNA of BRCA1 in concentrations ranging from 5 aM to 5 fM, and its detection limit of 1.2 aM was obtained, which is two or three orders of magnitude lower than those by single signal amplification strategy such as CESA or QD-labeled DNA probes. The as-prepared biosensor was successfully used to detect the miRNA of BRCA1 in human serum samples with acceptable stability, good reproducibility, and good recovery. The proposed DNA biosensor based on double signal amplification strategy provided a feasible, rapid, and sensitive platform for early clinical diagnosis and practical applications.

A novel label-free fluorescent detection of histidine based upon Cu2+-specific DNAzyme and hybridization chain reaction

A novel label-free fluorescent sensor for histidine was developed based upon Cu²⁺-specific DNAzyme, hybridization chain reaction(HCR) and triplex DNA. Cu²⁺ can bind to the histidine, in the presence of histidine, leading to the inhibition of the cleavage of substrate strand of Cu²⁺-dependent DNAzyme, then the intact substrate strand trigger the HCR between H1 and H2. The HCR product can be recognized by triplex-forming oligonucleotide (TFO) through triplex formation and reported by the fluorescence of berberine, the fluorescence intensity of the sensing system was proportional to the concentration of histidine during the range of 5.7-455 nmol L^-1, with a detection limit of 2.0 nmol L^-1.

Liquid biopsy of circulating tumor DNA and biosensor applications

Circulating tumor DNA (ctDNA) as a class of liquid biopsy is a type of gene fragment that contains tumor-specific gene changes in body fluids such as human peripheral blood. More and more evidences show that ctDNA is an excellent tumor biomarker for diagnosis, prognosis, tumor heterogeneity and so on. ctDNA is a tumor code in the blood. Liquid biopsy of ctDNA is firstly summarized. Compared with the traditional detection technologies of ctDNA, the biosensor is an excellent choice for the detection of ctDNA because of its portability, sensitivity, specificity and ease of use. This review mainly evaluates various biosensors applied to the detection of ctDNA. We discuss the most commonly used bioreceptors to specifically identify and bind ctDNA, including complementary DNA (cDNA), peptide nucleic acid (PNA) and anti-5 MethylCytosines, and the biotransducers which convert biological signals to analysable signs. The review also discusses signal amplification strategies in biosensors to detect ctDNA.

Molecular Machine Powered Surface Programmatic Chain Reaction for Highly Sensitive Electrochemical Detection of Protein

A bipedal molecular machine powered surface programmatic chain reaction was designed for electrochemical signal amplification and highly sensitive electrochemical detection of protein. The bipedal molecular machine was built through aptamer-target specific recognition for the binding of one target protein with two DNA probes, which hybridized with surface-tethered hairpin DNA 1 (H1) via proximity effect to expose the prelocked toehold domain of H1 for the hybridization of ferrocene-labeled hairpin DNA 2 (H2-Fc). The toehold-mediated strand displacement reaction brought the electrochemical signal molecule Fc close to the electrode and meanwhile released the bipedal molecular machine to traverse the sensing surface by the surface programmatic chain reaction. Eventually, a large number of duplex structures of H1-H2 with ferrocene groups facing to the electrode were formed on the sensor surface to generate an amplified electrochemical signal. Using thrombin as a model target, this method showed a linear detection range from 2 pM to 20 nM with a detection limit of 0.76 pM. The proposed detection strategy was enzyme-free and allowed highly sensitive and selective detection of a variety of protein targets by using corresponding DNA-based affinity probes, showing potential application in bioanalysis.

Electrochemical detection of sequence-specific DNA based on formation of G-quadruplex-hemin through continuous hybridization chain reaction

A high-sensitive detection of sequence-specific DNA was established based on the formation of G-quadruplex-hemin complex through continuous hybridization chain reaction (HCR). Taking HIV DNA sequence as an example, a capture probe complementary to part of HIV DNA was firstly self-assembled onto the surface of Au electrode. Then a specially designed assistant probe with both terminals complementary to the target DNA and a G-quadruplex-forming sequence in the center was introduced into the detection solution. In the presence of both the target DNA and the assistant probe, the target DNA can be captured on the electrode surface and then a continuous HCR can be conducted due to the mutual recognition of the target DNA and the assistant probe, leading to the formation of a large number of G-quadruplex on the electrode surface. With the help of hemin, a pronounced electrochemical signal can be observed in differential pulse voltammetry (DPV), due to the formation of G-quadruplex-hemin complex. The peak current is linearly related with the logarithm of the concentration of the target DNA in the range from 10 fM to 10 pM. The electrochemical sensor has high selectivity to clearly discriminate single-base mismatched and three-base mismatched sequences from the original HIV DNA sequence. Moreover, the established DNA sensor was challenged by detection of HIV DNA in human serum samples, which showed the low detection limit of 6.3 fM. Thus it has great application prospect in the field of clinical diagnosis and environmental monitoring.

Biomacromolecular nanostructures-based interfacial engineering: from precise assembly to precision biosensing

Biosensors are a type of important biodevice that integrate biological recognition elements, such as enzyme, antibody and DNA, and physical or chemical transducers, which have revolutionized clinical diagnosis especially under the context of point-of-care tests. Since the performance of a biosensor depends largely on the bio–solid interface, design and engineering of the interface play a pivotal role in developing quality biosensors. Along this line, a number of strategies have been developed to improve the homogeneity of the interface or the precision in regulating the interactions between biomolecules and the interface. Especially, intense efforts have been devoted to controlling the surface chemistry, orientation of immobilization, molecular conformation and packing density of surface-confined biomolecular probes (proteins and nucleic acids). By finely tuning these surface properties, through either gene manipulation or self-assembly, one may reduce the heterogeneity of self-assembled monolayers, increase the accessibility of target molecules and decrease the binding energy barrier to realize high sensitivity and specificity. In this review, we summarize recent progress in interfacial engineering of biosensors with particular focus on the use of protein and DNA nanostructures. These biomacromolecular nanostructures with atomistic precision lead to highly regulated interfacial assemblies at the nanoscale. We further describe the potential use of the high-performance biosensors for precision diagnostics.

Binding-induced DNA walker for signal amplification in highly selective electrochemical detection of protein

A binding-induced DNA walker-assisted signal amplification was developed for highly selective electrochemical detection of protein. Firstly, the track of DNA walker was constructed by self-assembly of the high density ferrocene (Fc)-labeled anchor DNA and aptamer 1 on the gold electrode surface. Sequentially, a long swing-arm chain containing aptamer 2 and walking strand DNA was introduced onto gold electrode through aptamers-target specific recognition, and thus initiated walker strand sequences to hybridize with anchor DNA. Then, the DNA walker was activated by the stepwise cleavage of the hybridized anchor DNA by nicking endonuclease to release multiple Fc molecules for signal amplification. Taking thrombin as the model target, the Fc-generated electrochemical signal decreased linearly with logarithm value of thrombin concentration ranging from 10pM to 100nM with a detection limit of 2.5pM under the optimal conditions. By integrating the specific recognition of aptamers to target with the enzymatic cleavage of nicking endonuclease, the aptasensor showed the high selectivity. The binding-induced DNA walker provides a promising strategy for signal amplification in electrochemical biosensor, and has the extensive applications in sensitive and selective detection of the various targets.

Hybridization chain reaction: a versatile molecular tool for biosensing, bioimaging, and biomedicine

This review provides a comprehensive overview of the fundamental principles, analysis techniques, and application fields of hybridization chain reaction and its development status.