DNA framework-engineered electrochemical biosensors

Responsive DNA hydrogels: design strategies and prospects for biosensing

Hydrogels, water-filled networks that can adapt to external stimuli by altering their volume, are known for their high flexibility and biocompatibility. DNA, a critical biomolecule renowned for its exceptional characteristics including information transmission, molecular recognition, and editability, has found widespread applications in the biosensing field as well. The integration of these two biomaterials offers promising opportunities for the development of novel biosensors with enhanced sensitivity, specificity, and adaptability. Therefore, by virtue of the collective features, researchers have recently focused on the construction of responsive DNA hydrogel systems. This feature article describes recent developments in fabricating DNA hydrogels and their applications in the biosensing area. Initially, it focuses on the design strategies employed in preparing DNA hydrogels, encompassing both pure DNA hydrogels and hybridized DNA hydrogels. Subsequently, it summarizes the use of DNA hydrogels in biosensing applications, highlighting their applications in visual detection, electrochemical sensing, and optical biosensing analyses. Furthermore, the underlying responsive mechanisms within these biosensing systems are also described. Lastly, this article presents a comprehensive discussion on the existing challenges and prospects of responsive DNA hydrogels, offering insights into their potential to revolutionize the field of biosensing.

Biomedical Utility of Non-Enzymatic DNA Amplification Reaction: From Material Design to Diagnosis and Treatment

Nucleic acid nanotechnology has become a promising strategy for disease diagnosis and treatment, owing to remarkable programmability, precision, and biocompatibility. However, current biosensing and biotherapy approaches by nucleic acids exhibit limitations in sensitivity, specificity, versatility, and real-time monitoring. DNA amplification reactions present an advantageous strategy to enhance the performance of biosensing and biotherapy platforms. Non-enzymatic DNA amplification reaction (NEDAR), such as hybridization chain reaction and catalytic hairpin assembly, operate via strand displacement. NEDAR presents distinct advantages over traditional enzymatic DNA amplification reactions, including simplified procedures, milder reaction conditions, higher specificity, enhanced controllability, and excellent versatility. Consequently, research focusing on NEDAR-based biosensing and biotherapy has garnered significant attention. NEDAR demonstrates high efficacy in detecting multiple types of biomarkers, including nucleic acids, small molecules, and proteins, with high sensitivity and specificity, enabling the parallel detection of multiple targets. Besides, NEDAR can strengthen drug therapy, cellular behavior control, and cell encapsulation. Moreover, NEDAR holds promise for constructing assembled diagnosis-treatment nanoplatforms in the forms of pure DNA nanostructures and hybrid nanomaterials, which offer utility in disease monitoring and precise treatment. Thus, this paper aims to comprehensively elucidate the reaction mechanism of NEDAR and review the substantial advancements in NEDAR-based diagnosis and treatment over the past five years, encompassing NEDAR-based design strategies, applications, and prospects.

A trivalent aptasensor by using DNA tetrahedron as scaffold for label-free determination of antibiotics

Owing to advantage in high sensitivity and fast response, aptamer based electrochemical biosensors have attracted much more attention. However, inappropriate interfacial engineering strategy leads to poor recognition performance, which ascribe to the following factors of immobilized oligonucleotide strand including steric hindrance, interchain entanglement, and unfavorable conformation. In this work, we proposed a DNA tetrahedron based diblock aptamer immobilized strategy for the construction of label-free electrochemical biosensor. The diblock aptamer sequence is composite of T-rich anchor domain and recognition domain, where T-rich domain enabling anchored on the edge of DNA tetrahedron via Hoogsteen hydrogen bond at neutral condition. The DNA tetrahedron scaffold offers an appropriate lateral space for target recognition of diblock aptamer. More importantly, this trivalent aptamer recognition interface can be regenerated by simply adjusting the pH environment to alkaline, resulting in the dissociation of diblock aptamer. Under the optimum condition, proposed electrochemical aptasensor manifested a satisfied sensitivity for aminoglycosides antibiotic, kanamycin with a limit of detection of 0.69 nM, which is 45-fold lower than traditional Au-S immobilization strategy. Moreover, the proposed aptasensor had also successfully been extended to ampicillin detection by changing the sequence of recognition domain in diblock aptamer. This work paves a new way for the rational design of aptamer-based electrochemical sensor.

A homogeneous label-free electrochemical aptasensor based on an omega-like DNA nanostructure for progesterone detection

A novel homogeneous label-free electrochemical aptamer sensor for the detection of progesterone was prepared by combining a well-designed omega (Ω)-like DNA (Ω-DNA) nanostructure, with an isothermal cycling amplification strategy based on the highly efficient exonuclease III (Exo III). The omega-like (Ω) DNA is composed of two oligonucleotide strands: DNA1 and DNA2. The Pro aptamer triggers a chain displacement reaction of Ω-DNA nanostructures, forms a new double-stranded DNA structure (aptamer precursor-DNA2), and releases DNA1. Then, Exo III selectively cleaves the DNA duplex and releases the Pro aptamer to participate in a new displacement reaction. Meanwhile, the released DNA1 strands gain access to the strongly bound hemin, forming a hemin/G-quadruplex (DNAzyme). In the presence of hydrogen peroxide (H2O2), differential pulse voltammetry (DPV) was used to detect the current signal from the oxidation of o-phenylenediamine (OPD) to aminoazobenzene (DAP) catalyzed by DNAzyme. However, the amount of released DNA1 from the Ω-DNA nanostructures is reduced in the presence of the target Pro, and the DPV signal declines because of the small amount of DNAzyme formed. The developed electrochemical aptasensor has a wide dynamic linear relationship in the range of 1 pg mL-1 to 10 ng mL-1 under optimal conditions. Its detection limit is down to 0.3 pg mL-1, providing a potential platform for a sensitive Pro assay among electrochemical assays.

Novel DNA nanoflower biosensing technologies towards next-generation molecular diagnostics

DNA nanoflowers (DNFs) are topological flower-like nanostructures based on ultralong-strand DNA and inorganic metal-ion frameworks. Because of their programmability, biocompatibility, and controllable assembly size for specific responses to molecular recognition stimuli, DNFs are powerful biosensing tools for detecting biomolecules. Here, we review the current state of DNF-based biosensing strategies for in vivo and in vitro detection, with a view of how the field has evolved towards molecular diagnostics. We also provide a detailed classification of DNF-based biosensing strategies and propose their future utility. Particularly as transduction elements, DNFs can accelerate biosensing engineering by signal amplification. Finally, we discuss the key challenges and further prospects of DNF-based biosensing technologies in developing applications of a broader scope.

Screen-printed electrode-based biosensors modified with functional nucleic acid probes and their applications in this pandemic age: a review

Electrochemical methodology has probably been the most used sensing platform in the past few years as they provide superior advantages. In particular, screen-printed electrode (SPE)-based sensing applications stand out as they provide extraordinary miniaturized but robust and user-friendly detection system. In this context, we are focusing on the modification of SPE with functional nucleic acid probes and nanostructures to improve the electrochemical detection performance in versatile sensing applications, particularly in the fight against the COVID-19 pandemic. Aptamers are immobilized on the electrode surface to detect non-nucleic acid targets and complementary probes to recognize and capture nucleic acid targets. In a step further, SPE-based biosensors with the modification of self-assembled DNA nanostructures are emphasized as they offer great potential for the interface engineering of the electrode surface and promote the excellent performance of various interface reactions. By equipping with a portable potentiostat and a smartphone monitoring device, the realization of this SPE-based miniaturized diagnostic system for the further requirement of fast and POC detection is revealed. Finally, more novel and excellent works are previewed and future perspectives in this field are mentioned.

Prospects and challenges of dynamic DNA nanostructures in biomedical applications

The physicochemical nature of DNA allows the assembly of highly predictable structures via several fabrication strategies, which have been applied to make breakthroughs in various fields. Moreover, DNA nanostructures are regarded as materials with excellent editability and biocompatibility for biomedical applications. The ongoing maintenance and release of new DNA structure design tools ease the work and make large and arbitrary DNA structures feasible for different applications. However, the nature of DNA nanostructures endows them with several stimulus-responsive mechanisms capable of responding to biomolecules, such as nucleic acids and proteins, as well as biophysical environmental parameters, such as temperature and pH. Via these mechanisms, stimulus-responsive dynamic DNA nanostructures have been applied in several biomedical settings, including basic research, active drug delivery, biosensor development, and tissue engineering. These applications have shown the versatility of dynamic DNA nanostructures, with unignorable merits that exceed those of their traditional counterparts, such as polymers and metal particles. However, there are stability, yield, exogenous DNA, and ethical considerations regarding their clinical translation. In this review, we first introduce the recent efforts and discoveries in DNA nanotechnology, highlighting the uses of dynamic DNA nanostructures in biomedical applications. Then, several dynamic DNA nanostructures are presented, and their typical biomedical applications, including their use as DNA aptamers, ion concentration/pH-sensitive DNA molecules, DNA nanostructures capable of strand displacement reactions, and protein-based dynamic DNA nanostructures, are discussed. Finally, the challenges regarding the biomedical applications of dynamic DNA nanostructures are discussed.

Interfacial DNA Framework-Enhanced Background-to-Signal Transition for Ultrasensitive and Specific Micro-RNA Detection

Interfacial DNA self-assembly is fundamental to solid nucleic acid biosensors, whereas how to improve the signal-to-noise ratio has always been a challenge, especially in the charge-based electrochemical DNA sensors because of the large noise from the negatively charged DNA capture probes. Here, we report a DNA framework-reversed signal-gain strategy through background-to-signal transition for ultrasensitive and highly specific electrical detection of microRNAs (miRNAs) in blood. By using a model of enzyme-catalyzed deposition of conductive molecules (polyaniline) targeting to DNA, we observed the highest signal contribution per unit area by the highly charged three-dimensional (3D) tetrahedral DNA framework probe, relative to the modest of two-dimensional (2D) polyA probe and the lowest of one-dimensional (1D) single-stranded (ss)DNA probe, suggesting the positive correlation of background DNA charge with signal enhancement. Using such an effective signal-transition design, the DNA framework-based electrochemical sensor achieves ultrasensitive miRNAs detection with sensitivity up to 0.29 fM (at least 10-fold higher than that with 1D ssDNA or 2D polyA probes) and high specificity with single-base resolution. More importantly, this high-performance sensor allows for a generalized sandwich detection of tumor-associated miRNAs in the complex matrices (multiple cell lysates and blood serum) and further distinguishes the tumor patients (e.g., breast, lung, and liver cancer) from the normal individuals. These advantages signify the promise of this miRNA sensor as a versatile tool in precision diagnosis.

DNA-Based Biosensors for the Biochemical Analysis: A Review

In recent years, DNA-based biosensors have shown great potential as the candidate of the next generation biomedical detection device due to their robust chemical properties and customizable biosensing functions. Compared with the conventional biosensors, the DNA-based biosensors have advantages such as wider detection targets, more durable lifetime, and lower production cost. Additionally, the ingenious DNA structures can control the signal conduction near the biosensor surface, which could significantly improve the performance of biosensors. In order to show a big picture of the DNA biosensor's advantages, this article reviews the background knowledge and recent advances of DNA-based biosensors, including the functional DNA strands-based biosensors, DNA hybridization-based biosensors, and DNA templated biosensors. Then, the challenges and future directions of DNA-based biosensors are discussed and proposed.

Dual Sensitization Smartphone Colorimetric Strategy Based on RCA Coils Gathering Au Tetrahedra and Its Application in the Detection of CK-MB

In recent years, the combination of DNA nanotechnology and biosensing has been extensively reported. Herein, we attempted to develop a dual sensitization smartphone colorimetric strategy based on rolling circle amplification (RCA) coils gathering Au tetrahedra and explore its application. The dual sensitization effect of this strategy was achieved by rolling circle amplification (RCA) and Au tetrahedra. Under the initiation of the complementary DNA, a large number of ssDNA were generated, achieving amplification of the reaction signal. At the same time, due to the formation of Au tetrahedra, more gold nanoparticles could be gathered under the same conditions, and the signal would be amplified again. Using software ImageJ, the gray value of the reaction solution can be analyzed, detecting the target timely under the practical conditions of lack of equipment. By selecting aptamers with strong binding affinity, we applied this strategy to detect creatine kinase isoenzymes (CK-MB), showing a limit of detection of 0.8 pM, which performed well in actual detection and can meet the needs for real-time detection of CK-MB. Therefore, a universal detection platform was developed, which has broad application prospects in biosensing, clinical diagnosis, food detection, and other fields.

Interspace-controlled biosensing interface with enhanced charge transfer based on tripod DNA probes

Binding of a target by a probe for selective detection depends on the state of the probes on the sensing interface. Here, the hanging strand length of triple-helix DNA was used to form tripod probes immobilized via π-π interactions on a reduced graphene-oxide substrate. The spacing between the probes was adjusted by controlling the lengths of the tripod "feet" on the substrate; that is, increased probe spacing occurred when foot size increased over the range of 6-12 bases. The surface coverages and electron-transfer rates mediated the tripod DNA probes were characterized by electrochemical methods and atomic force microscopy. The electron-transfer mediated by the tripod DNA probes was higher than that mediated by doubled-stranded DNA. Then different sizes tripod DNA probes were developed for protein-CEA detection. The DNA probes with 10 bases feet showed the best detection limit of detection of 10^-6 ng/mL in the detection linear range (10^-6 - 25 ng/mL). The result demonstrated the tripod DNA probes with different sizes could obtain excellent sensitivity when it applied to the target with appropriate size. This interspace-controlled biosensing interface of tripod DNA probes with enhanced charge transfer should find widespread applications in clinical, medical, biological, and environmental areas for precise detection of differently sized targets.

Printed Electrochemical Biosensors: Opportunities and Metrological Challenges

Printed electrochemical biosensors have recently gained increasing relevance in fields ranging from basic research to home-based point-of-care. Thus, they represent a unique opportunity to enable low-cost, fast, non-invasive and/or continuous monitoring of cells and biomolecules, exploiting their electrical properties. Printing technologies represent powerful tools to combine simpler and more customizable fabrication of biosensors with high resolution, miniaturization and integration with more complex microfluidic and electronics systems. The metrological aspects of those biosensors, such as sensitivity, repeatability and stability, represent very challenging aspects that are required for the assessment of the sensor itself. This review provides an overview of the opportunities of printed electrochemical biosensors in terms of transducing principles, metrological characteristics and the enlargement of the application field. A critical discussion on metrological challenges is then provided, deepening our understanding of the most promising trends in order to overcome them: printed nanostructures to improve the limit of detection, sensitivity and repeatability; printing strategies to improve organic biosensor integration in biological environments; emerging printing methods for non-conventional substrates; microfluidic dispensing to improve repeatability. Finally, an up-to-date analysis of the most recent examples of printed electrochemical biosensors for the main classes of target analytes (live cells, nucleic acids, proteins, metabolites and electrolytes) is reported.