Framework Nucleic Acid-Enabled Programming of Electrochemical Catalytic Properties of Artificial Enzymes

Amplified and Specific Staining of Protein Dimerization on Cell Membrane Catalyzed by Responsively Installed DNA Nanomachines for Cancer Diagnosis

In situ staining of protein dimerization on cell membrane has an important significance in accurate diagnosis during perioperative period, yet facile integration of specific recognition function and local signal conversion/amplification abilities on membrane surface remains a great challenge. Herein, a two-stage catalytic strategy is developed by installing DNA nanomachines and employing. Specifically, dual-aptamer-assisted DNA scaffold perform a "bispecific recognition-then-computing" operation and the output signal initiate a membrane-anchored biocatalysis for self-assembly of DNA catalytic converters, that is, G-quadruplex nanowire/hemin DNAzyme. Then, localized-deposition of chromogenic polydopamine is chemically catalyzed by horseradish peroxidase-mimicking DNAzyme and guided by supramolecular interactions between conjugate rigid plane of G-tetrad and polydopamine oligomer. The catalytic products exhibit nanofiber morphology with a diameter of 80-120 nm and a length of 1-10 µm, and one-to-one localize on DNA scaffold for amplified and specific staining of protein dimers. The bispecific staining leads to a higher (≈3.4-fold) signal intensity than traditional immunohistochemistry, which is beneficial for direct visualization. Moreover, an efficient discrimination ability of the bispecific staining strategy is observed in co-culture model staining. This study provides a novel catalytic method for controlling deposition of chromogens and paves a new avenue to sensitively stain of protein-protein interactions in disease diagnosis.

A two-step electrochemical biosensor based on Tetrazyme for the detection of fibrin

In this study, an electrochemical biosensor was constructed for the detection of fibrin, specifically by a simple two-step approach, with a novel artificial enzyme (Tetrazyme) based on the DNA tetrahedral framework as signal probe. The multichannel screen-printed electrode with the activated surface cannot only remove some biological impurities, but also serve as a carrier to immobilize a large number of antigen proteins. The DNA tetrahedral nanostructure was employed to ensure the high sensitivity of the probe for biological analysis. The hemin was chimeric into the G-quadruplex to constitute the complex with peroxidase catalytic activity (hemin/G4-DNAzyme), subsequently, Tetrazyme was formed through combining of this complex and DNA tetrahedral nucleic acid framework. The artificial enzyme signal probe formed by the covalent combination of the homing peptide (Cys-Arg-Glu-Lys-Ala, CREKA), which is the aptamer of fibrin and the new artificial enzyme is fixed on the surface of the multichannel carbon electrode by CREKA-specific recognition, so as to realize the sensitive detection of fibrin. The feasibility of sensing platform was validated by cyclic voltammetry (CV) and amperometric i-t curve (IT) methods. Effects of Tetrazyme concentration, CREKA concentrations and hybridization time on the sensor were explored. Under the best optimal conditions of 0.6 μmol/L Tetrazyme, 80 μmol/L CREKA, and 2.5 h reaction time, the immunosensor had two linear detection ranges, 10-40 nmol/L, with linear regression equation Y = 0.01487X - 0.011 (R2 = 0.992), and 50-100 nmol/L, with linear regression equation Y = 0.00137X + 0.6405 (R2 = 0.998), the detection limit was 9.4 nmol/L, S/N ≥ 3. The biosensor could provide a new method with great potential for the detection of fibrin with good selectivity, stability, and reproducibility.

Poly-adenine-mediated tetrahedral DNA nanostructure with multiple target-recognition sites for ultrasensitive and rapid electrochemical detection of Aflatoxin B1

Tetrahedral DNA nanostructures (TDNs) are widely used in the development of electrochemical biosensors due to their structural stability, programmability, and strong interfacial orderliness. However, the complex modifications on the electrode and the single vertex target recognition of the TDNs limit their applications in electrochemical biosensing. Herein, we developed a universal detection system based on a novel polyadenine-based tetrahedral DNA nanostructure (ATDN) using Aflatoxin B1 (AFB1) as the model target for analysis. In the absence of target AFB1, the signal probes (SP) modified with ferrocene would be anchored by five aptamers on ATDN. The target capture by aptamers led to a release of SP from the electrode surface, resulting in a significant reduction of the electrochemical signal. This new nanostructure was not only dispensed with multi-step electrode modifications and strong mechanical rigidity but also had five modification sites which enhanced the detection sensitivity for the target. As a result, this biosensor shows good analytical performance in the linear range of 1 fg mL-1 to 1 ng mL-1, exhibiting a low detection limit of 0.33 fg mL-1. Satisfactory accuracy has also been demonstrated through good recoveries (95.2%-98.9%). The proposed new tetrahedral DNA nanostructure can provide a more rapid and sensitive alternative to previous electrochemical sensors based on the conventional TDN. Since DNA sequences can be designed flexibly, the sensing platform in this strategy can be extended to detect various targets in different fields.

Engineering DNA quadruplexes in DNA nanostructures for biosensor construction

DNA quadruplexes are nucleic acid conformations comprised of four strands. They are prevalent in human genomes and increasing efforts are being directed toward their engineering. Taking advantage of the programmability of Watson-Crick base-pairing and conjugation methodology of DNA with other molecules, DNA nanostructures of increasing complexity and diversified geometries have been artificially constructed since 1980s. In this review, we investigate the interweaving of natural DNA quadruplexes and artificial DNA nanostructures in the development of the ever-prosperous field of biosensing, highlighting their specific roles in the construction of biosensor, including recognition probe, signal probe, signal amplifier and support platform. Their implementation in various sensing scenes was surveyed. And finally, general conclusion and future perspective are discussed for further developments.

Cobalt metal-organic framework modified carbon cloth/paper hybrid electrochemical button-sensor for nonenzymatic glucose diagnostics

In the growing pandemic, family healthcare is widely concerned with the increase of medical self-diagnosis away from the hospital. A cobalt metal-organic framework modified carbon cloth/paper (Co-MOF/CC/Paper) hybrid button-sensor was developed as a portable, robust, and user-friendly electrochemical analytical chip for nonenzymatic quantitative detection of glucose. Highly integrated electrochemical analytical chip was successfully fabricated with a flexible Co-MOF/CC sensing interface, effectively increasing the specific area and catalytic sites than the traditional plane electrode. Based on the button-sensor, rapid quantitative detection of glucose was achieved in multiple complex bio-matrixes, such as serum, urine, and saliva, with desired selectivity, stability, and durability. With the advantages of low cost, high environment tolerance, ease of production, our nanozyme-based electrochemical analytical chip achieved reliable nonenzymatic electrocatalysis, has great potential for the application of rapid on-site analysis in personalized diagnostic and disease prevention.

A tetrahedral DNA nanostructure-decorated electrochemical platform for simple and ultrasensitive EGFR genotyping of plasma ctDNA

In this study, we propose an on-site electrochemical platform for sensitive simultaneous genotyping of the two major EGFR mutations (19del and L858R) through plasma ctDNA based on tetrahedral DNA nanostructure decorated screen-printed electrodes.

Ultrasensitive Electrochemical DNA Biosensor Based on a Label-Free Assembling Strategy Using a Triblock polyA DNA Probe

Multiblock DNA probe attracted a large amount of scientific attention, for the development of multitarget biosensor and improved specificity/sensitivity. However, the development of multiblock DNA probes highly relied on the chemical synthesis of organic linkers or nanomaterials, which limited their practicability and biological compatibility. In this work, we developed a label-free assembling strategy using a triblock DNA capture probe, which connects two DNA probes with its intrinsic polyA fragment (probe-PolyA-probe, PAP). The middle polyA segment has a high affinity to the gold electrode surface, leading to excellent reproducibility, stability, and regeneration of our biosensor. Two flanking capture probes were tandemly co-assembled on the electrode surface with consistent spatial relationship and exactly the same amount. When combined with the target DNA, the hybridization stability was improved, because of the strong base stacking effect of two capture probes. The sensitivity of our biosensor was proved to be 10 fM, with a wide analysis range between 10 fM to 1 nM. Our PAP-based biosensor showed excellent specificity when facing mismatched DNA sequences. Even single nucleotide polymorphisms can be distinguished by each probe. The excellent practicability of our biosensor was demonstrated by analyzing genomic DNA both with and without PCR amplification.