A fluorometric histidine biosensor based on the use of a quencher-labeled Cu(II)-dependent DNAzyme

Microchimica Acta - The authors describe a biosensor for histidine that is based on the use of a DNAzyme catalytic beacon. The Cu(II)-dependent DNA-cleaving DNAzyme (Cu-Enzyme) was modified with a...     

基于单壁碳纳米管-DNA酶复合结构的电化学生物传感器

结合DNA酶优异的氧化还原催化特性和碳纳米管的电化学特性, 制备了单壁碳纳米管-DNA酶复合材料, 并通过壳聚糖将其固定到玻碳电极表面构建了电化学生物传感界面. 研究了单壁碳纳米管-DNA酶复合结构的氧化还原反应催化特性, 并以此为传感平台构建了葡萄糖氧化酶电化学生物传感器. 结果表明, 单壁碳纳米管-DNA酶复合材料修饰的电极对过氧化氢的响应具有较宽的线性范围(5×10^-6~1×10^-2 mol/L)和良好的检测灵敏度(检出限为1×10^-6 mol/L). 采用制备的葡萄糖氧化酶传感器实现了对葡萄糖的快速灵敏检测.     

聚多巴胺包埋G-四联体/血红素DNA酶制备过氧化氢生物传感器

利用多巴胺的氧化自聚实现对G-四联体/血红素DNA酶的包埋,成功构建了H2O2电化学生物传感器。DNA和血红素混合得到G-四联体/血红素复合物;DNA酶物理吸附在玻碳电极上后,将10μL 5 g/L多巴胺的磷酸盐缓冲液(pH 8.0)滴在表面,空气中的氧气氧化多巴胺形成聚多巴胺膜,实现DNA酶的固定。考察了不同DNA序列对传感器性能的影响,表明电化学与光学传感过程具有不同序列响应。此传感器对H2O2的检出限为2.2μmol/L;线性范围为0.01～1.5 mmol/L。本研究证实了利用聚多巴胺固定酶和用DNA酶代替天然酶构筑传感器的可行性。     

A SERS DNAzyme biosensor for lead ion detection

SERS biosensor for sensitive and selective detection of lead ions (Pb(2+)) based on DNAzyme was developed by taking advantage of the specific catalytic reaction of DNAzyme upon binding to Pb(2+) ions. Detection was accomplished by SERS nanoprobe labeled with DNA and Raman reporters for signal amplification.     

Microbial fuel cell-based self-powered biosensing platform for determination of ketamine as an anesthesia drug in clinical serum samples

A novel self-powered DNA biosensor was successfully developed based on a dual-chambered microbial fuel cell (MFC) apparatus as a power supply and ketamine (KET) as a hybridization indicator. A graphite electrode coated with gold nanoparticles (GNP/graphite electrode), which provided larger surface area for immobilization of thiolated single-stranded (ssDNA) probe, was used as biocathode in the MFC system. When KET was used as the hybridization indicator for detection of ssDNA probe, the indicator exhibited excellent selectivity in detecting and discriminating the complementary, single-base mismatched, and noncomplementary target sequences. Furthermore, this self-powered biosensor based on MFC apparatus served as the biosensing platform for determination of KET in clinical serum samples. Under the steady-state operation condition, the difference between power densities of the ssDNA probe-modified GNP/graphite cathode in the absence and presence of accumulated KET (ΔP) served as the detection signal with a detection limit of 0.54 nM. The proposed MFC-based self-powered biosensor, as a low-cost portable device, showed a high sensitivity, stability, and reproducibility. Therefore, it can become a promising platform for determination of KET in clinical researches.     

A proximity-dependent surface hybridization strategy for constructing an efficient signal-on electrochemical DNAzyme sensing system

A proximity-dependent surface hybridization strategy is employed for designing a "signal-on" electrochemical DNAzyme biosensor. By taking advantage of the high sensitivity of the PDSH strategy, and by realizing the enzymatic hydrolysis reaction in a homogenous system with a unimolecular design, the proposed biosensor shows a very high sensitivity to target molecules.     

DNAzyme based electrochemical sensors for trace uranium

We have developed a uranyl-specific DNAzyme that was immobilized on the surface of a gold electrode to give a highly sensitive and selective biosensor for uranyl ion. The typical DNAzyme system consisted of the RNA (rA) as the substrate (ADNA), and the other strand is the enzyme (TDNA) with a ferrocene (Fc). The presence of uranyl ion induces the cleavage of the DNA substrate strand at the rA position to form two fragments. The Fc unit thereby is released from the surface of the electrode, and this results in a decreased peak current. This electrochemical biosensor has a dynamic range from 2 nM to 14 nM of uranyl ion, with a detection limit at 1 nM. It exhibits high sensitivity and excellent selectivity over other metal ions, and thus represents a promising technique for simple, fast, on-site, and real-time electrochemical sensing of UO₂(II) ion. It also serves as a guide in choosing different methods for designing electrochemical sensors for other metal ions.

Lateral flow nucleic acid biosensor for Cu2+ detection in aqueous solution with high sensitivity and selectivity

A lateral flow nucleic acid biosensor based on copper-dependent DNA-cleaving DNAzyme and gold nanoparticles has been developed for the visual detection of copper ions (Cu(2+)) in an aqueous solution with a detection limit of 10 nM.     

Stretchable and bendable textile matrix based on cellulose fibers for wearable self-powered glucose biosensors

Cellulose - A wearable self-powered biosensor, fabricated from a stretchable and bendable textile matrix, senses glucose in urine. This textile matrix is made of cellulose fibers. A porous...     

Amplified fluorescence detection of mercury(II) ions (Hg2+) using target-induced DNAzyme cascade with catalytic and molecular beacons

In this work, a fluorescent sensing strategy was developed for the detection of mercury(II) ions (Hg(2+)) in aqueous solution with excellent sensitivity and selectivity using a target-induced DNAzyme cascade with catalytic and molecular beacons (CAMB). In order to construct the biosensor, a Mg(2+)-dependent DNAzyme was elaborately designed and artificially split into two separate oligonucleotide fragments. In the presence of Hg(2+), the specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) interaction induced the two fragments to produce the activated Mg(2+)-dependent DNAzyme, which would hybridize with a hairpin-structured MB substrate to form the CAMB system. Eventually, each target-induced activated DNAzyme could catalyze the cleavage of many MB substrates through true enzymatic multiple turnovers. This would significantly enhance the sensitivity of the Hg(2+) sensing system and push the detection limit down to 0.2 nM within a 20 min assay time, much lower than those of most previously reported fluorescence assays. Owning to the strong coordination of Hg(2+) to the T-T mismatched pairs, this proposed sensing system exhibited excellent selectivity for Hg(2+) detection, even in the presence of 100 times of other interferential metal ions. Furthermore, the applicability of the biosensor for Hg(2+) detection in river water samples was demonstrated with satisfactory results. These advantages endow the sensing strategy with a great potential for the simple, rapid, sensitive, and specific detection of Hg(2+) from a wide range of real samples.     

Adenosine Triphosphate Sensing by Electrocatalysis with DNAzyme

Electrocatalysis of redox enzymes shows wide application for biosensing. DNAzymes exhibiting specific catalytic activities have aroused great interest recently. However, there are few studies on the electrocatalysis between DNAzyme and electron mediator. In this paper, based on the electrocatalysis of methylene blue (MB) and horseradish peroxidase mimicking DNAzyme (HRP‐DNAzyme), an amplified electrochemical biosensor for the detection of adenosine triphosphate (ATP) was designed. In the present system, by means of the ATP‐aptamer interaction, two guanine‐rich DNA sequences, one of which was labeled with MB at the 5′ end, were assembled on the gold electrode. In the presence of K⁺ and hemin, the guanine‐rich DNA sequences transferred to HRP‐DNAzyme. The conformational change of the structure resulted in the approaching of MB and HRP‐DNAzyme which made the electrocatalytic process between MB and HRP‐DNAzyme possible. We used cyclic voltammetry and electrochemical impedance spectroscopy to study the electrocatalytic process. The system was therefore utilized for amplified detection of ATP without imposing any new constraints to the platform which showed satisfactory result.     

A novel signal-amplified electrochemical aptasensor based on supersandwich G-quadruplex DNAzyme for highly sensitive cancer cell detection

A novel electrochemical biosensor for cancer cell detection was developed based on aptamer-based competition and supersandwich G-quadruplex DNAzyme amplification strategy. Due to the stronger affinity between the aptamer and cancer cells than that with its complementary oligonucleotide, the complementary oligonucleotide will be facilely replaced. As a consequence, we can detect cancer cells indirectly by detecting the releasing DNA which is proportional to the concentration of K562 cells. Through the supersandwich G-quadruplex DNAzyme amplification strategy, the sensitivity can be dramatically enhanced with detection limit down to 14 cells.     

A colorimetric lead biosensor using DNAzyme-directed assembly of gold nanoparticles

A highly sensitive and selective colorimetric lead biosensor based on DNAzyme-directed assembly of gold nanoparticles is reported. It consists of a DNAzyme and its substrate that can hybridize to a 5'-thio-modified DNA attached to gold nanoparticles. The hybridization brings gold nanoparticles together, resulting in a blue-colored nanoparticle assembly. In the presence of lead, the DNAzyme catalyzes specific hydrolytic cleavage, which prevents the formation of the nanoparticle assembly, resulting in red-colored individual nanoparticles. The detection level can be tuned to several orders of magnitude, from 100 nM to over 200 muM, through addition of an inactive variant of the DNAzyme. The concept developed here can be applied to the design of nucleic acid enzyme/nanoparticle sensors for analytes that are subject to in vitro selection, and thus can significantly expand the scope of nanomaterial applications and provide a novel approach to designing simple colorimetric biosensors.     

A signal-on electrogenerated chemiluminescent biosensor for lead ion based on DNAzyme

A highly reproducible and sensitive signal-on electrogenerated chemiluminescence (ECL) biosensor based on the DNAzyme for the determination of lead ion was developed. The ECL biosensor was fabricated by covalently coupling 5′-amino-DNAzyme-tagged with ruthenium bis (2,2′-bipyridine) (2,2′-bipyridine-4,4′-dicarboxylic acid)-ethylenediamine (Ru1-17E′) onto the surface of graphite electrode modified with 4-aminobenzoic acid, and then a DNA substrate with a ribonucleotide adenosine hybridized with Ru1-17E′ on the electrode. Upon binding of Pb²⁺ to the Ru1-17E′ to form a complex which catalyzed the cleavage of the DNA substrate, the double-stranded DNA was dissociated and thus led to a high ECL signal. The signal linearly increases with the concentration of Pb²⁺ in the range from 5.0 to 80 pM with a detection limit of 1.4 pM and a relative standard derivation of 2.3%. This work demonstrates that using DNAzyme tagged with ruthenium complex as an ECL probe and covalently coupling method for the fabrication of the ECL biosensor with high sensitivity, good stability and significant regeneration ability is promising approach.     

Wearable self-powered biosensors

Wearable self-powered biosensors are devices that operate without an external electronic power source or onboard battery and that use a biorecognition detection element to relay sensing information. Such devices are becoming more widespread following the larger trend of more ubiquitous wearable devices in general. Self-powering can be a particularly important characteristic in situations where replacing/recharging a battery is either impossible or impractical. Most wearable self-powered biosensors rely primarily on enzymatic reactions to supply the energy required for operation, but there are also other innovative approaches that combine multiple signal transduction techniques to simultaneously provide power and produce a detection signal. Areas of needed research include developing higher power energy harvesting techniques and more wearable self-powered biosensor devices that have integrated low-power wireless electronics.     

Probing and modulating the interactions of the DNAzyme with DNA-functionalized nanoparticles

DNA-functionalized gold nanoparticles are one of the most versatile bionanomaterials for biomedical and clinical diagnosis. Herein, we discovered that the performance of DNAzyme cleaving the substrate is highly related to its length. This intriguing phenomenon only appears at the interfaces of DNAfunctionalized gold nanoparticles. We systematically investigated the causes of this phenomenon. We conjectured that the DNAzyme with extended nucleotides that do not match its substrate strand is vulne...     

Signal Propagation in Multi‐Layer DNAzyme Cascades Using Structured Chimeric Substrates

Signal propagation through enzyme cascades is a critical component of information processing in cellular systems. Although such systems have potential as biomolecular computing tools, rational design of synthetic protein networks remains infeasible. DNA strands with catalytic activity (DNAzymes) are an attractive alternative, enabling rational cascade design through predictable base‐pair hybridization principles. Multi‐layered DNAzyme signaling and logic cascades are now reported. Signaling between DNAzymes was achieved using a structured chimeric substrate (SCS) that releases a downstream activator after cleavage by an upstream DNAzyme. The SCS can be activated by various upstream DNAzymes, can be coupled to DNA strand‐displacement devices, and is highly resistant to interference from background DNA. This work enables the rational design of synthetic DNAzyme regulatory networks, with potential applications in biomolecular computing, biodetection, and autonomous theranostics.     

Nucleic Acid Driven DNA Machineries Synthesizing Mg2+‐Dependent DNAzymes: An Interplay between DNA Sensing and Logic‐Gate Operations

Polymerase/nicking enzymes and nucleic‐acid scaffolds are implemented as DNA machines for the development of amplified DNA‐detection schemes, and for the design of logic gates. The analyte nucleic acid target acts, also, as input for the logic gates. In the presence of two DNA targets, acting as inputs, and appropriate DNA scaffolds, the polymerase‐induced replication of the scaffolds, followed by the nicking of the replication products, are activated, leading to the autonomous synthesis of the Mg²⁺‐dependent DNAzyme or the Mg²⁺‐dependent DNAzyme subunits. These biocatalysts cleave a fluorophore/quencher‐functionalized nucleic‐acid substrate, thus providing fluorescence signals for the sensing events or outputs for the logic gates. The systems are used to develop OR, AND, and Controlled‐AND gates, and the DNA‐analyte targets represent two nucleic acid sequences of the smallpox viral genome.     

A Reagentless Electrochemical DNA Sensor Based on a Self-powered DNA Machine

Herein, a reagentless electrochemical DNA sensor based on a self-powered DNA machine for detecting survivin mRNA in cells is developed. The metal-organic framework (MOFs) loaded with DNAzyme cofactors (Mn²⁺) is coated on PTFE rods on the Au surface and assembled with the DNA walker, overcoming the complexity of adding metal ions from the external environment. In addition, the orbital chain is modified by a synthetic bisferrocene signal marker, which further enables signal amplification. Under optimal conditions, the sensor exhibits a range from 1×10⁻¹⁴ mol/L to 1×10⁻⁸ mol/L with a detection limit (S/N=3) of 1.28 fM.     

An Electrochemical Sensor for the Detection of Cu2+ Based on Gold Nanoflowers‐modifed Electrode and DNAzyme Functionalized Au@MIL‐101 (Fe)

In this study, we developed an electrochemical sensor for sensitive detection of Cu²⁺ based on gold nanoflowers (AuNFs)‐modified electrode and DNAzyme functionalized Au@MIL‐101(Fe) (MIL: Materials of Institute Lavoisier). The AuNFs‐modified indium tin oxide modified conductive glass electrode(AuNFs/ITO) prepared via electrodeposition showed improved electronic transport properties and provided more active sites to adsorb large amounts of oligonucleotide substrate (DNA1) via thiol‐gold bonds. The stable Au@MIL‐101(Fe) could guarantee the sensitivity because of its intrinsic peroxidase mimic property, while the Cu²⁺‐dependent DNA‐cleaving DNAzyme linked to Au@MIL‐101(Fe) achieved the selectivity toward Cu²⁺. After the DNAzyme substrate strand (DNA2) was cleaved into two parts due to the presence of Cu²⁺, the oligonucleotide fragment linked to MIL‐101(Fe) was able to hybridize with DNA1 adsorbed onto the surface of AuNFs/ITO. Due to the peroxidase‐like catalytic activity of MIL‐101(Fe) and the affinity recognition property of DNAzyme toward Cu²⁺, the electrochemical biosensor showed a sensitive detection range from 0.001 to 100 μM, a detection limit of 0.457 nM and a high selectivity, demonstrating its potential for Cu²⁺ detection in real environmental samples.