DNA Walker Amplification Research Articles

Target-induced DNA nanomachine operation for the detection of proteins

Accurate and sensitive detection of disease-associated proteins in early stage of patients plays an important role in timely treatment and successfully extending patients' lives. To meet this demand, we herein rationally designed a flexible target-induced DNA nanomachine operation (TIDNMO) sensor for the detection of proteins. The TIDNMO system was composed of DNA nanoswitch and DNA walker. Triplex DNA nanoswitch was triggered by specific target, followed by the release of the walking strand, which initiated the DNA walker amplification as signal output. In addition, the Exo III could drive walking strand autonomously move on gold nanoparticle surface to realize 2 orders of magnitude signal amplification. What's more, this sensor could transform its suitable functional recognition element of DNA nanoswitch to recognize other specific molecule and realize different targets sensing based on identical walking tracks. Considering the facile reporter elements and efficient amplification performance, the present DNA nanomachine as a sensor could achieve a detection limit of 68 pM for anti-Dig antibody, 0.95 pM for mucin-1 respectively, along with a superb specificity. Furthermore, the method reported here opened a new chapter in disease-related protein sensing for the development of clinical early diagnosis.

A laser-induced zinc oxide/graphene photoelectrode for a photocurrent-polarity-switching photoelectrochemical biosensor with bipedal DNA walker amplification.

A photocurrent-polarity-switching photoelectrochemical (PEC) biosensor was developed for the ultrasensitive detection of tobramycin (TOB) through bipedal DNA walker amplification with hemin-induced photocurrent-polarity-switching using a laser-induced zinc oxide/graphene (ZnO/LIG) photoelectrode. Specifically, the ZnO/LIG photoelectrode was synthesized in situ by a laser direct writing (LDW) technique. In the presence of TOB, it reacted with HP1 and HP2 and the DNA walker response was activated to form a stable hemin/G-quadruplex. Furthermore, hemin induced a polarity shift in the photocurrent signal. The developed analytical platform exhibited excellent photoelectron transport performance of ZnO/LIG, the signal amplification effect of the DNA walker strategy, and the photocurrent-polarity-switching ability of hemin. Therefore, it demonstrated satisfying photocurrent responses to the target TOB within the working range of 20 nM-1.0 μM at a low detection limit of 5.43 nM. The PEC platform exhibited good stability, reproducibility, sufficient sensitivity and high selectivity for complex experimental samples. Moreover, the photocurrent-polarity-switching PEC biosensor improved the anti-interference ability and avoided false positives or negatives.

In-situ growth of hydrogen-bonded organic framework on conductive PEDOT:PSS polymer to realize conductivity-enhanced electrochemiluminescence for fabricating ultrasensitive biosensor

Hydrogen-bonded organic frameworks (HOFs) have gradually received research interest in the electrochemiluminescence (ECL) realm for their high porosity, large surface area, low toxicity, and remarkable biocompatibility, whereas the poor electrical conductivity of HOFs limits electrochemical excitation of ECL luminophores to cause low utilization ratio of ECL luminophores. To circumvent the problem, we prepared a conductive HOF composite (H3TATB-HOF/PEDOT:PSS) by in-situ growth of H3TATB-HOF (H3TATB = 2,4,6-tris(4-carboxyphenyl)− 1,3,5-triazine) on highly conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) polymer. Satisfactorily, the ECL intensity of H3TATB-HOF/PEDOT:PSS presented a respective 14.94-time, 4.71-time, and 2.82-time improvement than those of H3TATB monomers, H3TATB aggregates, and H3TATB-HOF, which was mainly attributed to the high-conductivity PEDOT:PSS that facilitated charge transport throughout the H3TATB-HOF/PEDOT:PSS framework, enabling more H3TATB to be excited electrochemically. Considering the H3TATB-HOF/PEDOT:PSS featuring superior ECL properties, an ultrasensitive ECL biosensor for microRNA-21 assay was designed by combining H3TATB-HOF/PEDOT:PSS as an ECL beacon with a 3D DNA walker amplification strategy, exhibiting broad linear range (100 aM to 1 nM) with a low detection limit (45.7 aM). Overall, this work demonstrates that the ECL performance of HOF-based ECL materials can be significantly improved by enhancing electrical conductivity, thus providing a new idea to explore high-efficiency ECL emitters for building high-sensitivity ECL biosensors.

A novel fluorescent sensor based on aptamer recognition and DNA walker amplification strategy and its determination of 17β-estradiol

17β-Estradiol (E2) is a common environmental endocrine and excessive estrogen will disturb the endocrine balance of human body and lead to diseases because of its accumulation in human body. The main aim of this study is to determine the trace amount of E2 in various foods. Based on aptamer specific recognition, DNA walker molecular machine and Exonuclease III-assisted dual cycle signal amplification technology, a fluorescent aptamer sensor was constructed and applied to the detection of 17β-estradiol. Atomic force microscopy (AFM) and polyacrylamide gel electrophoresis (PAGE) were used to verify the feasibility of DNA walker participating in the reaction. Under the optimal conditions, 17β-estradiol concentration showed a good linear relationship with fluorescence in the range of 5.0 × 10−10–1.8 × 10−8 M, and the detection limit was 5.6 × 10−11 M. The fluorescent aptamer sensor established in this study has good selectivity, simple operation and good specificity, and the results of its application in the determination of milk samples are satisfactory. Research findings revealed that the E2 concentration in water and milk is less than the safe limits, indicating the foods in the market are safe and can be consumed. Though the foods are safe in present content, the health risk still exists because of continuous intake of trace E2.

Electrochemical Biosensors Containing Fe-Metal Organic Framework Doped Polyaniline Nanocomposites for Sensitive Detection of miR-574-5P Based on DNA Walker Amplification

Electrochemical Biosensors Containing Fe-Metal Organic Framework Doped Polyaniline Nanocomposites for Sensitive Detection of miR-574-5P Based on DNA Walker Amplification

Zr4+-mediated DNAzyme-driven DNA walker amplification strategy for electrochemical assay of protein kinase a activity and inhibition

Protein kinase A (PKA) can regulate many cellular biological processes by phosphorylation substrate peptide or protein. Sensitive detection of PKA activity is critical for the PKA-related drug discovery and disease diagnosis. A new electrochemical biosensing method was developed for detection of PKA activity based on Zr4+-mediated DNAzyme-driven DNA walker signal amplification strategy. In this strategy, the special designed substrate peptide and a thiolated methylene blue-labeled hairpin DNA (MB-hpDNA) containing a single ribonucleic acid group (rA) could be anchored on the surface of gold electrode by Au–S bond. In the presence of adenosine triphosphate (ATP) and PKA, substrate peptide was phosphorylated and linked with walker DNA (WD) via the robust phosphate-Zr4+-phosphate chemistry. The linked WD hybridized with the loop region of MB-hpDNA to form a Mn2+-dependent deoxynuclease (DNAzyme), which cleaved the MB-hpDNA into MB-labeled fragment releasing away from electrode surface, resulting in a dramatic decrease of electrochemical signal and providing an electrochemical sensing platform for PKA activity detection. The response signal of the developed biosensor is proportional to the logarithm of PKA concentration in the range of 0.05 U mL−1 to 100 U mL−1, with a detection limit of 0.017 U mL−1 at a signal to noise ratio of 3. Furthermore, the proposed method can also be applied for the evaluation of PKA inhibition and PKA activity assay in cell samples. Therefore, the proposed biosensor shows great promise as a universal tool for diagnostics and drug discovery of PKA-related diseases.

Electrochemical biomimetic enzyme cascade amplification combined with target-induced DNA walker for detection of thrombin

Fe-N-doped carbon nanomaterials (Fe-N/CMs) were designed as a novel biomimetic enzyme with excellent peroxidase-like activity to achieve high-efficient enzyme cascade catalytic amplification with the aid of glucose oxidase (GOx), which was further combined with target-induced DNA walker amplification to develop a sensitive electrochemical biosensor for thrombin detection. Impressively, massive output DNA was transformed from small amounts of target thrombin by highly effective DNA walker amplification as protein-converting strategy, which could then induce the immobilization of functionalized nanozyme on the electrode surface to achieve the high-efficient electrochemical biomimetic enzyme cascade amplification. As a result, an amplified enzyme cascade catalytic signal was measured for thrombin detection ranging from 0.01pM to 1nM with a low detection limit of 3 fM. Importantly, the new biomimetic enzyme cascade reaction coupled the advantages of natural enzyme and nanozyme, which paved an avenue to construct varied artificial multienzymes amplification systems for biosensing, bioanalysis, and disease diagnosis applications.

A microfluidic chip-based multivalent DNA walker amplification biosensor for the simultaneous detection of multiple food-borne pathogens.

The rapid, simultaneous, sensitive detection of the targets has important application prospects for disease diagnosis and biomedical studies. However, in practical applications, the content of the targets is usually very low, and signal amplification strategies are often needed to improve the detection sensitivity. DNAzyme-driven DNA walkers are an excellent signal amplification strategy due to their outstanding specificity and sensitivity. Food-borne pathogens have always been a foremost threat to human health, and it is an urgent demand to develop a simple, rapid, sensitive, and portable detection method for food-borne pathogens. In addition, there are various species of pathogens, and it is difficult to simultaneously detect multiple pathogens by a single DNA walker. For this reason, a substrate strand with three rA cleavage sites was cleverly designed, and a multivalent DNA walker sensor combined with the microfluidic chip technology was proposed for the simultaneous, rapid, sensitive analysis of Vibrio parahaemolyticus, Salmonella typhimurium, and Staphylococcus aureus. The developed sensor could be used to detect pathogens simultaneously and efficiently with low detection limits and wide detection ranges. Moreover, the combination of gold stirring rod enrichment and DNA walker achieved double amplification, which greatly improved the detection sensitivity. More importantly, by changing the design of the substrate chain, the sensor was expected to be used to detect other targets, thus broadening the scope of practical applications. Therefore, the sensor can build novel detection tool platforms in the field of biosensing.

Copper nanocluster-Ru(dcbpy)32+ as a cathodic ECL-RET probe combined with 3D bipedal DNA walker amplification for bioanalysis.

In this study, a cathodic intra-molecular electrochemiluminescence resonance energy transfer (ECL-RET) probe was exquisitely designed via the integration of an ECL donor (Cu NCs) with an acceptor (Ru(dcbpy)32+), and further employed the 3D bipedal DNA walker amplification strategy to monitor the platelet-derived growth factor BB (PDGF-BB). Specifically, blue emission Cu NCs with low consumption, biocompatibility and numerous resources, act as well-overlapped donors and significantly improve the ECL efficiency of Ru(dcbpy)32+. More impressively, the intra-molecular ECL-RET of Cu NC-Ru endowed a better and more stable ECL signal by reducing the electron-transfer distance and decreasing the energy loss. Furthermore, 3D bipedal DNA walker amplification was employed to efficiently convert the target PDGF-BB into numerous DNA strands, achieving sensitive target amplification. By virtue of such design, the constructed aptasensor exhibited a sensitive and selective assay for PDGF-BB with a detection range from 0.01 pM to 10 nM and a detection limit of 3.3 fM. The intramolecular ECL-RET and 3D bipedal DNA walker amplification strategy designed in this study will provide valuable insight into promising ultrasensitive ECL bioanalysis.

Pt@Tetraphenyl-1,3-butadiene Nanocrystals with Coreaction Acceleration and Crystallization-Induced Enhanced Electrochemiluminescence for Ultrasensitive MicroRNA Detection.

Herein, Pt@tetraphenyl-1,3-butadiene nanocrystals (Pt@TPB NCs) with high electrochemiluminescence (ECL) efficiencies as ECL emitters were developed to construct an ultrasensitive biosensing platform for the detection of microRNA-21 (miRNA-21). Interestingly, Pt@TPB NCs not only exhibited high carrier densities and electron mobilities to achieve efficient electron-hole pair recombinations for high ECL emission but also served as coreaction accelerators of endogenous coreactant-dissolved O2 with good electrocatalytic activities to produce abundant reactive oxygen species (ROS) for facilitating the interactions between TPB NCs and ROS, which further obtain intense ECL emission. Impressively, Pt@TPB NCs with dissolved O2 as coreactants displayed high ECL efficiencies (ΦECL) of 7.83, taking the ΦECL of Ru(bpy)32+/dissolved O2 ECL system as 1. Herein, Pt@TPB NCs with strong ECL signals were used as ECL emitters to combine target-induced DNA walker amplification with high conversion efficiency for the construction of an ultrasensitive ECL biosening platform which accomplished microRNA-21 detection with a low detection limit of 83.8 aM. Therefore, the developed synergy effects in Pt@TPB NCs are expected to guide the progress of highly efficient ECL emitters for sensing analysis and disease diagnosis.

Metal-Organic Framework UiO-66-Mediated Dual-Signal Ratiometric Electrochemical Sensor for microRNA Detection with DNA Walker Amplification.

Electrochemical nanotags with strong signal input are necessary for a ratiometric electrochemical sensor to overcome the drawbacks of inaccurate detection results. In this paper, the metal-organic framework (MOF) UiO-66 was utilized as an electrochemical signal tag. A stable and strong current response at +0.9 V can be detected in neutral conditions. MicroRNA (miRNA) was employed as the model analyte. Herein, an enzyme-free DNA-walker-based ultrasensitive ratiometric electrochemical biosensor in combination with Zr MOF (UiO-66) signal tags to detect miRNA was demonstrated. In the presence of miRNA, the autonomous walker movement can be initiated by miRNA, leading to the release of biotin-modified fragments. Thus, streptavidin-labeled UiO-66 nanomaterials were not bound to the electrode, generating a low signal response of UiO-66 at +0.9 V. However, the current signal of electrolyte solution as reference at +0.2 V was increased due to the enhancement of electrode conductivity. This ratiometic sensor demonstrated high sensitivity, selectivity, and reproducibility. It can eliminate the disturbance of environmental factors and basic electrode characteristics, providing more accurate signals. A limit of detection (LOD) of 0.17 fM was achieved. Moreover, the method was also used to detect miRNA-21 spiked in real serum samples.

Electrochemical aptasensor based on Ce3NbO7/CeO2@Au hollow nanospheres by using Nb.BbvCI-triggered and bipedal DNA walker amplification strategy for zearalenone detection

Herein, an electrochemical aptasensor combining Nb.BbvCI-triggered bipedal DNA walking strategy was constructed for ultrasensitive assay of zearalenone (ZEN). The aptasensor used Ce3NbO7/CeO2 @Au hollow nanospheres as electrode modification material and PdNi@MnO2/MB as the signal label. Importantly, the Ce3NbO7/CeO2 synthesized by hydrothermal method were combined with Au nanoparticles and applied to the electrode surface. The as-prepared Ce3NbO7/CeO2 @Au possessed a large surface area, excellent electrical conductivity, stability and more binding sites. PdNi@MnO2 with high specific surface area and porosity combined with molecule methylene blue (MB) was introduced into electrodes as the signal label. The proposed aptasensor utilized the advantages of specific recognition of aptamers and target molecules to release bipedal DNA walker (w-DNA), and then the w-DNA was triggered by Nb.BbvCI and entered the cycle to release more signal probes. The feasibility of this strategy was recorded by the differential pulse voltammetry (DPV) method. Under the optimized conditions, the electrochemical aptasensor exhibited a wide linear dynamic range from 1 × 10−4 to 1 × 103 ng mL−1 with a low detection limit of 4.57 × 10–6 ng mL−1. Moreover, the aptasensor had high selectivity, good stability, excellent repeatability and provided an effective method for the trace detection of ZEN in real samples.

Photoelectrochemical platform with tailorable anode-cathode activities based on semiconductors coupling DNA walker for detection of miRNA

Herein, an anode-cathode cooperative paper photoelectrochemical (PEC) platform was fabricated by the mutual attraction mechanism of different conductive semiconductors to realize the ultrasensitive monitoring of miRNA-155. Concretely, n-type ZnCdS nanorods and p-type BiOI hollow microspheres were sensitized simultaneously by CdS quantum dots (QDs) to amplify the initial signals of photoanode and photocathode, respectively. After the anode and cathode were integrated through the paper chip device, the bipolar synergy realized the secondary promotion of photocurrent signal. With the participation of target miRNA-155 and T7 Exo, DNA walker amplification was triggered to promote CdS QDs away from the electrode surface to destroy the matched energy level structure, leading to obvious signal attenuation. Excitedly, the quenching effect of photocurrent signal was twofold due to the fact that both photoelectrodes were equipped with sensing and identification steps. On the basis of the multifold amplification mechanisms, the designed platform exhibited excellent sensitivity, while the electrode zoning and cathode detection improved its selectivity. As far as I know, there is no research of using two photoelectrodes for simultaneous sensing construct to accomplish cascade amplification and quenching of signals, so it provides a novel reference for the fabrication of PEC analysis device.

Versatile electrochemiluminescence sensor for dual-potential “off” and “on” detection of double targets based on a novel terbium organic gel and multifunctional DNA network probes

In this work, a multifunctional signal probe with DNA network-loaded Ru(phen)32+ and Ag nanocluster (NCs) was assembled, and combined with a novel terbium organic gel to design a versatile electrochemiluminescence (ECL) biosensor for dual-potential “on” “off” assays of Cd2+ and Mg2+. Firstly, target Cd2+-driven DNA walker-amplification process produced a large amount of output DNA, which was used to link the multifunctional DNA network (DNA Net) structure probes with both Ru(phen)32+ and C-rich base to the terbium organic gel (TOG)-modified electrode. Thus the positive potential ECL signal of Ru(phen)32+ was generated, and the negative-potential ECL signal of TOG was quenched by Ag NCs via resonance energy transfer and co-reactant-competition simultaneously, achieving dual signal “on” and “off” assay of Cd2+. Furthermore, the present Mg2+ (second-target) specifically sheared the substrate of DNA enzyme on the electrode, releasing the DNA Net probes with Ru(phen)32+ and Ag NCs to realize “off” and “on” detection of Mg2+ by dual-potential signals. This strategy developed a new versatile biosensor by using dual-potential ECL probes and novel DNA network structure, and opened up a new way for multi-target detection by dual “on” “off” signals, which shows great potential in practical detection. The multifunctional sensing platform was also applied to Cd2+ assay in rice.

A stochastic DNA walker electrochemiluminescence biosensor based on quenching effect of Pt@CuS on luminol@Au/Ni-Co nanocages for ultrasensitive detection of I27L gene

The common I27L mutations of the hepatocyte nuclear factor-1α (HNF1A) significantly increase the incidence of maturity-onset diabetes of the young (MODY). Hence, the establishment of an ultrasensitive detection strategy for I27L gene is crucial for the diagnosis and treatment of MODY. Herein, a signal-off electrochemiluminescence resonance energy transfer (ECL-RET) biosensor with effective target-induced stochastic DNA walker amplification was fabricated for I27L detection. In this biosensor, Prussian blue analogues (Ni-Co) nanocages/Au-supported luminol (luminol@Au/Ni-Co) were used as ECL donors and exhibited excellent luminous efficiency. On the other hand, Pt nanoparticles-grown on copper sulphide (Pt@CuS) were used as energy acceptors to quench the initial signal based on RET between luminol and CuS. Moreover, the autonomous locomotion of I27L assisted by Exo III is the key in this DNA walker biosensor, as it continually induces new digestion processes on the electrode surface and quenches signals caused by the introduction of numerous acceptors. The efficient donor/acceptor pairs and DNA walker amplification system of the ECL-RET allowed the proposed biosensor to effectively detect I27L with a wide linear range of 0.0001 to 100 nM and a limit of detection as low as 23 fM. Thus, the ECL-RET biosensor provides a promising sensing platform for the diagnosis and typing of diabetes.

Rapid 16S rDNA electrochemical sensor for detection of bacteria based on the integration of target-triggered hairpin self-assembly and tripedal DNA walker amplification

Diseases caused by bacteria pose great challenges to human health. The key to reduce disease transmission and mortality is to develop accurate and rapid methods for the detection and identification of bacteria. Herein, a rapid bacteria 16S rDNA electrochemical sensor based on target-triggered hairpin self-assembly and tripedal DNA walker (TD walker) amplification strategy was constructed. Specific variable region of 16S rDNA fragment of bacteria was used as biomarker. The target-triggered hairpin self-assembly strategy was used to prepare a TD walker. The hairpin DNA probes labeled with ferrocene (Fc) were designed and modified on surface of electrode. The “legs” of TD walker hybridized with three hairpin probes and opened their hairpin structures. Exo III enzyme recognised hybrid duplexes and selectively digest hairpin probes. The “legs” of TD walker was released and hybridized with the other three hairpin probes. In this way, the enzyme drived the walkers to walk along electrode interface, until hairpin DNA probes were all removed from the electrode, the Fc was far away from electrode interface. A significantly current reduction signal was obtained and bacteria were detected by recording this response. This strategy was low-cost and scalable, it could continuously recycle low-concentration targets, thus enhanced the detection sensitivity. As the proof-of-concept work, the electrochemical sensor was utilized as detector. The limit of detection (LOD) of detecting Staphylococcus aureus (S. aureus) was 20 CFU mL−1 and detection time was less than 3 h. It was expected to be widely used in clinical early diagnosis.

Rational engineering the DNA tetrahedrons of dual wavelength ratiometric electrochemiluminescence biosensor for high efficient detection of SARS-CoV-2 RdRp gene by using entropy-driven and bipedal DNA walker amplification strategy

Fast and effective detection of epidemics is the key to preventing the spread of diseases. In this work, we constructed a dual-wavelength ratiometric electrochemiluminescence (ECL) biosensor based on entropy-driven and bipedal DNA walker cycle amplification strategies for detection of the RNA-dependent RNA polymerase (RdRp) gene of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The entropy-driven cyclic amplification reaction was started by the SARS-CoV-2 RdRp gene to generate a bandage. The bandage could combine with two other single-stranded S1 and S2 to form a bipedal DNA walker to create the following cycle reaction. After the bipedal DNA walker completed the walking process, the hairpin structures at the top of the DNA tetrahedrons (TDNAs) were removed. Subsequently, the PEI-Ru@Ti3C2@AuNPs-S7 probes were used to combine with the excised hairpin part of TDNAs on the surface of Au-g-C3N4, and the signal change was realized employing electrochemiluminescence resonance energy transfer (ECL-RET). By combining entropy-driven and DNA walker cycle amplification strategy, the ratiometric ECL biosensor exhibited a limit of detection (LOD) as low as 7.8 aM for the SARS-CoV-2 RdRp gene. As a result, detecting the SARS-CoV-2 RdRp gene in human serum still possessed high recovery so that the dual-wavelength ratiometer biosensor could be used in early clinical diagnosis.

Cathode-Anode Spatial Division Photoelectrochemical Platform Based on a One-Step DNA Walker for Monitoring of miRNA-21.

Photoelectrochemical (PEC) biosensors carried out the whole reaction process in the same solution, which would limit the sensitivity and selectivity of detection in the sensing system. Herein, we reported a promising new cathode-anode spatial division PEC platform based on the two-electrode synergistic enhancement strategy. With the photoanode and photocathode integrated in the same current circuit, the platform exhibited an increased photocurrent response, as well as an improved anti-interference ability led by separating the two electrodes spatially. In this proposal, red light-driven AgInS2 nanoparticles (NPs) served as the photoanode to build biometric steps and amplify the signal, whereas p-type PbS quantum dots were selected as the photocathode to increase the signal. With the participation of alkaline phosphatase (ALP) labeled on Au NPs-DNA, ascorbic acid 2-phosphate was catalyzed to produce ascorbic acid as an electron donor, resulting in the enhancement of the PEC signal. Interestingly, in the presence of miRNA-21 and T7 Exo, the one-step DNA walker amplification can be triggered to reduce the PEC signal by releasing ALP-Au NP-DNA. The constructed PEC biosensor exhibited a detection limit of as low as 3.4 fM for miRNA-21, which was expected to be applied to early clinical diagnosis. Also, we believe that the proposed cathode-anode spatial division PEC platform can open up a new view for the establishment of other types of PEC biosensors.

Versatile photoelectrochemical and electrochemiluminescence biosensor based on 3D CdSe QDs-DNA nanonetwork-SnO2 nanoflower coupled with DNA walker amplification for HIV detection

A novel 3D CdSe quantum dots (QDs)-DNA nanonetwork was assembled to sensitize the mesoporous SnO2 photoelectrochemical (PEC) substrate, which was coupled with a biped-DNA walker multiple amplification technique to design a versatile electrochemiluminescence (ECL) and PEC biosensor for dual detection of HIV. Firstly, the photosensitive CdSe QDs and SnO2 nanoflowers have well-matched band-edge energy level, thus their complex can promote effective transfer of the photogenerated carriers, and show better PEC and ECL property. Then, a novel 3D CdSe QDs-DNA nanonetwork was assembled and loaded with a large amount of QDs, which was used as multifunctional PEC and ECL probes. Moreover, the target-triggered biped DNA walker-cascade amplification method was introduced to generate a large amount of output DNA, which was used to link numerous 3D CdSe QDs-DNA nanonetwork probes to the electrode, generating greatly amplified signals for sensitive assay of HIV. The highly photosensitive 3D CdSe QDs-DNA reticulated nanomaterials have high stability and controllability, and display significantly improved PEC and ECL signals of the biosensor. This method opened a new photoelectric nanocomposite of QDs-sensitized SnO2 nanoflower, and developed a versatile biosensing strategy using the 3D CdSe QDS DNA sensitization probes for ultra-sensitive detection of biomolecules, which is important for the early diagnosis of diseases.

A SERS biosensor constructed by calcined ZnO substrate with high-efficiency charge transfer for sensitive detection of Pb2+

Herein, calcined ZnO submicron flowers (ZnO SFs) with excellent surface enhanced Raman scattering (SERS) activity were employed as substrate to fabricate a novel SERS biosensor for sensitive detection of Pb2+, which improved SERS effect of ZnO submicron particles (ZnO SPs). Compared with ZnO SPs, calcined ZnO SFs substrate possessed narrow energy band to enhance the efficiency of charge transfer owing to easily generate exciton transition to achieve eminent Raman enhancement effect. Furthermore, free-legged DNA walker amplification strategy was utilized to convert trace amounts of Pb2+ into vast trigger DNAs for construction an ultrasensitive biosensor, which exhibited a liner relationship ranged from 10 pM to 100 μM with a low detection limit of 3.55 pM. Therefore, this work not only provided a novel approach for detection of heavy metal ions, but also broadened the application of semiconductor SERS substrate.