Helical au nanostructure for SERS detection of hazardous molecular and chiral enantiomers.

In recent years, incidents of pesticide pollution and abuse of feed additives have occurred frequently, which pose a great threat to human health. Raman spectroscopy has become an important method in the field of food safety due to its rapidity, simplicity and sensitivity. It is important to obtain complex structure to promote surface-enhanced Raman scattering (SERS) effect. In this study, gold helical nanoparticles with rich surface structure were synthesized using cysteine as induce agent. Notably, the complex helical structure and tip led to an excellent electromagnetic enhancement property. The helical structure showed ultra-sensitive detection of hazardous molecular, such as thiram and ractopamine. Interestingly, the D/L-Au structure had significant chiral optical activity and could be used as an unlabeled SERS platform for enantiomer identification. This study provided an effective strategy for the detection of pesticides and feed additives, which could be applied in other aspects of food safety in the future.

A close-looped DNAzyme walker with an available catalytic domain for electrochemiluminescent detection of acetamiprid.

Traditional DNA walkers face enormous challenges due to limited biostability and reaction kinetics. Herein, we designed a self-driven close-looped DNAzyme walker (cl-DW) with high structural biostability and catalytic activity that enabled rapid electrochemiluminescence (ECL) detection of pesticide residue acetamiprid. Specifically, cl-DW exhibited increasing ability to resist nuclease degradation with a 570-fold longer half-degradation time than that of the single-stranded DNAzyme walker (ss-DW) due to the protected DNA terminal. Furthermore, cl-DW achieved high catalytic activity with a 4.3-fold faster reaction kinetic than that of ss-DW due to the circularized nanostructure of an available catalytic domain. Consequently, we utilized cl-DW as a signal amplifier and tin-based sulfide (SnS2) nanoflowers as ECL emitters to construct an ECL aptasensor, which realized the sensitive detection of acetamiprid with a limit of detection of 0.85 nM. This work provides a reliable approach to exploring DNA walkers with high catalytic activity and better biostability for molecular monitoring.

Pyrenetetrasulfonate-grafted 2D ultrathin metal-organic layer as new electrochemiluminescence emitters for ultrasensitive microRNA-21 assay.

The exploration of novel electrochemiluminescence (ECL) luminophores with excellent ECL properties is a current research hotspot in the ECL field. Herein, a novel high-efficiency Ru-complex-free ECL emitter PyTS-Zr-BTB-MOL has been prepared by using porous ultrathin Zr-BTB metal-organic layer (MOL) as carrier to coordinatively graft the cheap and easily available polycyclic aromatic hydrocarbon (PAH) derivative luminophore PyTS whose ECL performance has never been investigated. Gratifyingly, the ECL intensity and efficiency of PyTS-Zr-BTB-MOL were markedly enhanced compared to both PyTS monomers and PyTS aggregates. The main reason was that the distance between pyrene rings was greatly expanded after the PyTS grafting on the Zr6 clusters of Zr-BTB-MOL, which overcame the aggregation-caused quenching (ACQ) effect of PyTS and thus enhanced the ECL emission. Meanwhile, the porous nanosheet structure of PyTS-Zr-BTB-MOL could distinctly increase the exposure of PyTS luminophores and shorten the diffusion paths of coreactants and electrons/ions, which effectively promoted the electrochemical excitation of more PyTS luminophores and thus achieved a further ECL enhancement. In light of the remarkable ECL property of PyTS-Zr-BTB-MOL, it was employed as an ECL indicator to build a novel high-sensitivity ECL biosensor for microRNA-21 determination, possessing a satisfactory response range (100 aM to 100 pM) and an ultralow detection limit (10.4 aM). Overall, this work demonstrated that using MOLs to coordinatively graft the PAH derivative luminophores to eliminate the ACQ effect and increase the utilization rate of the luminophores is a promising and efficient strategy to develop high-performance Ru-complex-free ECL materials for assembling ultrasensitive ECL biosensing platforms.

Nanoconfined Silver Nanoclusters Combined with X-Shaped DNA Recognizer-Triggered Cascade Amplification for Electrochemiluminescence Detection of APE1.

Apurinic/apyrimidinic endonuclease 1 (APE1), as a vital base excision repair enzyme, is essential for maintaining genomic integrity and stability, and its abnormal expression is closely associated with malignant tumors. Herein, we constructed an electrochemiluminescence (ECL) biosensor for detecting APE1 activity by combining nanoconfined ECL silver nanoclusters (Ag NCs) with X-shaped DNA recognizer-triggered cascade amplification. Specifically, the Ag NCs were prepared and confined in the glutaraldehyde-cross-linked chitosan hydrogel network using the one-pot method, resulting in a strong ECL response and exceptional stability in comparison with discrete Ag NCs. Furthermore, the self-assembled X-shaped DNA recognizers were designed for APE1 detection, which not only improved reaction kinetics due to the ordered arrangement of recognition sites but also achieved high sensitivity by utilizing the recognizer-triggered cascade amplification of strand displacement amplification (SDA) and DNAzyme catalysis. As expected, this biosensor achieved sensitive ECL detection of APE1 in the range of 1.0 × 10-3 U·µL-1 to 1.0 × 10-10 U·µL-1 with the detection limit of 2.21 × 10-11 U·µL-1, rendering it a desirable approach for biomarker detection.

Highly Specific Aptamer-Antibody Birecognized Sandwich Module for Ultrasensitive Detection of a Low Molecular Weight Compound.

Herein, the aptamer-antibody sandwich module was first introduced to accurately recognize a low molecular weight compound (mycotoxin). Impressively, compared with the large steric hindrance of a traditional dual-antibody module, the aptamer-antibody sandwich with low Gibbs free energy and a low dissociation constant has high recognition efficiency; thus, it could reduce false positives and false negatives caused by a dual-antibody module. As a proof of concept, a sensitive electrochemiluminescence (ECL) biosensor was constructed for detecting mycotoxin zearalenone (ZEN) based on an aptamer-antibody sandwich as a biological recognition element and porous ZnO nanosheets (Zn NSs) supported Cu nanoclusters (Cu NCs) as the signal transduction element, in which the antibody was modified on the vertex of a tetrahedral DNA nanostructure (TDN) with a rigid structure to increase the kinetics of target recognition for promoting the detection sensitivity. Moreover, the Cu NCs/Zn NSs exhibited an excellent ECL response that was attributed to the aggregation-induced ECL enhancement through electrostatic interactions. The sensing platform achieved trace detection of ZEN with a low detection limit of 0.31 fg/mL, far beyond that of the enzyme-linked immunosorbent assay (ELISA, the current rapid detection method) and high-performance liquid chromatography (HPLC, the national standard detection method). The strategy has great application potential in food analysis, environmental monitoring, and clinical diagnosis.

Electrochemiluminescence of Ultrasmall Silica Nanoparticles from Size Modulation and Multipath Surface State Adjustment for Ultrasensitive HIV-DNA Fragment Detection.

Here, ultrasmall SiO2 nanoparticles (u-SiO2 NPs, <5 nm) with obvious electrochemiluminescence (ECL) phenomenon, which was absent for conventional silica nanoparticles (c-SiO2 NPs), were reported. In a finite ultrasmall volume, the u-SiO2 NPs exhibited increasing ground state energy and higher optical absorption strength due to the electron-hole confinement model and favored catalyzing the reaction through the rapid diffusion of bulk charge, resulting in apparent ECL emission. Then, Zn2+-induced u-SiO2 nanoaggregates (Zn/u-SiO2-Ov nAGG) were synthesized and exhibited improved ECL performance via multipath surface state adjustment of u-SiO2 from several aspects, including aggregation-induced ECL, the generation of oxygen vacancy (Ov), and more positive surface charge. In addition, an ECL biosensor was constructed for ultrasensitive human immunodeficiency virus-related deoxyribonucleic acid detection from 100 aM to 1 nM with a low limit of 50.48 aM, combining the ECL luminescence of Zn/u-SiO2-Ov nAGG with three-dimensional DNA nanomachine-mediated multioutput amplification for enhanced accuracy and sensitivity compared to the single-output method. Therefore, exploring the ECL of ultrasmall nanoparticles via the adjustment of size and surface state provided a valuable indication to a wider investigation and application of novel ECL materials for clinical diagnostic.

New quasi-Co/Cu-MOF nanozyme coupled with entropy-driven DNA amplification cascades for highly sensitive electrochemical aptamer growth differentiation factor 15 assay.

BACKGROUND: The monitoring of concentration variation of the newly developed growth differentiation factor 15 (GDF15) biomarker in human serum is of great significance for diagnosing cardiovascular diseases. Current methods for the detection of the GDF15 protein mainly are based on antibody-assisted immunoassays, which encounter the limitations in terms of sensitivity, complexity and costs. The development of simple and sensitive biosensors for GDF15 can therefore facilitate the diagnosis of cardiovascular diseases. RESULTS: A new bimetallic quasi-Cu/Co-MOF nanozyme with high catalytic performance for electrochemical reduction of H2O2 is synthesized via simple one-step precipitation and low-temperature calcination method. Such nanozymes are further employed as amplification tags and coupled with cyclic entropy-driven DNA signal enhancement strategies to construct ultrasensitive aptamer-based biosensor for detecting GDF15 in human serums. GDF15 molecules associate with two aptamers and release the ssDNA trigger sequences via target-binding induced displacement reaction. These ssDNAs subsequently initiate cyclic DNA-fueled strand displacement and catalytic hairpin assembly (CHA) reaction cascades for confining many quasi-Cu/Co-MOF nanozymes on sensor electrode, which yield drastically amplified H2O2 reduction current for detecting GDF15 down to 0.12 pg mL-1 with a dynamic range of 0.5 pg mL-1 to 20 ng mL-1. The electrochemical aptasensor also presents good reproducibility and selectivity and exhibits the capability to detect GDF15 in diluent serums. SIGNIFICANCE: Our aptamer-based GDF15 protein electrochemical assay clearly outperforms current existing antibody-based methods and the quasi-Cu/Co-MOF nanozyme/entropy-driven cascaded signal amplification means can be used as a universal strategy for sensitive monitoring of different biomolecular markers for diverse applications.

Ultrahigh-Speed 3D DNA Walker with Dual Self-Protected DNAzymes for Ultrasensitive Fluorescence Detection and Intracellular Imaging of microRNA.

Herein, a dual self-protected DNAzyme-based 3D DNA walker (dSPD walker), composed of activated dual self-protected walking particles (ac-dSPWPs) and track particles (TPs), was constructed for ultrasensitive and ultrahigh-speed fluorescence detection and imaging of microRNAs (miRNAs) in living cells. Impressively, compared with the defect that "one" target miRNA only initiates "one" walking arm of the conventional single self-protected DNAzyme walker, the dSPD walker benefits from the secondary amplification and spatial confinement effect and could guide "one" target miRNA to generate "n" secondary targets, thereby initiating "n" nearby walking strands immediately, realizing the initial rate over one-magnitude-order faster than that of the conventional one. Moreover, in the process of relative motion between ac-dSPWPs and TPs, the ac-dSPWPs could cleave multiple substrate strands simultaneously to speed up movement and reduce the derailment rate, as well as combine with successive TPs to facilitate a large amount of continuous signal accumulation, achieving an ultrafast detection of miRNA-221 within 10 min in vitro and high sensitivity with a low detection limit of 0.84 pM. In addition, the DNA nanospheres obtained by the rolling circle amplification reaction can capture the Cy5 fluorescence dispersed in liquids, which achieves the high-contrast imaging of miRNA-221, resulting in further ultrasensitive imaging of miRNA-221 in cancer cells. The proposed strategy has made a bold innovation in the rapid and sensitive detection as well as intracellular imaging of low-abundance biomarkers, offering promising application in early diagnosis and relevant research of cancer and tumors.

Dual-Ligand Europium-Organic Gels as a Highly Efficient Anodic Annihilation Electrochemiluminescence Emitter for Ultrasensitive Detection of MicroRNA.

In this study, a novel europium dual-ligand metal-organic gel (Eu-D-MOGs) with high-efficient anodic annihilation electrochemiluminescence (ECL) was synthesized as an ECL emitter to construct a biosensor for ultrasensitive detection of microRNA-221 (miR-221). Impressively, compared to the ECL signal of europium single-ligand metal-organic gels (Eu-S-MOGs), the ECL signal of Eu-D-MOGs was significantly improved since the two organic ligands could jointly replace the H2O and coordinate with Eu3+, which could remarkably reduce the nonradiative vibrational energy transfer caused by the coordination between H2O and Eu3+ with a high coordination demand. In addition, Eu-D-MOGs could be electrochemically oxidized to Eu-D-MOGs•+ at 1.45 V and reduced to Eu-D-MOGs•- at 0.65 V to achieve effective annihilation of ECL, which overcame the side reaction brought by the remaining emitters at negative potential. This benefited from the annihilation ECL performance of the central ion Eu3+ caused by its redox in the electrochemical process. Furthermore, the annihilation ECL signal of Eu3+ could be improved by sensitizing Eu3+ via the antenna effect. In addition, combined with the improved rolling circle amplification-assisted strand displacement amplification strategy (RCA-SDA), a sensitive biosensor was constructed for the sensitive detection of miR-221 with a low detection limit of 5.12 aM and could be successfully applied for the detection of miR-221 in the lysate of cancer cells. This strategy offered a unique approach to synthesizing metal-organic gels as ECL emitters without a coreactant for the construction of ECL biosensing platforms in biomarker detection and disease diagnosis.

Dual-sensitized heterojunction Ag2S/ZnS/NiS composites with entire visible-light region absorption for ultrasensitive photoelectrochemical detection of tobramycin.

In this study, an ultrasensitive photoelectrochemical (PEC) aptasensor based on dual-sensitized heterojunction Ag2S/ZnS/NiS composites as a signal probe was proposed for the detection of tobramycin (TOB) by combining a cascaded quadratic signal amplification strategy. Specifically, compared to the limited visible light-harvesting capability of single sensitized composites, Ag2S/ZnS/NiS composites with p-n and n-n heterojunction could greatly improve the light energy utilization to tremendously strengthen the optical absorption in the entire visible-light region. Moreover, dual-sensitized heterojunction could effectively hinder the rapid recombination of photoelectrons and holes (carriers) to obtain a good photocurrent for improving the sensitivity of the aptasensor. Furthermore, a cascaded quadratic signal amplification strategy was applied to convert trace target TOB into plentiful gold nanoclusters (Au NCs) labelled double-stranded DNA for the construction of PEC aptasensor, with a broad linear detection range from 0.01 to 100 ng mL-1 and a low detection limit of 3.38 pg mL-1. Importantly, this study provided a versatile and sensitive PEC biosensing platform for TOB analysis, and demonstrated its successful application for TOB detection in milk samples. This protocol provides a novel dual-sensitized heterojunction composites to develop a highly efficient and harmfulless PEC aptasensor, which is expected to be used in food safety, environmental monitoring and other areas.

Highly catalytic sulfur-doped and bimetal-coordinated CoFe(CN)5NO nanoparticles coupled with PER/HCR amplification cascades for sensitive electrochemical aptamer luteinizing hormone assay.

Sensitive monitoring of luteinizing hormone (LH), a glycoprotein that regulates the synthesis of regulatory steroid hormones, can facilitate the diagnosis of various reproductive diseases. In this work, a new and highly catalytic Sulfur-doped and bimetal-coordinated CoFe(CN)5NO (denoted as S-CoFe(CN)5NO) nanoparticles are synthesized. Such material is further used to construct high performance sensing interface and coupled with primer exchange reaction (PER) and hybridization chain reaction (HCR) amplification cascades for sensitive electrochemical aptamer-based LH assay. Target LH molecules bind aptamer sequences in DNA duplex probes to liberate ssDNA strands, which initiate subsequent PER/HCR amplification cascades for the capture of many ferrocene (Fc)-tagged DNAs on sensing interface. S-CoFe(CN)5NO subsequently leads to catalytic oxidation of these Fc tags for yielding substantially magnified currents for realizing ultrasensitive assay of LH with the detection limit of 0.69 pM in range from 5 pM to 10 nM. Owing to the high specificity of aptamer, such sensor has high selectivity and can achieve low levels of LH assay in diluted serum samples. With the successful demonstration for detecting trace LH, such sensor can be easily extended as a universal aptamer-based electrochemical sensing method for monitoring various target analytes in the biomedical and biological fields.

Exploring the Effect of Steric Hindrance on Trans-cleavage Activity of CRISPR-cas12a for Ultrasensitive SERS Detection of P53 DNA.

The trans-cleavage properties of Cas12a make it important for gene editing and disease diagnosis. In this work, the effect of spatial site resistance on the trans-cleavage activity of Cas12a was studied. First, we have explored the cutting effect of Cas12a when different-sized nanoparticles are linked with various spacings of DNA strands using the fluorescence method. The minimum spacing with different-sized nanoparticles that cas12a can cut was determined. We found that when the size of the nanoparticles increases, the minimum spacing that cas12a can cut gradually increases. Subsequently, we verified the conclusion using the surface-enhanced Raman scattering (SERS) method, and at the same time, we designed a SERS biosensor that can achieve ultrasensitive detection of P53 DNA with a linear range of 1 fM-10 nM and a limit of detection of 0.40 fM. Our work develops a deep study of the trans-cleavage activity of Cas12a and gives a guide for DNA design in cas12a-related studies, which can be applied in biomedical analysis and other fields.

Dual-Ligand Ruthenium Coordination Polymer-Derived Self-Enhanced Electrochemiluminescent Emitters for Sensitive Detection of Procalcitonin.

Ru-based electrochemiluminescence (ECL) coordination polymers are widely employed for bioanalysis and medical diagnosis. However, commonly used Ru-based coordination polymers face the limitation of low efficiency due to the long distance between the ECL reagent and the coreactant dispersed in detecting solution. Herein, we report a dual-ligand self-enhanced ECL coordination polymer, composed of tris(4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)32+) as ECL reactant ligand and ethylenediamine (EDA) as corresponding coreactant ligand into Zn2+ metal node, termed Zn-Ru-EDA. Zn-Ru-EDA shows excellent ECL performance which is attributed to the effective intramolecular electron transport between the two ligands. Furthermore, the dual-ligand polymer allows an anodic low excitation potential (+1.09 V) luminescence. The shift in the energy level of the highest occupied molecular orbital (HOMO) upward after the synthesis of the Zn-Ru-EDA has resulted in a reduced excitation potential. The low excitation potential reduced biomolecular damage and the destruction of the modified electrodes. The ECL biosensor has been constructed using Zn-Ru-EDA with high ECL efficiency for the ultrasensitive detection of a bacterial infection and sepsis biomarker, procalcitonin (PCT), in the range from 1.00 × 10-6 to 1.00 × 10 ng·mL-1 with outstanding selectivity, and the detection limit was as low as 0.47 fg·mL-1. Collectively, the dual-ligand-based self-enhanced polymer may provide an ideal strategy for high ECL efficiency improvement as well as designing new self-enhanced multiple-ligand-based coordination in sensitive biomolecular detection for early disease diagnostics.

Stimulus-Responsive Four-Stranded DNA Nanoring Assembly to Host Multiple Nanosilver Clusters for Cooperatively Enhanced Fluorescence Biosensing.

Exploring the ability of four-stranded DNA nanorings (fsDNRs) to host multiple nanosilver clusters (NAgCs) for cooperatively amplifiable fluorescence biosensing to a specific initiator (tI*) is fascinating. By designing three DNA single strands and three analogous stem-loop hairpins, we developed a functional fsDNR through sequential cross-opening and overlapped hybridization. Note that a substrate strand (SS) was programmed with six modules: two severed splits (sT and sT') of NAgCs template, two sequestered segments by a middle unpaired spacer, and a partition for tI*-recognizable displacement, while sT and sT' were also tethered in two ends of three hairpins. At first, a triple dsDNA complex with stimulus-responsiveness was formed to guide the specific binding to tI*, while the exposed toehold of the SS activated the forward cascade hybridization of three hairpins, until the ring closure in the tailored self-assembly pathway for forming the fsDNR. The resulting four duplexes forced each pair of sT/sT' to be merged as the parent template in four nicks, guiding the preferential synthesis of four clusters in the shared fsDNR, thereby cooperatively amplifying the green fluorescence signal for sensitive assay of tI*. Meanwhile, the topological conformation of fsDNR can be stabilized by the as-formed cluster adducts to rivet the pair of two splits in the nicks. Benefitting from the self-enhanced effect of multiple emitters, this label-free fluorescent sensing strategy features simplicity, rapidity, and high on-off contrast, without involving complicated nucleic acid amplifiers.

CsPbBr3 Perovskite Quantum Dots Encapsulated by a Polymer Matrix for Ultrasensitive Dynamic Imaging of Intracellular MicroRNA.

Herein, CsPbBr3 perovskite quantum dots (CPB PQDs)@poly(methyl methacrylate) (PMMA) (CPB@PMMA) nanospheres were used as energy donors with high Förster resonance energy transfer (FRET) efficiency and exceptional biocompatibility for ultrasensitive dynamic imaging of tiny amounts of microRNAs in living cells. Impressively, compared with traditional homogeneous single QDs as energy donors, CPB@PMMA obtained by encapsulating numerous CPB PQDs into PMMA as energy donors could not only significantly increase the efficiency of FRET via improving the local concentration of CPB PQDs but also distinctly avoid the problem of cytotoxicity caused by divulged heavy metal ions entering living cells. Most importantly, in the presence of target miRNA-21, DNA dendrimer-like nanostructures labeled with 6-carboxy-tetramethylrhodamine (TAMRA) were generated by the exposed tether interhybridization of the Y-shape structure, which could wrap around the surface of CPB@PMMA nanospheres to remarkably bridge the distance of FRET and increase the opportunity for effective energy transfer, resulting in excellent precision and accuracy for ultrasensitive and dynamic imaging of miRNAs. As proof of concept, the proposed strategy exhibited ultrahigh sensitivity with a detection limit of 45.3 aM and distinctly distinguished drug-irritative miRNA concentration abnormalities with living cells. Hence, the proposed enzyme-free CPB@PMMA biosensor provides convincing evidence for supplying accurate information, which could be expected to be a powerful tool for bioanalysis, diagnosis, and prognosis of human diseases.

Target-promoted autocatalytic hairpin assembly of bivalent DNAzymes for sensitive and label-free electrochemical metallothionein assay.

Metallothionein (MT) has shown to be an important biomarker for environmental monitoring and various diseases, due to its significant binding ability to heavy metal ions. On the basis of such a characteristic and the Hg2+-stabilized DNA duplex (Hg2+-dsDNA) probe, as well as a new autocatalytic hairpin assembly (aCHA)/DNAzyme cascaded signal enhancement strategy, the construction of a highly sensitive and label-free electrochemical MT biosensor is described. Target MT molecules bind Hg2+ in Hg2+-dsDNA to disrupt the duplex structure and to release ssDNA sequences, which trigger subsequent aCHA for efficient production of mimic aCHA triggering strands and many bivalent DNAzymes. The signal hairpins on the electrode are then cyclically cleaved by DNAzyme amplification cascade to liberate plenty G-quadruplex sequences, which bind hemin and yield largely enhanced currents for sensitive assay of MT with a detection limit of 0.217 nM in a label-free approach. Such sensor also shows selective discrimination capability to MT against other interfering proteins and assay of MT in normal serums with dilution has also been verified, indicating its potential for highly sensitive detection of different heavy metal ion binding molecules for various application scenarios.

Dual emitting aggregation-induced electrochemiluminescence from tetrastyrene derivative for chloramphenicol detection.

Chloramphenicol (CAP) poses a threat to human health due to its toxicity and bioaccumulation, and it is very important to measure it accurately and sensitively. This work explored a host-guest recognition strategy to mediate dual aggregation-induced electrochemiluminescence (AIECL) of 1,1,2,2-tetrakis(4-(pyridin-4-yl) phenyl)-ethene (TPPE) for ratio detection of CAP, in which, cucurbit[8]uril (CB[8]) served as host to assemble guest TPPE. The resulting supramolecular complex CB[8]-TPPE exhibited excellent dual-AIECL-emission with signal strength approximately four times that of TPPE aggregates and black hole quencher-1 (BHQ1) could efficiently quench dual-AIECL signal. CB[8]-TPPE coupled dual-function quencher BHQ1 and high-efficiency DNA reactor to achieve ultra-sensitive detection of CAP, exhibiting a linearity range of 10 fmol·L-1-100 nmol·L-1 and limit of detection of 1.81 fmol·L-1. CB[8]-TPPE provides a novel way to improve the dual-emission of TPE derivatives and sets up a promising platform for CAP detection, demonstrating a good practical application potential.

Organic polymer/inorganic heterostructure coupled with efficient allosteric bicycle strand displacement for photochemical sensing.

In this work, a high-performance conjugated microporous polymer (CMP) decorated with BiOBr (Tr(PhXOD)3-CMP/BiOBr) is synthesized to application in construction of ultrasensitive photoelectrochemical (PEC) biosensor for sensing miRNA-122, by firstly coupling with efficient clip toehold-mediated allosteric bicycle strand displacement (ABSD). Notably, the Tr(PhXOD)3-CMP/BiOBr not only owns self-enhanced D-A-D structure that extremely shortens migration distance of photo-generated electron, but also forms Z-type heterostructure for accelerating electron-hole separation, thereby significantly enhancing the photocurrent with 10-fold higher than commonly used methods. Meanwhile, the clip toehold-mediated ABSD based on ternary linkage structure transformation avoids the attrition of invading strand, endowing the conservation of high concentration for undergoing rapid reaction with high-efficiency DNA amplification, which dramatically improves reaction time and superior target conversion. The experimental results indicate that proposed PEC biosensor had a high sensitivity to miRNA-122 with a detection limit of 0.49 fM, which provides a newly organic/inorganic photosensitive nanomaterials and efficient DNA strand displacement in bioanalytical and early clinical disease diagnosis.

Cascaded autocatalytic hairpin assembly molecular circuit for amplified fluorescent aptamer luteinising hormone assay.

The quantitative detection of luteinising hormone (LH) is critical for the study of the physiological mechanism of reproductive function and the assessment of infertility and the clinical treatment of reproductive disorders. However, conventional approaches for LH detection are mostly based on an antibody recognition module with the limitations of sensitivity, simplicity and cost. The development of robust LH sensing methods is therefore highly demanded for facilitating the diagnosis of LH-related diseases. We establish a convenient, amplified and sensitive fluorescent aptamer LH assay based on new target-triggered and cascaded autocatalytic hairpin assembly (C-aCHA) circuit amplification means via initiator sequence replication. Target LH molecules bind the aptamers in the aptamer/initiator duplexes to release the initiator sequences, which trigger CHA formation of DNA three-way junctions (TWJs) and the unfolding of fluorescently quenched signal hairpins to show amplified fluorescence. The TWJs further activate another CHA cycle for the yield of more initiator sequences to form the C-aCHA circuit amplification cycles, which lead to the unfolding of many signal hairpins to exhibit substantially magnified fluorescence recovery for detecting LH down to 8.56 pM in the range from 10 pM to 50 nM. In addition, the monitoring of trace LH in diluted serums by this sensing approach has been also verified. Our LH assay clearly outperforms current existing antibody-based methods and the C-aCHA signal amplification strategy can be easily extended as a robust means for sensitively monitoring various biomolecular markers with simple replacement of the corresponding aptamers for diverse applications.

Single-Atom Iron Doped Carbon Dots with Highly Efficient Electrochemiluminescence for Ultrasensitive Detection of MicroRNAs.

Herein, single-atom iron doped carbon dots (SA Fe-CDs) were successfully prepared as novel electrochemiluminescence (ECL) emitters with high ECL efficiency, and a biosensor was constructed to ultrasensitively detect microRNA-222 (miRNA-222). Importantly, compared with the conventional without single-atom doped CDs with low ECL efficiency, SA Fe-CDs exhibited strong ECL efficiency, in which single-atom iron as an advanced coreactant accelerator could significantly enhance the generation of reactive oxygen species (ROS) from the coreactant S2O82- for improving the ECL efficiency. Moreover, a neoteric amplification strategy combining the improved strand displacement amplification with Nt.BbvCI enzyme-induced target amplification (ISDA-EITA) could produce 4 output DNAs in every cycle, which greatly improved the amplification efficiency. Thus, a useful ECL biosensor was built with a detection limit of 16.60 aM in the range of 100 aM to 1 nM for detecting traces of miRNA-222. In addition, miRNA-222 in cancer cell lysate (MHCC-97L) was successfully detected by using the ECL biosensor. Therefore, this strategy provides highly efficient single-atom doped ECL emitters for the construction of sensitive ECL biosensing platforms in the biological field and clinical diagnosis.