Dual-mode Biosensor Research Articles

Detecting miRNA-21 using dual-mode biosensor via click chemistry-mediated variable temperature amplification reaction

miRNAs regulate several life activities and they have emerged as biomarkers in cancer diagnosis. Pursuing highly sensitive sensing platforms for detecting miRNAs, signal amplification strategies are the most frequently utilized means. In this research, a click chemistry-mediated variable temperature amplification (CCVTA) biosensor was developed for the highly selective and sensitive detection of miRNA-21. Sensing depended on enzyme-free amplification and copper-free type click chemistry, which greatly simplified the pre-treatment procedure and the conditions for sensing. In addition, the amplification products were used to output two signals, which are electrochemical and colorimetric modes. The dual-mode biosensor respectively achieved a detection limits of 0.57 and 17.19 fmol/mL, as well as excellent selectivity, stability, and applicability. It can be expected that CCVTA-biosensor sparkle with attractive prospects in the sensing field.

HOF-101-based dual-mode biosensor for photoelectrochemical/electrochemiluminescence detection and imaging of oxytetracycline

A unique hydrogen-bonded organic frameworks (HOF-101)-based photoelectrochemical (PEC) and electrochemiluminescence (ECL) dual-mode biosensor using polydopamine nanoparticles (PDAs) as quencher was constructed for ultrasensitive detection and imaging of oxytetracycline (OXY). In particular, HOF-101 was a superior ECL material and can be observed with the naked eye. Furthermore, it also had outstanding PEC signal, so HOF-101 was a new dual-signal material with excellent performance, thus it was explored to realize dual-mode detection. As the main component of natural melanin, PDAs not only had good biocompatibility, but also contained rich functional groups on the surface. Additionally, PDAs had excellent light absorption ability and poor conductivity, which made it the excellent photoquencher. In this work, PDAs were introduced on the surface of HOF-101 to quench its ECL and PEC signals by using the dual-aptamer sandwich method, achieving ultrasensitive detection of antibiotic OXY. Particularly for ECL detection, HOF-101 was firstly used to visually detect OXY. The detection range can reach 0.1 pM-100 nM, and the limit of detection (LOD) can reach 0.04 pM. This work showed a great contribution to the development of new ECL-PEC materials and ECL visualization analysis, which had outstanding application potential in the fields of food safety and biochemical analysis.

A dual-mode biosensor featuring single-atom Fe nanozyme for multi-pesticide detection in vegetables

The single-atom iron nanozyme (SA-Fe-NZ) exhibits high catalytic activity and excellent electron transfer efficiency in biosensors. However, the binding of bioreceptors to the surface of SA-Fe-NZ results in a decrease in the catalytic activity of the nanozyme due to its toxic effects. We utilized the toxic effects and excellent electrochemical properties of the SA-Fe-NZ to successfully construct a smartphone-assisted dual-mode biosensor. The complex formed by the binding of organophosphorus pesticides (OPs) to the aptamer exhibited toxic effects and inhibited the catalytic activity of the nanozyme, preventing the colorimetric substrate from being catalyzed. Simultaneously, the aptamers labeled with electrochemical signal molecules approached the electrode surface, causing a change in the electrochemical signal. The results demonstrated that the constructed broad-spectrum aptamer biosensor exhibited a low limit of detection of 3.55 fM and a wide linear range of 10-13-10-2 M, allowing for qualitative and quantitative detection of multiple OPs in vegetables.

One stone two birds: electrochemical and colorimetric dual-mode biosensor based on copper peroxide/covalent organic framework nanocomposite for ultrasensentive norovirus detection

Norovirus (NoV) is regarded as one of the most common causes of foodborne diarrhea in the world. It is urgent to identify the pathogenic microorganism of the diarrhea in short time. In this work, we developed an electrochemical and colorimetric dual-mode detection for NoV based on the excellent dual catalytic properties of copper peroxide/COF-NH2 nanocomposite (CuO2@COF-NH2). For the colorimetric detection, NoV can be directly detected by the naked eye based on CuO2@COF-NH2 as a laccase-like nonazyme using “peptide-NoV-antibody” recognition mode. The colorimetric assay displayed a wide and quality linear detection range from 1 copy/mL to 5000 copies/mL of NoV with a low limit of detection (LOD) of 0.125 copy/mL. For the electrochemical detection of NoV, CuO2@COF-NH2 showed an oxidation peak of copper ion from Cu+ to Cu2+ using “peptide-NoV-antibody” recognition mode. The electrochemical assay showed a linear detection range was 15000 copies/mL with a LOD of 0.152 copy/mL. It’s worthy to note that this assay does not need other electrical signal molecule, which provide the stable and sensitive electrochemial detection for NoV. The electrochemical and colorimetric dual-mode detection was used to detect NoV in foods and faceal samples, which has the potential for improving food safety and diagnosing of NoV-infected diarrhea.

Vinyl-functionalized covalent organic frameworks with photoelectric property and light-responsive oxidase-mimetic activity for photoelectrochemical and colorimetric dual-mode assay of PTP1B activity

The sensitive and precise assay of protein tyrosine phosphatase 1B (PTP1B) activity plays a considerable role in clinical diagnosis and cancer therapy. Herein, a photoelectrochemical (PEC)-colorimetric (CL) dual-mode biosensor based on magnetic Fe3O4 nanospheres and vinyl-functionalized covalent organic framework (COF-V) with photoelectric property and light-responsive oxidase-mimetic activity was developed for PTP1B activity assay. Fe3O4 nanospheres modified with polydopamine (PDA) and chelated Ti4+ (Fe3O4@PDA-Ti4+) were synthesized by the self-polymerization of dopamine and the chelation reaction between hydroxyl groups in the PDA shell and Ti4+. Subsequently, the PTP1B-specific peptide (P-peptide) was modified on the surface of Fe3O4@PDA-Ti4+ nanosphere via the formation of Ti-O-P bonds between Ti4+ and phosphate group on the P-peptide. Before PTP1B activity assay, COF-V was introduced to the Fe3O4@PDA-Ti4+/P-peptide complex by thiol-ene click reaction of the vinyl group on COF-V with the thiol group of P-peptide, and the Fe3O4@PDA-Ti4+/P-peptide/COF-V complex was obtained. With addition of PTP1B, it can specifically identify and dephosphorylate the P-peptide, resulting in the release of some P-peptide and COF-V from the Fe3O4@PDA-Ti4+/P-peptide/COF-V complex. Then, the undamaged Fe3O4@PDA-Ti4+/P-peptide/COF-V complex was obtained by magnetic separation and used for PEC and CL analysis. Based on the excellent photoelectric property and light-responsive oxidase-mimetic activity of COF-V, PTP1B activity was sensitively assayed, and the linear ranges of 0.01 ng mL−1–1000 ng mL−1 (detection limit, 0.006 ng mL−1) for PEC technique and 0.1 ng mL−1–1000 ng mL−1 (detection limit, 0.03 ng mL−1) for CL method were obtained. Such a design opens a new avenue to detect protein phosphatases activity in biomedical study, disease diagnosis, and cancer treatment.

PEC-SERS Dual-Mode Detection of Foodborne Pathogens Based on Binding-Induced DNA Walker and C3N4/MXene-Au NPs Accelerator.

In this paper, a photoelectrochemical (PEC)-surface-enhanced Raman scattering (SERS) dual-mode biosensor is constructed coupled with a dual-recognition binding-induced DNA walker with a carbon nitride nanosheet (C3N4)/MXene-gold nanoparticles (C/M-Au NPs) accelerator, which is reliable and capable for sensitive and accurate detection of Staphylococcus aureus (S. aureus). Initially, a photoactive heterostructure is formed by combining C3N4 and MXene via a simple electrostatic self-assembly as they possess well-matched band-edge energy levels. Subsequently, in situ growth of gold nanoparticles on the formed surface results in better PEC performance and SERS activity, because of the synergistic effects of surface plasmon resonance and Schottky barrier. Furthermore, a three-dimensional, bipedal, and dual-recognition binding-induced DNA walker is introduced with the formation of Pb2+-dependent DNAzyme. In the presence of S. aureus, a significant quantity of intermediate DNA (I-DNA) is generated, which can open the hairpin structure of Methylene Blue-tagged hairpin DNA (H-MB) on the electrode surface, thereby enabling the switch of signals for the quantitative determination of S. aureus. The constructed PEC-SERS dual-mode biosensor that can be mutually verified under one reaction effectively addresses the problem of the low detection accuracy of traditional sensors. Experimental results revealed that the effective combination of PEC and SERS is achieved for amplification detection of S. aureus with a detection range of 5-108 CFU/mL (PEC) and 10-108 CFU/mL (SERS), and a detection of limit of 0.70 CFU/mL (PEC) and 1.35 CFU/mL (SERS), respectively. Therefore, this study offers a novel and effective dual-mode sensing strategy, which has important implications for bioanalysis and health monitoring.

Dual-responsive amplification strategy for ultrasensitive detection of norovirus in food samples: Combining magnetic relaxation switching and fluorescence assay

Ultra-sensitive, accurate, and specific diagnostic probes are urgently developed to overcome the limitations of conventional norovirus (NV) probes. Herein, we presented the fabrication of a dual-signal probe using multifunctionalized gold and magnetic nanoparticles hybrid composite (Fe3O4 @Au NPs) carriers for the specific detection of NV by magnetic relaxation-fluorescence bimodal sensing. The dual-specific probes were created by modifying Fe3O4 @Au NPs with antibody (Ab) and aptamer-FAM. The antigen-Ab immunoreaction caused aggregation of Fe3O4 @Au NPs, altering the magnetic relaxation signal; simultaneously, the aptamer-FAM that were originally adsorbed on the Au surface were desorbed and cleaved into the solution in the presence of NV, causing a change in the fluorescence signal. Ultrahigh detection sensitives of 0.38 and 3.45 pg/mL were obtained for the dual-modality detection platform, respectively. Furthermore, two quantitative methods obtained satisfactory spiked recoveries for NV-spiked oyster, scallop, strawberry, and tomato samples, consistent with the results of commercial ELISA kits. The results indicated that this dual-specificity assay not only was ultrasensitive but also markedly boosted analysis reliability and precision. Hence, the dual-mode biosensor exhibits high potential for NV detection in the field of food safety.

Dual-Modal Biosensor for Staphylococcus aureus Detection Based on a Porphyrin-Based Porous Organic Polymer FePor-TPA with Excellent Peroxidase-like, Catalase-like, and Photoelectrochemical Properties.

Bacterial infections seriously harm human health and cause many severe diseases, which triggered urgent demands to exploit specific and sensitive biosensor strategies for Staphylococcus aureus detection. Here, a colorimetric and photoelectrochemical dual-mode biosensor for S. aureus assay based on FePor-TPA was constructed. 2D FePor-TPA thin film and its bulk powder (FePor-TPA) were synthesized by in situ growth on ITO and a solvothermal condition, respectively, both of which exhibited excellent peroxidase-like and catalase-like activity, originating from their metalloporphyrin linkers. Benefiting from the in situ growth on ITO electrodes, the 2D FePor-TPA thin film also possessed a more ordered stacking mode and in turn exhibited good electrical conductivity, stable initial photocurrent, and high sensitivity to O2. As for bulk FePor-TPA, its porous structure and high specific surface area make it a possible scaffold to load an amount of AuNPs, the rabbit anti-Staphylococcus aureus Rosenbach tropina antibody (Ab2), and GOx for constructing the signal probe (GOx/Ab2@Au@FePor-TPA) and realizing catalytic amplification. With these satisfactory features in mind, the 2D FePor-TPA thin film and its bulk powder (FePor-TPA) were utilized to construct a dual and signal-on bioplatform for sensitively and selectively detecting S. aureus, which, as far as we know, has not been reported.

Sensitive dual-mode sensing platform for Amyloid β detection: Combining dual Z-scheme heterojunction enhanced photoelectrochemistry analysis and dual-wavelength ratiometric electrochemiluminescence strategy

As a tumor biomarker, the accumulation of amyloid β oligomers (Aβo) in the brain has been suggested as a key feature in the pathogenesis and progression of Alzheimer's disease (AD). In this work, we designed a novel photoelectrochemical (PEC) and electrochemiluminescence resonance energy transfer (ECL-RET) dual-mode biosensor to achieve ultra-sensitive detection of Aβo. Specifically, the electrode surface modified Carbon Dots (C Dots) and the electrodeposited polyaniline (PANI) film formed a Z-scheme heterojunction reversing the photocurrent signal, and then the Aβo specific recognition peptide was attached to the surface via amide bonding between the amino group of PANI and carbonyl group of peptide. After that, in the presence of CdTe labeled specific recognition aptamer for Aβ (CdTe-Apt), Aβo was captured to construct a sandwich-type biosensor and exhibited a significantly enhanced cathodic photocurrent response because the formed dual Z-scheme heterojunction promoted charge separation efficiency. Interestingly, the proposed biosensor also caused a ratiometric change in the ECL intensity at 555 nm and 640 nm. Therefore, the developed biosensor achieved dual-mode detection of Aβo, where the PEC detection range of Aβo was from 10 fM to 0.1 μM (with a detection limit of 4.27 fM) and the ECL method provided a linear detection range of 10 fM to 10 nM (with a detection limit of 6.41 fM). The stability and reliability of the experimental results indicate that this has been a promising biosensing pattern and could be extended to the analysis of other biomarkers.

Polyhedral Au Nanoparticle/MoOx Heterojunction-Enhanced Ultrasensitive Dual-Mode Biosensor for miRNA Detection Combined with a Nonenzymatic Cascade DNA Amplification Circuit.

A novel homologous surface-enhanced Raman scattering (SERS)-electrochemical (EC) dual-mode biosensor based on a 3D/2D polyhedral Au nanoparticle/MoOx nanosheet heterojunction (PAMS HJ) and target-triggered nonenzyme cascade autocatalytic DNA amplification (CADA) circuit was constructed for highly sensitive detection of microRNA (miRNA). Mixed-dimensional heterostructures were prepared by in situ growth of polyhedral Au nanoparticles (PANPs) on the surface of MoOx nanosheets (MoOx NSs) via a seed-mediated growth method. As a detection substrate, the resulting PAMS HJ shows the synergistic effects of both electromagnetic and chemical enhancements, efficient charge transfer, and robust stability, thus achieving a high SERS enhancement factor (EF) of 4.2 × 109 and strong EC sensing performance. Furthermore, the highly efficient molecular recognition between the target and smart lock probe and the gradually accelerated cascade amplification reaction further improved the selectivity and sensitivity of our sensing platform. The detection limits of miRNA-21 in SERS mode and EC mode were 0.22 and 2.69 aM, respectively. More importantly, the proposed dual-mode detection platform displayed excellent anti-interference and accuracy in the analysis of miRNA-21 in human serum and cell lysates, indicating its potential as a reliable tool in the field of biosensing and clinical analysis.

A high performance dual-mode biosensor based on Nd-MOF nanosheets functionalized with ionic liquid and gold nanoparticles for sensing of ctDNA.

A dual-mode biosensor constructed based on photoelectrochemical (PEC) and electrochemical (EC) property was developed for assaying circulating tumor DNA (ctDNA), which is commonly used for triple-negative breast cancer diagnosis. Ionic liquid functionalized two-dimensional Nd-MOF nanosheets were successfully synthesized through a template-assisted reagent substituting reaction. Nd-MOF nanosheets integrated with gold nanoparticles (AuNPs) were able to improve photocurrent response and supply active sites for assembling sensing elements. To achieve selective detection of ctDNA, thiol-functionalized capture probes (CPs) were immobilized on the Nd-MOF@AuNPs modified glassy carbon electrode surface, thereby generating a "signal-off" photoelectrochemical biosensor for ctDNA under visible light irradiation. After the recognition of ctDNA, ferrocene-labeled signaling probes (Fc-SPs) were introduced into the biosensing interface. After hybridization between ctDNA and Fc-SPs, the oxidation peak current of Fc-SPs generated from square wave voltammetry can be employed as a "signal-on" electrochemical signal for ctDNA quantification. Under the optimized conditions, a linear relationship was obtained to the logarithm of ctDNA concentration in between 1.0fmolL-1 to 10nmolL-1 for the PEC model and 1.0fmolL-1 to 1.0nmolL-1 for the EC model. The dual-mode biosensor can provide accurate results for ctDNA assays, effectively eliminating the probable occurrence of false-positive or false-negative results in single-model assays. By switching DNA probe sequences, the proposed dual-mode biosensing platform can serve as a strategy for detecting other DNAs and possesses broad applications in bioassay and early disease diagnosis.

Sulfur Quantum Dot-Based Electrochemiluminescence Resonance Energy Transfer System for a Dual-Mode Ultrasensitive Detection of MC-LR Using Ag+ as a Signal Amplification Switch.

Improving the sensitivity and accuracy of bioimmunoassays has been the focus of research into the development of electrochemiluminescence (ECL) sensing platforms, as this is a critical factor in their application to practical analysis. In this work, an electrochemiluminescence-electrochemistry (ECL-EC) dual-mode biosensing platform based on an "off-on-super on" signals pattern strategy was developed for the ultrasensitive detection of Microcystin-LR (MC-LR). In this system, sulfur quantum dots (SQDs) are a novel class of ECL cathode emitter with almost no potentially toxic effects. The sensing substrate is made from rGO/Ti3C2Tx composites, whose huge specific surface area greatly reduces the possibility of aggregation-caused quenching of SQDs. The ECL detection system was constructed based on the ECL-resonance energy transfer (ERET) strategy, where methylene blue (MB) with an ECL receptor function was bound to the aptamer of MC-LR by electrostatic adsorption and the center actual distance between the donor and the acceptor was calculated to be 3.84 nm, which was verified to be in accordance with the ERET theory. Meanwhile, the introduction of Ag+ as an ECL signal-amplifying molecule greatly improved the sensitivity of sensing analysis. Based on the specific binding of MC-LR to the aptamer, the concentration of MC-LR was found to have a positive correlation with the ECL signal. Also, EC detection was realized with the benefit of the excellent electrochemical properties of MB. The dual-mode biosensor greatly improves the confidence of the detection, examination areas of 0.001-100 pg/mL with MC-LR for ECL and EC were obtained, and the detection limits are 0.17 and 0.24 pg/mL, respectively.

A fluorescence-electrochemiluminescence dual-mode sensor based on a "switch" system for highly selective and sensitive K-ras gene detection

Herein, an fluorescence (FL)−electrochemiluminescence (ECL) dual-mode biosensor is constructed based on the dual-signal “turn-on” strategy of functionalized metal-organic frameworks nanosheets (RuMOFNSs)-tetraferrocene for K-ras gene detection, and the mechanism of bursting through front-line orbital theory is explained for the first time. Amino-functionalized tetraferrocene-labeled probe DNA molecules are linked to RuMOFNSs by covalent amide bonds, acting as FL and ECL intensity switches. The target DNA, complementary to the probe DNA, triggers cyclic amplification of the target by nucleic acid exonuclease III (Exo III), repelling tetraferrocene reporter groups away from RuMOFNSs and inhibiting the electron transfer process and photoinduced electron transfer (PET) effect. These phenomena induce a double turn-on of FL and ECL signals with a high signal-to-noise ratio. The developed FL-ECL dual-mode sensing platform provides sensitive detection of the K-ras gene with detection limits of 0.01 fM (the detection range is 1 fM to 1 nM) and 0.003 fM (the detection range is 0.01 fM to 10 pM), respectively. In addition, the proposed dual-mode sensor can be easily extended to detect other disease-related biomarkers by changing the specific target and probe base sequences, depicting potential applications in bioanalysis and early disease diagnosis.

A convenient fluorescent/electrochemical dual-mode biosensor for accurate detection of Pb2+ based on DNAzyme cycle

The presence of heavy metals in the ecological environment is a serious threat to human health. Therefore, it is very important to establish a simple and sensitive method for the detection of heavy metals. Currently, most of the methods are single-channel sensing, and these methods are prone to false-positive signals, which reduces the accuracy. In this work, Pb2+-DNAzyme was immobilized on magnetic beads (MBs) using a linkage of biotin and streptavidin and successfully applied to the construction of a fluorescent/electrochemical dual-mode (DM) biosensor. The supernatant after magnetic separation formed a double strand on the electrode, which was combined with methylene blue (MB) for electrochemical detection (EC). At the same time, FAM-d was added to the precipitate, and after magnetic separation, the supernatant was subjected to fluorescent detection (FL). Under optimal conditions, the signal response of the constructed dual-mode biosensor showed a good linear relationship with the concentration of Pb2+. The DNAzyme-based dual-mode biosensor achieved sensitive and selective detection of Pb2+ with good accuracy and reliability, opening a new way for the development of biosensing strategies for the detection of Pb2+. More importantly, the sensor has high sensitivity and accuracy for the detection of Pb2+ in actual sample analysis.

Self-Powered DNAzyme Walker Enables Dual-Mode Biosensor Construction for Electrochemiluminescence and Electrochemical Detection of MicroRNA.

Herein, an electrochemiluminescence (ECL) and electrochemical (EC) dual-mode biosensor platform with a self-powered DNAzyme walking machine was established for accurate and sensitive detection of miRNA-21. By employing a magnesium ion (Mn2+)-dependent DNAzyme cleavage cycling reaction, the walking machine was built by assembling DNAzyme walking strands and ferrocene (Fc)-labeled substrate strands on the Au nanoparticles and graphitic carbon nitride nanosheet (g-C3N4 NS)-covered electrode. The DNAzyme walking strand was first prohibited by a blocker strand. After the addition of target miRNA-21 and Mn2+, the DNAzyme walker could be activated and produce autonomous movements along the electrode track fueled by Mn2+-dependent DNAzyme-catalyzed substrate cleavage without additional energy supply. Notably, each walking step resulted in the cleavage of a substrate strand and the release of a Fc-labeled DNA strand fragment, allowing us to acquire an extreme ECL signal recovery of g-C3N4 inhibited by Fc. Meanwhile, numerous Fc-labeled DNA fragments escaped from the surface of the electrode, directly producing an obvious decrease in the square wave voltammetry (SWV) signal from Fc on the same sensing platform. This work not only avoided difficultly assembling various signal indicators but also significantly improved the sensitivity through using self-powered DNAzyme-walker amplification. Moreover, the proposed design employed the same reaction to produce two signal output modes, which could eliminate the interference from diverse reactive pathways on the outcome to mutually improve the accuracy. Therefore, the dual-mode miRNA-21 biosensor exhibited wide detection ranges of 100 aM to 100 nM with low detection limits of 54.3 and 78.6 aM by ECL and SWV modes, respectively, which provided an efficient and universal biosensing approach with extensive applications in early disease diagnosis and bioanalysis.

Dual-mode colorimetric-electrochemical biosensor for Vibrio parahaemolyticus detection based on CuO2 nanodot-encapsulated metal-organic framework nanozymes

Rapid and accurate detection of Vibrio parahaemolyticus (VP) in a variety of testing environments is critical for preventing the spread of foodborne illnesses. Therefore, a dual-mode colorimetric-electrochemical biosensor was prepared for the rapid and sensitive detection of VP. Phenylboronic acid-decorated CuO2 nanodot-mediated organic metal-organic framework (CP@MOF) nanozymes were constructed to produce colorimetric and electrochemical signals. Furthermore, an electrode surface was fabricated using tetrahedral DNA nanostructure-functionalized poly(amidoamine) dendrimer-Au nanoparticles to specifically bind VP. Under acidic environments, the CP@MOF nanozymes disintegrated, enabling the simultaneous release of Cu2+ and H2O2. This in turn causes a Fenton-type reaction, generating a hydroxyl radical, which then oxidizes 3,3′,5,5′-tetramethylbenzidine, thereby enabling visual detection of VP. Moreover, the produced copper ions can be used for the electrochemical detection of VP. This dual-mode biosensor achieved an accuracy of 88.7 %, which was higher than that of single-mode assays (81.1 %). Hence, this dual-mode assay may facilitate the effective on-site detection of pathogens in shrimp samples.

Highly sensitive photoelectrochemical and electrochemical dual-mode biosensing of polynucleotide kinase based on multifunctional BiOBr0.8I0.2 /CuSCN composite and biocatalytic precipitation

Polynucleotide kinase (PNK) plays an important role in maintaining genome integrity and is directly related to many severe human diseases, so its detection is of great significance. To accurately and reliably detect PNK, a photoelectrochemical (PEC) - electrochemical (EC) dual-mode biosensor is created based on BiOBr0.8I0.2/CuSCN multifunctional nanocomposite. In this protocol, the nanocomposite loaded Au nanoparticles (AuNPs) are used to immobilize capture probe P1, while the signal probe P2 is labeled by glucose oxidase modified AuNPs (GOx@AuNPs-P2). They precisely hybridize to produce a double-stranded DNA (ds-DNA)-contained composite at the ITO electrode, which can be phosphorylated in the presence of PNK before being cleaved selectively by λ-exonuclease and leaving the electrode surface. The uncut ds-DNA with GOx@AuNPs-P2 catalyzes glucose to generate H2O2, and under the catalysis of peroxidase-like BiOBr0.8I0.2/CuSCN, 4-chlorohexadione precipitation is produced, which amplifies PEC and EC signals. Owing to the coordination effect of different elements, including enzyme and aptamers, the proposed PEC-EC dual-mode platform displays high sensitivity and selectivity. Furthermore, the sensor shows high repeatability and stability. Further experiments indicate it has excellent application potential in the detection and inhibitor screening of PNK.

DNA-Templated Silver Nanoclusters as Dual-Mode Sensitive Probes for Self-Powered Biosensor Fueled by Glucose.

Nanomaterials have been extensively explored in developing sensors due to their unique properties, contributing to the development of reliable sensor designs with improved sensitivity and specificity. Herein, we propose the construction of a fluorescent/electrochemical dual-mode self-powered biosensor for advanced biosensing using DNA-templated silver nanoclusters (AgNCs@DNA). AgNC@DNA, due to its small size, exhibits advantageous characteristics as an optical probe. We investigated the sensing efficacy of AgNCs@DNA as a fluorescent probe for glucose detection. Fluorescence emitted by AgNCs@DNA served as the readout signal as a response to more H2O2 being generated by glucose oxidase for increasing glucose levels. The second readout signal of this dual-mode biosensor was utilized via the electrochemical route, where AgNCs served as charge mediators between the glucose oxidase (GOx) enzyme and carbon working electrode during the oxidation process of glucose catalyzed by GOx. The developed biosensor features low-level limits of detection (LODs), ~23 μM for optical and ~29 μM for electrochemical readout, which are much lower than the typical glucose concentrations found in body fluids, including blood, urine, tears, and sweat. The low LODs, simultaneous utilization of different readout strategies, and self-powered design demonstrated in this study open new prospects for developing next-generation biosensor devices.

Iridium Complex with Specific Intercalation in the G-Quadruplex: A Phosphorescence and Electrochemiluminescence Dual-Mode Homogeneous Biosensor for Enzyme-Free and Label-Free Detection of MicroRNA

Design and exploitation of high-property and multifunctional emitters for achieving immobilization-free, label-free, enzyme-free, and dual-mode determination of microRNA (miRNA) with high sensitivity and selectivity are particularly urgent but remain a huge challenge. Herein, for the first time, we reported an Ir3+-based N-heterocyclic complex, namely, IrPyPt, ascertained its phosphorescence and electrochemiluminescence (ECL) dual-emission behavior in homogeneous solution, and discovered its turn-up phosphorescence and signal-off ECL response to G-quadruplex DNA over other DNAs. Inspired by this, IrPyPt was pioneered as an emitter to combine nucleic acid probes (ON1 and ON2) for developing a phosphorescence and ECL dual-mode homogeneous biosensor, which was applied to label-free, enzyme-free, highly sensitive, and credible analysis of miRNA-21 used as a target analyte. miRNA-21 triggered the hybridization chain reaction of ON1 and ON2 to generate abundant G-quadruplexes, which caught IrPyPt to yield IrPyPt@G-quadruplex, in which the intramolecular rotary motion of IrPyPt was inhibited and IrPyPt was unable to diffuse to the electrode, contributing to a highly boosted phosphorescence emission and a sharply declined ECL emission. With this design, dual-mode analysis of miRNA-21 was achieved with limits of detection down to 1.40 and 0.18 pM, respectively. Furthermore, the dual-mode biosensor was triumphantly applied to determine the concentration of miRNA-21 in cancer cell lysates and thus provided a great potential alternative for miRNA-related diseases' early and accurate diagnosis.

Dual-Mode Biosensor for Simultaneous and Rapid Detection of Live and Whole Salmonella typhimurium Based on Bioluminescence and Fluorescence Detection.

Both live and dead Salmonella typhimurium (S.T) are harmful to human health, but there are differences in pathological mechanism, dosage, and security. It is crucial to develop a rapid and simultaneous assay to distinguish and quantify live and dead S.T in foods. Herein, one dual-mode biosensor for simultaneous detection of live and dead S.T was fabricated based on two phage probes, using portable bioluminescence and fluorescent meter as detectors, respectively. Firstly, a magnetic phage capture probe (M-P1) and a phage signal tag (P2-S) labeled with SYTO 13 fluorescent dye were prepared, respectively. Both M-P1 and P2-S can specifically conjugate with S.T to form a magnetic sandwich complex. After magnetic separation, the isolated complex can emit a fluorescent signal under an excited 365 nm laser, which can reflect the total amount of S.T. Afterwards, the lysozyme was added to decompose the captured live S.T, which can release ATP and produce a bioluminescent signal corresponding to the live S.T amount. The dead S.T concentration can be deduced by the difference between total and live examples. The detection limit of 55 CFU/mL for total S.T and 9 CFU/mL for live ones was within 20 min. The assay was successfully employed in milk samples and prospectively for on-site screening of other dead and live bacteria, while changing the phages for the targets.