Signal Amplification Effect Research Articles

Aptamer-Triggered Nucleic Acid Amplification Strategy for the Electrochemiluminescence Detection of Perfluorooctanoic Acid.

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent micropollutants. Due to their chemical stability and bioaccumulation, concentrations of PFASs in environmental media, even at ultratrace levels, pose significant environmental and health risks. However, currently reported detection methods lack an effective signal amplification strategy, and the detection sensitivity is limited, which can not meet the requirements of ultratrace detection. Herein, a groundbreaking aptamer-recognition-driven nucleic acid strategy was developed to significantly amplify the detection signal of perfluorooctanoic acid (PFOA). Furthermore, step pulse (SP) was used instead of cyclic voltammetry (CV) as an electrochemical excitation method to modulate the low electrochemiluminescence (ECL) triggering potential of poly [9,9-bis (3'-(N, N-dimethylamino) propyl) -2,7-fluorene]-alt-2,7-(9,9-dioctylfluorene)] (PFN) nanoparticles (NPs) so that a strong signal of +0.80 V was emitted without any exogenous coreactants. PFN NPs coupled rolling circle amplification-assisted PAM-free CRISPR/Cas12a system to construct an ultrasensitive ECL aptasensor for PFOA detection and the limit of detection was as low as 1.97 × 10-15 M. This ECL system integrated the advantages of no exogenous coreactants, low trigger potential, and nucleic acid amplification strategy and provided an ultrasensitive method for monitoring trace PFOA in the real water sample.

Monolithic integration of waveguide amplifiers and passive polymer photonic devices using photolithography

The monolithic integration of rare-earth-doped waveguide amplifiers with passive photonic devices has long been a subject of extensive research. Herein, we propose a method for active-passive monolithic integration based on polymer photonic integrated devices. The monolithic integration of passive devices with active waveguide amplifiers is achieved by spin-coating an active layer atop a passive polymer waveguide and subjecting specific regions of the active layer to selective photolithography. To validate the proposed monolithic integration scheme's impact on the performance of passive devices, performance tests were conducted on both passive and active-passive integrated 8-channel arrayed waveguide grating (AWG) devices. The crosstalk (CT) of the AWG devices before and after adding the active layer ranged from −12.04 dB to −14.72 dB and from −10.02 dB to −14.88 dB, respectively, with channel spacings of 9.29 nm and 8.80 nm, indicating consistent performance of the passive devices with the addition of the active layer. In a 0.5 cm-long active waveguide, internal net gain was achieved across all eight channels of the AWG, with a gain bandwidth ranging from 1518 nm to 1580 nm. Notably, an internal net gain of 9.5 dB was attained at 1527 nm. The successful integration of rare-earth-doped waveguide amplifiers with passive components on a monolithic chip has been achieved for the first time, requiring only two straightforward photolithography steps. This milestone not only preserves the inherent functionality of passive components but also enables effective signal amplification. This technological innovation holds the promise of fully harnessing the potential of rare-earth-doped waveguide amplifiers in the realm of photonic integrated circuits, thereby catalyzing significant breakthroughs and advancements in the field of optoelectronics.

A nanopore-based label-free CRISPR/Cas12a system for portable and ultrasensitive detection of zearalenone

BackgroundFood safety has become a serious global concern. Therefore, there is a need for effective detection technologies in this field. Currently, the development of effective on-site detection techniques is extremely important for food safety. However, the traditional on-site detection methods currently lack effective signal amplification. Herein, the aim of this study was to construct a nanopore-based label-free CRISPR/Cas12a system for the detection of Zearalenone (ZEN). The method is expected to be highly sensitive for portable detection of ZEN in food. ResultsThe proposed strategy was mainly involved three steps, including the displacement of the target DNA, the triggering of the cleavage of hairpin DNA probes (probes 1) by the trans-cleavage of CRISPR/Cas12a, and the generation of a measurable nanopore current signal. The probes 1 and DNA after the cleavage of probes 1 (probes 2) produce different characteristic nanopore signals as they pass through the nanopore. The established method achieved a low limit of detection (LOD) of 6.52 fM for ZEN and a wide liner range under optimized conditions. Furthermore, the practical applicability of this method was verified in real maize samples and showed good recoveries (90.68–101.98 %) and low relative standard deviations (RSD) (9.21–9.72 %). Therefore, this method is a promising option for rapid and ultrasensitive detection of ZEN. Significance and noveltyThe study presented a portable nanopore-based CRISPR/Cas12a signal amplification detection system for the detection of ZEN in food, which had a low LOD and the advantages of rapid, portability, and on-site detection potential. In conclusion, the method presented a promising prospect and universal platform for the detection of ZEN and other mycotoxins, offering a novel insight into on-site food safety detection.

Ultrasensitive Electrochemiluminescence Biosensor with ZIF-67@MXene as an Efficient Co-Reaction Accelerator and Plasmonic Nanozyme as a Smart Signal Amplification Probe.

Exploring novel electrochemiluminescence (ECL) co-reaction accelerators to construct ultrasensitive sensing systems is a prominent focus for developing advanced ECL sensors. However, challenges still remain in finding highly efficient accelerators and understanding their promoting mechanisms. In this paper, ZIF-67@MXene nanosheet composites, with highly conductive in-plane structure and confined-stable pore/channel, are designed to act as high-efficient co-reaction accelerators and achieve a significant enhancement in the luminol-H2O2 based ECL system. Mechanism investigation suggests that hydroxyl radicals (·OH) and singlet oxygen (1O2) can be selectively and preferentially generated on ZIF-67@MXene due to the stable and efficient absorption of ·OH and 1O2, leading to a remarkable enhancement in the ECL efficiency of luminol (830%). Finally, by designing a plasmonic NH2-MIL-88@Pd nanozyme, an "on-off" switch immunosensor is constructed for the detection of prostate-specific antigen (PSA). Based on the multiple signal amplification effect, the linear detection range for PSA is expanded by three orders of magnitude. The detection limit is also improved from 1.44 × 10-11 to 9.1 × 10-13 g mL-1. This work proposes an effective method for the preparation of highly efficient co-reaction accelerators and provides a new strategy for the sensitive detection of cancer markers.

Nanochannel-confined platinum nanostructure for enhancement of luminol-dissolved oxygen electrochemiluminescence coupled with gated aptasensor for sensitive detection of carcinoembryonic antigen

Rapid and precise detection of tumor biomarkers in serum is of great significance for early diagnosis, treatment assessment, and recurrence monitoring of cancers. The fabrication of user-friendly electrochemiluminescence (ECL) aptasensors with effective signal amplification is highly desirable. In this study, an ECL aptasensor was developed with luminol-based ternary ECL platform using dissolved oxygen as endogenous co-reactant and nanochannel-confined platinum nanoparticles (PtNPs) as co-reactant promoter, which can realize highly sensitive detection of the tumor biomarker, carcinoembryonic antigen (CEA). On the cost-effective indium tin oxide (ITO) electrode, amino-modified vertically-ordered mesoporous silica film (NH2-VMSF) was easily grown to form high-density nanochannel array with ultrasmall nanochannels. PtNPs were then in-situ synthesized within the nanochannels via electrodeposition. Ternary ECL system was successfully fabricated as confined PtNPs can catalyze the electroreduction of dissolved oxygen at negative potentials as well as electrochemical oxidation of luminol, enhancing the ECL signal of luminol. The recognitive aptamer (Apt) was covalently immobilized on the outer surface of NH2-VMSF, resulting in the fabrication of an aptasensor. In presence of CEA, a decreased ECL signal was obtained as the formed complex on the recognition interface hindered the diffusion of ECL emitter to the supporting electrode. Based on this signal turn-off mode, sensitive detection of CEA was achieved ranged from 10 fg mL−1 to 100 ng mL−1, with a low detection limit (DL, 0.4 fg mL−1). The aptasensor displayed high selectivity and good reproducibility. The nanochannel-based aptasensor and ternary ECL system demonstrates great potential in convenient and sensitive detection of cancer biomarker.

Research on channel-exposed carbon-based FET humidity sensor

Abstract The ability to detect humidity is crucial for a variety of sectors, including industrial manufacturing, meteorological surveillance, and the preservation of materials, among others. Field effect transistor (FET) based sensor, renowned for its signal amplification effect, plays a pivotal role in detecting trace-level analytes with high sensitivity. Our work demonstrates the preparation of a humidity sensor based on carbon-based FET architecture, employing micro-nano processing techniques. In this work, semiconducting carbon nanotubes serve as the sensing material and channel at the same time. The outcomes indicate that the sensor exhibits a linear response ranging from 0% to 80% relative humidity (RH) and good repeatability. It also shows long-term stability in a 40-day test, proving potential applications in FET-type humidity sensors.

Methylene blue-encapsulated Cu(I)/(Ⅱ) mixed-valence MOF with spontaneously recycled catalysis for electrochemical-colorimetric dual-signal readout aptasensor

The sensitive and accurate detection of thrombin (Tb) is of significance for early diagnosis of thrombosis, vascular injuries, and cancers. A dual-signal aptasensor with effective signal amplification is a promising approach to improve accuracy and sensitivity simultaneously for detection of Tb. Herein, an electrochemistry (EC)-colorimetry dual-readout aptasensor was proposed for Tb detection based on a multifunctional probe, MB@ZIF-90/Cu(I)/(Ⅱ). Methylene blue (MB), as an electroactive and colorimetric dual-signal molecule, was encapsulated into ZIF-90 along with introducing Cu species to form MB@ZIF-90/Cu. After post-treatment heating, MB@ZIF-90/Cu(I)/(Ⅱ) formed with the catalysis toward MB even without the addition of substrate. The catalysis was further enhanced by the “confinement effect” of Cu(I)/Cu(Ⅱ) system and MB in the pore for amplified electrochemical signals. While, the unbounded probes were collected for colorimetric analysis. As a result, EC-colorimetric dual-readout aptasensor exhibits wider linear ranges of 1 pM–10 μM and 0.1 nM–100 μM and lower detection limit down to 0.3 pM and 0.03 nM for Tb, respectively. The mixed-valence MOFs-based dual-signal aptasensor achieved ultrasensitive detection of Tb with more reliable results, revealed its promising application in clinical diagnosis of Tb and even other biomarkers.

User-Friendly and Responsive Electrochemical Detection Approach for Triclosan by Nano-Metal-Organic Framework.

Antimicrobial resistance poses a significant challenge to public health, and is worsened by the widespread misuse of antimicrobial agents such as triclosan (TCS) in personal care and household products. Leveraging the electrochemical reactivity of TCS's phenolic hydroxyl group, this study investigates the electrochemical behavior of TCS on a Cu-based nano-metal-organic framework (Cu-BTC) surface. The synthesis of Cu-BTC via a room temperature solvent method, with triethylamine as a regulator, ensures uniform nanoparticle formation. The electrochemical properties of Cu-BTC and the signal enhancement mechanism are comprehensively examined. Utilizing the signal amplification effect of Cu-BTC, an electrochemical sensor for TCS detection is developed and optimized using response surface methodology. The resulting method offers a simple, rapid, and highly sensitive detection of TCS, with a linear range of 25-10,000 nM and a detection limit of 25 nM. This research highlights the potential of Cu-BTC as a promising material for electrochemical sensing applications, contributing to advancements in environmental monitoring and public health protection.

Exo I-based cyclic digestion coupled with synergistic enhancement strategy for integrating dual-mode optical aptasensor platform

The improvement of dual-mode techniques was of particular interest to researchers, which might enhance the detection performance and applicability. Here, a dual-mode optical aptasensor (DO-aptasensor) platform based on exonuclease I (Exo I) cyclic digestion and synergistic enhancement strategy had proposed for zearalenone (ZEN). Following the preparation of dumbbell-shaped signal probe, the Exo I-based cyclic digestion amplification performed, and then the synergistic enhancement effect carried out to achieve the Poly-HRP-based colorimetry and FAM-SGI-based fluorescence. The efficient homogeneous system realized through the magnetic separation, while the signal interference further eliminated by the graphene oxide (GO). The LOD values were as low as 0.067 ng mL−1 for colorimetry mode and 0.009 ng mL−1 for fluorescence mode, which reduced 23-fold and 172-fold than ELASA by same ZEN-Apt. This promising platform gave rise to a dual-mode optical readout, improved sensitivity and positively correlated detection. Meanwhile, the DO-aptasensor also exhibited the acceptable specificity, desirable reliability and excellent practicability. This novel avenue of aptasensor platform hold great potential for dual-mode optical monitoring of other targets, which can further expand the application scope of Exo I-based signal amplification and synergistic enhancement effect.

Enhancing Preamplifier Design for Acoustic Emission Detection Instrument

With the development of the industry, the safety of pressure vessels is crucial for both production and personnel safety. The application of acoustic emission testing technology as a dynamic non-destructive testing method in the detection of pressure vessels is becoming increasingly prevalent. This paper presents the design of a low-frequency acoustic emission preamplifier with a frequency range of 30KHz to 200KHz and a gain of 20dB. The preamplifier is composed of amplification circuits, power supply circuits, and filtering components. By utilizing the PXR04 series high-sensitivity resonant acoustic emission sensor and Texas Instruments' OPA333 operational amplifier, along with a clever power supply design, effective signal amplification and system stability are ensured. Experimental results validate the correctness of the design, providing a feasible and effective solution for enhancing the performance of acoustic emission testing equipment.

A novel photoelectrochemical self-screening aptamer biosensor based on CAU-17-derived Bi2WO6/Bi2S3 for rapid detection of quorum sensing signal molecules

Quorum sensing signal molecule is an important biomarker released by some microorganisms, which can regulate the adhesion and aggregation of marine microorganisms on the surface of engineering facilities. Thus, it is significant to exploit a convenient method that can effectively monitor the formation and development of marine biofouling. In this work, an advanced photoelectrochemical (PEC) aptamer biosensing platform was established and firstly applied for the rapid and ultrasensitive determination of N-(3-Oxodecanoyl)-l-homoserine lactone (3-O-C10-HL) released from marine fouling microorganism Ponticoccus sp. PD-2. The visible-light-driven Bi2WO6/Bi2S3 heterojunction derived from metal-organic frameworks (MOFs) CAU-17 and self-screened aptamer were employed as the photoactive materials and bioidentification elements, respectively. Appropriate amount of MoS2 quantum dots (QDs) conjugated with single-stranded DNA were introduced by hybridization to enhance the photocurrent response of the PEC biosensor. The self-screening aptamer can specifically recognize 3-O-C10-HL, accompanied by increasing the steric hindrance and forcing MoS2 QDs to leave the electrode surface, resulting in an obvious reduction of photocurrent and achieving a dual-inhibition signal amplification effect. Under the optimized conditions, the photocurrent response of PEC aptasensor was linear with 3-O-C10-HL concentration from 1 nM to 10 μM, and the detection limit was as low as 0.26 nM. The detection strategy also showed a high reproducibility, superior specificity and good stability. This work not only provides a simple, rapid and ultrasensitive PEC aptamer biosensing strategy for monitoring quorum sensing signal molecules in marine biofouling, but also broadens the application of MOFs-based heterojunctions in PEC sensors.

Clinically applicable assay of cardiac troponin I by CRISPR/Cas12a-amplified single-particle collision electrochemistry

Owing to its rapid response and ultra-high sensitivity at single-entity level, single-particle collision electrochemistry (SPCE) shows great application prospects in sensitive detection of biomolecules. However, its widespread use in actual samples is constrained by the poor signal conversion efficiency and heavy interference from complicated samples. Here, a new SPCE biosensor for clinical analysis of cardiac troponin I (cTnI) was developed based on the effective signal amplification of CRISPR/Cas12a as well as the good separation and enrichment capabilities of magnetic nanobeads (MBs). The trans-cleavage capability of CRISPR/Cas12a can only be triggered in the presence of target cTnI to effectively cleave ssDNA2 on the surface of Au@Pt nanoparticles (Au@Pt NPs) within 30 min. Each cTnI molecule could cause the release of 4.68×104 Au@Pt NPs by utilizing the superior cleaving activity of CRISPR/Cas12a, significantly amplifying the signal and improving the sensitivity of analysis. The developed SPCE biosensor for cTnI had a detection limit as low as 0.35 fg/mL, which was 2–6 orders in magnitude less than existing cTnI detection techniques. Additionally, MBs allow the biosensor to detect cTnI in patient samples with excellent sensitivity and specificity by directly sampling from the complex matrix.

Programmable DNA tweezers-SDA for ultra-sensitive signal amplification fluorescence sensing strategy

BackgroundDNA tweezers, classified as DNA nanomachines, have gained prominence as multifunctional biosensors due to their advantages, including a straightforward structure, response mechanism, and high programmability. While the DNA tweezers demonstrate simultaneous, rapid, and stable responses to different targets, their detection sensitivity requires enhancement. Some small molecules, such as mycotoxins, often require more sensitive detection due to their extremely high toxicity. Therefore, more effective signal amplification strategies are needed to further enhance the sensitivity of DNA tweezers in biosensing. ResultsWe designed programmable DNA tweezers that detect small-molecule mycotoxins and miRNAs through simple sequence substitution. While the DNA tweezers demonstrate simultaneous, rapid, and stable responses to different targets, their detection sensitivity requires enhancement. We introduced the Strand Displacement Amplification (SDA) technique to address this limitation, proposing a strategy of novel programmable DNA tweezers-SDA ultrasensitive signal amplification fluorescence sensing. We specifically investigate the effectiveness of this approach concerning signal amplification for two critical mycotoxins: aflatoxin B1 (AFB1) and zearalenone (ZEN). Results indicate that the detection ranges of AFB1 and ZEN via this strategy were 1–10,000 pg mL −1 and 10–100,000 pg mL −1, respectively, with corresponding detection limits of 0.933 pg mL −1 and 1.07 pg mL −1. Compared with the DNA tweezers direct detection method for mycotoxins, the newly constructed programmable DNA tweezers-SDA fluorescence sensing strategy achieved a remarkable 104-fold increase in the detection sensitivity for AFB1 and ZEN. SignificanceThe constructed programmable DNA tweezers-SDA ultrasensitive signal-amplified fluorescence sensing strategy exhibits excellent detection performance for mycotoxins. The superb versatility of this strategy allows the developed method to be easily used for detecting other analytes by simply replacing the aptamer and cDNA, which has incredible potential in various fields such as food safety screening, clinical diagnostics, and environmental analysis.

Label-free and highly sensitive detection of microRNA from cancer cells via target-induced cascade amplification generation of lighting-up RNA aptamers

The abnormal expression levels of miRNAs have been proven to be highly related to the generation of various diseases and are also closely associated with the stages and types of disease development. The novel RNA aptamers-based homogenous fluorescent methods were simple, with low background signal and high signal-to-noise ratio, but lacked effective signal amplification technology to achieve sensitive detection of trace miRNA markers. There is an urgent need for combining effective nucleic acid amplification technology with RNA aptamer to achieve highly sensitive and accurate detection of miRNA. For this purpose, a new DNA multi-arm nanostructure-based dual rolling circle transcription machinery for the generation of lighting-up MG RNA aptamers is constructed for label-free and highly sensitive sensing of miRNA-21. In this system, the target miRNA-21 induces a structural transformation of the DNA multi-arm nanostructure probe to recycle miRNA-21 and trigger two independent rolling circle transcription reactions to generate two long RNAs, which can partially hybridize with each other to generate large amounts of complete MG RNA aptamers. These RNA aptamers can associate with organic MG dye to produce significantly enhanced fluorescence signals to accomplish ultrasensitive miRNA-21 detection down to 0.9 fM. In addition, this method exhibits high selectivity to distinguish miRNA-21 even with single nucleotide mismatch, and also has potential application capability to monitor different expression levels of miRNA-21 from different cancer cells. The effective collaboration between MG RNA aptamer and rolling circle transcription reaction makes this fluorescent method show the significant advantages of low background signal, high signal-to-noise ratio and high detection sensitivity. It has great potential to be a promising means to achieve label-free and highly sensitive monitoring of other trace biological markers via a simple change of target sequence.

Electroactive polymer tag modified nanosensors for enhanced intracellular ATP detection.

ATP plays a crucial role in cell energy supply, so the quantification of intracellular ATP levels is particularly important for understanding many physio-pathological processes. The intracellular quantification of this non-electroactive molecule can be realized using aptamer-modified nanoelectrodes, but is hindered by the limited quantity of modification and electroactive tags on the nanosized electrodes. Herein, we developed a simple but effective electrochemical signal amplification strategy for intracellular ATP detection, which replaces the regular ATP aptamer-linked ferrocene monomer with a polymer, thus greatly magnifying the amounts of electrochemical reporters linked to one chain of the aptamer and enhancing the signals. This ferrocene polymer-ATP aptamer was further immobilized onto Au nanowire electrodes (SiC@C@Au NWEs) to achieve accurate quantification of intracellular ATP in single cells, presenting high electrochemical signal output and high specificity. This work not only provides a powerful tool for quantifying intracellular ATP but also offers a simple and versatile strategy for electrochemical signal amplification in the detection of broader non-electroactive molecules involved in different kinds of intracellular physiological processes.

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.

Signal Amplification by Spatial Concentration for Immunoassay on Cellulose Media.

Immunoassay is one of the most common bioanalytical techniques from lab-based to point-of-care settings. Over time, various approaches have been developed to amplify signals for greater sensitivity. However, the need for effective, versatile, and simple signal amplification methods persists yet. This paper presents a novel signal amplification method for immunoassay that utilizes spatial concentration of a cellulose-based plate possessing sensor transducers, specifically gold nanoparticles. By modifying the dimensions of the plate, the density of nanoparticles increased, resulting in intensified color signals. The coating material, polydopamine, which is utilized to protect the gold nanoparticles. Chemical changes in nanocomposites are characterized using scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The application of this method to colorimetric quantification demonstrated great consistency across various concentrations of nanoparticles, with better reliability at lower concentration ranges. A model immunoassay is designed to evaluate the analytical performance. As a result, this method successfully corrected a false-negative result with a lowered Kd of 0.509pmol per zone. This method shows strong signal enhancement capability that can correct false-negative signals in the immunoassays, with potential benefits including versatility, simplicity, low cost, and the ability to operate multiple plates simultaneously.

Signal Modulation of Organic Photoelectrochemical Transistor by a Z-Scheme Photocathodic Gate: An Innovative Dual Amplification Strategy for Sensitive Aptasensing Application.

Pursuing a more efficient signal amplification strategy is highly demanded for improving the performance of the promising cathodic photoelectrochemical (PEC) sensors. In this work, we present an extremely effective dual signal amplification strategy by the integration of a Z-scheme nanohybrids-based photocathode with the effective signal modulation of an organic photoelectrochemical transistor (OPECT) device. Specifically, photocathodic gate material of CdTe-BiOBr nanohybrids with a Z-scheme electron-transfer route was designed and synthesized for preliminary improvement of the activity of the photogate; afterward, signal modulation of the OPECT system by the photocathodic gate of CdTe-BiOBr was then accomplished for further signal amplification by 2 orders of magnitude. As a result, the output PEC signal of CdTe-BiOBr was enhanced by 17.5-fold as compared to BiOBr, and the channel current (IDS) of the OPECT device was 117-fold magnified than its gate current (IG) response. Exemplified by tetracycline (TC) as a model target and aptamer as the specific recognition element, a versatile cathodic aptasensing platform was constructed based on the proposed OPECT device. The introduced OPECT aptasensor merits advantages, including a good linear range (1.0 × 10-12 to 1.0 × 10-6 M), a low limit of detection (4.2 × 10-13 M), and superior sensitivity than the traditional PEC methods for TC detection, which represents a universal protocol for developing the innovative photocathodic OPECT sensing platform toward accurate analysis.

Homogeneous Electrochemical Aptasensor for Sensitive Detection of Zearalenone Using Nanocomposite Probe and Silica Nanochannel Film.

Developing rapid and efficient analytical methods is of great importance for food safety Herein, we present a novel homogeneous electrochemical aptasensor for ultrasensitive quantitative determination of zearalenone (ZEN) based on a nanocomposite probe and silica nanochannel film. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV-Vis characterization techniques confirm that graphene oxide (GO) bears an aromatic conjugated structure, along with hydroxyl and carboxyl groups, facilitating the subsequent adsorption of cationic redox hexa-ammine-ruthenium (III) (Ru(NH3)63+) and anionic ZEN aptamer, to form a Ru(NH3)63+-ZEN aptamer-GO nanocomposite probe in a homogeneous solution. Vertically-ordered mesoporous silica films (VMSF) bearing silanol groups can be simply grown on the solid indium tin oxide (ITO) electrode surface and enable the selective preconcentration of Ru(NH3)63+, eventually leading to signal amplification. Since the detachment of Ru(NH3)63+ from the GO surface by the recognized ZEN aptamer in the presence of ZEN, more free Ru(NH3)63+ is released in solution and produces enhanced redox signals at the VMSF modified ITO electrode, allowing quantitative detection of ZEN. On the basis of the above sensing strategy, the proposed homogeneity, due to the assistance of graphene, as well as of the signal amplification and anti-fouling effects of VMSF, accurate analysis of ZEN can be realized in maize and Chinese chestnut samples.

Multiplex bacteria detection using one-pot CRISPR/Cas13a-based droplet microfluidics

High-throughput detection of bacteria at low levels is critical in public health, food safety, and first response. Herein, for the first time, we present a platform based on droplet microfluidics coupling with the recombinase aided amplification (RAA)-assisted one-pot clustered regularly interspaced short palindromic repeats together with CRISPR-associated proteins 13a (CRISPR/Cas13a) assay, and droplet encoding strategy for accurate and sensitive determination of nucleic acids from various foodborne pathogens. The workflow takes full advantage of CRISPR/Cas13a signal amplification and droplet confinement effects, which enhances the detection sensitivity and enables end-point quantitation. Meanwhile, by varying the color of droplets, the number of bacteria detected at the same time is greatly improved. It possesses the capability to simultaneously detect seven different types of foodborne pathogens. Notably, the system is also applied to real food samples with satisfactory results. Overall, in view of superiorities in high sensitivity, outstanding selectivity, and large-scale multiplexing, the one-pot CRISPR/Cas13a-based droplet microfluidic system could be expanded and universalized for identifying other bacteria.