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A terahertz metamaterial microfluidic sensing chip for ultrasensitive detection is proposed to investigate the response of substances to terahertz radiation in liquid environments and enhance the molecular fingerprinting of trace substances. The structure consists of a cover layer, a metal microstructure, a microfluidic channel, a metal reflective layer, and a buffer layer from top to bottom, respectively. The simulation results show that there are three obvious resonance absorption peaks in the range of 1.5–3.0 THz and the absorption intensities are all above 90%. Among them, the absorption intensity at M1 = 1.971 THz is 99.99%, which is close to the perfect absorption, and its refractive index sensitivity and Q-factor are 859 GHz/RIU and 23, respectively, showing excellent sensing characteristics. In addition, impedance matching and equivalent circuit theory are introduced in this paper to further analyze the physical mechanism of the sensor. Finally, we perform numerical simulations using refractive index data of normal and cancer cells, and the results show that the sensor can distinguish different types of cells well. The chip can reduce the sample pretreatment time as well as enhance the interaction between terahertz waves and matter, which can be used for early disease screening and food quality and safety detection in the future. [ABSTRACT FROM AUTHOR]

The ultrasensitive detection of hepatitis C virus (HCV) nucleic acid is crucial for the early diagnosis of hepatitis C. In this study, by combining Ag@Au core/shell nanoparticle (Ag@AuNP)-based surface-enhanced Raman scattering (SERS) tag with hybridization chain reaction (HCR), a novel SERS-sensing method was developed for the ultrasensitive detection of HCV nucleic acid. This SERS-sensing system comprised two different SERS tags, which were constructed by modifying Ag@AuNP with a Raman reporter molecule of 4-ethynylbezaldehyde, two different hairpin-structured HCR sequences (H1 or H2), and a detection plate prepared by immobilizing a capture DNA sequence onto the Ag@AuNP layer surface of the detection wells. When the target nucleic acid was present, the two SERS tags were captured on the surface of the Ag@AuNP-coated detection well to generate many "hot spots" through HCR, forming a strong SERS signal and realizing the ultrasensitive detection of the target HCV nucleic acid. The limit of detection of the SERS-sensing method for HCV nucleic acid was 0.47 fM, and the linear range was from 1 to 105 fM. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive investigation into the synthesis, characterization, and application of an exceptionally sensitive electrochemical sensor designed for the ultrasensitive detection of 2,4-dinitrotoluene (DNT), a notorious explosive compound. The sensor employs bimetallic nickel-cobalt oxide (NiCo2O4) nanoparticles, synthesized through a facile hydrothermal method. Extensive analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS), were employed to validate the crystallinity and purity of the NiCo2O4 nanoparticles. These nanoparticles, possessing remarkable properties, form the core of our electrochemical sensor, enabling it to offer heightened sensitivity and selectivity even under ambient conditions. Most notably, this sensor boasts an impressively low limit of detection (LOD) of 18 nM, coupled with a broad linear detection range (LDR) spanning from 10 nM to 100 nM. The sensor exhibits robust sensitivity, excellent selectivity, and an outstandingly low detection threshold, collectively demonstrating its potential for precise and accurate detection of DNT. This research underscores the significant potential of bimetallic oxide nanoparticles, specifically NiCo2O4, in the precise quantification of nitro-aromatic analytes. This study opens up promising avenues for assessing hazardous compounds in complex environmental matrices, thereby contributing to the advancement of electrochemical sensing. Additionally, this novel sensing platform holds substantial promise for enhancing security measures and environmental monitoring through its improved sensitivity and selectivity in the detection of explosives.

Meeting the demands of sustainable energy economy requires diagnostics of the chemical processes surrounding future fuels and contemporary combustion applications. Pioneered in 1970, Intracavity Laser Absorption Spectroscopy (ICAS) has evolved to be a powerful instrument in the toolbox of combustion diagnostics. It owes its ultra-high sensitivity to the enhancement of the effective absorption pathlength by placing the absorber inside the cavity of a broadband laser. In this review we introduce the complementary strengths of ICAS to other methods: ultra-high sensitivity to narrowband absorption alongside the immunity to broadband losses, multiplexed detection and (µs-scale)-temporal resolution. We outline the basic concepts and features of ICAS, focusing on the laser dynamics regime where an absorbing sample in the laser resonator yields the well-known Lambert-Beer law. We chart the progress made over the years in visible (dye-jet laser) and near infrared (fiber laser) ICAS speciation in flames, by highlighting case studies where species like long considered ''hard-to detect'' 1CH2 and HCO radicals, along with O-atoms, C2, NH2, HNO, CN, and HCN were measured, as well as thermometry and speciation applications demonstrated in shock tubes, flow-cells and flames based on (stationary or time-resolved) measurements of multicomponent spectral matrices containing lines of CH4, C2H2, CO2, CO, OH and H2O. We highlight the contributions of ICAS in gas-phase nanomaterial synthesis, exemplified in prototypical iron-doped flames and discuss prospective applications in spray-flame pyrolysis and metal-powder combustion. Finally, we present advances in the development of lasing media based on Cr2+ and Fe2+-doped chalcogenide crystals and fluoride crystals doped with trivalent lanthanides, that meet the (ICAS-specific) requirement associated with the necessity to have a gain media lasing directly in the desired wavelength range, and therefore to expand this technique into the important mid-infrared and ultraviolet spectral ranges.

A terahertz metamaterial microfluidic sensing chip for ultrasensitive detection is proposed to investigate the response of substances to terahertz radiation in liquid environments and enhance the molecular fingerprinting of trace substances. The structure consists of a cover layer, a metal microstructure, a microfluidic channel, a metal reflective layer, and a buffer layer from top to bottom, respectively. The simulation results show that there are three obvious resonance absorption peaks in the range of 1.5–3.0 THz and the absorption intensities are all above 90%. Among them, the absorption intensity at M1 = 1.971 THz is 99.99%, which is close to the perfect absorption, and its refractive index sensitivity and Q-factor are 859 GHz/RIU and 23, respectively, showing excellent sensing characteristics. In addition, impedance matching and equivalent circuit theory are introduced in this paper to further analyze the physical mechanism of the sensor. Finally, we perform numerical simulations using refractive index data of normal and cancer cells, and the results show that the sensor can distinguish different types of cells well. The chip can reduce the sample pretreatment time as well as enhance the interaction between terahertz waves and matter, which can be used for early disease screening and food quality and safety detection in the future.

The present work reported, for the very first time, a crystallographic junction formed of (002) and (110) oriented crystals of bismuth ferrite (BFO) for ultrasensitive carbon monoxide (CO) detection. Growth orientation and crystallinity of the solution-processed BFO were controlled by varying calcination times. The sensor demonstrated a maximum response of six times for 30 ppm of CO, with response and recovery times of 149 and 226 s, respectively, with a significant specificity over other chemically compatible species. The device showed excellent stability when tested continuously for a period of 150 days with a maximum response deviation of ±0.35 times for 30 ppm of CO. The sensitivity of the sensor significantly increased in comparison to other polycrystalline variants with less or no junctions. In order to understand the effect of crystallographic junctions on sensing performance, an analytical model was put forward. The proposed model established the dependency of the sensor response pattern on the carrier diffusion coefficient (Dg) of the exposed gas and the ease of carrier diffusion through the gas–surface junction, which is controlled by the junction bias and the drift current. Hence, the proposed junction-based sensor provides additional control over the sensor efficiency in comparison to its resistive counterparts, thereby significantly improving the device performance without significantly complicating the device. [ABSTRACT FROM AUTHOR]

Ultrasensitive electrochemical detection on hazardous substances like antibiotics and pesticides is essential but still challenging in rapid test technology. Herein, the first electrode using highly conductive metal–organic frameworks (HCMOFs) for electrochemical detection of chloramphenicol is proposed. The design of electrocatalyst Pd(II)@Ni3(HITP)2 with ultra‐sensitivity in detection of chloramphenicol is demonstrated by loading Pd onto HCMOFs. An ultra‐low limit of detection (LOD) of 0.2 nM (64.6 pg/mL) was observed for these materials, which is 1–2 orders of magnitude lower than the other reported materials for chromatographic detection. Moreover, the proposed HCMOFs showed long‐time stability over 24 h. The superior detection sensitivity can be attributed to the high conductivity of Ni3(HITP)2, and the large Pd loading. The experimental characterizations and computational investigation determined the Pd loading mechanism in Pd(II)@Ni3(HITP)2, revealing PdCl2 adsorption on the abundant adsorption sites of Ni3(HITP)2. The proposed electrochemical sensor design using HCMOFs was demonstrated to be both effective and efficient, showing that the adoption of HCMOFs decorated with other effective electrocatalysts, which combine high conductivity and high catalytic activity, is of great advantage for ultrasensitive detection. [ABSTRACT FROM AUTHOR]

Bioluminescence (BL) and chemiluminescence (CL) are interesting and intriguing phenomena that involve the emission of visible light as a consequence of chemical reactions. The mechanistic basis of BL and CL has been investigated in detail since the 1960s, when the synthesis of several models of cyclic peroxides enabled mechanistic studies on the CL transformations, which led to the formulation of general chemiexcitation mechanisms operating in BL and CL. This review describes these general chemiexcitation mechanisms—the unimolecular decomposition of cyclic peroxides and peroxide decomposition catalyzed by electron/charge transfer from an external (intermolecular) or an internal (intramolecular) electron donor—and discusses recent insights from experimental and theoretical investigation. Additionally, some recent representative examples of chemiluminescence assays are given. [ABSTRACT FROM AUTHOR]

As a major public health issue, early cancer detection is of great significance. A field-effect transistor (FET) based on an MoS2/C60 composite nanolayer as the channel material enhances device performance by adding a light source, allowing the ultrasensitive detection of cancer-related miRNA. In this work, atomic layer deposition (ALD) was used to deposit MoS2 layer by layer, and C60 was deposited by an evaporation coater to obtain a composite nanolayer with good surface morphology as the channel material of the FET. Based on the good absorption of C60 by blue-violet light, a 405 nm laser was selected to irradiate the channel material, improving the function of FET biosensors. A linear detection window from 10 pM to 1 fM with an ultralow detection limit of 5.16 aM for miRNA-155 was achieved. [ABSTRACT FROM AUTHOR]

Malondialdehyde (MDA), one of the most important products of lipid peroxidation, has been widely accepted as a biomarker to indicate food rancidity as well as the progress of some human diseases. However, ready detection of MDA with ultra-high sensitivity remains a challenge. In this work, a microfluidic surface-enhanced Raman scattering (SERS) sensing chip based on phosphoric acid induced nanoparticles aggregation was proposed for ultrasensitive MDA detection. The sensing chip was composed of an ultrafast microfluidic mixer, which efficiently transferred analytes to hot spots via the mixer assisted hot spots occupying (MAHSO) SERS strategy. Phosphoric acid, a reagent used in MDA detection, played the role of aggregator to induce aggregation of silver nanoparticles (Ag NPs); meanwhile, as fast as a few milliseconds mixing time effectively prevented over-aggregation of Ag NPs. Therefore, this process generated a uniform and dense SERS substrate with analyte molecules located in hot spots. As a result, the MDA SERS sensing chip possessed a limit of detection (LOD) lower than 3.3 × 10−11 M, high spot-to-spot uniformity with a relative standard deviation (RSD) of 9.0% and an excellent batch-to-batch reproducibility with a RSD of 3.9%. This method also demonstrated excellent specificity and reliability in real sample detection with recoveries of 90.4–109.8% in spiked tests. [ABSTRACT FROM AUTHOR]

Nanotechnology has attracted much attention, and may become the key to a whole new world in the fields of food, agriculture, building materials, machinery, medicine, and electrical engineering, because of its unique physical and chemical properties, including high surface area and outstanding electrical and optical properties. The bottom-up approach in nanofabrication involves the growth of particles, and we were inspired to propose a novel nanoplasmonic method to detect the formation of nanoparticles in real time. This innovative idea may contribute to the promotion of nanotechnology development. An increase in nanometer particle size leads to optical extinction or density (OD)-value changes in our nanosensor chip at a specific wavelength measured in a generic microplate reader. Moreover, in applying this method, an ultrasensitive nanoplasmonic immunoturbidimetry assay (NanoPITA) was carried out for the high-throughput quantification of hypersensitive C-reactive protein (CRP), a well-known biomarker of cardiovascular, inflammatory, and tumor diseases. The one-step detection of the CRP concentration was completed in 10 min with high fidelity, using the endpoint analysis method. The new NanoPITA method not only produced a linear range from 1 ng/mL to 500 ng/mL CRP with the detection limit reduced to 0.54 ng/mL, which was an improvement of over 1000 times, with respect to regular immunoturbidity measurement, but was also effective in blood detection. This attractive method, combined with surface plasmon resonance and immunoturbidimetry, may become a new technology platform in the application of biological detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasensitive detection is of great significance for the study of ancient leather artifacts. • A specific anti-collagen polyclonal antibody was well designed and prepared. • An electrochemical immunosensor was developed for detecting ancient leather. • The sensor excels in both qualitative and quantitative analysis. • The sensor has excellent specificity, sensitivity and stability. As one of the earliest and wieldiest used natural materials, leather played a significant role in the development of human civilization. However, as the main component of the leather protein is very susceptible to degradation by light, heat, microorganism and other adverse factors, leather relics are difficult to preserve. To trace leather remnants in ancient sites, a specific anti-collagen polyclonal antibody was designed and prepared through animal immunization. Then, a label-free electrochemical immunosensor based on tailored polyclonal antibody and cobalt hydroxide oxide nanoflakes (CoOOH NFs) was constructed and applied for the detection of leather artifacts in ancient sites. The limit of detection (LOD) of this electrochemical immunosensor reached as low as 0.2858 ng/mL, with a linear range of 1–100 ng/mL. The immunosensor exhibits excellent performance in terms of specificity, stability, and repeatability, especially in the qualitative and quantitative detection of ancient leather samples unearthed from six sites in Xinjiang region, which also enabled the identification of the species of leather artifacts. The present work provides a novel strategy for the trace identification of ancient leather and a reference for the determination of other ancient proteins in ancient sites. [ABSTRACT FROM AUTHOR]

Ultrasensitive detection is crucial for the early warning and intervention of risk factors, ultimately benefiting the environment and human health. Low levels of ochratoxin A (OTA) present a hidden yet significant threat, and rapid detection via high-performing biosensors is therefore essential. A cascade isothermal amplification aptasensor (CIA-aptasensor) was designed for OTA detection. On the surface of a magnetic bead probe, the OTA level was converted into positively correlated trigger cDNA through its competitive binding with OTA-Apt. The released trigger cDNA activated catalytic hairpin assembly followed by coupling with a hybridization chain reaction to achieve CIA. After adding graphene oxide and SYBR Green I, the background interference was eliminated to specifically obtain OTA-related fluorescence. The ultrasensitive limit of detection was 0.22 pg mL−1, an improvement of 1368-fold over conventional enzyme-linked aptamer sorbent assay by the same OTA-Apt, demonstrating satisfactory reliability and practicability. Thus, the CIA-aptasensor provides an enzyme- and label-free simplified homogeneous system with minimal background interference using isothermal conditions. This study provides a polymerase chain reaction–like approach for enhancing the sensitivity and performance of a biosensor, which could be extended for the application of CIA and label-free signaling strategy to other risk factors. [Display omitted] • CIA-aptasensor owned an enzyme-free, label-free, simplified and homogeneous system. • CHA and HCR-based cascade isothermal amplification was performed. • Ultrasensitive LOD was 0.22 pg mL−1, improved 1368-fold than ELASA. • Minimized background interference by GO, reflected bright fluorescence by SGI. • New guidance of performance improvements for other biosensors might recommend. [ABSTRACT FROM AUTHOR]

The abuse of 17β-estradiol(E2) has aroused wide concern in environmental and biomedical fields, which severely affects the endocrine function of human and animals. Therefore, an ultrasensitive and accurate assay of E2 is critically important. Traditional chromatography or immunoassay techniques exhibited good sensitivity and selectivity, but expensive instruments and antibodies may pose cost and stability issues, as well as difficulties in meeting on-site detection requirements. Ultrasensitive, reliable, and on-site detection of E2 at trace level remains a challenge. Hence, developing a simple, ultrasensitive assay to simultaneously achieve accurate detection and rapid visual analysis of E2 is extremely crucial. We developed a versatile dual-mode photoelectrochemical (PEC) and colorimetric biosensor based on isothermal nucleic acid amplification strategy for the ultrasensitive and accurate detection of E2. The method modified titanium dioxide (TiO 2) with tungsten selenide (WSe 2) nanoflowers to synthesize WSe 2 /TiO 2 heterostructures as a substrate for signal amplification and nanoprobe modification. Isothermal nucleic acid amplification strategy has been proven to be a powerful tool for strong signal amplification. The presence of a target triggered the nucleic acid amplification reaction, and produced a large amount of tDNA that competed with G-quadruplex immobilized on the electrode surface. The remaining G-quadruplex/hemin catalyzed the 4-chloro-1-naphthol (4-CN) to form biocatalytic precipitation (BCP) and ABTS-H 2 O 2 chromogenic reaction, thus, the dual-mode platform was capable of achieving PEC-colorimetric ultrasensitive detection based on the catalytic activity of G-quadruplex/hemin DNAzyme. Within optimal conditions, the dual-mode biosensor exhibited a remarkable detection limit as low as 0.026 pM. Benefiting from the superior performance of WSe 2 /TiO 2 and the power signal amplification of isothermal nucleic acid amplification strategy, this aptasensor achieved the ultrasensitive detection of E2. The independent transmission paths of photoelectrochemical and colorimetric provide mutual support and flexible switching, significantly enhancing the overall sensitivity and accuracy of the detection strategy, which can meet the needs for E2 precise quantification and rapid on-site detection. [Display omitted] • WSe 2 /TiO 2 enhanced PEC performance as a novel photoelectric material. • The nucleic acid amplification strategy significantly improves the sensitivity. • The dual-mode sensing mutually improved the detection accuracy for 17β-estradiol. • The biosensor exhibited a low detection limit of 0.026 pM. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has highlighted the need for rapid and sensitive detection of SARS-CoV-2. Here, we report an ultrasensitive SARS-CoV-2 immunosensor by integration of an AlGaN/GaN high-electron-mobility transistor (HEMT) and anti-SARS-CoV-2 spike protein antibody. The AlGaN/GaN HEMT immunosensor has demonstrated the capability to detect SARS-CoV-2 spike proteins at an impressively low concentration of 10−22 M. The sensor was also applied to pseudoviruses and SARS-CoV-2 ΔN virions that display the Spike proteins with a single virion particle sensitivity. These features validate the potential of AlGaN/GaN HEMT biosensors for point of care tests targeting SARS-CoV-2. This research not only provides the first HEMT biosensing platform for ultrasensitive and label-free detection of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Sensitive, rapid and low‐cost nucleic acid detection is critical for controlling infectious pathogens. Here, we develop a ready‐to‐use and multimodal detection based on a rebuilding‐free, ultrasensitive and selective strategy named dual hairpin ligation‐induced isothermal amplification pro (DHLApro). Taking influenza A, influenza B, MERS‐CoV, SARS‐CoV‐2 as model targets, we demonstrate DHLApro provides ≈zM level ultra‐sensitivity, being equaling to 0.45 copy/μL in original sample. By simply changing the recognition module, a set of DHLApro components can be applied to a new target without performance loss. Moreover, DHLApro innovatively allows flexible logic/multiplex assay using one set of primer, for example, the "N pathogens‐in‐1" OR gate screening and accurate multi‐channel multiplex assay. Compared with traditional methods, the cost of this logic/multiplex assay has been largely reduced and the cross‐interference between the multiple primer sets is also avoided. [ABSTRACT FROM AUTHOR]

Early detection and diagnosis are vitally important in reducing the mortality rate of fatal diseases but require highly sensitive detection of biomarkers. Presently, detection methods with the highest sensitivity require in vitro processing, while in vivo compatible fluorescence detections require a much higher concentration of biomarkers or limit of detection (LOD). In this paper, a fundamentally new strategy for ultrasensitive detection based on color‐switchable lasing with a cavity‐enhanced reduction of LOD is demonstrated, down to 1.4 × 10−16 mg ml−1 for a quantitative detection, lower than both the fluorescence method and plasmonic enhanced method. For a qualitative or a yes/no type of detection, the LOD is as low as 10–17 mg ml−1. The approach in this work is based on a dye‐embedded, in vivo compatible, polystyrene‐sphere cavity, penetrable by biomarkers. A polystyrene sphere serves the dual roles of a laser cavity and an in vivo bio‐reactor, in which dye molecules react with a biomarker, reporting biomarker information through lasing signals. The cavity‐enhanced emission and lasing with only a single biomarker molecule per cavity allow improved visual distinguishability via color changes. Furthermore, when combined with a narrow‐band filter, the color‐switchable lasers act as an "on‐off" logic signal and can be integrated into multiplexing detection assay biochips. [ABSTRACT FROM AUTHOR]

Greatly improving the sensitivity and detection range of lateral flow immunoassays (LFAs) by at least 100 times without using additional instruments remains challenging. Herein, we develop a three-dimensional (3D) film-like nanozyme (GO-Pt 30 -AuPt 5 ) by ordered assembly of one layer of 30 nm Pt nanoparticles (NPs) and one layer of small Au@Pt satellites (5 nm) onto a two-dimensional (2D) graphene oxide (GO) nanofilm, in which GO greatly increased the interface area and stability of the nanozyme whereas Pt and Au@Pt NPs synergistically enhanced colorimetric/catalytic activities. The grafting of outer Au@Pt satellites converted the 2D nanofilm into a 3D flexible nanozyme with numerous catalytic sites for enzymatic deposition signal amplification and binding sites for target capture. The introduction of GO-Pt 30 -AuPt 5 into multiplex LFA achieved the ultrasensitive and simultaneous detection of two important respiratory viruses with sensitivity of 1 pg/mL level, which was about 100 times higher than that without signal enrichment and at least 20 and 1900 times higher than those of traditional enzyme-linked immunosorbent assay and AuNP-based LFA, respectively. The clinical utility of the proposed assay was validated through the diagnosis of 49 real clinical respiratory tract specimens. Our proposed LFA shows great potential for the ultrasensitive screening of pathogens in the field.

Electrochemical sensors actually involve an electrocatalytic process involving an efficient and selective energy conversion that is related to the morphology and size of the interface of the modified materials. Ultrasmall nanoclusters or single atoms generate a greater catalytic ability than normal nanomaterials. In this study biochar-supported Cu nanoclusters (CuNCs@CNFs) were fabricated via a carbon confinement synthesis method toward ultrasensitive electrochemical sensing of ractopamine (RAC). RAC is a β-adrenergic receptor agonist that is illegally used as a feed additive to significantly improve muscle accretion, resulting in RAC accumulation in meat-based food products. The unique structure of CuNCs@CNFs and the interconnectivity between the CuNCs and the CNFs enable the nanocomposite to significantly enhance conductivity and electrocatalytic activity. Using the CuNCs@CNFs-based sensor, RAC was determined with a high sensitivity of 1641 μA μM−1 cm−2. The feasibility of detecting RAC in spiked meat samples was also carried out with satisfactory recoveries ranging from 91.39 % to 94.58 %.

Abstract Early detection and diagnosis are vitally important in reducing the mortality rate of fatal diseases but require highly sensitive detection of biomarkers. Presently, detection methods with the highest sensitivity require in vitro processing, while in vivo compatible fluorescence detections require a much higher concentration of biomarkers or limit of detection (LOD). In this paper, a fundamentally new strategy for ultrasensitive detection based on color‐switchable lasing with a cavity‐enhanced reduction of LOD is demonstrated, down to 1.4 × 10−16 mg ml−1 for a quantitative detection, lower than both the fluorescence method and plasmonic enhanced method. For a qualitative or a yes/no type of detection, the LOD is as low as 10–17 mg ml−1. The approach in this work is based on a dye‐embedded, in vivo compatible, polystyrene‐sphere cavity, penetrable by biomarkers. A polystyrene sphere serves the dual roles of a laser cavity and an in vivo bio‐reactor, in which dye molecules react with a biomarker, reporting biomarker information through lasing signals. The cavity‐enhanced emission and lasing with only a single biomarker molecule per cavity allow improved visual distinguishability via color changes. Furthermore, when combined with a narrow‐band filter, the color‐switchable lasers act as an “on‐off” logic signal and can be integrated into multiplexing detection assay biochips.

Ultrasensitive and selective determination of biomarkers of the bone metabolism in serum is crucial for early screening, timely treatment, and monitoring of the curative effect of osteoporosis, which is a silent disease with serious health threats. Immunoassay with a simple sensing interface and ultrahigh sensitivity is highly desirable. Herein, a simple electrochemical immunosensor is demonstrated based on gold nanoparticles (AuNPs) electrodeposited on chitosan-reduced graphene oxide (CS-G) composite modified electrode, which can achieve sensitive determination of the important biomarker of bone metabolism, bone gamma-carboxyglutamate protein (BGP). To overcome the agglomeration of graphene and introduce a biocompatible matrix with functional amino groups, CS-G is prepared and modified on the supporting glassy carbon electrode (GCE). Then, AuNPs are electrodeposited on CS-G through their interaction between amine groups of CS. The immobilized AuNPs provide numerous binding sites to immobilize anti-BGP antibodies (AbBGP). The specific recognition between BGP and AbBGP results in a reduction in the mass transfer of the electrochemical probe (Fe(CN)63-/4-) in solution, leading to a reduced electrochemical signal. Based on this mechanism, fast and ultrasensitive electrochemical detection of BGP is achieved when the concentration of BGP ranges from 100 ag ml−1 to 10 μg mL−1 with a limit of detection (LOD) of 20 ag ml−1 (S/N = 3). The determination of BGP in human serum is also realized with high reliability.

Manipulation of a multi‐physical quantity to steer a molecular photophysical property is of great significance in improving sensing performance. Here, an investigation on how a physical quantity rooted in the molecular structure induces an optical behavior change to facilitate ultrasensitive detection of ethylenediamine (EDA) is performed by varying a set of thiols. The model molecule consisting of a thiol with dual‐carboxyl exhibits the strongest fluorescence, which is ascribed to the electron‐donating ability and prompted larger orbital overlap and oscillator strength. The elevated fluorescence positively corelated to the increased EDA, endowing an ultrasensitive response to the nanomolar‐liquid/ppm‐vapor. A gas detector with superior performance fulfills a contactless and real‐time management of EDA. We envisage this electron‐tuning strategy‐enabled fluorescence enhancement can offer in‐depth insight in advancing molecule‐customized design, further paving the way to widening applications. [ABSTRACT FROM AUTHOR]

COVID-19 continues to spread and has been declared a global emergency. Individuals with current or past infection should be identified as soon as possible to prevent the spread of disease. Surface-enhanced Raman spectroscopy (SERS) is an analytical technique that has the potential to be used to detect viruses at the site of therapy. In this context, SERS is an exciting technique because it provides a fingerprint for any material. It has been used with many COVID-19 virus subtypes, including Deltacron and Omicron, a novel coronavirus. Moreover, flexible SERS substrates, due to their unique advantages of sensitivity and flexibility, have recently attracted growing research interest in real-world applications such as medicine. Reviewing the latest flexible SERS-substrate developments is crucial for the further development of quality detection platforms. This article discusses the ultra-responsive detection methods used by flexible SERS substrate. Multiplex assays that combine ultra-responsive detection methods with their unique biomarkers and/or biomarkers for secondary diseases triggered by the development of infection are critical, according to this study. In addition, we discuss how flexible SERS-substrate-based ultrasensitive detection methods could transform disease diagnosis, control, and surveillance in the future. This study is believed to help researchers design and manufacture flexible SERS substrates with higher performance and lower cost, and ultimately better understand practical applications. [ABSTRACT FROM AUTHOR]

Sensitive and accurate analysis of low‐concentration of tumor‐derived exosomes (Exos) in biofluids is essential for noninvasive cancer diagnosis but is still challenging due to the lack of high‐sensitive methods with low‐cost and easy‐operation. Herein, exploiting target Exos as a three‐dimensional (3D) track for the first time, we developed a self‐serviced‐track DNA walker (STDW) for wash‐free detection of tumor Exos using exosomal glycoprotein, which was enabled by split aptamer‐recognition‐initiated autonomous running powered by a catalytic hairpin assembly (CHA). Benefiting from high selectivity and sensitivity of the STDW assay, direct detection of tumor Exos in cell culture medium and serum could also be realized. Furthermore, this method exhibited high accuracy in clinical sample analysis, offering the potential for early cancer diagnosis and postoperative response prediction. [ABSTRACT FROM AUTHOR]

The isolation and identification of pathogenic bacteria from a variety of samples are critical for controlling bacterial infection-related health problems. The conventional methods, such as plate counting and polymerase chain reaction-based approaches, tend to be time-consuming and reliant on specific instruments, severely limiting the effective identification of these pathogens. In this study, we employed the specificity of the cell wall-binding (CBD) domain of the Staphylococcus aureus bacteriophage 80 alpha (80α) endolysin towards the host bacteria for isolation. Amidase 3-CBD conjugated magnetic beads successfully isolated as few as 1 × 102 CFU/mL of S. aureus cells from milk, blood, and saliva. The cell wall hydrolyzing activity of 80α endolysin promoted the genomic DNA extraction efficiency by 12.7 folds on average, compared to the commercial bacterial genomic DNA extraction kit. Then, recombinase polymerase amplification (RPA) was exploited to amplify the nuc gene of S. aureus from the extracted DNA at 37 °C for 30 min. The RPA product activated Cas12a endonuclease activity to cleave fluorescently labeled ssDNA probes. We then converted the generated signal into a fluorescent readout, detectable by either the naked eye or a portable, self-assembled instrument with ultrasensitivity. The entire procedure, from isolation to identification, can be completed within 2 h. The simplicity and sensitivity of the method developed in this study make it of great application value in S. aureus detection, especially in areas with limited resource supply. [ABSTRACT FROM AUTHOR]

Peanut allergy has garnered worldwide attention due to its high incidence rate and severe symptoms, stimulating the demand for the ultrasensitive detection method of peanut allergen. Herein, we successfully developed a novel electrochemical aptasensor for ultrasensitive detection Ara h1, a major allergenic protein present in peanuts. A conductive nickel atoms Anchored Hydrogen-Bonded Organic Frameworks (PFC-73-Ni) were utilized as excellent electrocatalysts toward hydroquinone (HQ) oxidation to generate a readable current signal. The developed electrochemical aptasensor offers wide linear range (1–120 nM) and low detection limit (0.26 nM) for Ara h1. This method demonstrated a recovery rate ranging from 95.00% to 107.42% in standard addition detection of non-peanut food samples. Additionally, the developed electrochemical method was validated with actual samples and demonstrated good consistency with the results obtained from a commercial ELISA kit. This indicates that the established Ara h1 detection method is a promising tool for peanut allergy prevention. • A novel biosensor was constructed using aptamers and HOF for Ara h1 detection. • This sensor offers low detection limit (0.26 nM) and wide linear range (1–120 nM). • Method was used to test 45 actual samples with good accuracy. [ABSTRACT FROM AUTHOR]

The exploitation of carbon dots (CDs) is now flourishing; however, more effort is needed to overcome their lack of intrinsic specificity. Herein, instead of synthesizing novel CDs, we reinvestigated three reported CDs and discovered that plain ammonium citrate CDs (AC-CDs) exhibited surprising specificity for Helicobacter pylori. Notably, we showed that the interfacial mechanism behind this specificity was due to the affinity between the high abundant urea/ammonium transporters on H. pylori outer membrane and the surface-coordinated ammonium ions on AC-CDs. Further, we justified that ammonium sulfate-citric acid CDs also possessed H. pylori-specificity owing to their NH4+ doping. Thereby, we suggested that the incorporation of a molecule that could be actively transported by abundant membrane receptors into the precursors of CDs might serve as a basis for developing a plain CD with intrinsic specificity for H. pylori. Moreover, AC-CDs exhibited specificity towards live, dead, and multidrug-resistant H. pylori strains. Based on the specificity, we developed a microfluidics-assisted in vitro sensing approach for H. pylori, achieving a simplified, rapid and ultrasensitive detection with two procedures, shortened time within 45.0 ​min and a low actual limit of detection of 10.0 ​CFU ​mL−1. This work sheds light on the design of more H. pylori-specific or even bacteria-specific CDs and their realistic translation into clinical practice.

Principle of An rolling circle amplification-assisted CRISPR/Cas12a for HbA1c detection: [Display omitted] • The clever combination of magnetic beads, antibody and rolled loop amplification improves sensitivity. • The PAM sequence on the double-stranded DNA specifically recognized by CRISPR Cas12a is split into two parts. • High sensitivity, high specificity, short detection time, simple operation. • The detection limit in buffer is 0.129 pg/mL. The detection limit in serum is 0.317 pg/mL. Glycated hemoglobin (HbA1c) has been extensively studied as a pivotal marker for monitoring and diagnosing diabetes. In this study, we introduce a highly sensitive and rapid enzyme-catalyzed rolling circle amplification (RCA)-assisted nicked-PAM CRISPR/Cas12a assay (termed "RANPC"). The RANPC system initially recognizes and captures the target using immunomagnetic beads and antibodies, forming a sandwich structure. The antibodies, upon ligating the primers, trigger the RCA reaction, resulting in the generation of single-stranded DNA with numerous repetitive sequences. The product strand of RCA then initiates the trans -cutting activity of nicked-PAM CRISPR/Cas12a, ultimately reporting the target concentration through fluorescent signaling. This study combines dual antibody capture, signal amplification through RCA, and signal output by Cas12a, resulting in high sensitivity, high specificity, and high signal-to-noise ratio. Moreover, the strategic incorporation of an incomplete PAM design in the CRISPR/Cas12a system substantially reduces background interference and enhances assay specificity relative to previous conventional Cas12a detection methods. RANPC possesses advantages such as ultra-sensitivity (with the lowest detection limit up to 0.129 pg/mL and a linear range of 12.8 pg/mL to 1 µg/mL), high specificity, rapid reaction time (approximately 50 min), and straightforward operation. Under optimized experimental conditions, we successfully detected HbA1c in eight real-world blood samples, and the results were in good agreement with the theoretical values. This suggests that this method holds promise as a new approach for the analysis of HbA1c levels in the clinical setting. [ABSTRACT FROM AUTHOR]

As a major public health issue, early cancer detection is of great significance. A field-effect transistor (FET) based on an MoS2/C60 composite nanolayer as the channel material enhances device performance by adding a light source, allowing the ultrasensitive detection of cancer-related miRNA. In this work, atomic layer deposition (ALD) was used to deposit MoS2 layer by layer, and C60 was deposited by an evaporation coater to obtain a composite nanolayer with good surface morphology as the channel material of the FET. Based on the good absorption of C60 by blue-violet light, a 405 nm laser was selected to irradiate the channel material, improving the function of FET biosensors. A linear detection window from 10 pM to 1 fM with an ultralow detection limit of 5.16 aM for miRNA-155 was achieved.

Ultrasensitive and specific detection of prostate-specific antigen (PSA) in complex biological samples is crucial for early diagnosis and treatment of prostate-related diseases. Immunoassay with a simple sensing interface and ultrahigh sensitivity is highly desirable. Herein, a novel electroluminescence (ECL) immunosensing platform is demonstrated based on the equipment of vertically ordered mesoporous silica-nanochannel films (VMSFs) with PSA antibody, which is able to realize ultrasensitive detection of PSA in human serum. Through the electrochemically assisted self-assembly (EASA) method, the VMSF is easily grown on an indium tin oxide (ITO) electrode in a few seconds. Owing to a large surface area and the negatively charged surface, VMSF nanochannels display strong electrostatic attraction to the positively charged ECL luminophores (tris(2,2-bipyridyl) dichlororuthenium (II), (Ru(bpy)32+), leading to two orders-of-magnitude enhancement of ECL emission compared with that of the bare ITO electrode. The outer surface of the VMSF is functionalized with reactive epoxy groups, which further allows covalent attachment of PSA antibody (Ab) on the entry of nanochannels. As the combination of PSA with Ab decreases the ECL signal by hindering the mass transfer of ECL luminophores and coreactant, the developed immunosensor can achieve ultrasensitive detection of PSA ranging from 1 pg ml−1 to 100 ng ml−1 with a limit of detection (LOD) of 0.1 pg ml−1. Considering the antifouling ability of the VMSF, sensitive detection of PSA in human serum is also realized. The proposed nanochannel-based immunosensor may open up a new way for the facile development of the universal immunosensing platform for rapid and ultrasensitive detection of disease markers.

Objective: The spread of bovine spongiform encephalopathy (BSE) agent to small ruminants is still a major issue in the surveillance of transmissible spongiform encephalopathies (TSEs). L-type bovine spongiform encephalopathy (L-BSE) is an atypical form of BSE with an unknown zoonotic potential that is transmissible to cattle and small ruminants. Our current knowledge of bovine atypical prion strains in sheep and goat relies only on experimental transmission studies by intracranial inoculation. To assess oral susceptibility of goats to L-BSE, we orally inoculated five goats with cattle L-BSE brain homogenates and investigated pathogenic prion protein (PrPsc) distribution by an ultrasensitive in vitro conversion assay known as Real-Time Quaking Induced Conversion (RT-QuIC). Results: Despite a prolonged observation period of 80 months, all these animals and the uninfected controls did not develop clinical signs referable to TSEs and tested negative by standard diagnostics. Otherwise, RT-QuIC analysis showed seeding activity in five out of five examined brain samples. PrPsc accumulation was also detected in spinal cord and lymphoreticular system. These results indicate that caprine species are susceptible to L-BSE by oral transmission and that ultrasensitive prion tests deserve consideration to improve the potential of current surveillance systems against otherwise undetectable forms of animal prion infections. [ABSTRACT FROM AUTHOR]

Recently, nitrogen-doped graphene quantum dots (NGQDs), as a new type of quantum semiconductor and photoelectrochemical material, are promising candidates in photoelectric sensing, water splitting, and biological imaging and have various potential application prospects. In this work, NGQDs were prepared by a simple calcination method, and then a photoelectrochemical sensing platform based on the NGQDs electrode with superior photoelectrochemical activity was designed and fabricated for the detection of dopamine (DA). Benefitting from the quantum effect and size effect, NGQDs displayed an enhanced photocurrent effective within ultra-low detection limit (0.03 μm), wide detection range (0.03–450 and 450–9680 μm), and high sensitivity in detecting DA with the assistance of ultraviolet light irradiation. The NGQDs electrode also showed continuous and stable photocurrent densities after long-term experiment, indicating the excellent durability of NGQDs for DA detection.

Malondialdehyde (MDA), one of the most important products of lipid peroxidation, has been widely accepted as a biomarker to indicate food rancidity as well as the progress of some human diseases. However, ready detection of MDA with ultra-high sensitivity remains a challenge. In this work, a microfluidic surface-enhanced Raman scattering (SERS) sensing chip based on phosphoric acid induced nanoparticles aggregation was proposed for ultrasensitive MDA detection. The sensing chip was composed of an ultrafast microfluidic mixer, which efficiently transferred analytes to hot spots via the mixer assisted hot spots occupying (MAHSO) SERS strategy. Phosphoric acid, a reagent used in MDA detection, played the role of aggregator to induce aggregation of silver nanoparticles (Ag NPs); meanwhile, as fast as a few milliseconds mixing time effectively prevented over-aggregation of Ag NPs. Therefore, this process generated a uniform and dense SERS substrate with analyte molecules located in hot spots. As a result, the MDA SERS sensing chip possessed a limit of detection (LOD) lower than 3.3 × 10−11 M, high spot-to-spot uniformity with a relative standard deviation (RSD) of 9.0% and an excellent batch-to-batch reproducibility with a RSD of 3.9%. This method also demonstrated excellent specificity and reliability in real sample detection with recoveries of 90.4–109.8% in spiked tests.

Tracking trace protein analytes in precision diagnostics is an ongoing challenge. Here, we developed an ultrasensitive detection method for the detection of SARS-CoV-2 nucleocapsid (N) protein by combining enzyme-linked immunosorbent assay (ELISA) with the clustered regularly interspaced short palindromic repeat/CRISPR-associated protein (CRISPR/Cas) system. First, the SARS-CoV-2 N protein bound by the capture antibody adsorbed on the well plate was sequentially coupled with the primary antibody, biotinylated secondary antibody, and streptavidin (SA), followed by biotin primer binding to SA. Subsequently, rolling circle amplification was initiated to generate ssDNA strands, which were targeted by CRISPR/Cas12a to cleave the FAM-ssDNA-BHQ1 probe in trans to generate fluorescence signals. We observed a linear relationship between fluorescence intensity and the logarithm of N protein concentration ranging from 3 fg/mL to 3 × 10 7 fg/mL. The limit of detection (LOD) was 1 fg/mL, with approximately nine molecules in 1 μL of the sample. This detection sensitivity was 4 orders magnitude higher than that of commercially available ELISA kits (LOD: 5.7 × 10 4 fg/mL). This method was highly specific and sensitive and could accurately detect SARS-CoV-2 pseudovirus and clinical samples, providing a new approach for ultrasensitive immunoassay of protein biomarkers.

Nanotechnology has attracted much attention, and may become the key to a whole new world in the fields of food, agriculture, building materials, machinery, medicine, and electrical engineering, because of its unique physical and chemical properties, including high surface area and outstanding electrical and optical properties. The bottom-up approach in nanofabrication involves the growth of particles, and we were inspired to propose a novel nanoplasmonic method to detect the formation of nanoparticles in real time. This innovative idea may contribute to the promotion of nanotechnology development. An increase in nanometer particle size leads to optical extinction or density (OD)-value changes in our nanosensor chip at a specific wavelength measured in a generic microplate reader. Moreover, in applying this method, an ultrasensitive nanoplasmonic immunoturbidimetry assay (NanoPITA) was carried out for the high-throughput quantification of hypersensitive C-reactive protein (CRP), a well-known biomarker of cardiovascular, inflammatory, and tumor diseases. The one-step detection of the CRP concentration was completed in 10 min with high fidelity, using the endpoint analysis method. The new NanoPITA method not only produced a linear range from 1 ng/mL to 500 ng/mL CRP with the detection limit reduced to 0.54 ng/mL, which was an improvement of over 1000 times, with respect to regular immunoturbidity measurement, but was also effective in blood detection. This attractive method, combined with surface plasmon resonance and immunoturbidimetry, may become a new technology platform in the application of biological detection.

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An ultrasensitive electrochemical sensor has been constructed for the detection of single nucleotide polymorphisms (SNPs) based on DNA-functionalized Cd-MOFs-74 as cascade signal amplification probe under enzyme-free conditions. Interestingly, the introduction of an auxiliary probe did not disturb the detection of SNP targets, but could bind more Cd-MOFs-74 signal elements to enhance the different pulse voltammetry electrochemical signal 2~3 times as compared to sensing system without auxiliary probe, which obviously improves the sensitivity of the proposed sensor. Experimental results taking p53 tumor suppressor gene as SNP model demonstrated that the proposed method can be employed to sensitively and selectively detect target p53 gene fragment with a linear response ranging from 0.01 to 30 pmol/L (detection limit of 6.3 fmol/L) under enzyme-free conditions. Utilizing this strategy, the ultrasensitive SNP electrochemical sensor is a promising tool for the determination of SNPs in biomedicine. [ABSTRACT FROM AUTHOR]

A combination of SiO 2 @AuNPs@PDA molecularly imprinted and surface-assisted laser desorption/ionization–time-of-flight mass spectrometry (SALDI–TOF MS) was devised as a method for highly specific and ultrasensitive detection of two biogenic amines—histamine (HIS) and tryptamine (TRP)—in real samples. In this strategy, AuNPs modified amino-abundant silica nanospheres (SiO 2 @AuNPs). The prepared SiO 2 @AuNPs were used as a substrate to synthesize a molecularly imprinted polymer (MIP) through in situ dopamine self-polymerization with HIS and TRP as the template molecules (SiO 2 @AuNP@PDA-MIP). The as-prepared MIP structure, properties, and target-analyte identification conditions were characterized and optimized and it was used as the matrix for MS. Compared to the case of nonimprinted materials, the imprinting function endowed the matrix with a higher selectivity for capturing the target molecules. The enriched analytes were directly and rapidly identified using SALDI–TOF MS without elution. Meanwhile, the proposed method has low background interference, good reproducibility and stability, high salt tolerance, and satisfactory linearity (R2 > 0.99), and it enables ultrasensitive detection of HIS and TRP (limits of detection for HIS and TRP were 0.2 and 0.1 ng mL−1, respectively). Moreover, the proposed method was applied to analyze samples of real beer, sausage, and chicken, and the results agreed with those obtained via liquid chromatography–MS, suggesting that the method has excellent practical applications in the field of food safety. Integration of double template MIP and SALDI-TOF MS was developed for simple, rapid, highly selective and sensitive identification of two BAs in real samples. [Display omitted] • Integration of MIP and SALDI-TOF MS for simple, rapid and highly selective and sensitive detection of BAs. • The imprinted sites in adsorbents can selectivity enrich targtet analytes. • The enriched anlytes-MIP can be directly analysized, while no elution. • The good biocompatibility of PDA-imprinted material contributes to satisfactory reproducibility. [ABSTRACT FROM AUTHOR]

• Metribuzine is a commonly used triazinone herbicide and should be monitored rigorously in terms of food and environmental safety. • Surface enhanced raman spectroscopy which utilises conductive nano particles enables detection of metrubizine at even ultra low concentrations. • SERS method does not require any expensive consumables and provides the analysis results in a few seconds. • Ag nanocubes which are synthesized for detection of metrubizine at ultra low concentrations displayed an excellent performance in terms of chemical stability, reproducibility and sensitivity. Metribuzin, which is a triazinone herbicide, is extensively used in agricultural activities in order to control the spread of broad leaved weeds and grasses. This herbicide is treated as a hazardous chemical, since it multiplies the contamination in the ecosystem by infiltrating to groundwater and soil layers. Thus, detection of Metribuzin in even low concentrations is of vital importance. To date, analytical methods such as High Performance Liquid Chromatography (HPLC), reversed-phase thin-layer chromatography (RP-TLC) with UV absorption detection, Gas chromatography, and Mass spectrometry were utilized in order to detect Metribuzin. At this point, Surface Enhanced Raman Spectroscopy (SERS), while being not as analytical as the methods discussed above, emerges as a significant alternative, since it requires almost no consumables, requires a very short time for analysis and it allows on site analysis. In this study Ag nanocubes were synthesized as a SERS substrate and They were utilized for detection of Metribuzin at concentrations from 10−3 to 10−10 M. Reproducibility, sensitivity and chemical stability tests exhibited that Ag nanocubes were excellent candidates of SERS substrates by allowing detection at ultra- low concentrations up to 10−10 M. [Display omitted] [ABSTRACT FROM AUTHOR]

The detection of melanoma circulating biomarker in liquid biopsies is current under evaluation for being potentially utilized for earlier cancer diagnosis and its metastasis. Herein, we developed a non-invasive electrochemical approach for ultrasensitive detection of the S100B, serving as a potential promising blood circulating biomarker of melanoma, based on an aggregation-induced signal amplification (AISA) strategy via in-situ peptide self-assembly. The fundamental principle of this assay is that the designed amphiphilic peptides (C 16 -Pep-Fc), fulfilling multiple functions, feature both a recognition region for specific binding to S100B and an aggregation (self-assembly) region for the formation of peptide nanomicelles under mild conditions. The C 16 tails were encapsulated within the hydrophobic core of the aggregates, while the relatively hydrophilic recognition fragment Pep and Fc tag were exposed on the outer surface for subsequent recognition of S100B and signal output. AISA provided remarkable accumulation of electroactive Fc moieties that enabled ultrasensitive S100B detection of as low as 0.02 nM, which was 10-fold lower than un-amplified approach and better than previously reported assays. As a proof-of-concept study, further experiments also highlighted the good reproducibility and stability of AISA and demonstrated its usability when applied to simulated serum samples. Hence, this work not only presented a valuable assay tool for ultrasensitive detecting protein biomarker, but also advocated for the utilization of aggregation-induced signal amplification in electrochemical biosensing system, given its considerable potential for future practical applications. An aggregation-induced signal amplification (AISA) strategy based on in-situ peptide self-assembly is developed for ultrasensitive electrochemical detection of melanoma biomarker. The designed amphiphilic peptide can fulfill multiple functions including both specific recognition for biomarker S100B binding and aggregation to enhance the loading capacity of signal tags (Fc) for signal enhancement, resulting in 10-fold decrease in the detection limit. [Display omitted] • A new aggregation-induced signal amplification based on in-situ peptide self-assembly. • Simultaneous signal amplification and specific recognition due to amphiphilic peptide. • The ability to achieve reduced time-cost and improved detection efficiency. • The signal amplification strategy displays 10-fold higher than un-amplified strategy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-layer architecture of NiMOFs was synthesized and characterized by SEM, XRD, XPS, Raman, IR, and EIS. • The insertion of helical-shaped MWCNTs into NiMOFs has been done for enhanced electrocatalytic sensing applications. • The surface adsorption efficiency of the different modified electrodes was discussed. • The designed binder-free (GCE/MWCNT@NiMOFs) electrochemical probe exhibited a satisfactory limit of detection and wide linear response. • The designed electrochemical probe was successfully employed in real-world samples and achieved excellent recovery ranges with high reproducibility. Nitroimidazole-based drugs are widely used as an antibiotic for the treatment of anaerobic bacterial and parasite illnesses. The widespread use of these drugs in animal feed and the consequent environmental pollution have become significant concerns in recent years. Simple, sensitive, and rapid detection of the antibody in various real samples is demanding research interest. Herein, we report a Nickel-metal organic framework functionalized Multiwalled Carbon nanotubes modified glassy carbon electrode (MWCNT@NiMOFs) as an ultrasensitive and rapid voltammetric sensor for the detection of ornidazole (ORDZ) in a neutral pH solution. The MWCNT@NiMOFs were prepared using a microwave-assisted solvothermal technique accompanied by an ultrasonication method. The designed MWCNT@NiMOFs offered a low charge transfer resistance (R ct) of 141 Ω along with excellent electrocatalytic activity, and high current density at the lowered cathodic peak potential (-0.62 V vs Ag/AgCl) for ORDZ detection. The surface adsorption capacity (Γ s) in terms of surface excess and heterogeneous charge transfer rate constant (k 0) of the MWCNT@NiMOFs were calculated to be 3.29 × 10-9 mol cm−2 and 5.33 × 10-3 cm s−1, respectively. Under an optimal working condition, differential pulse voltammetry measurements of ORDZ have shown concentration linearity in a window, 100 nm to 10 µM range with excellent sensitivity, 5.69 × 10-5A µM−1 cm−2, and detection limit, 26 nM (3.3/s). The designed MWCNT@NiMOFs offered appreciable reproducibility, and repeatability up to 30 days of storage time. The real-time quantitative evaluation of ORDZ in human urine and tap water specimens was done along with ∼ 100 % recovery values. Since the new approach is simple, selective, and separation-free, it can be extendable to a variety of real-time practical applications. [ABSTRACT FROM AUTHOR]

Ultrasensitive analytical methods are still urgent for the discovery of trace level biomarkers and the early clinical diagnosis of disease. In this work, an ultrasensitive universal sensing platform was constructed by integrating fluorescent assay with chemical-chemical redox cycling signal amplification strategy. Using Ru@SiO 2 nanoparticles wrapped by MnO 2 nanosheets (Ru@SiO 2 @MnO 2) as fluorescent probe, the chemical-chemical redox cycling system was conducted upon ascorbic acid (AA) and tris(2-carboxyethyl)phosphine (TCEP) as reductants and MnO 2 nanosheets as oxidant. The MnO 2 nanosheets not only could quench the fluorescence of Ru@SiO 2 nanoparticles to reduce the background, but also could serve as oxidants to react with AA, generating dehydroascorbic acid (DHA). The DHA was reduced by TCEP in turn to form AA that participated in the next cycling of chemical-chemical redox reaction. Thus, the constantly released AA from the chemical-chemical redox cycling system could massively etch MnO 2 nanosheets on Ru@SiO 2 surface, making the fluorescence of Ru@SiO 2 nanoparticles greatly recovered. It was shown that the sensitivity of the fluorescent assay was improved almost 52 times by utilizing the chemical-chemical redox cycling signal amplification strategy. This strategy was further employed to detect DNA methylation with the aid of AA-encapsulated liposomes that were modified with 5 mC antibodies to bind with the methylated DNA captured in 96-well plate. A detection of limit down to 16.2 fM was achieved for the detection of methylated DNA. It's believed that the incorporation of chemical-chemical redox cycling signal amplification strategy into fluorescent sensing paves a new way for ultrasensitive detection of biomarkers. Liposome assisted chemical-chemical redox cycling signal amplification for ultrasensitive fluorescent detection of DNA methylation. [Display omitted] • Chemical-chemical redox cycling signal amplification strategy was firstly integrated into fluorescent sensing. • The sensitivity of fluorescent assay was improved almost 52 times. • This proof-of-concept was employed to detect of DNA methylation with the assistance of liposomes. • A detection limit (LOD) down to 16.2 fM was achieved for methylated DNA detection. [ABSTRACT FROM AUTHOR]

COVID-19 continues to spread and has been declared a global emergency. Individuals with current or past infection should be identified as soon as possible to prevent the spread of disease. Surface-enhanced Raman spectroscopy (SERS) is an analytical technique that has the potential to be used to detect viruses at the site of therapy. In this context, SERS is an exciting technique because it provides a fingerprint for any material. It has been used with many COVID-19 virus subtypes, including Deltacron and Omicron, a novel coronavirus. Moreover, flexible SERS substrates, due to their unique advantages of sensitivity and flexibility, have recently attracted growing research interest in real-world applications such as medicine. Reviewing the latest flexible SERS-substrate developments is crucial for the further development of quality detection platforms. This article discusses the ultra-responsive detection methods used by flexible SERS substrate. Multiplex assays that combine ultra-responsive detection methods with their unique biomarkers and/or biomarkers for secondary diseases triggered by the development of infection are critical, according to this study. In addition, we discuss how flexible SERS-substrate-based ultrasensitive detection methods could transform disease diagnosis, control, and surveillance in the future. This study is believed to help researchers design and manufacture flexible SERS substrates with higher performance and lower cost, and ultimately better understand practical applications.

In the present work, we reported a one pot simple colloidal–gel synthesis of molybdenum bismuth vanadate (MoBiVO4). The charge transfer property of MoBiVO4 was improved by developing a composite with graphene oxide (GO) through sonochemical technique. The optical and morphological analysis revealed that successful formation of GO-MoBiVO4 composite without any other filth. As prepared composite was used to modify the superficial surface of glassy carbon electrode (GO-MoBiVO4/GCE) and applied for the selective detection of environmental pollutant 2, 4, 6 trichrlorophenol (TCP). The electron channeling capability of GO with molybdenum bismuth vanadate possessed a superior electrochemical response in cyclic voltammetry (CV), whereas bare GCE and other modified electrodes provided an inferior response with lower current response. The differential pulse voltammetry (DPV) response of TCP at GO-MoBiVO4/GCE outcomes with low level detection of 0.4 nM and higher sensitivity of 2.49 μA μM−1 cm−2 with wider linear response 0.199–17.83 μM. Furthermore, the proposed sensor applied in practicability analysis and the results indicates GO-MoBiVO4/GCE prominent towards electrochemical detection of TCP.

Using dendritic mesoporous silica nanoparticles (DMSNs) for quantum dots (QDs) enrichment and signal amplification is an emerging strategy for improving the detection sensitivity of lateral flow immunoassay (LFIA). In this study, a new and convenient approach is developed to prepare water‐dispersible DMSNs‐QDs. A series of DMSNs with various diameters (138, 251, 368, and 471 nm) are studied for loading QDs and LFIA applications. The resultant water‐dispersible DMSNs‐QDs exhibit a high fluorescence retention of 81.8%. The increase in particle size from 138 to 471 nm results in an increase in loading capacity of QDs and a decrease in binding quantity of the DMSNs‐QDs in the test line of LFIA. This trade‐off leads to an optimal DMSNs‐QDs size of 368 nm with a limit of detection reaching 10 pg mL−1 (equivalent to 9.0 × 10−14m) for the detection of C‐reactive protein, which is nearly an order of magnitude more sensitive than the literature. To the best of the authors' knowledge, this study is the first to demonstrate the distinctive role of DMSN's size for QDs enrichment and LFIA. The strategy developed from this work is useful for the rational design of high‐quality QDs‐based nanoparticles for ultrasensitive detection. [ABSTRACT FROM AUTHOR]

Signal amplification is a key step that determines the sensitivity of molecular assays. Although studies on aptamers have mostly focused on their target-binding ability, taking advantage of the gene-coding function of nucleic acids, we demonstrate here that aptamers can be engineered into diagnostic reagents that can both recognize a target and generate highly amplified detection signals. We developed a strategy that employs a 'readable' aptamer that consists of a single-stranded aptamer and a double-stranded reporter gene. After binding to its target via the aptamer region, the reporter gene of the readable aptamer produces amplified number of signal-generating enzymes through a subsequent in vitro expression reaction. In contrast to conventional enzyme-conjugation methods, this method allows the generation of far more amplified detection signals, thereby markedly increasing the sensitivity of detection enough to analyze a target present in aM concentrations. Image 1 • Efficiency of signal amplification determines the sensitivity of a bioassay method. • Compared to antibodies, aptamers carry substantial advantages, including lower production cost and higher stability. • Readable aptamers can both recognize and produce amplified number of signal-generating enzymes. • The ALIVE assay that employs the readable aptamers could detect thrombin present in attomolar concentrations. [ABSTRACT FROM AUTHOR]

The development of a rapid and sensitive method for the detection of fluoride ion (F−) in aqueous systems is of great significance for human health and environmental monitoring. In this study, a zirconium porphyrinic luminescent metal-organic framework (LMOF), PCN-222, was employed as a novel fluorescent probe for the ultrasensitive, rapid and selective detection of F− in water. The PCN-222 probe was prepared by a facile solvothermal method. It exhibited good fluorescence stability and was highly stable in water. The fluorescence emission of PCN-222 could be effectively and selectively quenched by F− due to the strong coordination affinity of F− to the zirconium clusters in PCN-222. The proposed fluorescence method for F− detection based on PCN-222 probe afforded a linear response range of 1–20 μmol/L and a very low detection limit (0.048–0.065 μmol/L) in reference to many reported F− fluorescent probes. Moreover, a rapid response time (<10 s) was obtained due to the open and uniform pore structure of PCN-222 that allowed the fast diffusion of F− to interact with the zirconium recognition sites. Finally, the PCN-222 probe was successfully applied for the fluorescence detection of F− in real water samples. These results highlight the great application potential of LMOF in the sensing fields. Image 1 • Highly stable zirconium-based LMOF (PCN-222) was successfully applied in F− detection in water. • PCN-222 afforded very short F− response time (<10 s) due to its open and uniform pore structure. • The LOD was markedly lower than WHO and US EPA guidelines and many reported F− sensors. [ABSTRACT FROM AUTHOR]

Accurately acquiring crucial data on the ambient surroundings and physiological processes delivered via subtle temperature fluctuation is vital for advancing artificial intelligence and personal healthcare techniques but is still challenging. Here, we introduce an electrically induced cation injection mechanism based on thermal-mediated ion migration dynamics in an asymmetrical polymer bilayer (APB) composed of nonionic polymer and polyelectrolyte layers, enabling the development of ultrasensitive flexible temperature sensors. The resulting optimized sensor achieves ultrahigh sensitivity, with a thermal index surpassing 10,000 K -1 , which allows identifying temperature differences as small as 10 mK with a sensitivity that exceeds 1.5 mK. The mechanism also enables APB sensors to possess good insensitivity to various mechanical deformations─features essential for practical applications. As a proof of concept, we demonstrate the potential impact of APB sensors in various conceptual applications, such as mental tension evaluation, biomimetic thermal tactile, and thermal radiation detection.