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It is highly desirable to detect malononitrile in organisms and human bodies owning to its inherent toxicity. With dicyanovinyl as the recognition site, a Michael addition reaction-based fluorescent probe Hcy-DCV was developed for malononitrile detection. A notable advantage of this probe is that it responds quickly to malononitrile without any additive to speed the sensing reaction. It has a good water solubility and the detection limit was determined to be 6.92 ppb in 100% aqueous solution. In particular, Hcy-DCV exhibited good selectivity towards malononitrile over other interfering substances including hydrazine and other active methylene compounds. The probe was applied successfully to quantitate malononitrile in pure water with satisfying recovery and relative standard deviation. Additionally, the ability of visualizing malononitrile by using probe-coated strip papers was displayed, which may facilitate the on-site detection of malononitrile. Moreover, the bioimaging of malononitrile in living H1975 cells and zebrafish larvae was also demonstrated. All the experimental results suggested the potential of Hcy-DCV for practical detection of malononitrile in both environmental and biological samples. [ABSTRACT FROM AUTHOR]

Tracing toxic cyanide (CN−) in water and cyanogenic food samples is a demanding task for the research community. However, the poor solubility of organic probes in aqueous media often becomes a huge hurdle for in-field application. Herein, a novel colorimetric water-soluble polymeric probe, p(N,N′-dimethylacrylamide-co-azo-dicyano) (p(DMA-co-azo-dicyano)), P1, was created and synthesized for the purpose of detecting CN− in 100% water. Specifically, P1 was synthesized via post-polymerization modification of (p(DMA-co-azo-aldehyde)) with malononitrile. P1 demonstrated selective sensing behaviour toward CN− in water at physiological pH using intramolecular charge transfer (ICT) as a mechanism. Upon the inclusion of CN−, the color of P1 changed from red to yellow (a ∼57 nm blue shift) with the lower limit of detection (LOD) of 0.008 mM. Additionally, P1-coated test strips were used for "in-the-field" measurements for CN− detection in aqueous solution and cyanogenic food samples. [ABSTRACT FROM AUTHOR]

In this paper, NiCo-X (X = OH, S, P, Se) nanodiscs (NDs) were synthesized. Firstly, nickel-cobalt hydroxide (NiCo-OH) precursors with a nanodisc-like structure were prepared by a hydrothermal method. In the next step, nickel-cobalt sulfide nanodiscs (NiCo-S NDs), nickel-cobalt selenide nanodiscs (NiCo-Se NDs), and nickel-cobalt phosphide nanodiscs (NiCo-P NDs) were obtained from the synthesized NiCo-OH NDs in the previous step. The NiCo-Se NDs and NiCo-P NDs were prepared by selenization and phosphidation processes of the NiCo-OH NDs in a tube furnace containing a N2 atmosphere. The electrocatalytic performance of the mentioned nanodiscs is compared in the electrochemical determination of isoprenaline (IP) as a template. The results showed that the NiCo-Se NDs show better electrocatalytic activity compared to the other nanodiscs studied. The NiCo-Se ND-modified glassy carbon electrode (NiCo-Se NDs/GCE) showed a low detection limit (0.16 μM) and wide linear range (0.5−750 μM) of IP. The proposed substrate was successfully used for measuring IP in human blood serum samples. This study provides insights into the development of polymetallic nanodiscs in the field of electrochemical applications. In addition, our results are promising for usage in other electrochemical applications. [ABSTRACT FROM AUTHOR]

A TPA-ME fluorescent probe, based on triphenylamine derivative TPA-CHO, has been designed, synthesized and characterized by different spectroscopic methods successfully. TPA-ME and TPA-CHO present similar aggregation-induced emission (AIE) effects under same conditions. Due to the deprotection reaction of mercaptal promoted by mercury ions (Hg2+), TPA-ME exhibits excellent selectivity and anti-inference properties over other tested ions in the DMF/H2O (fw 70%, pH 6.8) medium. Upon increasing Hg2+, the fluorescence of the TPA-ME probe shows an obvious red-shift from blue to green. The fluorescence intensity has a good linearity toward Hg2+, with the limit of detection (LOD) below 1.23 × 10−7 mol L−1. A theoretical calculation was carried out to understand the difference between TPA-ME and TPA-CHO, and experimental results have been met with simulation calculations. Along with the result of the fluorescence change, Hg2+ can be easily tested through a conveniently prepared test paper. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescence method based on carboxylated graphitic carbon nitride nanosheets (C-g-C3N4) and Eu3+ (C-g-C3N4-Eu3+) is described for the detection of tetracyclines (TCs), a broad-spectrum antibiotic. C-g-C3N4, which was used as a fluorescence enhancer of Eu3+, was prepared by direct pyrolysis of melamine and post-functionalization. In the presence of TCs, the fluorescence intensity of Eu3+ at 616 nm increased, accompanied by a decrease of fluorescence intensity of C-g-C3N4 at 435 nm. Under the optimal conditions, the ratio of fluorescence intensity at 616 nm to the one at 435 nm (I616/I415) increases linearly in the 10 nM to 40 μM TC concentration range with a detection limit of 7.7 nM (S/N = 3). It has been successfully applied in the detection of TCs in spiked tap water and soil samples with satisfactory recovery (96.6–107.2%) and high precision. Furthermore, a test paper and smartphone can assist in rapidly detecting TCs due to the emission color change from blue to red with the addition of TCs. This shows that the proposed method has great potential for the rapid detection TCs in real samples. [ABSTRACT FROM AUTHOR]

Excessive Fe3+ and Bi3+ can cause serious hazards to human-beings and microorganisms. However, it remains a great challenge to exploit more efficient methods to detect them. In this work, a two-dimensional (2-D) metal–organic framework (MOF) [Cd(3-L)(NDA)(H2O)]n (1) (3-L = 3,3′-((9H-fluoren-9-ylidene)-methylene)dipyridine; H2NDA = 1,4-naphthalenedicarboxylic acid) was successfully fabricated by a new fluorenyl-containing aggregation-induced emission (AIE) functional ligand. 1 features a 2-D (4,4) network, and good water and thermal stabilities. In its stacking structure, the fluorene rings from neighboring layers overlap with each other in the opposite direction, and show very weak π–π interactions. Accordingly, 1 exhibits superior luminescence enhancement ("turn-on") sensing of Fe3+ and Bi3+ with extremely high sensitivity in aqueous media. The detection limits of 1 for Fe3+ and Bi3+ are 4.86 × 10−4 and 1.87 × 10−5 mM, respectively, which are significantly lower than the corresponding reported works (only 23.6% and 0.8%). Interestingly, it has obviously enhanced Bi3+ detecting ability because of the larger ionic radius of Bi3+. More importantly, this is the first MOF-based "turn-on" sensor for Bi3+ reported to date. [ABSTRACT FROM AUTHOR]

The current luminescent metal-organic framework (MOF) based fluorescence detection mostly focuses on achiral molecules. The stereospecific recognition and determination of MOF-based detection remain challenging. A novel luminescent terbium-based MOF (Tb-MOF) based biosensing system with excellent performance for stereoselective detection of D-amino acids (D-AAs) was introduced in this paper. D-Amino acid oxidase catalyzes stereospecific oxidative deamination of D-AAs, producing H2O2. The generated H2O2 effectively quenches the fluorescence of Tb-MOF. Under optimum conditions, the D-AAs were detected with excellent efficiency. The linear working range was 0.5-100 mM for D-Alanine (D-Ala) and 0. 5-5 mM for D-Proline (D-Pro), respectively. The limit of detection (Ksv detection) for D-Ala and D-Pro was 0.09 mM and 0.14 mM, respectively. The detection can be performed within 30 min with high selectivity and long-term stability. The fluorescent sensing platform required simple fabrication and operation and was free from complicated reaction processes and expensive reagents. The present sensing system was successfully applied in D-AA detection in human serum with good recovery, indicating its potential application in detection in biological samples. [ABSTRACT FROM AUTHOR]

A novel oxime-based fluorescent chemosensor (E)-2-(4′-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1′-biphenyl]-4-yl)ethen-1-ol (PBO) has been developed for the fluorimetric detection of hypochlorite ion (OCl−). On account of the optical behavior of the sensor PBO, distinctive spectral alterations in the presence of OCl− were detected. Furthermore, an obvious fluorescent color change from cyan to blue was also observed. An explicit linear relationship was found between the fluorimetric ratio of PBO and the concentration of OCl−. The detection limit (LOD) of PBO was evaluated to be 8 nM. The optical response was caused by the nucleophilic attack of OCl− on the imine group of the PBO probe, which stimulates intramolecular charge transfer. NMR titration investigation verified the detection mechanism. The PBO probe causes a quick spectral response towards OCl−, within 10 seconds. Furthermore, the practical utility of PBO was investigated through test paper analysis. The detection of OCl− in various water samples was also explored. The fluorescence bio-imaging experiment indicates the potential ability of the sensor PBO to detect OCl− in live E. coli cells. [ABSTRACT FROM AUTHOR]

Considering the scarcity of palladium ion probes with subcellular organelle targeting, especially probes with near-infrared (NIR) emission wavelength fluorophores, our group has been working to overcome this problem and looking forward to providing potential practical tools for exploring the toxicity of palladium ions at the subcellular level. In this paper, a novel colorimetric and NIR fluorescent probe, BHCy-Pd, for the specific detection of palladium ions (Pd2+) in lysosomes via an internal charge-transfer (ICT) mechanism was designed and synthesized. As expected, BHCy-Pd exhibited a rapid, selective, and sensitive response for palladium with an ultralow limit of detection at 5.9 nM, accompanied by a distinct color change from purple to blue. Furthermore, BHCy-Pd can be made into a simple test strip for rapid and easy detection of Pd2+ in practical applications. Importantly, BHCy-Pd is capable of specific distribution in lysosomes, and thus can detect Pd2+ in real-time, thereby providing a potential tool for studying the cytotoxicity of Pd2+ ions at the subcellular level. [ABSTRACT FROM AUTHOR]

Scientists are still working on developing a "turn-on" fluorescence sensor for Co2+, especially in acidic solutions. A novel "on–off–on" fluorescence sensor based on g-C3N4 nanosheets was designed and prepared in this paper. It was able to detect (2-(5-bromo-2-pyridylazo)-5(diethylamino)phenol (abbreviated to 5-Br-PADAP) and Co2+ quantitatively by quenching and restoring the fluorescence of the g-C3N4 nanosheet system, respectively. Also discussed are the effects of solvent, pH, order of addition, and interaction time of 5-Br-PADAP and Co2+, as well as the concentration range of the object on measurement. Furthermore, in acidic conditions, the sensor demonstrated good selectivity and sensitivity. In the solvent system EtOH : H2O (v/v = 1 : 9, pH = 3), the fluorescence intensity had a good linear relationship with 5-Br-PADAP and Co2+ concentrations in the ranges of 0–15 μM and 0–10 μM, with low detection limits of 64 nM and 44 nM, respectively. Experiments and theoretical calculations were used to describe the interaction characteristics and sensing mechanism. It was eventually successful in detecting Co2+ in environmental samples. [ABSTRACT FROM AUTHOR]

Dipicolinic acid (DPA) is an anthrax biomarker. Its serious consequences make its detection a great need. In this paper, three novel metal–organic frameworks (MOFs) with different coordination modes were synthesized by a simple solvothermal method, which can be used as highly efficient fluorescence sensors for the highly selective and sensitive trace detection of DPA. MOFs 1–3 showed rapid responses to DPA (<30 s), and the limits of detection (LODs) were calculated to be 1.01 × 10−6 M−1 (MOF 1), 1.17 × 10−6 M−1 (MOF 2) and 2.07 × 10−6 M−1 (MOF 3). DPA detection based on MOFs 1–3 in fetal bovine serum is highly reliable based on the high recovery rates (90% to 115%). Hence, the three MOF-based sensors can be used in the real-time detection of DPA. [ABSTRACT FROM AUTHOR]

In this work, 2(3),9(10),16(17),23(24)-octamethoxyphthalocyanine (Pc(OH)8) was first used to modify Cu/CuFe2O4(Cu/CFO) nanospheres, and Pc(OH)8–Cu/CFO nanocomposites with enhanced peroxidase mimetic enzyme activity was obtained compared to the performance of Cu/CFO alone. SEM, XRD, and XPS were used to study the surface morphology, phase composition and elemental analysis of the newly synthesized Pc(OH)8–Cu/CFO. Using TMB as the chromogenic substrate, Pc(OH)8–Cu/CFO accelerate the oxidation process of chromogenic substrate 3,3′,5,5′- tetramethylbenzidine (TMB) by hydrogen peroxide in three minutes. The catalytic oxidation mechanism of Pc(OH)8–Cu/CFO on TMB was comprehensively investigated through free radical and fluorescence probe experiments. Based on the excellent catalytic performance of the composite materials, a simple and fast colorimetric sensing platform for the colorimetric detection of H2O2 and glutathione (GSH) was constructed in the range of 0.6–5 mM and 2–10 μM with detection limits (LODs) of 0.35 mM and 0.55 μM, respectively. In addition, using Pc(OH)8–Cu/CFO colorimetric detection for GSH has a lower detection limit, good selectivity and high sensitivity, which is expected to become an ideal material for GSH colorimetric detection. [ABSTRACT FROM AUTHOR]

The ruthenium (Ru)-based functional structure has been well understood in catalytic performance due to its special particularity in structural fabrication. In this work, the controllable synthesis of core–shell Ru nanomaterials is first reported, which were not only realized via ice bath conditions with amorphous characterization but also showed a flexible design in the controllable synthesis of crystalline Ru after high intensity focused ultrasound (HIFU) treatment. The achieved amorphous Ru particles (∼115 ± 3 nm) and crystalline Ru (∼5 ± 0.5 nm) exhibit hydrogen peroxide catalytic performance and can be considered as an electrochemical sensing platform. The Km value of core–shell Ru for 3,3′,5,5′-tetramethylbenzidine (TMB) was 0.221 mM, which exhibits higher affinity for TMB and prominent catalytic performance than horseradish peroxidase (HRP). For selectivity and sensitivity towards the detection of H2O2 molecules, it expressed a wide linear range from 0.5 to 100 mM with an H2O2 detection limit of 1.45 μM (S/N = 3) and a sensitivity of 2.07 μA μM−1. After HIFU treatment, the diameter of the achieved crystalline Ru was about one-twentieth that of the core–shell Ru structure. An enhancement in catalytic performance was observed as a sensor platform for detecting H2O2, its detection range was wider, from 0.5 to 110 mM, its limit of detection was 0.007 μM (S/N = 3), and it exhibited a higher sensitivity of 443 μA μM−1. Hence, this flexible design in the synthesis of Ru NMs (amorphous and crystalline in status) could provide a novel synthetic strategy and make achievements in catalytic performance. [ABSTRACT FROM AUTHOR]

In this work, a gold-supported cerium-based organic framework hybrid structure (Au@Ce-MOF@COF) and gold@molybdenum disulfide@graphene oxide (Au@MoS2@rGO) were successfully prepared, and used for constructing an electrochemical aptasensor to detect carcinoembryonic antigen (CEA). Au@MoS2@rGO has a large surface area and good electron transfer rate, so it was used as the substrate to immobilize more aptamers (Apt1). The prepared Ce-MOF@COF was also used as a substrate for the immobilization of aptamers (Apt2) and horseradish peroxidase (HRP). When CEA exists, CEA binds to Au@Ce-MOF@COF-HRP-Apt2. In the presence of H2O2, it can effectively promote the oxidation of hydroquinone (HQ) to benzoquinone (BQ), and the electrochemical reduction signal of BQ was significantly amplified. So, the highly sensitive and selective detection of CEA was achieved. The linear range of the aptasensor is 0.1 pg mL−1–100 ng mL−1, and the detection limit is 0.019 pg mL−1, which shows excellent selectivity, reproducibility and stability. Finally, the aptasensor was applied to detect CEA in serum. [ABSTRACT FROM AUTHOR]

Digital PCR is a powerful method for absolute nucleic acid quantification and is widely used in the absolute quantification of viral copy numbers, tumor marker detection, and prenatal diagnosis. However, for most of the existing droplet-based dPCR systems, the droplet generation, PCR reaction, and droplet detection are performed separately using different instruments. Making digital PCR both easy to use and practical by integrating the qPCR workflow into a superior all-in-one walkaway solution is one of the core ideas. A new innovative and integrated digital droplet PCR platform was developed that utilizes cutting-edge microfluidics to integrate dPCR workflows onto a single consumable chip. This makes previously complex workflows fast and simple; the whole process of droplet generation, PCR amplification, and droplet detection is completed on one chip, which meets the clinical requirement of "sample in, result out". It provides high multiplexing capabilities and strong sensitivity while all measurements were within the 95% confidence interval. This study is the first validation of the DropXpert S6 system and focuses primarily on verifying its reliability, repeatability, and consistency. In addition, the accuracy, detection limit, linearity, and precision of the system were evaluated after sample collection. Among them, the accuracy assessment by calculating the absolute bias of each target gene yielded a range from -0.1 to 0.08, all within ±0.5 logarithmic orders of magnitude; the LOB for the assay was set at 0, and the LoD value calculated using probit curves is MR4.7 (0.002%); the linearity evaluation showed that the R2 value of the BCR-ABL was 0.9996, and the R2 value of the ABL metrics calculated using the ERM standard was 0.9999; and the precision evaluation showed that all samples had a CV of less than 4% for intra-day, inter-day, and interinstrument variation. The CV of inter-batch variation was less than 7%. The total CV was less than 5%. The results of the study demonstrate that dd-PCR can be applied to molecular detection and the clinical evaluation of CML patients and provide more precise personal treatment guidance, and its reproducibility predicts the future development of a wide range of clinical applications. [ABSTRACT FROM AUTHOR]

In this work, a new d10-configuration based Cd(II) coordination polymer (CP) with the formula [Cd2(CH3COO)2(bimb)2]·2ClO4 (1) have been synthesized using 4,4′-bis(imidazolyl)biphenyl (bimb) ligand and characterized. Single-crystal X-ray analysis reveals that the CP forms a 2D layer connected to a 3D supramolecular framework with weak packing interactions between benzyl and imidazolyl rings. CP 1 has been used as a photoluminescent sensor and a photocatalyst for the photodegradation of antibiotics, in particular nitrofurantoin (NFT). Sensing experiments indicate that 1 can selectively detect nitrofurantoin with a limit of detection of 0.025 μM, whereas when employed as a photocatalyst, CP 1 can photodecompose NFT up to 91.83% in a time span of 20 min. The decline in the photoluminescence intensity of CP 1 in the presence of NFT and the photocatalytic mechanism are addressed using theoretical calculations. [ABSTRACT FROM AUTHOR]

Visually colorimetric sensing of hazardous metallic ions based on gold nanoparticles (AuNPs) has been considered a facile, on-site, and reliable monitoring route, yet the improvement of detection limit, as well as environmental pH tolerance, is still needed. Herein, we present an integrated probe design based on functionalizing AuNP cores with carbon quantum dots (CQD) as colorimetric probes for tracing Cu2+ ions with a limit of detection as low as 18.7 nM. Improved detection selectivity was elucidated with the reduction in thiol groups bound between CQD decorations and AuNP probes initiated by oxidation of Cu2+ ion analytes, thus separating crossly connected probes, depending on tracing Cu2+ concentrations. Moreover, distributed CQDs with negative potentials allowed the stabilization of dispersed AuNPs against re-aggregation, which caused the gradual morphological transition from aggregated features to dispersed states in microscopic view, and eventually, reflected the gradual color change from red to purple-red. The correlated practicality of colorimetric detection of the Cu2+ ion was further validated with sound-sensing selectivity, environmental pH resistance and tests on real samples. [ABSTRACT FROM AUTHOR]

The effective assembly of hollow nanomaterials is of great importance for the rapid advancement of electroanalytical platforms. Herein, the hollow tubular zeolite imidazolium framework-8 (HTZIF-8) was carefully constructed via the precursor conversion pathway. Subsequently, the predictable assembly of HTZIF-8 with carbon nanotubes (CNTs) occurred to form a unique hollow dual-tube MOF hybrid material (HTZIF-8@CNTs). Meanwhile, the HTZIF-8@CNTs electroanalytical platform was established with dopamine (DA) as the objective biomolecule. In the electrochemical evaluation, the linear intervals of 0.06–600 μmol L−1 and detection limit of 0.02 μmol L−1 (S/N = 3) were determined, which were mainly ascribed to nano-synergistic engineering of HTZIF-8 and CNTs. The HTZIF-8@CNTs hybrid material exhibited superior electrocatalytic performance for DA compared to the solid rod-like MOF composite (SRZIF-8@CNTs), which was majorly based on the faster mass transfer characteristics of hollow MOFs. Additionally, the HTZIF-8@CNTs electrochemical sensor presented outstanding anti-interference capabilities as well as stability and could be utilized for the detection of DA in real samples. The employment of F and t statistics were employed to ensure the reliability of the results. This study will offer novel thoughts toward the application of hollow MOF composites in the area of electroanalytical platforms. [ABSTRACT FROM AUTHOR]

The development of a facile and reliable assay for arsenic (As) detection is crucial for its pollution control, which is a well-known heavy-metal pollutant in the environment. In this work, an efficient colorimetric method was established for As(V) detection based on a novel cuboid-shape Mn-Urea nanozyme (UMnzyme) with arsenic-enhanced oxidase-like activity. The UMnzyme was prepared through the coordination of Mn ions and carbonyl groups in urea, which possesses outstanding oxidase-like activity that can generate the superoxide anion free radical (O2˙−) by catalyzing the dissolved O2, triggering the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction. Furthermore, the free oxygen atoms in UMnzyme provide potential sites to bind with As, in which the formation of As–O will not destroy the morphology and structure of UMnzyme. The capture of As by UMnzyme results in the improvement of its oxidase-like activity; therefore, a colorimetric method for As(V) detection was developed with a linear range of 12.5–250 μg L−1. The limit of detection was determined to be 2.4 μg L−1 (S/N = 3), which is lower than the threshold (10 ppb) recommended by the World Health Organization. Moreover, the developed method was applied in the detection of As(V) in environmental water, and the recoveries are 89.5–103.6%. In short, this study provides an efficient and reliable strategy for As(V) detection based on a novel Mn-based nanozyme and a new idea for the reasonable design of Mn-based nanozymes with enhanced catalytic performance. [ABSTRACT FROM AUTHOR]

Herein, we introduce a novel method for tryptophan detection via a reduction reaction facilitated by its interaction with a copper(II) phthalocyanine (CuPc) electrocatalytic electrode. This method addresses challenges associated with the susceptibility of the oxidation response to interference from various species when measuring tryptophan in bodily fluids. The reduction currents exhibit a linear increase with tryptophan concentrations in two ranges: 0.0013–0.10 mM and 0.10–1.20 mM, with the sensitivities of 14.7 ± 0.5 μA mM−1 and 3.5 ± 0.1 μA mM−1, respectively. The limit of detection (LOD, 3SB/m) is determined to be 0.39 μM. The sensor exhibits excellent reproducibility, with the relative standard deviation of <5%. Application of the sensor to authentic urine samples yields a % recovery of 101 ± 4%. [ABSTRACT FROM AUTHOR]

Tumor necrosis factor-alpha (TNF-α) serves as a crucial biomarker in various diseases, necessitating sensitive detection methodologies. This study introduces an innovative approach utilizing an aptamer-functionalized surface plasmon resonance (SPR) substrate together with an ultrasensitive measure, the Goos–Hänchen (GH) shift, to achieve sensitive detection of TNF-α. The developed GH-aptasensing platform has shown a commendable figure-of-merit of 1.5 × 104 μm per RIU, showcasing a maximum detectable lateral position shift of 184.7 ± 1.2 μm, as characterized by the glycerol measurement. Employing aptamers as the recognition unit, the system exhibits remarkable biomolecule detection capabilities, including the experimentally obtained detection limit of 1 aM for the model protein bovine serum albumin (BSA), spanning wide dynamic ranges. Furthermore, the system successfully detects TNF-α, a small cytokine, with an experimental detection limit of 1 fM, comparable to conventional SPR immunoassays. This achievement represents one of the lowest experimentally derived detection limits for cytokines in aptamer-based SPR sensing. Additionally, the application of the GH shift marks a ground breaking advancement in aptamer-based biosensing, holding significant promise for pushing detection limits further, especially for small cytokine targets. [ABSTRACT FROM AUTHOR]

Dissolved lead is a serious but common health hazard in drinking water, yet there is still no practical way to monitor its levels continuously in the distribution system or at the point of use. Here we propose using a lead-selective membrane on top of a chemiresistive device to continuously measure Pb2+ ion concentrations in real time. The detection limit was lowered by stabilizing the surface of the resistive film with sodium hydroxide and 15-crown-5 ether and optimizing the sensor geometry to maximize the effective surface area. The detection mechanism is based on the complexation of the Pb2+ ions by the lead ionophores within the membrane, thus modulating the interactions between the ionophores and the chemiresistive film. The limit of detection of the fabricated devices was reliably below 2 μg L−1, with concentrations up to 3 mg L−1 routinely quantifiable over several measurement cycles. The chemiresistive sensors can thus achieve lower detection limits than potentiometric devices while being more robust and simpler to fabricate by omitting the reference electrode. Ion-selective membrane-covered chemiresistors can therefore be deployed to continuously monitor drinking water sources and detect harmful levels of lead in real time. [ABSTRACT FROM AUTHOR]

A new strategy for doping selenium and phosphide in hollow N-doped carbon nanobox (N-CNB)-based porous electrospun N-doped carbon nanofibers (CNFs) was developed. First, lightweight N-CNBs were produced. Then, a hybrid of N-CNBs and CNFs (CNBs/CNFs) was prepared using electrospinning/carbonization techniques. Eventually, P and Se atoms were doped into CNBs/CNFs using a thermal treatment approach to prepare Se/P@CNBs/CNFs. The electrocatalytic capability of the Se/P@CNBs/CNFs composite toward H2O2 oxidation was investigated for H2O2 sensing, which showed performance in a linear range from 200 μM to 1800 μM with a high sensitivity of 171 μA mM−1 cm−2 and a limit of detection (LOD) of 58 μM (S/N = 3). In addition, the ability of Se/P@CNBs/CNFs toward H2O2 sensing in human serum was studied. These results indicated the excellent electrocatalytic performance of the as-prepared Se/P@CNBs/CNFs, which could be related to the unique hollow CNBs/CNFs doped with P and Se elements with a mesoporous structure, the open channels for effective H2O2 diffusion, fast mass/electron transport, and synergistic effect between the P and Se and CNBs/CNFs. [ABSTRACT FROM AUTHOR]

Coordination polymers (CPs) with a d10-configuration containing metal cations offer interesting photoluminescent properties and hence can be employed as sensors to detect various classes of analytes. Moreover, due to their tuneable pore size they can be employed as adsorbents for various species. Herein, a new d10-configuration Cd(II)-based CP with composition {[Cd(bip)4(H2O)2]n·2NO3} (1) (bip = 3,5-bis(1-imidazol)pyridine) has been synthesized and characterized. Single-crystal X-ray analysis reveals that the Cd(II) center adopts octahedral geometry that is satisfied by four N atoms from the four bip linkers and two aqua ligands, and the resultant CP displays sql topology with the point symbol of (44·62). The CP offers prospective application as a photoluminescent sensor for dichromate anions with a limit of detection of 1.28 ppm and a Stern–Volmer constant (KSV) of 1.51 × 105. Furthermore, CP 1 was employed as an efficient adsorbent for dichromate ions, reaching an equilibrium adsorption capacity of 389.82 mg g−1 within 80 min. The effects of temperature, pH and concentration of dichromate were further investigated, which revealed that CP 1 displays the best adsorption at 30 °C and pH 4 with a dichromate concentration of 200 mg L−1. The possible adsorption mechanism has been proposed with the aid of Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

Detection of pathogens is one of the key concerns for hospitals, the food industry, water suppliers, or other environmental engineering practices because pathogens can cause a wide range of infectious risks. Staphylococcus aureus (S. aureus) is one of the most common pathogens that are hazardous to human health and its existence is an important index to the safety of food, environmental sanitation, or medical products. In this study, we prepared an electrode with designed surface multilevel 3D micro/nano protrusions for facile and efficient S. aureus detection. The existence of these multilevel protrusions enhanced the adsorption of S. aureus. Hence, the detection limit could be as low as 10 CFU mL−1. Furthermore, the electrode was also successfully used to detect S. aureus in actual samples, such as milk and artificial human tissue fluid. It was found that the recovery of the reported approach showed no significant difference from that of the traditional plate count method. However, compared with the plate count method, the detection process of our approach is much more time-saving and easy-operating. These advantages of the approach we report, such as high sensitivity, reliability, quickness, and user-friendliness, make it a potential platform for detecting S. aureus in relation to the food industry and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Nipah virus (NiV), a bat-borne zoonotic viral pathogen with high infectivity and lethality to humans, has caused severe outbreaks in several countries of Asia during the past two decades. Because of the worldwide distribution of the NiV natural reservoir, fruit bats, and lack of effective treatments or vaccines for NiV, routine surveillance and early detection are the key measures for containing NiV outbreaks and reducing its influence. In this study, we developed two rapid, sensitive and easy-to-conduct methods, RAA-CRISPR/Cas12a-FQ and RAA-CRISPR/Cas12a-FB, for NiV detection based on a recombinase-aided amplification (RAA) assay and a CRISPR/Cas12a system by utilizing dual-labeled fluorophore–quencher or fluorophore-biotin ssDNA probes. These two methods can be completed in 45 min and 55 min and achieve a limit of detection of 10 copies per μL and 100 copies per μL of NiV N DNA, respectively. In addition, they do not cross-react with nontarget nucleic acids extracted from the pathogens causing similar symptoms to NiV, showing high specificity for NiV N DNA detection. Meanwhile, they show satisfactory performance in the detection of spiked samples from pigs and humans. Collectively, the RAA-CRISPR/Cas12a-FQ and RAA-CRISPR/Cas12a-FB methods developed by us would be promising candidates for the early detection and routine surveillance of NiV in resource-poor areas and outdoors. [ABSTRACT FROM AUTHOR]

Sensitive and high-throughput analysis of trace elements in biological samples with limited volume is of great significance for clinical studies. However, traditional analysis methods often require complex sampling systems, leading to large sample consumption and hindering the rapid detection of trace samples. In this study, we have developed a simple, sensitive and portable droplet cathode glow discharge (DCGD) array for the rapid analysis of micro-volume serum samples. It requires only 10 μL of sample and utilizes a pipette gun for sample introduction, eliminating the need for pumps and valves in conventional solution discharge systems. The triggering and signal acquisition of each droplet sample can be completed within 300 ms, enabling the detection of approximately 240 samples per hour using the droplet array DCGD-OES. Under optimized conditions, the detection limits for Li, Ca and K were determined to be 0.002 mg L−1 (20 pg), 0.078 mg L−1 (780 pg), and 0.005 mg L−1 (50 pg), respectively. The accuracy of the proposed DCGD-OES method was verified through the analysis of two certified standard substances (Seronorm serum L-1 and L-2 RUO) and 20 real human serum samples, and the obtained relative standard deviation (RSD) is approximately 5% (n = 5). The results demonstrate that the low-cost, low-power DCGD-OES offers a promising and reliable approach for the rapid and high-throughput detection of Li, Ca, K and other important elements in volume-limited serum samples. [ABSTRACT FROM AUTHOR]

The eyes provide rich physiological information and offer diagnostic potential as a sensing site, and probing tear constituents via the wearable contact lens could be explored for healthcare monitoring. Herein, we propose a novel adhesive contrast contact lens platform that can split tear film by natural means of tear secretion and blinking. The adhesive contrast is realized by selective grafting of a lubricant onto a polydimethylsiloxane (PDMS)-based contact lens, leading to high pinning zones on a non-adhesive background. The difference in contact angle hysteresis facilitates the liquid splitting. Further, the method offers control over the droplet volume by controlling the zone dimension. The adhesive contrast contact lens is coupled with fluorescent spectroscopic as well as colorimetric techniques to realize its potential as a diagnostic platform. The adhesive contrast contact lens is exploited to detect the level of lactoferrin in tear by sensitizing split droplets with Tb3+ ions. The adhesive contrast contact lens integrated with a fluorescence spectrometer was able to detect the lactoferrin level up to a concentration of 0.25 mg mL-1. Additionally, a colorimetric detection based on the fluorescence of the lactoferrin-terbium complex is demonstrated for the measurement of lactoferrin, with a limit of detection in the physiological range up to 0.5 mg mL-1. [ABSTRACT FROM AUTHOR]

In this work, we developed a rapid and sensitive label-free ratiometric fluorescent (FL) probe for the detection of bleomycin (BLM). The probe consists of a DNA sequence (D6) and two fluorophore groups, 2-amino-5,6,7-trimethyl-1,8-naphthalene (ATMND) and SYBR Green I (SGI). The D6 sequence could be folded into a three-way junction structure containing a C–C mismatch position in the junction pocket. The unique "Y" structure not only could entrap ATMND in the mismatch pocket with high affinity, leading to FL quenching at 408 nm, but also embed SGI in the grooves of the double-stranded portion, resulting in FL enhancement at 530 nm. In the presence of BLM–Fe(II), the "Y" structure of D6 was destroyed due to the specific cleavage of the BLM recognition site, the 5′-GT-3′ site in D6. This caused the release of ATMND and SGI and thus the ratiometric signal change of FL enhancement by ATMND and FL quenching by SGI. Under optimal conditions, the ratiometric probe exhibited a linear correlation between the intensity ratio of F408/F530 and the concentration of BLM in the range of 0.5–1000 nM, with a detection limit of 0.2 nM. In addition, the probe was applied to detect BLM in human serum samples with satisfactory results, indicating its good clinical application potential. [ABSTRACT FROM AUTHOR]

Time-of-flight ICP-mass spectrometry (ICP-ToF-MS) allows acquisition of almost the entire periodic table in only a few tens of microseconds, with several mass spectra combined into a single readout. When hyphenated with a low-dispersion laser ablation (LA) unit, it allows for 2D elemental mapping at a laser repetition rate of several hundred hertz, with each laser shot recorded as a single pixel. Although its use in geosciences is increasing, the technique is often referred to as semi-quantitative. Here, we present the outcomes of ultra-fast high-resolution 2D mapping and quantification of the constituting elements of geological reference materials and micrometeorites with LA-ICP-ToF-MS, carried out in a period of over a year. Quantitative data for each pixel were obtained through a combination of multi-point external calibration and normalization of the sum of all element oxide contents to 100%. Detection limits ranging from 0.1 to 10 μg g−1 were attained for most elements when using a 5 μm × 5 μm square laser spot. Repeated analysis of reference materials in a period of over one year demonstrates an intermediate precision down to 3% RSD. [ABSTRACT FROM AUTHOR]

Large-geometry secondary ion mass spectrometry (LG-SIMS) is routinely used to determine the elemental and isotopic compositions, thanks to its high sensitivity and in situ micro-analysis capability. Its large volumes of transfer and coupling column, however, might bring low vacuum and high background of volatile elements (esp. H), which hampers its application in ultralow H2O content measurement. In this study, we report a modified analytical procedure to accurately analyze samples with ultralow-level H2O content by using a LG-SIMS of type CAMECA IMS 1280-HR. Based on four new water content working reference materials of quartz glasses with H2O contents ranging from ca. 0 to 39 ppm, the estimated detection limit of LG-SIMS is 0.15 ppm for H2O. This ultralow detection limit is achieved mainly by the intrinsic high sensitivity of the instrument and the conjunctive usage of a stabilized temperature-controlled cooling trap device and a novel tin–bismuth alloy mount preparation technology, which are able to maintain a vacuum pressure at 1.7 × 10−9 mbar in the analysis chamber. Based on these new improvements, our approach can potentially become a routine choice for analyses of H2O content and oxygen–hydrogen isotopes for (extra)terrestrial materials with ultralow-level water content. [ABSTRACT FROM AUTHOR]

A fluorescent probe based on single metal–organic framework material without additional fluorophores and active sites can significantly improve the stability of the probe for detection, and has very important application value in environmental analysis and detection. In this paper, a simple and rapid fluorescence detection method was established with Zn-MOF, which realized the highly sensitive detection of tetracycline antibiotics and NH4+ in water. The prepared Zn-MOF has abundant pores and can exist stably in water. When tetracycline antibiotics are present in Zn-MOF aqueous solution, based on the unique coordination ability between Zn and N, tetracycline antibiotics rich in N will be adsorbed into the pore canals of MOF, and aggregation-induced luminescence will occur. The original non-fluorescent Zn-MOF will immediately produce yellow fluorescence, realizing the detection of tetracycline antibiotics in water, with the limit of detection reaching 0.017 μM in a linear range of 0.02–13 μM. Zn-MOF is further used for the detection of tetracycline antibiotics in actual samples of milk and honey. Oxytetracycline (OTC) with the best fluorescence response of tetracycline antibiotics was coated on Zn-MOF to synthesize OTC@Zn-MOF fluorescent probe. NH4+ will replace the original ligand of Zn-MOF, which will disintegrate MOF and release OTC, resulting in a fluorescence decrease. Therefore, NH4+ can be detected with low limit of detection (0.038 μM) in a linear range of 0 to 3 mM. The probe is expected to be able to detect ammonia in the environment. [ABSTRACT FROM AUTHOR]

The electrochemical quantification of analytes in droplets of PBS separated by a fluorinated phase was investigated. PDMS-fused silica chips with pyrolysed photoresist electrodes were prepared using a simple fabrication technique and used to analyze droplets in flow. Potentiostatic chronoamperometry provided current readouts consistent with mass transport and the concentration inside the droplets. This paper highlights measurements of dopamine in droplets in T-junction microfluidic chips at unprecedently low concentrations, with a limit of detection of 207 nM and a linear range of 0.21-20 µM, giving results similar to continuous flow electrochemistry and allowing the analysis in the striatal extracellular range (<1 µM). The system was applied to the quick and reliable on-line detection of dopamine concentration steps in droplets collected with a microsampling probe in vitro, demonstrating the usefulness of the electrochemical device as a quantification module for microsampled chemicals in droplets. [ABSTRACT FROM AUTHOR]

Human immunodeficiency virus (HIV) continues to be a major burden on public health globally with ongoing increases in the number of new infections each year. Rapid and sensitive point-of-care tests allow timely interventions and are essential to control the spread of the disease. However the highly variable nature of the virus, resulting in the evolution of many subtypes and inter-subtype recombinants, poses important challenges for its diagnosis. Here we describe a variant-tolerant reverse-transcription RT-LAMP amplification of the virus's INT gene, providing a simple to use, rapid (<30 min) in vitro point-of-care diagnostic test with a limit of detection <18 copies/reaction. The assay was first validated in clinical studies of patient samples, using both established RT-LAMP and RT-qPCR assays for reference, with results showing that this new variant-tolerant HIV-1 RT-LAMP diagnostic test is highly sensitive without compromising its high specificity for HIV-1 subtypes. The diagnostic test was subsequently configured within an easy-to-read paper microfluidic lateral flow test and was validated clinically using patient samples, demonstrating its future potential for use in timely, effective, low cost HIV diagnostics in global regions where healthcare resources may be limited. [ABSTRACT FROM AUTHOR]

Sandwich immunoassays such as the enzyme-linked immunosorbent assay (ELISA) have been miniaturized and performed in a lab-on-a-chip format, but the execution of the multiple assay steps typically requires a computer or complex peripherals. Recently, an ELISA for detecting antibodies was encoded structurally in a chip thanks to the microfluidic chain reaction (Yafia et al. Nature, 2022, 605, 464–469), but the need for precise pipetting and intolerance to commonly used surfactant concentrations limit the potential for broader adoption. Here, we introduce the ELISA-on-a-chip with aliquoting functionality that simplifies chip loading and pipetting, accommodates higher surfactant concentrations, includes barrier channels that delay the contact between solutions and prevent undesired mixing, and that executed a quantitative, high-sensitivity assay for the SARS-CoV-2 nucleocapsid protein in 4×-diluted saliva. Upon loading the chip using disposable pipettes, capillary flow draws each reagent and the sample into a separate volumetric measuring reservoir for detection antibody (70 μL), enzyme conjugate (50 μL), substrate (80 μL), and sample (210 μL), and splits washing buffer into 4 different reservoirs of 40, 40, 60, and 20 μL. The excess volume is autonomously drained via a structurally encoded capillaric aliquoting circuit, creating aliquots with an accuracy of >93%. Next, the user click-connects the assay module, comprising a nitrocellulose membrane with immobilized capture antibodies and a capillary pump, to the chip which triggers the step-by-step, timed flow of all aliquoted solutions to complete the assay in 1.5 h. A colored precipitate forming a line on a nitrocellulose strip serves as an assay readout, and upon digitization, yielded a binding curve with a limit of detection of 54 and 91 pg mL−1 for buffer and diluted saliva respectively, vastly outperforming rapid tests. The ELISA chip is 3D-printed, modular, adaptable to other targets and assays, and could be used to automate ELISA in the lab; or as a diagnostic test at the point of care with the convenience and form factor of rapid tests while preserving the protocol and performance of central laboratory ELISA. [ABSTRACT FROM AUTHOR]

L -Cysteine is a common amino acid that plays an important role in human livelihood and production. Therefore, a novel method for the simultaneous quantitative and qualitative determination of L -cysteine by a colorimetric detection system is proposed. As a viable oxidase mimic, [N4444]Cl-G/MnO2, which consisted of MnO2 nanosheets functionalized by a tetrabutylammonium chloride–glycerol ([N4444]Cl-G) based deep eutectic solvent (DES) was fabricated. Owing to the oxidation of MnO2 nanosheets, [N4444]Cl-G/MnO2 could oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue product (oxTMB) with the characteristic UV–vis spectrum absorbance at 652 nm. The oxidation of TMB by DES/MnO2 was inhibited when L -cysteine was introduced, and the absorbance decreased proportionally with the increase in L -cysteine concentration. Due to this inhibition effect, a colorimetric detection system ([N4444]Cl-G/MnO2-TMB) was developed for the quantitative determination of L -cysteine. Under optimal conditions, the assay showed good linearity over the concentration range of 0.125–2.00 μg mL−1 with a low detection limit of 5.96 ng mL−1. A study of the inhibition mechanism demonstrated that the sulfhydryl group of L -cysteine could decompose [N4444]Cl-G/MnO2 into Mn2+, thus limiting the conversion of TMB to oxTMB. In addition, the [N4444]Cl-G/MnO2-TMB system was used in test strips for the visual qualitative detection of L -cysteine. The selectivity and test strip results demonstrated the high selectivity, simple operation, and rapid response of the [N4444]Cl-G/MnO2-TMB system for the qualitative detection of L -cysteine. Given the satisfying performance of the detection strategy, colorimetric sensing based on the [N4444]Cl-G/MnO2-TMB system is considered to have prospective application value in the quantitative and qualitative detection of L -cysteine. [ABSTRACT FROM AUTHOR]

Ratiometric fluorescent nanosensors were developed to detect mercury ions (Hg2+) using enhanced dual emissions from glutathione stabilized gold nanoclusters/indium-based metal–organic frameworks modified with cysteine (AuNCs/MIL-68(In)-NH2/Cys). The nanosensors exhibited bright pink fluorescence with AuNCs evenly distributed on MIL-68(In)-NH2. Under 370 nm excitation, the obtained sensor presented double fluorescence emission around 438 nm and 668 nm, which was attributed to MIL-68(In)-NH2 and GSH-AuNCs, respectively. The fluorescence emission was remarkably enhanced after modification with Cys. In the presence of Hg2+, the red fluorescence peak at 668 nm was quenched, while the blue fluorescence peak at 438 nm was slightly altered. The prepared AuNCs/MIL-68(In)-NH2/Cys nanosensors exhibited two linear ranges for the detection of Hg2+, namely from 20 pM to 0.2 μM and 0.2 μM to 60 μM, with a detection limit of 6.7 pM. They also presented high selectivity towards other ions and good performance in real water samples. Moreover, a radial star-shaped microfluidic paper-based analytical device (μPAD), as a straightforward and convenient platform, was successfully fabricated for the visual detection of Hg2+ with a wide detection range from 5 nM to 50 μM. [ABSTRACT FROM AUTHOR]

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(μ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 μA mM−1 and a detection limit that has reached 1.9 μM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors. [ABSTRACT FROM AUTHOR]

Due to their hazard to biological systems, it is urgent to develop materials that can rapidly and sensitively detect the concentration of H2PO4− and OCN− ions. In this work, a new CdII-based luminescent metal–organic framework with the formula [Cd(BTDB)(2,6-BBIP)]n (JXUST-47, H2BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid, 2,6-BBIP = 2,6-bis(benzimidazol-1-yl)pyridine) and sql topology was successfully synthesized using a mixed-ligand strategy. JXUST-47 shows good chemical and thermal stability. It also exhibits weak quenching and fluorescence blue shift for H2PO4− and red shift for OCN−, with the detection limits of 0.106 and 0.128 mM, respectively. In addition, considering the demand for H2PO4− and OCN− ion detection, by combining this with the functions of a smartphone, the chroma of photographs have been used to realize the consecutive visual detection of the concentration of these ions. [ABSTRACT FROM AUTHOR]

Nanozymes, as artificial enzymes, overcome the low catalytic efficiency, poor stability, and cost-effectiveness of previous artificial enzymes. In this work, vanadium carbide@vanadium oxide (V2C@VOx) nanosheets were synthesized by a one-pot hydrothermal method using V2C as a precursor and H2O2 as an oxidant. The prepared V2C@VOx nanosheets exhibited excellent multi-enzyme activity such as peroxidase-like activity, superoxide dismutase-like activity, and oxidase-like activity. The entire synthetic process of V2C@VOx nanosheets does not need any additional intercalation agent, strong acid, or base. Meanwhile, the synthesized method of nanozymes was simple, time-saving, and environmentally friendly. In particular, based on the multi-enzyme activity of V2C@VOx nanosheets, the nanozymes catalyzed H2O2 and dissolved O2 to oxidize 3′,3,5,5′-tetramethylbenzidine (TMB). Additionally, glucose reacted with glucose oxidase (GOx) to form H2O2 under water bath conditions. Therefore, the colorimetric sensing strategy of glucose was constructed based on the multi-enzyme activity of V2C@VOx nanosheets and the enzymatic reaction of glucose. The detection limit of the sensor was as low as 0.08 μM. Furthermore, the colorimetric method was successfully used to detect glucose in human serum. The sensor exhibited low cost, high stability, and easy construction. Overall, this work proposed a promising strategy based on novel vanadium-based nanozymes with excellent multi-enzyme activity for biomedical detection. [ABSTRACT FROM AUTHOR]

Ultratrace-enriching biomarker analysis is an effective method for achieving highly accurate and enhanced sensitive detection. In this study, we have developed an enrichment detection platform by combining a minipillar array with an aqueous two-phase system (ATPS) for ultratrace enriching biomarker analysis. After optimizing the enrichment conditions of ATPS, target miRNAs at ultratrace levels specifically accumulate in the DEX-rich phase, which significantly increases the target miRNA concentration-related fluorescence intensity. Compared to non-enriched miRNA in the single-phase PEG solution, the detection limit of ATPS-enriched miRNA had improved more than 200-fold. The ATPS-based enrichment detection strategy offers a novel and convenient approach for the simultaneous detection of biomarkers with ultratrace. [ABSTRACT FROM AUTHOR]

Copper ions (Cu2+), as a crucial trace element, play a vital role in living organisms. Thus, the detection of Cu2+ is of great significance for disease prevention and diagnosis. Nanochannel devices with an excellent nanoconfinement effect show great potential in recognizing and detecting Cu2+ ions. However, these devices often require complicated modification and treatment, which not only damages the membrane structure, but also induces nonspecific, low-sensitivity and non-repeatable detection. Herein, a 2D MXene–carboxymethyl chitosan (MXene/CMC) freestanding membrane with ordered lamellar channels was developed by a super-assembly strategy. The introduction of CMC provides abundant space charges, improving the nanoconfinement effect of the nanochannel. Importantly, the CMC can chelate with Cu2+ ions, endowing the MXene/CMC with the ability to detect Cu2+. The formation of CMC–Cu2+ complexes decreases the space charges, leading to a discernible variation in the current signal. Therefore, MXene/CMC can achieve highly sensitive and stable Cu2+ detection based on the characteristics of nanochannel composition. The linear response range for Cu2+ detection is 10−9 to 10−5 M with a low detection limit of 0.095 nM. Notably, MXene/CMC was successfully applied for Cu2+ detection in real water and fetal bovine serum samples. This work provides a simple, highly sensitive and stable detection platform based on the properties of the nanochannel composition. [ABSTRACT FROM AUTHOR]

In this work, we prepared a simple and low-cost cobalt-doped Prussian blue analog (Co-PBA), which can directly oxidize 10-acetyl-3,7-dihydroxyphenoxazine and 3,3′,5,5′-tetramethylbenzidine (TMB) to produce resorufin (ox-AR) with high fluorescent quantum yield and ox-TMB with blue color, respectively, without the need for unstable H2O2. Using the Michaelis–Menten curve and Lineweaver–Burk equation, the Michaelis–Menten constant of Co-PBA and the substrate TMB was found to be 0.033 mM, which was much lower than horseradish peroxidase and other reported nanozymes, showing satisfactory substrate affinity. Uric acid (UA) can cause erosion of the Co-PBA structure, and it significantly reduces the catalytic activity of Co-PBA, resulting in the decrease of the fluorescence emission signal of ox-AR and the absorption signal of ox-TMB. Based on this, a simple, sensitive, and fast fluorescence/colorimetric dual-mode uric acid detection platform was established. The detection range for UA by fluorescence method is 0.625–40 μM, and the detection limit (LOD, S/N = 3) is as low as 0.389 μM. The detection system was applied to serum samples with good recovery and can be used for field detection of UA in biological samples under different environments to meet different needs. [ABSTRACT FROM AUTHOR]

In the current study a simple and highly specific label-free impedimetric neuron specific enolase (NSE) immunosensor based on a copolymer matrix-coated disposable electrode was designed and tested. The copolymer matrix was prepared using a very conductive EDOT monomer and semi-conductive thiophene-bearing epoxy groups (ThEp), and the combination of the two monomers enhanced the conductivity and protein loading capacity of the electrode surface. The P(ThEp-co-EDOT) copolymer matrix was prepared via a drop-casting process and anti-NSE recognition biomolecules were immobilized directly on the epoxy groups of the copolymer. After the coupling of NSE molecules on the P(ThEp-co-EDOT) copolymer matrix-coated electrode surface, the charge transfer resistance (Rct) of the biosensor changed dramatically. These changes in Rct were proportional to the NSE molecule amounts captured by anti-NSE molecules. Under optimized experimental conditions, the increment in the Rct value was proportional to the NSE concentration over a range of 0.01 to 25 pg mL−1 with a detection limit (LOD) of 2.98 × 10−3 pg mL−1. This copolymer-coated electrode provided a lower LOD than the other biosensors. In addition, the suggested electrochemical immuno-platform showed good selectivity, superior reproducibility, long-term stability, and high recovery of NSE in real serum (95.64–102.20%) and saliva (95.28–105.35%) samples. These results showed that the present system had great potential for electrochemical biosensing applications. [ABSTRACT FROM AUTHOR]

In this study, we aimed to improve the detection of hexavalent chromium (Cr(VI)) in seawater by using large volume injection and in-line matrix elimination device in conjunction with LC-ICP-MS. Firstly, the sample solution was introduced into the chromatographic separation system through a 1000 μL quantitative loop. Then, the chromatographically separated solution was precisely introduced into the ICP-MS for analysis at the time of the Cr(VI) peak (2.8–4.2 min) by the valve switch in the in-line matrix elimination. And the separation of Cr(VI) was performed on a Dionex IonPac AG7 analytical column (50 mm × 4 mm, 10 μm) with 60 mmol L−1 NH4NO3 as the mobile phase at a flow rate of 1.0 mL min−1 for 5 min. The detection limits (LOD) and limit of quantitation (LOQ) were found to be 0.002 and 0.007 μg L−1, respectively. Method precision and accuracy were satisfactory at 3.5% relative standard deviations (RSDs) for 0.1 μg L−1 of Cr(VI), and 90% ∼ 105% recoveries for real samples. The developed method was successfully applied for the analysis of Cr(VI) in environmental seawater samples. [ABSTRACT FROM AUTHOR]

Gastrointestinal bleeding (GIB) is a serious medical condition, which requires immediate attention to establish the cause of the bleeding. Here, we present the development of a miniaturised electrochemical impedance spectroscopy (EIS) device for the detection of GIB. The device performs EIS measurements up to 100 kHz. Following the development of an immunosensor for haemoglobin (Hb) on screen printed electrodes, the EIS device was used for detecting Hb as an early indication of bleeding. The sensor was able to detect Hb in a redox solution in a linear range between 5 μg mL−1 and 60 μg mL−1, with a limit of detection of 13.3 μg mL−1. It was also possible to detect Hb in simulated intestinal fluid, without the need for a redox solution, within a range of 10 μg mL−1 to 10 mg mL−1 with a limit of detection of 2.31 mg mL−1. The miniature EIS device developed in this work is inexpensive, with an estimated cost per unit of £30, and has shown a comparable performance to existing commercial tools, demonstrating its potential to be used in the future as an ingestible sensor to detect GIB. All these measurements were carried out in a purpose built flow cell with supporting hardware electronics outside the cell. Integration of the hardware and the sensing electrodes was demonstrated in pill form. This pill after integration sampling fluidics has potential to be used in detecting gastrointestinal bleeding. [ABSTRACT FROM AUTHOR]

The pH working range of solid-contact ion-selective electrodes (ISEs) with plasticizer-free poly(decyl methacrylate) sensing membranes is shown to be expanded by covalent attachment of H+ ionophores to the polymeric membrane matrix. In situ photopolymerization not only incorporates the ionophores into the polymer backbone, but at the same time also attaches the sensing membranes covalently to the underlying inert polymer and nanographite solid contact, minimizing sensor drift and preventing failure by membrane delamination. A new pyridine-based H+ ionophore, 3-(pyridine-3-yl)propyl methacrylate, has lower basicity than trialkylamine ionophores and expands the upper detection limit. This reduces in particular the interference from hydrogen phthalate, which is a common component of commercial pH buffers. Moreover, the lower detection limit is improved by replacing the CH2CH2 spacer of previously reported dialkylaminoethyl methacrylates with a (CH2)10 spacer, which increases its basicity. Notably, for the more basic and highly cation-selective ionophore 10-(diisopropylamino)decyl methacrylate, the extent of counterion interference from hydrogen phthalate shifted the upper detection limit to lower pH by nearly one pH unit when the crosslinker concentration was decreased. [ABSTRACT FROM AUTHOR]

The poor solubility of iridium complexes severely hampers its application in the electrochemiluminescence (ECL) sensing field. The doping of an iridium complex with silica (SiO2) nanospheres provides feasible solution for this problem. Herein, one kind of water insoluble iridium complex ([Ir(dFppy)2(d(CF3)bpy)](PF6)) was doped with SiO2 nanoparticles to obtain a luminescent nanocomposite (SiO2@Ir) which could generate strong ECL signals to act as a beacon molecule. An "off–on–off" mode ECL sensor was proposed based on the competitive host–guest interactions between 2-adamantanamine (2-ADA), ferrocene (Fc) and cucurbit[7]uril (Q[7]). Fc could be used as an inhibitor to decrease the ECL signal, while Q[7] could wrap Fc to recover the ECL signal. Q[7] has a stronger binding ability with 2-ADA than Fc. As a result, 2-ADA could replace Fc from the cavity of Q[7], and the ECL signal was inhibited again. Under the optimal conditions, the ECL intensity varied linearly with 2-ADA concentration in the range of 1.0 × 10−8 to 1.0 × 10−6 mol L−1 with a detection limit of 2.5 × 10−10 mol L−1. The results not only provided a new avenue for the application of water insoluble iridium complexes in ECL sensing, but also revealed the attractive potential of host–guest interactions in the fabrication of biosensors. [ABSTRACT FROM AUTHOR]

In this study, the carboxy silane 4-(triethoxysilyl)butanoic acid (TESBA) was used to modify titanium dioxide (TiO2) to create a self-assembled monolayer (SAM) and then directionally immobilize a capture antibody using protein A. We selected the amino silane (3-aminopropyl)triethoxysilane (APTES) to perform a comparative analysis with TESBA, and employed glutaraldehyde (GA) as the control. The modification and detection effects and the limit of detection (LOD) were evaluated by detecting human immunoglobulin G (IgG). The average normalized sensitivity of the dual-grating coupler waveguide biosensor was 49.63 ± 0.27 RIU−1 and the optimum resolution was 1.30 × 10−6 RIU. When the SAM was prepared using TESBA and APTES followed by GA, the LOD was 4.59 × 10−7 g mL−1 and 5.29 × 10−7 g mL−1, respectively. We analyzed the modification and detection effects by the t-test and concluded that the differences in the modification effects using TESBA and APTES followed by GA were significant and the differences in the detection effects using TESBA and APTES followed by GA were insignificant. The use of TESBA as the SAM led to the modification effect being superior to that obtained using APTES followed by GA. The detection effect using TESBA was as outstanding as that using APTES followed by GA. Our findings demonstrate the feasibility and effectiveness of using TESBA as the SAM to carboxylate the surface of TiO2, thereby enabling immobilization of biomolecules for human IgG detection. [ABSTRACT FROM AUTHOR]

Streptococcus pneumoniae (S. pneumoniae) represents a significant pathogenic threat, often responsible for community-acquired pneumonia with potentially life-threatening consequences if left untreated. This underscores the pressing clinical need for rapid and accurate detection of this harmful bacteria. In this study, we report the screening and discovery of a novel biomarker for S. pneumoniae detection. We used S. pneumoniae nucleases as biomarker and we have identified a specific oligonucleotide that works as substrate. This biomarker relies on a specific nuclease activity found on the bacterial membrane, forming the basis for the development of both fluorescence and electrochemical biosensors. We observed an exceptionally high sensitivity in the performance of the electrochemical biosensor, detecting as low as 102 CFU mL−1, whereas the fluorescence sensor demonstrated comparatively lower efficiency, with a detection limit of 106 CFU mL−1. Moreover, the specificity studies have demonstrated the biosensors' remarkable capacity to identify S. pneumoniae from other pathogenic bacteria. Significantly, both biosensors have demonstrated the ability to identify S. pneumoniae cultured from clinical samples, providing compelling evidence of the potential clinical utility of this innovative detection system. [ABSTRACT FROM AUTHOR]