Sensitive Detection Method Research Articles

Analysis of Trace Heavy Metal in Solution Using Liquid Cathode Glow Discharge Spectroscopy

Heavy metal pollution, particularly from cadmium (Cd) and copper (Cu), poses significant environmental and health risks. To address the need for efficient, portable, and sensitive detection methods, this study introduces an improved atmospheric pressure glow discharge atomic emission spectrometry (APGD-AES) technique for quantifying Cd and Cu in water samples. The APGD-AES method offers key advantages, including low energy consumption (<33 W), high excitation energy, and compact design. The system was optimized for a discharge voltage of 550 V (Cd) and 570 V (Cu), a flow rate of 3.6 mL/min, and a solution pH of 1.0. Under these conditions, detection limits reached 16 µg/L for Cd and 1.3 µg/L for Cu. APGD-AES was tested on real water samples, including sewage and tap water, demonstrating compliance with national safety standards and comparable performance to graphite furnace atomic absorption spectrometry (GFAAS). This technique shows promise for real-time, on-site monitoring of trace heavy metals due to its portability, precision, and cost-efficiency.

Point-of-care testing diagnosis of African swine fever virus by targeting multiple genes with enzymatic recombinase amplification and CRISPR/Cas12a System

African swine fever virus (ASFV) infection is causing devastating outbreaks globally; pig farming has suffered severe economic losses due to the ASFV. Currently, strict biosecurity control measures can mitigate the incidence of ASF. Rapid, cost-effective, and sensitive detection of ASFV can significantly reduce disease transmission and mortality. CRISPR/Cas-associated proteins can detect polymorphisms with high specificity and sensitivity, making them ideal for detecting pathogens. In this study, based on CRISPR/Cas12a integrated with enzymatic recombinase amplification (ERA) technology, a CRISPR/Cas12a detection system capable of identifying ASFV E183L, K205R, and C962R gene sequences has been developed. The ERA-CRISPR/Cas12a detection system detected ASFV precisely without cross-reactivity with other porcine pathogen templates and with a sensitivity detection limit of 10 copies per reaction; it takes 60 minutes to complete the detection process. In combination with this integrated ERA pre-amplification and Cas12a/crRNA cutting assay, it provides a rapid, straightforward, sensitive, and specific method for ASFV detection in the field.

Ultrasensitive electrochemical detection of thymol using areca nut fibre-derived carbon sensors for environmental protection

The increasing use of thymol (THY) as a common pesticide in agriculture raises significant concerns regarding its potential environmental and human health risks. Therefore, developing a sensitive detection method for thymol residues is essential for monitoring and ensuring safety standards. This study presents a novel approach for sensitively detecting thymol using activated carbon derived from areca nut (Arecanut catechu L) fibre, an agricultural by-product as the precursor. Cetyltrimethylammonium bromide (CTAB) is added to the test solution to improve the material's surface properties and increase the number of active sites. Electrochemical sensing techniques, specifically cyclic voltammetry (CV) and square wave voltammetry (SWV), are employed to evaluate the performance of Cetyltrimethylammonium bromide mediated activated carbon as a thymol detection sensor. The sensor exhibits outstanding sensitivity with an ultralow limit of detection (DL) of 1.84 × 10⁻⁸ M and a limit of quantification (QL) of 6.14 × 10⁻⁸ M, enabling the quantification of trace amounts of thymol in complex matrices. Furthermore, the sensor demonstrates exceptional reproducibility and long-term stability, making it suitable for real-time applications. Utilizing areca nut fibre as a precursor represents a sustainable and eco-friendly approach. This method offers a promising solution for pesticide detection, contributing to enhanced food safety, environmental protection, and regulatory compliance in the agricultural sector.

Paper-based immunosensor for quantitative detection of African swine fever virus p54 protein

African swine fever virus (ASFV) has resulted in significant economic detriment to the livestock industry in recent years. Highly sensitive and accurate detection methods are currently the most effective means for ASFV prevention and control. In this work, the ASFV p54 recombinant protein was successfully expressed by plasmid construction, prokaryotic expression and purification. Monoclonal antibodies (mAbs) were obtained using hybridoma cell technology. Through pair analysis, mAb-6E5 and mAb-4D7 were selected for p54 detection, both exhibiting high affinity and no cross-reactivity with other ASFV proteins. Based on the sandwich colloidal gold immunochromatographic assay principle, a p54 test strip was constructed using 6E5 as the capture antibody and 2D7 as the detection antibody, with a limit of detection of 1.51 ng/mL. The intra- and inter-assay recoveries ranged from 87.8% to 110.6%, with variable coefficient of less than 11.1%. Positive serum samples further confirmed the accuracy of the assay. This developed test strip has the potential to serve as an effective tool for ASFV detection and could play a crucial role in the prevention and management of African Swine Fever (ASF) outbreaks.

One stone two birds: NH2-UiO-66@MB-based bimodal aptasensor for sensitive and rapid detection of zearalenone in cereal products

Zearalenone (ZEN), a prevalent mycotoxin found in cereal crops, poses a significant threat to food safety and human health. To address this issue, there is an urgent need for rapid, sensitive, and cost-effective detection methods. In this study, we developed a novel bimodal aptasensor based on NH2-UiO-66@MB composites for ZEN detection. Methylene blue (MB) was encapsulated within NH2-UiO-66 nanoparticles to enhance fluorescence intensity, and the ZEN aptamer was attached to NH2-UiO-66 via Zr-O-P bonds and Coulombic forces to create a gating effect. In the presence of ZEN, the aptamer bounded to ZEN, triggering a conformational change that released MB, resulting in decreased fluorescence intensity and absorbance. Under optimal conditions, the bimodal aptasensor exhibited wide linear ranges (2.5-300 ng/mL for colorimetry and 0.125-200 ng/mL for fluorescence) and low limits of detection (1.16 ng/mL for colorimetry and 0.03 ng/mL for fluorescence). Furthermore, the aptasensor demonstrated high specificity and reproducibility, with recovery rates ranging from 97.43% to 103.71% in spiked cereal products. These findings highlight the potential of the developed bimodal aptasensor as a novel tool for the rapid, accurate, and cost-effective detection of ZEN in cereal products, contributing to improved food safety monitoring.

Metal organic framework modified with carbon nanotube as an electrochemical sensor: Fabrication, excellent stability and sensitive detection of dopamine

Dopamine (DA) is a very important drug, however, excessive use can lead to DA becoming a micropollutant in water environments, which is an unfortunate consequence. The accurate determination of dopamine content is of great significance and has also attracted high attention from people. In this work, an electrochemical sensor (MOFCN) based on carbon nanotubes (CNTs) modified copper-based metal–organic framework (Cu-MOF) was developed using the hydrothermal method for sensitive detection of dopamine. The Cu-MOF, which are surrounded by CNTs, provide a favorable surface for the full utilization of the excellent conductivity property of carbon nanotube. The surface area of MOFCN is bigger than that of original Cu-MOF. The electrochemical sensing functions of the prepared MOFCN were evaluated by cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques. Under optimal conditions, there was a good linear relationship between peak current and DA concentration in the range of 0.5 to 100 µM with a detection limit (LOD) as low as 0.13 µM. The current modified MOFCN sensor was employed to quantify trace DA concentrations in actual water sample, reaching satisfactory recovery rates ranging from 97.5 % to 105 %. The interference effect on the determination of DA showed the excellent selectivity of MOFCN using the DPV technique. A comprehensive investigation was undertaken into the kinetics and underlying mechanisms of the electrochemical reaction. The transfer of electrons and hydrogen ions facilitates the transformation of DA into dopaminoquinones (DQ), a process that is accelerated by the augmented availability of active sites in the designed sensor. The present study proposes a method for the precise and efficient analysis, which proves that the proposed sensor is highly effective for detecting DA in Environmental water samples.

Using diatom chain length as a bioindicator of heavy-metals contamination in marine environments

The increasing release of toxic heavy metals into marine environments poses significant risks due to their persistence and bioaccumulation. Diatoms are ideal bioindicators because of their sensitivity to environmental changes. Despite traditional methods for detecting these persistent pollutants effectively identify composition and concentration, they are time-consuming, they often require the use of harmful reagents, and do not allow a fast assessment of detrimental impacts on marine organisms. To fill this gap, we have successfully investigated the toxicity of different heavy metals in the marine diatom Skeletonema pseudocostatum thanks to a newly developed high-power terahertz (THz) spectrometer. By combining THz spectroscopy, microscopy and ecotoxicological assays, we found that the formation of long diatom chains is significantly inhibited by the presence of lead, copper, and chromium, which disrupt their metabolism. Although the THz absorption and refractive index spectra were not affected by diatom concentration in undoped samples, THz frequencies were highly sensitive to changes in diatom chain length due to heavy metals exposure. These findings suggest that this approach allows to investigate the biochemical processes involved in chain formation in S. pseudocostatum and related algae. THz spectroscopy could therefore provide deeper insights into the microscopic metabolic activity of diatoms, addressing key biochemical questions surrounding these organisms. Furthermore, we propose this novel approach for environmental pollution monitoring, since it could provide a rapid, harmless and sensitive detection method to assess heavy metal toxicity in marine diatoms, key organisms at the basis of the trophic chain.

Rapid and multiple visual detection of Fasciola hepatica in feces via recombinase polymerase amplification integrated with CRISPR/Cas12a technology

Fasciola hepatica is a foodborne zoonotic parasite causing significant economic losses and impacting human and livestock health in resource-limited regions. We developed a rapid, reliable, and sensitive detection method combining recombinase polymerase amplification (RPA) with CRISPR/Cas12a, allowing visualization with the naked eye or a fluorescence reader. Multiple visual methods were used to analyze the assay results. Fluorescence signals were collected using a fluorescence reader or observed under UV or blue light. Lateral flow strips (LFS) were used for visual detection. Among seven primer pairs and three CRISPR RNA (crRNA) screened, F1/R1 and crRNA3 were optimal. The Cas12a reaction buffer was optimized with 50 mM Tris-HCl and 80 mM NaCl, with an RPA reaction time of 20 min. The assay showed high specificity and excellent sensitivity for F. hepatica, detecting 0.122 copies/μL with fluorescence and 8.6 copies/μL with LFS. Testing of 143 sheep and 43 human fecal samples showed 98.39 % consistency with qPCR and nested PCR, with prevalence rates of 52.45 % and 18.6 % in sheep and humans, respectively. Our assay offers substantial potential for point-of-care testing in resource-limited areas, addressing the need for rapid and accurate diagnosis of F. hepatica.

Urine PLA2R Antibody Detection in Hazard Stratification of PLA2R-Associated Membranous Nephropathy.

M-type phospholipase A2 receptor (PLA2R) is the major autoantigen of membranous nephropathy (MN). As the specific antibodies of MN, the correlation between serum PLA2R antibody (sPLA2R-Ab) levels and PLA2R-associated MN (PMN) risk stratification is still controversial. To apply the time-resolved fluorescence immunoassay (TRFIA) method on urine PLA2R-Ab (uPLA2R-Ab), detect, and then establish a more sensitive method of combined serum and urine PLA2R-Ab detection for PMN hazard stratification. A highly sensitive TRFIA method was used to detect the initial serum and urine samples of patients with PMN. Patients were grouped into remission and nonremission groups according to the outcomes after 12 months of treatment and the data were analyzed. The cutoff values of sPLA2R-IgG (sPLA2R-immunoglobulin G), uPLA2R-IgG, sPLA2R-IgG4, and uPLA2R-IgG4 for distinguishing between remission and nonremission groups were 50 relative units (RU)/mL, 3.51 RU/mL, 6835 ng/mL, and 143.4 ng/mL, respectively. The average value in the remission group for sPLA2R-IgG, uPLA2R-IgG, sPLA2R-IgG4, and uPLA2R-IgG4 was 37.39 RU/mL, 1.10 RU/mL, 3498.99 ng/mL, and 33.83 ng/mL, respectively. The average value in the nonremission group for sPLA2R-IgG, uPLA2R-IgG, sPLA2R-IgG4, and uPLA2R-IgG4 was 279.96 RU/mL, 45.36 RU/mL, 25762.47 ng/mL, and 1383.89 ng/mL, respectively. For sPLA2R-Ab as the primary factor, in combination with uPLA2R-Ab, the high-risk predictive value of combined detection of serum and urine PLA2R-IgG and of serum and urine PLA2R-IgG4 was upgraded from 54.55% to 100% and from 75% to 100%, respectively. A highly sensitive TRFIA method was applied in this study; the combined detection of serum and urine PLA2R-Ab improves the efficiency of PMN risk stratification, and can provide a better assessment of PMN monitoring.

Silver nano-colloid particles embedded on Langmuir-Blodgett film matrix of stearic acid serving as a SERS active sensor for detecting the herbicide ‘Paraquat’

The herbicide Paraquat, widely used for efficient weed control, poses significant health risks to humans viz., severe toxicity to vital organs and induction of neurodegenerative disorder like Parkinson’s disease, underscoring the urgent need for developing sensitive detection methods for the herbicide. This study aims at fabricating a novel SERS-active substrate SA-LB/Ag (silver nano-colloids adsorbed on Langmuir-Blodgett film of stearic acid), as a SERS based sensor having high sensitivity, uniformity, and reproducibility to detect ultra-trace amounts of paraquat. The sensor was built up by immersing bilayer LB films of SA in silver nano-colloid suspension, prepared by mixing silver nitrate and sodium borohydride with vigorous stirring. Quantitative evaluations establish a significant linear regression across the concentration spectrum (100 ppm to 75 ppb) of paraquat, with a remarkable 15 ppb limit of detection (LOD) value. In practical terms, this SERS based sensor exhibits notable proficiency in detecting paraquat residues in (a) agricultural water from rice and vegetable fields and environmental water from adjoining water-logged areas, and (b) soil extracts of the agricultural fields. Moreover, the minimum toxic concentration of paraquat at the developmental stage of zebrafish embryos and larvae is found to be approximately 20 ppb, implying that the SA-LB/Ag sensor is sensitive enough to determine the limiting toxic level of paraquat for animal systems. Thus, the designed sensor holds far-reaching implications in ensuring food safety, monitoring the environment, and framing regulatory measures for paraquat use.

Signal amplification strategy electrochemiluminescence based on porous graphite-phase carbon nitride: A novel ECL sensor for ultrasensitive detection of tigecycline

Tigecycline (TGC) is a third-generation tetracycline antibiotic known for its broad-spectrum antibacterial properties. However, the misuse of tigecycline can lead to significant issues, including environmental concerns and the escalation of drug resistance. Consequently, it is essential to develop an efficient and sensitive detection method for tigecycline. In this study, a novel solid-state electrochemical luminescence sensor was firstly developed for highly sensitive detection of TGC. The sensor incorporated porous graphite-phase carbon nitride (PCN) as a luminescent reagent, triethanolamine (TEA) as a co-reagent, Fe3O4 and ZIF-8@Ag NPs as luminescence accelerators, resulting in a robust and stable luminescence signal. Detailed characterization of PCN, comparison of ECL efficiency between PCN and g-C3N4, and optimization of experimental conditions were conducted to showcase the superior ECL performance of PCN. The sensor exhibited a linear relationship between the change of ECL signal and the logarithm of tigecycline concentration in the range of 1.0 × 10−14 to 1.0 × 10−7 mol/L, with a low detection limit of 3.33 × 10−15 mol/L (S/N = 3). Furthermore, the sensor demonstrated excellent stability, selectivity, and reproducibility, making it suitable for detecting TGC in milk samples.

A dual-recognition precise nucleic acid probe based on tetrahedron and Cas12a reveals gene-environment interactions

Precise detection of gene expression is crucial for understanding the interactions between organisms and their environment. In this study, we developed a highly sensitive dual-recognition gene detection method based on the CRISPR-Cas12a system and DNA tetrahedron and validated its application in biological samples. By optimizing the Cas12a signal readout system, the method demonstrated excellent sensitivity and stability. Further experiments showed that the method could accurately detect the expression of the LKB1 gene, with good linearity observed in the concentration range of 10 pM to 10 nM, and a detection limit as low as 1 pM. Using an arsenic-induced mouse liver injury model, we validated the applicability in complex biological samples and found that this detection system outperformed traditional RT-qPCR in recognizing gene expression differences, offering higher sensitivity and specificity.

Poly(p-Phenyleneethynylene)s-Based Sensor Array for Diagnosis of Clinical Diseases.

Inspired by the mammalian taste and olfactory systems, array-based pattern recognition technology has demonstrated significant potential in discerning subtle differences between highly similar compounds and complex mixtures, owing to their unique parallel detection mechanism based on cross-reactive signals. While optical sensor array has been extensively employed in the field of chemical sensing, they encounter significant challenges in non-specific recognition of multiple analytes at low concentrations, particularly in rife environments with complex interferences. Poly(p-phenylene ethynylene)s (PPEs) offer substantial advantages in detecting multi-analytes at low concentrations, owing to its distinctive optical properties, including the "molecular wire" effect, fluorescence super-amplification and super-quenching. This is particularly promising for the parallel detection of ultra-low concentration multi-biomarkers in clinical diseases. As the continuous development of PPEs sensor array, more sensitive methods for rapid detection of clinical disease will be further developed. It will promote the further development of the field of early diagnosis of clinical diseases.

Magnetic metal-organic frameworks-based ratiometric SERS aptasensor for sensitive detection of patulin in apples

Patulin (PAT), a major contaminant in apples, poses a considerable food safety risk, necessitating a rapid, sensitive and reliable detection method. This study developed a novel magnetic metal-organic frameworks (MOFs)-based ratiometric surface-enhanced Raman scattering (SERS) aptasensor. The sensor consists of magnetic MOFs loaded with 4-Mercaptobenzoic acid (4-MBA) internal labeled AuMBA@Ag as the SERS substrate, and gold nanorods (AuNRs) modified with Rhodamine 6G and aptamers as capture probes. This strategy enhances sensitivity through magnetic separation and abundant SERS hotspots provided by the magnetic MOF nanocomposites. The SERS intensity ratio showed a negative correlation with PAT concentrations from 0.01 to 100 ng/mL, with a LOD of 0.0465 ng/mL. Moreover, the aptasensor achieved 95.90 % ∼ 105.83 % recoveries in apple samples, indicating high accuracy and anti-interference capability. The excellent sensing performance demonstrates great potential of the SERS nanosensor for mycotoxin detection in actual food matrices.

Au@Ag hollow nanoshells-based SERS integrated microfluidic chip as a sample-to-answer platform for the ultra-sensitive detection of geosmin

BackgroundGeosmin (GSM) can compromise the immune systems of aquatic organisms, rendering them more vulnerable to viral and bacterial infections, thereby adversely affecting their growth, reproduction, yield, and quality. Given the relatively low odor thresholds of GSM, there is a critical demand for the development of a highly sensitive and rapid detection method. According to the principle of Surface-enhanced Raman spectroscopy (SERS), localized surface plasmon resonance (LSPR) greatly enhances the Raman signals of adsorbed molecules. To date, no study has reported the application of SERS to detect GSM. ResultsDual-metal nanomaterials with hollow structures have been proven to provide a large surface area and heightened localized surface plasmon resonance, thereby enhancing the sensitivity of Raman signals. In this study, a sample-to-answer platform was constructed by integrating Au@Ag hollow nanoshells (HNSs)-based SERS and a microfluidic chip for the sensitive, fast, and direct determination of GSM. Under 532 nm excitation, GSM exhibit Raman peaks on the SERS-active Au@Ag HNSs, and there is a relationship between the peak intensity and the concentration of GSM. Owing to the integration of the microfluidic chip, only microliters of reagent are required, and the test results can be achieved within 4 min. The constructed sample-to-answer platform showed a good linear response to GSM in the range of 1 ng/L–1 mg/L, with a detection limit of 0.16 ng/L. An optimal calibration model is established by combining stoichiometric algorithms. SignificanceThis work realized the ultra-highly sensitive and fast determination of GSM based on SERS-active Au@Ag HNSs, which provides new insights and is very promising for the on-site monitoring of earthy odors. Our study makes a significant contribution to the literature because the developed SERS-based detection method does not require labels or biomaterials, providing the possibility of highly sensitive and on-site testing of contaminants in food and the environment.

A Dual-Ion Synergistic Catalysis Utilizing Zn2+-Regulated CdSySe1-y ECL Immunosensor Employed for the Ultrasensitive CA19-9 Detection.

Carbohydrate antigen 19-9 is a well-known malignancy biomarker, and its sensitive detection is particularly crucial in the diagnosis and assessment of pancreatic cancer. In this study, an ultrasensitive CA19-9 immunosensor was constructed using the Zn2+-regulated CdSySe1-y (Zn-CdSySe1-y) nanospheres (NSs) as the electrochemiluminescence (ECL) emitter and FeCoS2 nano octahedrons (NOs) as a coreactant enhancer. The microstructure of ternary transition metal chalcogenide CdSySe1-y was precisely tuned by Zn2+ doping to avoid aggregation and thus enable stable and efficient cathodic ECL responses. The bimetallic sulfide FeCoS2 was synthesized using a metal organic framework (MOF) as the template by ion permeation. It was able to catalyze the coreactant efficiently due to the synergistic effect of the Fe2+ and Co2+. The immunosensor exhibited low detection limit (7.6 × 10-5 U mL-1) in the wide linear range of 0.0001-100 U mL-1, offering a sensitive CA19-9 detection method.

MicroRNA Triggered Dimerization of DNA Tetrahedron for Enhanced Biosensing Performance of Solid-State Nanochannels Functionalized with MoS2 Nanosheets.

Solid-state nanochannels (SSN) have great development potential as a biosensing interface. The integration of two-dimensional nanomaterials with nanochannels endows SSN with diverse properties, including distinguishing DNA nanostructures. In this study, by modifying MoS2 nanosheets, the outer surface of SSN could be endowed with robust adsorption properties for single-stranded DNA. Therefore, DNA tetrahedrons connected with single-stranded DNA could remain on the SSN surface, whereas DNA tetrahedron dimers with full double-stranded structures formed by the presence of target microRNA cannot be retained on the surface of nanochannels. The change in the DNA nanostructure generated by the target recognition process could cause variations of steric hindrance and electrostatic repulsion on the surface of the SSN. The variations were reflected by the free diffusion flux of [Fe(CN)6]3-. Then, the sensitive electrochemical detection method for microRNA was established, and the detection limit of the method for microRNA-31 was as low as 0.5 fM. The study provided a promising approach for the ultrasensitive detection of biomarkers, thereby offering potential means for early diagnosis of the related diseases.

Ammonia and temperature sensing applications using fluorometric and colorimetric microparticles and polymeric films doped with BODIPY-emitters.

Fourfunctionalized BODIPY derivatives(BDP1 to BDP4) were synthesizedand their optical properties investigatedboth in solution and when incorporated into a solid matrix. Recognizing the versatility of BODIPY derivatives and the increasing interest in developing new luminescent organic dyes embedded in polymers, the BODIPY derivatives were dispersed into two types of polymeric matrices: Poly(methyl methacrylate) (PMMA) and Thermoplastic Polyurethane (TPU), both as films and microparticles. This resulted in eight new BODIPY-doped polymer films and eight types of BODIPY-doped polymeric microparticles for use in aqueous solutions. The integration of the BODIPY dyes into the polymeric matrices combines the unique properties of the polymer films, such as porosity, flexibility, and elasticity, with the excellent photophysical characteristics of the BODIPYs. Importantly, the dispersion minimized issues such as aggregation-caused quenching commonly observed in solid-state luminescent materials. The thermometric responses of all polymer films were evaluated by studying their solid-state emission spectra in the 25-200°C temperature range. The reversibility of these temperature-induced changes was also assessed, revealing excellent recovery of luminescence. These promising results suggest these materials could have applications as fluorescent thermometric sensors. Furthermore, we explored the potential of the brominated (BDP3) and chalcogenated (BDP4) BODIPY derivatives as ammonia sensors. The two derivatives produced yellow fluorescent products upon interaction with the analyte. Kinetic studies using solid-state emission spectra of BDP4@TPU and BDP4@PMMA showed significant differences in reaction rates (minutes for BDP4@TPU and hours in the case of BDP4@PMMA) attributable to the higher permeability of TPU when compared with PMMA. Detection and quantification of ammonia concentration were conducted by means of simple photographic analysis, measuring the "R" (red) and "G" (green) components of RGB color parameters. Theresults from the photographic method correlated well with the results from fluorimetric spectroscopy studies. The photographic analysis is straightforward, portable, and does not require expensive equipment. Finally, we successfully applied polymeric microparticles doped with BODIPYs to detect ammonia in water, demonstrating their effectiveness without the need for organic solvents. This highlights their potential for environmental monitoring and other applications requiring sensitive and selective detection methods.

Dual hot-spot SERS test strip for picomole level analysis of thiram

The misuse and improper disposal of thiram pesticide present significant health and environmental risks, emphasizing the need for highly sensitive detection methods, particularly in food safety. In this study, we introduce a novel approach for thiram detection using surface-enhanced Raman scattering (SERS) test strips with dual hot-spots. Thiram prevents Ag+ from acting as specific bridging molecules in a SERS hotspots model. Initially, the aggregation of 4-aminothiophenol (4-ABT) functionalized silver nanoparticles (AgNPs@4-ABT) can be efficiently triggered by Ag+ ions, simultaneously enhancing the SERS signal of 4-ABT. However, the introduction of thiram inhibits the aggregation of Ag NPs@4-ABT, leading to a reduction in the SERS signal. Based on this principle, we have developed a SERS analysis method for detecting thiram in solution. To address the reliance on initial signal intensity, we translocated the detection system onto cotton fabric. This adjustment not only amplifies the initial signal through the physical aggregation of nanoparticles, creating secondary hotspots, but also improves portability and reduces resource consumption. Compared to the single hotspot solution model, our dual hotspot configuration significantly enhances sensitivity due to the stronger initial signal, achieving an impressive broad linear detection range from 5 × 10−5 to 5 × 10−11 M. This range substantially outperforms the linear range of Ag NPs@4-ABT alone, which spans from 5 × 10−5 to 10−8 M. The SERS test strips exhibit a detection limit as low as 2.56 × 10−12 M, enabling picomolar level analysis. This innovative dual hotspot SERS approach provides a powerful tool for sensitive and practical detection of thiram in safety-critical applications.

A label-free electrochemical sensor based on π-structured bipedal DNA walker-triggered hybridization chain reaction and AuPt NPs/Zr-MOF for OTA detection

BackgroundOchratoxin A (OTA) is a serious food contaminant, not easily degradable, and capable of causing irreversible damage to the human body. Therefore, it is of great practical significance to establish a sensitive and efficient OTA detection method. The electrochemical aptasensor has a broad development prospect in OTA detection with its advantages of fast response speed and low cost. ResultsHerein, a cascade signal amplification strategy based on AuPt NPs/Zr-MOF and π-structure bipedal DNA walker-triggered hybridization chain reaction (HCR) was designed for the detection of ochratoxin A (OTA). AuPt NPs/Zr-MOF was employed as the electrode modification material, providing a large number of active sites and high conductivity, achieving 1.47 times signal amplification. Interestingly, bipedal DNA walker binds to hairpin 1 (H1) to form the π-structure. Under the activation of Pb2+, one bipedal DNA walker can simultaneously bind and cleave two H1. It exhibits a wide walking range and high recognition efficiency. After H1 is cleaved, the trigger sequence was exposed to trigger HCR and a large amount of methylene blue was loaded on the electrode. Under the optimal conditions, the linear range of the determined OTA is 1 × 10−3–500 ng/mL, and the limit of detection is as low as 0.525 pg/mL. SignificanceThe experimental results demonstrate that the constructed electrochemical aptasensor is a sensitive and efficient platform for OTA monitoring. The applicability in food samples was also confirmed, and the strategy was efficiently selective and reproducible for different analytes. This provides ideas for subsequent food safety testing.