Search Results (77)

Highly infectious and pathogenic viruses seriously threaten global public health, underscoring the need for rapid and accurate diagnostic methods to effectively manage and control outbreaks. In this study, we developed a comprehensive Surface-Enhanced Raman Scattering–Lateral Flow Immunoassay (SERS-LFIA) detection system that integrates SERS scanning imaging with artificial intelligence (AI)-based result discrimination. This system was based on an ultra-sensitive SERS-LFIA strip with SiO₂-Au NSs as the immunoprobe (with a theoretical limit of detection (LOD) of 1.8 pg/mL). On this basis, a negative–positive discrimination method combining SERS scanning imaging with a deep learning model (ResNet-18) was developed to analyze probe distribution patterns near the T line. The proposed machine learning method significantly reduced the interference of abnormal signals and achieved reliable detection at concentrations as low as 2.5 pg/mL, which was close to the theoretical Raman LOD. The accuracy of the proposed ResNet-18 image recognition model was 100% for the training set and 94.52% for the testing set, respectively. In summary, the proposed SERS-LFIA detection system that integrates detection, scanning, imaging, and AI automated result determination can achieve the simplification of detection process, elimination of the need for specialized personnel, reduction in test time, and improvement of diagnostic reliability, which exhibits great clinical potential and offers a robust technical foundation for detecting other highly pathogenic viruses, providing a versatile and highly sensitive detection method adaptable for future pandemic prevention. Full article

Arterial hypertension (HTN) is a growing global health concern, with limited tools available for early detection. Previous studies identified the overexpression of the epithelial sodium channel (ENaC) as a potential biomarker for HTN. In this work, we optimized and clinically validated a lateral flow immunoassay (LFIA) using gold nanoparticles (AuNPs) functionalized with anti-ENaC antibodies. The test strips were prepared with 10 µL of each component and performed in a 9-point herringbone format. For validation, a double-blind study was conducted using platelet lysates from 200 individuals, classified based on real-time blood pressure measurements. ENaC expression was assessed via both LFIA and Western blotting, which served as the reference method. Receiver operating characteristic (ROC) analysis yielded an AUC of 0.7314 for LFIA and 0.6491 for the Western blot, with LFIA demonstrating higher sensitivity (76.24%) and comparable specificity (61.54%) compared to the Western blot (68.31% and 60.34%, respectively). These results support LFIA as a practical, rapid, and moderately accurate tool for screening ENaC levels and identifying individuals at risk of hypertension. Full article

Procymidone (PCM) is an effective, low-toxicity fungicide commonly used to control plant diseases in grains, vegetables, and fruits. Its usage has significantly increased in recent years, resulting in higher residues in vegetables. This study developed a sensitive and rapid immunoassay method utilizing a gold- and fluorescence-labeled monoclonal antibody (mAb) for detecting PCM residues in vegetable samples. Under optimal conditions, the fluorescent microsphere-labeled monoclonal antibody immunochromatographic strips achieved a limit of detection (LOD) of 1.67 ng/mL, with a visual LOD of 50 ng/mL. Intra-batch accuracy ranged from 94.98% to 103.82%, with a coefficient of variation (CV) of 1.97% to 8.26%. Inter-batch accuracy ranged from 96.16% to 102.51%, with a CV of 4.62% to 8.91%. The visual detection range of the gold nanoparticle-labeled monoclonal antibody immunochromatographic strips was 50 to 200 ng/g. The method demonstrated excellent performance in actual vegetable samples, confirming its applicability across various matrices. This dual-method approach enables rapid screening of negative samples with gold test strips, followed by accurate quantitative analysis of positive samples using fluorescent test strips, thereby enhancing efficiency and addressing diverse detection needs. Consequently, this method holds significant market potential for practical applications. Full article

Ciprofloxacin is metabolized from enrofloxacin for use in poultry to manage respiratory and gastrointestinal diseases, raising concerns due to its widespread tissue distribution and prolonged systemic persistence. This lateral flow immunoassay was designed to detect ciprofloxacin using an alternative IgY antibody binded with gold nanoparticles to detect ciprofloxacin residue in raw pork meat samples. The developed strip test achieved adequate sensitivity and specificity under the optimized conditions for pH, which is 7.8, and 20% of MeOH in 0.01 M phosphate buffer containing 1% Tween-20 was used for the buffer composition. An antibody concentration of 1.25 µg/mL was used to bind with gold nanoparticles as a probe for detection. The concentration of the test line (coating antigen) and control line (anti-IgY secondary antibody) was 0.5 mg/mL and 0.2 mg/mL, respectively. The efficiency of the developed strip test showed sensitivity with a 50% inhibitory concentration (IC₅₀) of ciprofloxacin at 7.36 µg/mL, and the limit of detection was 0.2 µg/mL. The proposed strategy exhibited potential for monitoring ciprofloxacin in raw pork samples. Full article

Background/Objectives: Accurate surveillance of recent HIV infections is crucial for effective epidemic control and timely intervention. The Limited Antigen Avidity Enzyme Immunoassay (LAg-EIA) allows precise differentiation between recent and long-term HIV infections. To enhance accessibility, it has been developted into a point-of-care test, the Asanté™ HIV-1 Rapid Recency^® Assay (ARRA), a rapid immunoassay. This study evaluated the performance and false recent rates (FRRs) of the ARRA, interpreted both visually and via a strip reader, in comparison with the LAg-EIA. Methods: Plasma samples were collected from two groups: 634 long-term HIV-infected individuals, identified through routine diagnostic testing, who had not received antiretroviral therapy for over one year, and 224 individuals from high-risk populations. High-risk individuals, including pregnant women, female sex workers, and men who have sex with men, were selected based on behavioral and demographic risk factors. Concordance between the ARRA and LAg-EIA was assessed, and FRRs were calculated for both assays. McNemar’s test was used to evaluate agreement, while Spearman’s rho was applied to assess correlation between the two methods. Results: Visual interpretation of ARRA demonstrated perfect agreement with LAg-Avidity EIA results (FRR = 0.00%), while the strip reader misclassified two specimens as recent infections (FRR = 0.32%). McNemar’s test indicated no significant differences between the methods (p > 0.05). Moderate agreement (Spearman’s rho = 0.434) was observed between ARRA strip reader results and LAg-Avidity EIA optical density values. Among high-risk populations, ARRA misclassified one sample as recent, resulting in an inconsistency rate of 0.45%. Conclusions: This study highlights ARRA’s reliability in identifying long-term infections and its potential as a point-of-care tool. Its rapid results and ease of use make it a valuable asset for effective HIV surveillance, facilitating targeted epidemic monitoring and enhancing public health interventions. Full article

Multiplex lateral flow assays are one of the greatest advancements in the world of rapid diagnostics, achieving the performance of several tests in one. These tests meet the basic requirements of increasing ease of use, low detection limit, and high specificity, as they combine the use of novel strategies, such as the exploitation of multiple detection labels, and a variety of amplification methods. These tests have proven their usefulness in many different areas, including clinical diagnostics, food, and environmental monitoring. In this review paper, we attempt to highlight and discuss the predominant changes in multianalyte LFAs, as related to their principle, their development, and their combination with other methods. Attention is paid to their flexibility and the challenges associated with the use of LFA arrays, including strategies to improve the detectability, sensitivity, and reliability of the assays. Therefore, this review emphasizes the current advances in the field to underline the possible impact of multiplex LFAs on the future of diagnostics and analytical sciences. Full article

Porcine circovirus type 2 (PCV2) is the main and primary causative agent of Postweaning Multisystemic Wasting Syndrome (PMWS). To date, immunoperoxidase monolayer assay (IPMA), indirect immunofluorescent assay (IFA), and enzyme linked immunosorbent assay (ELISA) are the most commonly diagnostic methods for detecting PCV2 antigens. However, these methods require specialized equipment and technical expertise and are suitable for laboratory use only. This study aims to develop an immunochromatographic strip and a magnetic chemiluminescence immunoassay for the detection of PCV2 antigens. The recombinant protein was constructed using a prokaryotic expression system, and the polyclonal antibody was obtained by animal experiments. Polystyrene microspheres are used as solid phase carriers to covalently bind to the amino groups of proteins to form immunoprobes. Monodisperse beads are covalently bound to antigens or antibodies as solid phases to bind antibodies or antigens in the liquid phase in a superior manner, thereby capturing and separating antigens and antibodies in the liquid phase. The immunochromatographic strip is qualitative detection method, this method can detect PCV2a strain, PCV2b strain, and PCV2d strain. The immunochromatographic strip had minimum detection limits of 10^2.89TCID₅₀/0.1 mL, 10^3.19TCID₅₀/0.1 mL, and 10^3.49TCID₅₀/0.1 mL for PCV2a/LG, PCV2b/SH, and PCV2d/JH. The results of testing PEDV (CV777 strain), PRV (HB2000 strain), CSFV (WH-09 strain), PRRS (JXA1-R strain), PPV (WH-1 strain), and ASFV (SD strain) were negative. The agreement between the immunochromatographic strip and the ELISA kit was 93.33% (140/150) and the Kappa was 0.866 (Kappa > 0.81). On the premise of ensuring sensitivity, the most important feature of the immunochromatographic strip is that this method can save time when testing; results can be obtained within 5 to 10 min. Magnetic chemiluminescence immunoassay is quantitative detection method; this method can detect PCV2 Cap proteins in swine serum, the linear range of this method was 0.25 ng/mL to 32 ng/mL and R² of the standard curve was 0.9993. The limit of detection (LOD) is 0.051 ng/mL and the limit of quantitation (LOQ) is 0.068 ng/mL. The agreement between the magnetic chemiluminescence immunoassay and the ELISA kit (test PCV2 Cap proteins) was 97.14% (68/70). This method took less than 30 min to achieve results, which is less than the ELISA kit. The results of this study show that immunochromatographic strip and magnetic chemiluminescence immunoassay for PCV2 antigens had great sensitivity and specificity, which lays the foundation for PCV2 clinical detection. Full article

To ensure the safety of foodstuffs, widespread non-laboratory monitoring for pathogenic contaminants is in demand. A suitable technique for this purpose is lateral flow immunoassay (LFIA) which combines simplicity, rapidity, and productivity with specific immune detection. This study considered three developed formats of LFIA for Salmonella Typhimurium, a priority pathogenic contaminant of milk. Common sandwich LFIA with all immunoreagents pre-applied to the test strip (format A) was compared with incubation of the sample and (gold nanoparticle—antibody) conjugate, preceding the lateral flow processes (format B), and sequential passages of the sample and the conjugate along the test strip (format C). Under the chosen conditions, the detection limits and the assay times were 3 × 10⁴, 1 × 10⁵, and 3 × 10⁵ cells/mL, 10, 15, and 20 min for formats A, B, and C, respectively. The selected format A of LFIA was successfully applied to test milk samples. The sample’s dilution to a fat content of 1.0% causes pathogen detection, with 70–110% revealing and 1.5–8.5% accuracy. The obtained results demonstrate that the developed LFIA allows the detection of lower concentrations of Salmonella cells and, in this way, accelerates decision-making in food safety control. Full article

The development of a novel strategy for the measurement of SARS-CoV-2 IgG antibodies is of vital significance for COVID-19 diagnosis and effect of vaccination evaluation. In this investigation, an SiO₂@Au@CDs nanoparticle (NP)-based lateral flow immunoassay (LFIA) strip was fabricated and coupled with a miniaturized fluorimeter. The morphology features and particle sizes of the SiO₂@Au@CDs NPs were characterized carefully, and the results indicated that the materials possess monodisperse, uniform, and spherical structures. Finally, this system was employed for SARS-CoV-2 IgG antibody test. In this work, the strategy for the SARS-CoV-2 IgG antibody test possesses several merits, such as speed (less than 15 min), high sensitivity (1.2 × 10⁻⁷ mg/mL), broad linearity range (7.4 × 10⁻⁷~7.4 × 10⁻⁴ mg/mL), accurate results, high selectivity, good stability, and low cost. Additionally, future trends in LFAs using quantum dot-based diagnostics are envisioned. Full article

Gatifloxacin (GAT), an antibiotic belonging to the fluoroquinolone (FQ) class, is a toxicant that may contaminate food products. In this study, a method of ultrasensitive immunochromatographic detection of GAT was developed for the first time. An indirect format of the lateral flow immunoassay (LFIA) was performed. GAT-specific monoclonal antibodies and labeled anti-species antibodies were used in the LFIA. Bimetallic core@shell Au@Ag nanoparticles (Au@Ag NPs) were synthesized as a new label. Peroxidase-mimic properties of Au@Ag NPs allowed for the catalytic enhancement of the signal on test strips, increasing the assay sensitivity. A mechanism of Au@Ag NPs-mediated catalysis was deduced. Signal amplification was achieved through the oxidative etching of Au@Ag NPs by hydrogen peroxide. This resulted in the formation of gold nanoparticles and Ag⁺ ions, which catalyzed the oxidation of the peroxidase substrate. Such “chemical enhancement” allowed for reaching the instrumental limit of detection (LOD, calculated by Three Sigma approach) and cutoff of 0.8 and 20 pg/mL, respectively. The enhanced assay procedure can be completed in 21 min. The enhanced LFIA was tested for GAT detection in raw meat samples, and the recoveries from meat were 78.1–114.8%. This method can be recommended as a promising instrument for the sensitive detection of various toxicants. Full article

Background/Objectives: On-site diagnosis of infection in their early stages requires assays with high sensitivities that are compact and easy to operate out of the laboratory and hospital environments. However, current assay technologies fall short of these requirements and require highly skilled technicians to set up, operate, and interpret the results. Methods: To address these challenges, we developed and evaluated a Point-of-Care-Testing (PoCT) immunoassay platform called the D-strip. The D-strip platform combines the capabilities of a digital enzyme-linked immunoassay (ELISA) with a lateral flow assay (LFA). The D-strip sample flow cell is composed of the same components found in conventional LFAs, and its high sensitivity is due to its efficient implementation of ELISA. The fully integrated platform is simple and requires minimal user intervention to operate. Results: The D-strip exhibited a sample-to-result time of 15 min with a limit of detection (LOD) of 1.7 × 10³ copies/mL for severe acute respiratory syndrome coronavirus 2 (SARS-2-CoV) antigen. The LOD of the D-strip is 488-fold higher than that for conventional LFAs and is comparable to a clinical laboratory test. Conclusions: The D-strip is a compact and highly sensitive immunoassay platform with a strong potential for application as a confirmatory assay outside the clinical laboratory. Full article

The Alaotran gentle lemur (Hapalemur alaotrensis) is one of the world’s most endangered primates and shows low success rates in captive breeding programmes. This study tested biologically relevant scent enrichment using two synthesised mixtures likely to convey information about female fertility on the behaviour of three unsuccessful breeding pairs in captivity. Specifically, we compared the baseline and enrichment periods by combining behavioural observations (n = 240 h) with faecal endocrinology (n = 80 samples), focussing on cortisol and testosterone measurements via enzyme immunoassay techniques. Then, we tested two different mixtures to assess potential behavioural differences and evaluate the effectiveness of olfactory enrichment using scented and unscented cotton strips. Olfactory behaviours differed by sex and enrichment conditions, with both sexes exhibiting increased behaviours during enrichment compared to the baseline. Sexual behaviours increased during the enrichment period, with variations in frequency between males and females depending on the condition. No significant changes were observed in faecal cortisol levels. However, one male showed a significant increase in testosterone during the second enrichment mixture. Nevertheless, overall differences between baseline and enrichment were not significant. Our findings suggest that while the scent enrichment showed limited effectiveness, biologically meaningful scents may trigger species-specific behaviours. Full article

Interleukin-6 (IL-6) detection and monitoring are of great significance for evaluating the progression of many diseases and their therapeutic efficacy. Lateral flow immunoassay (LFIA) is one of the most promising point-of-care testing (POCT) methods, yet suffers from low sensitivity and poor quantitative ability, which greatly limits its application in IL-6 detection. Hence, in this work, we integrated Au_shell nanoparticles (NPs) as new LFIA reporters and achieved the colorimetric and photothermal dual-mode detection of IL-6. Au_shell NPs were conveniently prepared using a galvanic exchange process. By controlling the shell thickness, their localized surface plasmon resonance (LSPR) peak was easily tuned to near-infrared (NIR) range, which matched well with the NIR irradiation light. Thus, the Au_shell NPs were endowed with good photothermal effect. Au_shell NPs were then modified with IL-6 detection antibody to construct Au_shell probes. In the LFIA detection, the Au_shell probes were combined with IL-6, which were further captured by the capture IL-6 antibody on the test line of the strip, forming a colored band. By observation with naked eyes, the colorimetric qualitative detection of IL-6 was achieved with limit of 5 ng/mL. By measuring the temperature rise of the test line with a portable infrared thermal camera, the photothermal quantitative detection of IL-6 was performed from 1~1000 ng/mL. The photothermal detection limit reached 0.3 ng/mL, which was reduced by nearly 20 times compared with naked-eye detection. Therefore, this Au_shell-based LFIA efficiently improved the sensitivity and quantitative ability of commercial colloidal gold LFIA. Furthermore, this method showed good specificity, and kept the advantages of convenience, speed, cost-effectiveness, and portability. Therefore, this Au_shell-based LFIA exhibits practical application potential in IL-6 POCT detection. Full article

Lateral flow immunoassays (LFIAs) are recognized for their practicality in homecare and point-of-care testing, owing to their simplicity, cost-efficiency, and rapid visual readouts. Despite these advantages, LFIAs typically fall short in sensitivity, particularly in detecting viruses such as SARS-CoV-2, thus limiting their broader application. In response to this challenge, we have innovated an approach to substantially enhance LFIA sensitivity. This involves the integration of a water-soluble dextran–methacrylate polymer wall with a 15% grafting degree positioned between the test and control lines on the LFIA strip. This novel modification significantly improved the sensitivity of the assay, achieving detection limits as low as 50 pg mL⁻¹ and enhancing the sensitivity by 5–20-fold relative to existing LFIA kits available on the market. Furthermore, our developed LFIA kit (WSPW-LFIA) demonstrated exceptional specificity for SARS-CoV-2. Coupled with a straightforward fabrication process and robust stability, the WSPW-LFIA represents a promising advancement for real-time in vitro diagnosis across a spectrum of diseases. Full article

Mycotoxins, secondary metabolites synthesized by various filamentous fungi genera such as Aspergillus, Penicillium, Fusarium, Claviceps, and Alternaria, are potent toxic compounds. Their production is contingent upon specific environmental conditions during fungal growth. Arising as byproducts of fungal metabolic processes, mycotoxins exhibit significant toxicity, posing risks of acute or chronic health complications. Recognized as highly hazardous food contaminants, mycotoxins present a pervasive threat throughout the agricultural and food processing continuum, from plant cultivation to post-harvest stages. The imperative to adhere to principles of good agricultural and industrial practice is underscored to mitigate the risk of mycotoxin contamination in food production. In the domain of food safety, the rapid and efficient detection of mycotoxins holds paramount significance. This paper delineates conventional and commercial methodologies for mycotoxin detection in ensuring food safety, encompassing techniques like liquid chromatography, immunoassays, and test strips, with a significant emphasis on the role of electrochemiluminescence (ECL) biosensors, which are known for their high sensitivity and specificity. These are categorized into antibody-, and aptamer-based, as well as molecular imprinting methods. This paper examines the latest advancements in biosensors for mycotoxin testing, with a particular focus on their amplification strategies and operating mechanisms. Full article