Search Results (139)

The lateral flow immunoassay (LFIA) is a widely utilized, rapid diagnostic technique characterized by its short analysis duration, cost efficiency, visual result interpretation, portability and suitability for point-of-care applications. However, conventional LFIAs have limited sensitivity, a challenge that can be overcome by the introduction of gold nanoparticles, which provide enhanced sensitivity and selectivity (compared, for example, to latex beads or carbon nanoparticles) for the detection of target analytes, due to their optical properties, chemical stability and ease of functionalization. In this work, gold nanoparticle-based LFIAs are developed for the detection of aflatoxin B1, and the relative performance of different morphology particles is evaluated. LFIA using gold nano-labels allowed for aflatoxin B1 detection over a range of 0.01 ng/mL–100 ng/mL. Compared to spherical gold nanoparticles and gold nano-flowers, star-shaped gold nanoparticles show increased antibody binding efficiency of 86% due to their greater surface area. Gold nano-stars demonstrated the highest sensitivity, achieving a limit of detection of 0.01ng/mL, surpassing the performance of both spherical gold nanoparticles and gold nano-flowers. The use of star-shaped particles as nano-labels has demonstrated a five-fold improvement in sensitivity, underscoring the potential of integrating diverse nanostructures into LFIA for significantly improving analyte detection. Moreover, the robustness and feasibility of gold nano-stars employed as labels in LFIA was assessed in detecting aflatoxin B1 in a wheat matrix. Improved sensitivity with gold nano-stars holds promise for applications in food safety monitoring, public health diagnostics and rapid point-of-care diagnostics. This work opens the pathway for further development of LFIA utilizing novel nanostructures to achieve unparallel precision in diagnostics and sensing. Full article

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

Chronic kidney disease (CKD) is associated with heart failure and neurological disorders. Therefore, point-of-care (POC) detection of CKD is essential, allowing disease monitoring from home and alleviating healthcare professionals’ workload. Lateral flow immunoassays (LFIAs) facilitate POC testing for a renal function biomarker, serum Cystatin C (CysC). LF devices were fabricated and optimised by varying the diluted sample volume, the nitrocellulose (NC) membrane, bed volume, AuNPs’ OD value and volume, and assay formats of partial or full LF systems. Notably, 310 samples were analysed to satisfy the minimum sample size for statistical calculations. This allowed for a comparison between the LFIAs’ results and the general Roche standard assay results from the Southern Health and Social Care Trust. Bland–Altman plots indicated the LFIAs measured 0.51 mg/L lower than the Roche assays. With the 95% confidence interval, the Roche method might be 0.24 mg/L below the LFIAs’ results or 1.27 mg/L above the LFIAs’ results. In summary, the developed non-fluorescent LFIAs could detect clinical CysC values in agreement with Roche assays. Even though the developed LFIA had an increased bias in low CysC concentration (below 2 mg/L) detection, the developed LFIA can still alert patients at the early stages of renal function impairment. 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

Lateral flow immunoassay (LFIA) is a promising tool for rapid detection in the field of agricultural product analysis due to its advantages of cost-effectiveness and operational simplicity. In this work, Eu metal–organic frameworks (MOFs) were introduced to LFIA as a rapid detection method characterized by high stability and low interference. Key research objectives included strong fluorescence, ease of labeling, and the utilization of fluorescent probes. Eu-MOFs were synthesized in one step via the hydrothermal method, exhibiting a fluorescence lifetime of 163 μs and spherical particles with diameters ranging from 250 to 400 nm. These conditions fulfill the characteristics and requirements of LFIA. Eu-MOFs exploit the porous nature of MOFs to mitigate the drawbacks associated with complex crosslinking agents. This enables antibody proteins to be cross-linked merely upon contact, thereby simplifying the detection process. A time-resolved LFIA method was developed utilizing Eu-MOFs for the detection of aflatoxin B1 (AFB1) in corn, achieving a limit of detection (LOD, IC10) of 0.149 ng/mL. The accuracy and reliability of the Eu-MOFs-LFIA method were validated through comparisons with spiked concentrations during spiking and blind sample analyses, with verification conducted using ultra-high-performance liquid chromatography mass spectrometry (UPLC-MS). Furthermore, testing of real samples demonstrated that the Eu-MOFs-LFIA method can effectively facilitate rapid detection of AFB1 in corn. Full article

The Monkeypox virus (MPXV), a DNA virus classified under the Orthpoxvirus genus alongside variola virus, has recently garnered significant global health attention due to its increasing transmission and emerging genomic mutations. Point-of-care testing is essential for effective clinical response and outbreak mitigation. In this article, we developed a novel class of colored microspheres designed for application in a lateral flow immunoassay (LFIA) platform targeting MPXV-specific biomarkers. Polystyrene-maleic anhydride (SMA-MAA) microspheres were synthesized with a high-temperature soap-free emulsion polymerization optimized in our lab. Subsequent alkali and acid treatments were employed to introduce porosity into the microsphere matrix. Solvent Red 27 and Disperse Red 60 were incorporated via solvent-swelling and thermal-swelling methods, respectively, to generate high brightness (HB) carriers. A surface coating composed of a tannic acid–iron (TA–Fe³⁺) coordination complex was applied to form a stable metal–polyphenol film (MPF). This coating not only minimized dye leaching by establishing a robust shell but also improved dye distribution, thereby enhancing overall color intensity. The final HB-LFIA system, configured in a sandwich immunoassay format, demonstrated favorable sensitivity and linear detection range for Monkeypox antigen, indicating strong potential for clinical diagnostic use. Full article

Dinotefuran and clothianidin belong to the third generation of nicotinic insecticides and are widely used in crop pest control. It is necessary to detect their residues in food. The time-resolved fluorescent microspheres lateral flow immunoassay (TRFMs-LFIA) has the advantages of high sensitivity, short duration, and simple operation and is suitable for rapid field testing. In this study, two haptens (FCA-1, FCA-2) were synthesized in three steps and conjugated to the carrier proteins to obtain artificial antigens, which were subsequently used for monoclonal antibody preparation. A TRFMs-LFIA based on monoclonal antibodies was established to detect dinotefuran and clothianidin residues in food. The limit of detection (LOD) for dinotefuran was 0.045 ng/mL, with an IC₅₀ of 0.61 ng/mL and a linear range (IC₂₀~IC₈₀) of 0.12~3.11 ng/mL. The LOD for clothianidin was 0.11 ng/mL, with an IC₅₀ of 0.94 ng/mL and a linear range (IC₂₀~IC₈₀) of 0.24~3.65 ng/mL. Cross-reactivity rates with seven tested structural analogs were less than 1.5%. The pretreatment method was optimized for wheat, cucumber, and cabbage samples, which was time-saving (20 min) and easy to operate. The average recovery rates ranged from 88.0% to 114.8%, with the corresponding coefficients of variation appearing (CV) between 1.9% and 13.5%. The results of actual wheat, cucumber, and cabbage samples detected by the established TRFMs-LFIA were consistent with those of Ultra-Performance Liquid Chromatography coupled with Tandem Mass Spectrometry (UPLC-MS/MS). These results demonstrate that the established TRFMs-LFIA is sensitive, accurate, rapid, and suitable for real sample detection. Full article

Lateral flow immunoassays (LFIAs) were integrated into microfluidic chips and tested to enhance point-of-care testing (POCT), with the aim of improving sensitivity and expanding the range of CRP detection. The microfluidic approach improves upon traditional methods by precisely controlling fluid speed, thus enhancing sensitivity and accuracy in CRP measurements. The microfluidic approach also enables a one-step detection system, eliminating the need for buffer solution steps and reducing the nitrocellulose (NC) pad area to just the detection test line. This approach minimizes the non-specific binding of conjugated antibodies to unwanted areas of the NC pad, eliminating the need to block those areas, which enhances the sensitivity of detection. The gold nanoparticle method detects CRP in the high-sensitivity range of 1–10 $\mu$g/mL, which is suitable for chronic disease monitoring. To broaden the CRP detection range, including infection levels beyond 10 $\mu$g/mL, fluorescent labels were introduced, extending the measuring range from 1 to 70 $\mu$g/mL. Experimental results demonstrate that integrating microfluidic technology significantly enhances operational efficiency by precisely controlling the flow rate and optimizing the mixing efficiency while reducing fabrication resources by eliminating the need for separate pads, making these methods suitable for resource-limited settings. Microfluidics also provides greater control over fluid dynamics compared to traditional LFIA methods, which contributes to enhanced detection sensitivity even with lower sample volumes and no buffer solution, helping to enhance the usability of POCT. These findings highlight the potential to develop accessible, accurate, and cost-effective diagnostic tools essential for timely medical interventions at the POC. Full article

Point-of-care diagnostic tests, such as lateral-flow immunoassay (LFIA), have emerged as a fast diagnostic tool in both human and veterinary medicine. In this paper, a gold nanoparticle-based LFIA device was developed for the measurement of C-reactive protein (CRP) in porcine saliva, using a monoclonal anti-porcine CRP antibody. The dilution ratio for the saliva samples was optimized at 1:5 with an assay buffer. The reaction time was optimized to 20 min, since this provided a positive signal with high CRP concentration saliva samples, but a negative result with an assay buffer or samples with a low CRP concentration. Linear results were observed when two samples with a high CRP concentration were serially diluted. Also, a linear relationship was observed with a validated quantitative method. The assay was precise when samples with high CRP concentration were measured five times in a single assay run. No overlap was observed when samples from healthy and diseased animals were analyzed. The LFIA allowed the detection of high CRP concentrations in porcine saliva samples. The intensity of the result was proportional to the CRP concentration obtained with the quantitative method, allowing for the possible use of the test for semiquantitative purposes. Full article

Lateral flow immunoassays (LFIAs) are widely used for their low cost, simplicity, and rapid results; however, enhancing their reliability requires the meticulous selection of ligands and nanoparticles (NPs). SiO₂@QD@SiO₂ (QD²) nanoparticles, which consist of quantum dots (QDs) embedded in a silica (SiO₂) core and surrounded by an outer SiO₂ shell, exhibit significantly higher fluorescence intensity (FI) compared to single QDs. In this study, we prepared QD²@PEG@Aptamer, an aptamer conjugated with QD² using succinimidyl-[(N-maleimidopropionamido)-hexaethyleneglycol]ester, which is 130 times brighter than single QDs, for detecting carbohydrate antigen (CA) 19-9 through LFIA. For LFIA optimization, we determined the optimal conditions as a 1.0:2.0 × 10⁻² ratio of polyethylene glycol (PEG) to aptamer by adjusting the amounts of PEG and aptamer, phosphate-buffered saline containing 0.5% Tween^® 20 as a developing solution, and 0.15 μg NPs by setting the NP weight during development. Under these conditions, QD²@PEG@Aptamer selectively detected CA19-9, achieving a detection limit of 1.74 × 10⁻² mg·mL⁻¹. Moreover, FI remained stable for 10 days after detection. These results highlight the potential of QD² and aptamer conjugation technology as a reliable and versatile sensing platform for various diagnostic applications. Full article

A highly sensitive lateral flow immunoassay (LFIA) for imidacloprid, a widely used neonicotinoid insecticide, has been developed. The LFIA realizes the indirect coupling of anti-imidacloprid antibodies and gold nanoparticle (GNP) labels directly in the course of the assay. For this purpose, the common GNPs conjugate with anti-imidacloprid antibodies and are changed into a combination of non-modified, anti-imidacloprid antibodies, and the GNPs conjugate with anti-species antibodies. The given approach provides the possibility of selecting independent concentrations of GNPs and anti-imidacloprid antibodies to obtain the influence of minimal imidacloprid concentrations in the samples on the formation of detected, labeled immune complexes. A comparative study of imidacloprid LFIAs with common and indirect antibody–label coupling was implemented. The second variant reduced the limit of detection (LOD) of imidacloprid 20 times, reaching 0.2 ng/mL and 0.002 ng/mL for visual and instrumental detection, respectively, thus surpassing the existing LFIAs for imidacloprid. The developed highly sensitive LFIA was tested for imidacloprid detection in freshly squeezed fruits and berries without any additional sample preparation. The imidacloprids revealed were in the range of 75–97% for grape, 75–85% for orange, and 86–97% for apple samples. The time of the testing was 15 min. 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

In this study, two methods for assessing the purity of A2 fermented milk and β-casein genotypes in dairy cows were examined. The need for rapid and precise methods for herd screening and A2 milk quality control justified this study. Accordingly, an ELISA test was developed to identify β-casein A1 in fermented milk, and a commercial Lateral Flow Immunoassay (LFIA) was evaluated to determine A2A2 genotypes and the purity of A2 milk. The results demonstrated 100% sensitivity and specificity of the ELISA test in identifying β-casein A1. The LFIA test successfully identified A2A2 genotypes and confirmed the purity of A2 milk, with a minimum detectable contamination of 5% for raw milk and 10% for fermented milk. Both tests exhibited 100% sensitivity and specificity, resulting in positive and negative predictive values of 100%. The positive likelihood ratio was infinite, while the negative was zero, indicating a precise and reliable test with no false diagnoses. Compared to traditional genotyping, these methods proved to be more practical and showed potential for large-scale screening. It was concluded that ELISA and LFIA are valuable tools for ensuring the quality and authenticity of A2 milk, meeting the demands of producers and consumers for safe and healthy dairy products. 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