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Silanized quantum dots as labels in lateral flow test strips for C-reactive protein
摘要： The paper describes the first use of silanized semiconductor core-shell quantum dots as fluorescent labels for macromolecule, C-reactive protein determination in blood plasma. The controlled synthesis of CdSe cores, with successive shells of CdS, CdZnS, ZnS and coating with transparent, stable, and inert silica shell, provides quantum dots with a narrow emission band, high quantum yield, and prolonged signal stability. Finally, the quantum dots were conjugated with specific antibodies via carboxylic groups on the silica surface. The method was further used for the immunochromatographic assay of C-reactive protein, a diagnostically important inflammatory biomarker. Assays with both the fluorescent QDs and a widely used colloidal gold label were developed in parallel and compared. The silanized quantum dots provide a more sensitive assay with a detection limit of 1 ng/mL for C-reactive protein in standard solutions, whereas the common assay has a detection limit of 10 ng/mL. The possibility of quantitative evaluation of analyte content by a portable device was demonstrated; the accuracy of the measurements was in the range of 5%–10%. The tests were used to determine C-reactive proteins in human plasma samples. The selected optimized protocol for these samples is based on a 4-fold dilution. The final working range of the assay, 4–1,200 ng/mL, covers practically all important interval of C-reactive protein values for the characterization of acute, chronic, and local inflammatory processes. Due to their high physical stability and inertness as well as intense, stable, and reproducible fluorescence, silanized quantum dots may be applied for high-sensitive assays for different analytes.
关键词： C-reactive protein,Quantum dots,silanization,lateral flow immunoassay
更新于2025-11-19 16:46:39
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Smartphone-Based Fluorescent Lateral Flow Immunoassay Platform for Highly Sensitive Point-of-Care Detection of Zika Virus Nonstructural Protein 1
摘要： Simple, inexpensive, and rapid diagnostic tests in low-resource settings with limited laboratory equipment and technical expertise are instrumental in reducing morbidity and mortality from epidemic infectious diseases. We developed a smartphone-based fluorescent lateral flow immunoassay (LFIA) platform for the highly sensitive point-of-care detection of Zika virus nonstructural protein 1 (ZIKV NS1). An attachment was designed and 3D-printed to integrate the smartphone with external optical and electrical components, enabling the miniaturization of the instrument and reduction in cost and complexity. Quantum dot microspheres were utilized as probes in fluorescent LFIA because of their extremely bright fluorescence signal. This approach can achieve quantitative point-of-care detection of ZIKV NS1 within 20 min. Limits of detection (LODs) in buffer and serum were 0.045 and 0.15 ng mL-1, respectively. Despite the high structural similarity, a high-level Dengue virus NS1 as interferent showed limited cross-reactivity. Furthermore, this assay was successfully applied to detecte ZIKV NS1 and virions spiked in complex biological samples, indicating its practical application capability. Given its low cost, compact size, and excellent analytical performance, the proposed smartphone-based fluorescent LFIA platform holds considerable potential in rapid and accurate point-of-care detection of ZIKV NS1 and provides new insight into the design and application of molecular diagnostic methods in low-resource settings.
关键词： Quantum dot microsphere,Smartphone,Lateral flow immunoassay,Zika virus nonstructural protein 1,Point-of-care
更新于2025-09-23 15:23:52
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Ultrasensitive detection of avian influenza A (H7N9) virus using surface-enhanced Raman scattering-based lateral flow immunoassay strips
摘要： The development of biosensors that are portable, low-cost, and quantitative has long been sought for rapid, on-site, and timely detection of avian influenza virus (AIV). In this study, an antibody-based Raman lateral flow immunoassay strip was developed to detect AIV H7N9. This LFIA strip used a novel core-shell structure material, AuAg4(cid:3)ATP@AgNPs, as a Raman probe. An antibody specific for AIV and goat anti-mouse IgG antibody were immobilized on a nitrocellulose membrane as the test and control lines, respectively. Accumulation of antibody-virus-antibody-Raman probe complex at the test line could be visualized by the naked eye, and the Raman signal could be quantified using a portable Raman instrument. The testing process for the SERS-based LFIA strips could be completed in 20 min, which avoided the time-cost of current methods for AIV analysis. In our SERS-based biosensor, we estimated the limit of detection (LOD) for H7N9 to be 0.0018 HAU. This value is approximately three orders of magnitude more sensitive than the corresponding HA assays. When testing real sample, the results of the strip test were in accordance with those from real-time PCR testing. In conclusion, the SERS-based LFIA strip proposed in this study shows tremendous potential to detect targets quickly and sensitively using an elegantly simple method.
关键词： AuAg4(cid:3)ATP@AgNPs,Surface-enhanced Raman scattering,Avian influenza virus,Lateral flow immunoassay strips
更新于2025-09-23 15:23:52
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A quantum dot-based lateral flow immunoassay for the rapid, quantitative, and sensitive detection of specific IgE for mite allergens in sera from patients with allergic rhinitis
摘要： The prevalence of allergic rhinitis (AR) is increasing worldwide. However, the current systems used to measure levels of immunoglobulin E (IgE) in sera are associated with several disadvantages that limit their further application. Consequently, there is a need to develop novel highly sensitive strategies that can rapidly detect IgE in a quantitative manner. The development of such systems will significantly enhance our ability to diagnose, treat, and even prevent AR. Herein, we describe our experience of using quantum dot-based lateral flow immunoassay (QD-LFIA), combined with a portable fluorescence immunoassay chip detector (PFICD), to detect serum-specific IgE against Dermatophagoides pteronyssinus (Der-p) and Dermatophagoides farinae (Der-f), two common mite allergens in China. Our data showed that our system could detect serum-specific levels of IgE against Der-p and Der-f as low as 0.093 IU/mL and 0.087 IU/mL, respectively. We also established a standard curve to determine serum-specific IgE concentrations that correlated well with the clinical BioIC microfluidics system. The sensitivity of our assay was 96.7% for Der-p and 95.5% for Der-f, while the specificity was 87.2% for Der-p and 85.3% for Der-f. Collectively, our results demonstrate that QD-LFIA is a reliable system that could be applied to detect serum-specific IgE in accordance with clinical demands. This QD-LFIA strategy can be applied at home, in hospitals, and in pharmacies, with reduced costs and time requirements when compared with existing techniques. In the future, this system could be developed to detect other types of allergens and in different types of samples (for example, whole blood).
关键词： Quantum dots,Lateral flow immunoassay,Immunoglobulin E,Allergic rhinitis
更新于2025-09-19 17:13:59
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Dual-color magnetic-quantum dot nanobeads as versatile fluorescent probes in test strip for simultaneous point-of-care detection of free and complexed prostate-specific antigen
摘要： Simultaneous detection of free and complexed prostate-specific antigen (f-PSA and c-PSA) is critical to the prostate cancer (PCa) diagnostic accuracy for clinical samples with PSA values in the diagnostic gray zone between 4 and 10 ng mL?1. Herein, red and green magnetic-quantum dot nanobeads (MQBs) with superior magnetic property and high luminescence were fabricated via polyethyleneimine-mediated electrostatic adsorption of numerous quantum dots onto superparamagnetic Fe3O4 magnetic cores, and were conjugated with f-PSA antibody and c-PSA antibody, respectively, as versatile fluorescent probes in test strip for immune recognition, magnetic enrichment, and simultaneous detection of f-PSA and c-PSA analytes in complex biological matrix with t-PSA antibody on the test line. A low-cost and portable smartphone readout device with an application was also developed for the imaging of dual-color test strips and data processing. This assay can simultaneously detect f-PSA and c-PSA with the limits of detection of 0.009 ng mL?1 and 0.087 ng mL?1, respectively. Clinical serum samples of PCa and benign prostatic hyperplasia patients were evaluated to confirm the clinical feasibility. The results suggest that the proposed dual-color MQBs-based fluorescent lateral flow immunoassay is a promising point-of-care diagnostics technique for the accurate diagnosis of PCa even in resource-limited settings.
关键词： Free and complexed prostate-specific antigen,Fluorescent lateral flow immunoassay,Simultaneous detection,Prostate cancer,Magnetic-quantum dot nanobead,Point-of-care
更新于2025-09-16 10:30:52
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Detection of E. coli labeled with metal-conjugated antibodies using lateral-flow assay and laser-induced breakdown spectroscopy
摘要： This study explores the adoption of laser-induced breakdown spectroscopy (LIBS) for the analysis of lateral-flow immunoassays (LFIAs). Gold (Au) nanoparticles are standard biomolecular labels among LFIAs, typically detected via colorimetric means. A wide diversity of lanthanide-complexed polymers (LCPs) are also used as immunoassay labels but are inapt for LFIAs due to lab-bound detection instrumentation. This is the first study to show the capability of LIBS to transition LCPs into the realm of LFIAs, and one of the few to apply LIBS to biomolecular label detection in complete immunoassays. Initially, an in-house LIBS system was optimized to detect an Au standard through a process of line selection across acquisition delay times, followed by determining limit of detection (LOD). The optimized LIBS system was applied to Au-labeled Escherichia coli detection on a commercial LFIA; comparison with colorimetric detection yielded similar LODs (1.03E4 and 8.890E3 CFU/mL respectively). Optimization was repeated with lanthanide standards to determine if they were viable alternatives to Au labels. It was found that europium (Eu) and ytterbium (Yb) may be more favorable biomolecular labels than Au. To test whether Eu-complexed polymers conjugated to antibodies could be used as labels in LFIAs, the conjugates were successfully applied to E. coli detection in a modified commercial LFIA. The results suggest interesting opportunities for creating highly multiplexed LFIAs. Multiplexed, sensitive, portable, and rapid LIBS detection of biomolecules concentrated and labeled on LFIAs is highly relevant for applications like food safety, where in-field food contaminant detection is critical.
关键词： Lateral-flow immunoassay,E. coli,Laser-induced breakdown spectroscopy,Lanthanides,Metal-conjugated antibodies
更新于2025-09-16 10:30:52
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Magnetic quantum dot based lateral flow assay biosensor for multiplex and sensitive detection of protein toxins in food samples
摘要： Protein toxins, such as botulinum neurotoxin type A (BoNT/A) and staphylococcal enterotoxin B (SEB), easily pollute food and water and are ultra-toxic to humans and animals, thus requiring a sensitive on-site detection method. In this study, we reported a novel lateral flow assay (LFA) strip on the basis of magnetic quantum dot nanoparticles (MagQD NPs) for sensitive and multiplex protein toxin detection in food samples. A new type of MagQD NP was prepared by fixing the dense carboxylated QDs on the surface of polyethyleneimine-modified Fe3O4 magnetic NPs (MNPs) and applied in LFA with the following functions: capture and enrich target toxins from sample solutions and serve as advanced fluorescent labels for the quantitative determination of targets on the strip. Through this strategy, the assay realized quantified BoNT/A and SEB detection in 30 min with the limits of detection of 2.52 and 2.86 pg/mL, respectively. The selectivity and the ability of quantitative analysis of the method were validated in real food samples, including milk and juice. This MagQD-LFA biosensor showed considerable potential as a point-of-care testing tool for the sensitive detection of trace toxins.
关键词： Magnetic-quantum dot nanoparticles,Fluorescent lateral flow immunoassay,Simultaneous detection,Botulinum neurotoxin type A,Staphylococcal enterotoxin
更新于2025-09-16 10:30:52
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SERS-based lateral flow immunoassay of troponin I by using gap-enhanced Raman tags
摘要： The lateral flow immunoassay (LFIA) has emerged as a powerful tool for rapid screening owing to its simplicity and flexibility for detection of various biomarkers. However, conventional LFIA strips have several disadvantages, including limits in quantitative analysis and low sensitivity. Here we developed a novel surface-enhanced Raman scattering LFIA based on nonspherical gap-enhanced Raman tags (GERTs), with Raman molecules (RMs) embedded in a 1-nm gap between Au nanorod core and Au shell. Such tags have a strong and uniform SERS response, an order of magnitude higher than that of other common SERS tags such as Au nanorods, nanostars, Au nanoshells with surface-adsorbed RMs, or spherical GERTs with embedded RMs. The feasibility of the tags was demonstrated by the semiquantitative and sensitive detection of the heart disease biomarker cardiac troponin I (cTnI). GERTs were conjugated with monoclonal antibodies and used for LFIA in the same way as ordinary functionalized colloidal gold. The presence of the target antigen, cTnI, was identified by Raman microscopy mapping of the test zone. With the SERS-based LFIA, the limit of cTnI detection was about 0.1 ng/mL. This value is within the diagnostic range of cTnI in the blood serum of patients with heart infarction and is 30 times lower than that of the colorimetric LFIA test using the same antibodies and either GERTs or colloidal gold as labels.
关键词： gap-enhanced Raman tags,lateral flow immunoassay,SERS,cardiac Troponin I,Au core/shell nanorods
更新于2025-09-10 09:29:36
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Lateral flow immunoassays combining enrichment and colorimetry-fluorescence quantitative detection of sulfamethazine in milk based on trifunctional magnetic nanobeads
摘要： In this study, magnetic nanobeads (MNBs) were used as a trifunctional material in lateral flow immunoassay for quantitative detection of sulfamethazine (SM2) in milk. Magnetic enrichment aimed to reduce matrix effects. Naked-eye screening of SM2 was based on colorimetry of colored MNBs. The cut-off value of the naked-eye screening was 25 ng mL-1. When the concentration of SM2 in the samples is equal to the cut-off value or higher, the lateral flow strips can be quantitatively detected via grayscale intensity based on colored MNBs. When the concentration of SM2 in the samples is less than the cut-off value, the lateral flow strips can be quantitatively detected by means of fluorescence intensity based on the fluorescence quenching effect of MNBs. Under optimal conditions, the linear range and limit of detection (LOD) of fluorescence lateral flow immunoassay were 0.033-33 ng mL-1 and 0.026 ng mL-1 respectively, while the linear range and LOD of colorimetric lateral flow immunoassay was 1-100 ng mL-1 and 0.71 ng mL-1, respectively. This novel method can be used for rapid and quantitative detection of SM2 in milk.
关键词： lateral flow immunoassay,matrix effects,magnetic nanobeads,colorimetry,fluorescence,sulfamethazine
更新于2025-09-10 09:29:36
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Colorimetric-Fluorescent-Magnetic Nanosphere-Based Multimodal Assay Platform for Salmonella Detection
摘要： Rapid and sensitive foodborne pathogen detection assay, which can be applied in multiple fields, is essential to timely diagnosis. Herein, we proposed a multi-signal readout lateral flow immunoassay for Salmonella typhimurium (S. typhi) detection. The assay employs colorimetric-fluorescent-magnetic nanospheres (CFMNs) as labels, which possess multi-functional: target separation and enrichment, multi-signal readout and two formats of quantitation. The assay for S. typhi detection involves magnetic separation and chromatography. First, the S. typhi were separated and enriched from matrix by antibody labelled CFMNs, and then the S. typhi-containing suspension is added onto the sample pad to flow up the test strip. The introduction of magnetic separation enhances anti-interference ability and 10-fold sensitivity, making the assay possible for practical application. The assay has realized naked eye detection of 1.88×104 CFU/mL S. typhi, and 3.75×103 CFU/mL S. typhi can be detected with a magnetic assay reader, which is 2–4 orders of magnitude lower than other label-based LFIAs, with a quantitation range of 1.88×104 to 1.88×107 CFU/mL by measuring the fluorescence intensity and magnetic signal. Moreover, the successful detection of S. typhi in complex matrix (tap water, milk, fetal bovine serum and whole blood) indicated its potential application in real samples.
关键词： colorimetric-fluorescent-magnetic nanospheres,lateral flow immunoassay,Salmonella typhimurium,multimodal assay,pathogen detection
更新于2025-09-09 09:28:46