Fluorescent Lateral Flow Immunoassay Research Articles

Enhanced NIR-II Fluorescent Lateral Flow Biosensing Platform Based on Supramolecular Host-Guest Self-Assembly for Point-of-Care Testing of Tumor Biomarkers.

Point-of-care detection of tumor biomarkers with high sensitivity remains an enormous challenge in the early diagnosis and mass screening of cancer. Fluorescent lateral flow immunoassay (LFA) is an attractive platform for point-of-care testing due to its inherent advantages. Particularly, a fluorescent probe is crucial to improving the analytical performance of the LFA platform. Herein, we developed an enhanced second near-infrared (NIR-II) LFA (ENIR-II LFA) platform based on supramolecular host-guest self-assembly for detection of the prostate-specific antigen (PSA) as a model analyte. In this platform, depending on the effective supramolecular surface modification strategy, cucurbit[7]uril (CB[7])-covered rare-earth nanoparticles (RENPs) emitting in the NIR-II (1000-1700 nm) window were prepared and employed as an efficient fluorescent probe (RENPs-CB[7]). Benefiting from its superior optical properties, such as low autofluorescence, excellent photostability, enhanced fluorescence intensity, and increased antibody-conjugation efficiency, the ENIR-II LFA platform displayed a wide linear detection range from 0.65 to 120 ng mL-1, and the limit of detection was down to 0.22 ng mL-1 for PSA, which was 18.2 times lower than the clinical cutoff value. Moreover, the testing time was also shortened to 6 min. Compared with the commercial visible fluorescence LFA kit (VIS LFA) and the previously reported NIR-II LFA based on a RENPs-PAA probe, this ENIR-II LFA demonstrated more competitive advantages in analytical sensitivity, detection range, testing time, and production cost. Overall, the ENIR-II LFA platform offers great potential for the highly sensitive, rapid, and convenient detection of tumor biomarkers and is expected to serve as a useful technique in the general population screening of the high-incidence cancer region.

A fluorescent lateral flow immunoassay based on CdSe/CdS/ZnS quantum dots for sensitive detection of olaquindox in feedstuff.

A portable fluorescence immunosensor based on the CdSe/CdS/ZnS quantum dots (QDs) with multiple-shell structure was fabricated for the precise quantification of olaquindox (OLA). The QDs labeled anti-OLA antibody used as bioprobe played an important role in the design and preparation of a lateral flow test strip. Due to the strong fluorescent intensity of QDs, the sensitivity is greatly improved. The quantitative results were obtained using a fluorescent strip scan reader within 8min, and the calculated limit of detection for OLA at 0.12µg/kg, which was 2.7 times more sensitive than that of the conventional colloidal gold-based strips method. Acceptable recovery of 85.0%-95.5% was obtained by the spiked samples. This newly established QDs-based strip immunoassay method is suitable for the on-site detection and rapid initial screening of OLA in swine feedstuff, and is potentially applied for the detection of other veterinary drugs to ensure food safety.

Development and clinical evaluation of a quantitative fluorescent immunoassay for detecting canine CRP

ABSTRACT Canine C-reactive protein (cCRP) is one of the major positive acute phase proteins in dogs and is commonly measured to detect and monitor systemic inflammation as well as the efficacy of treatment. Traditional methods for testing cCPR, including enzyme-linked immunosorbent assay (ELISA), have some drawbacks, such as a long time for diagnosis and the requirement of well-equipped laboratories. Therefore, there is a need for a rapid and precise diagnostic test for cCRP at point-of-care. This study assessed the accuracy, precision, and validated clinical effectiveness of a diagnostic test based on fluorescent lateral flow immunoassay to detect cCRP. For the standard cCRP concentration ranging from 0 to 200 μg/mL, the cCRP diagnostic test showed strong linearity with R2 of 0.9977 (p < 0.001), and both inter- and intra-assay CVs were <14%. The limit of detection and limit of quantitation were found to be 4.0 μg/mL and 5.0 μg/mL, respectively. The cCRP serum concentration was evaluated in 21 client-owned dogs and the results were compared to a previously validated ELISA. The Pearson Correlation Coefficient between the diagnostic test kit and ELISA was 0.942 [95% confidence interval: 0.859 to 0.976, p < 0.001], and the Bland–Altman plot indicated a bias of 26.82% [95% limits of agreement: −56.03 to 109.67], indicating a significant correlation and the agreement between the data from the cCRP diagnostic test and ELISA. In conclusion, the fluorescent immunoassay based diagnostic test is a suitable option for rapidly and precisely detecting cCRP in dogs, providing a convenient alternative to traditional methods for diagnosing acute inflammation.

Competitive ratiometric fluorescent lateral flow immunoassay based on dual emission signal for sensitive detection of chlorothalonil

In this study, we develop a competitive ratiometric fluorescent lateral flow immunoassay (CRF-LFIA) based on dual emission fluorescence signal, which has great advantage in visual and quantitative detection of Chlorothalonil (CTN). Red-emitted fluorescent magnetic nanobeads (FMNBs) and green-emitted aggregation-induced emission fluorescent microsphere (AIEFM) are synthesized and conjugated to antibodies and antigens respectively, resulting in competitive binding with the analyte. The ratiometric fluorescence signal which comes from the overlap of these two fluorescence emissions. FMNBs probes also provide immunomagnetic separation (IMS) to enrich the analysts and resist complex matrix effects. This strip generates a visually discernible yellow-to-green fluorescence color change in the presence of CTN (2 ng/mL), which could be incisively observed by naked eye. Moreover, the limit of detection (LOD) reached 0.152 ng/mL by measurement of color (Red-Green-Blue, RGB) signals. Method validation shows a good correlation between CRF-LFIA and LC-MS/MS.

Development of a quantitative fluorescence lateral flow immunoassay (LFIA) prototype for point-of-need detection of anti-Müllerian hormone

ObjectiveAnti-Müllerian Hormone (AMH) is a quantitative marker for ovarian reserve and is used to predict response during ovarian stimulation. Streamlining testing to the clinic or even to the physician's office would reduce inconvenience, turnaround time, patient stress and potentially also the total cost of testing, allowing for more frequent monitoring. In this paper, AMH is used as a model biomarker to describe the rational development and optimization of sensitive, quantitative, clinic-based rapid diagnostic tests. Design and MethodsWe developed a one-step lateral-flow europium (III) chelate-based fluorescent immunoassay (LFIA) for the detection of AMH on a portable fluorescent reader, optimizing the capture/detection antibodies, running buffer, and reporter conjugates. ResultsA panel of commercial calibrators was used to develop a standard curve to determine the analytical sensitivity (LOD = 0.41 ng/ml) and the analytical range (0.41–15.6 ng/ml) of the LFIA. Commercial controls were then tested to perform an initial evaluation of the prototype performance and showed a high degree of precision (Control I CV 2.18%; Control II CV 3.61%) and accuracy (Control I recovery 126%; Control II recovery 103%). Conclusions: This initial evaluation suggests that, in future clinical testing, the AMH LFIA will likely have the capability of distinguishing women with low ovarian reserve (<1 ng/ml AMH) from women with normal (1–4 ng/ml AMH) ovarian reserve. Furthermore, the LFIA demonstrated a wide linear range, indicating the assay's applicability to the detection of other health conditions such as PCOS, which requires AMH measurement at higher concentrations (>6 ng/ml).

Ultrabright red-emitted aggregation-induced luminescence microspheres-based lateral flow immunoassay for furosemide detection in slimming products

Furosemide (Furo) is an effective diuretic drug, and it has been illegally used in slimming dietary supplements. Herein, an anti-Furo monoclonal antibody (anti-Furo mAb) was prepared, and the obtained anti-Furo mAb showed a high binding affinity of 3.48 × 109 L/mol to Furo molecules. Using an ultrabright red-emitted aggregation-induced luminescence microspheres (AIEFMs) as a signal amplification probe, a novel fluorescent lateral flow immunoassay (LFIA) was developed for the rapid and sensitive determination of Furo in slimming products. Under optimal conditions, the proposed AIEFM-LFIA exhibited a high sensitivity to Furo quantitative determination with half-maximal inhibitory concentration and limit of detection at 0.31 and 0.049 ng/mL, respectively. These values were 8.8- and 4.2-fold lower than those of enzyme-linked immunosorbent assay (ELISA). The intra- and inter-assays showed the average recovery of AIEFM-LFIA ranging from 88.71% to 111.78% with coefficient of variation ranging from 2.58% to 13.23%, indicating that the proposed method has an accepted accuracy and precision for furosemide quantitative determination. In addition, the proposed AIEFM-LFIA also showed a good consistency with the ELISA method. Given the signal amplification of AIEFMs and high affinity of the as-prepared mAb, the developed AIEFM-LFIA provides great potential for the sensitive and rapid detection of Furo in slimming products.

NIR-II fluorescent nanoprobe-labeled lateral flow biosensing platform: A high-performance point-of-care testing for carcinoembryonic antigen

Fluorescent lateral flow immunoassay (LFA) is one of the most common analytical platforms for point-of-care testing (POCT), which is capable of facile and early screening of biomarkers. Notably, fluorescent probes play a decisive role in analytical performances of LFA. Herein, we report a novel LFA based on the rare earth doped nanoparticles (RENPs) emitting in the second near-infrared (NIR-II) window for the detection of biomarkers, such as carcinoembryonic antigen (CEA). Benefiting from the dual fluorescent emission at NIR-II window, strong fluorescent penetration, low autofluorescence and excellent photostability of RENPs, this proposed NIR-II LFA displays a good linear relationship ranging from 1 to 320 ng mL−1. The detection limit is as low as 0.37 ng mL−1, which is of 13.5 times lower than the clinical cutoff value. Overall, NIR-II LFA biosensing platform based RENPs not only exhibits high sensitivity, accuracy and specificity, but also have characteristics of rapidity, simplicity and low cost. It holds high potential for early diagnosis of tumor biomarkers in POCT.

Bio-conjugated nanoarchitectonics with dual-labeled nanoparticles for a colorimetric and fluorescent dual-mode serological lateral flow immunoassay sensor in detection of SARS-CoV-2 in clinical samples.

Serological detection of antibodies for diagnosing infectious diseases has advantages in facile diagnostic procedures, thereby contributing to controlling the spread of the pathogen, such as in the recent SARS-CoV-2 pandemic. Lateral flow immunoassay (LFIA) is a representative serological antibody detection method suitable for on-site applications but suffers from low clinical accuracy. To achieve a simple and rapid serological screening as well as the sensitive quantification of antibodies against SARS-CoV-2, a colorimetric and fluorescent dual-mode serological LFIA sensor incorporating metal-enhanced fluorescence (MEF) was developed. For the strong fluorescence signal amplification, fluorophore Cy3 was immobilized onto gold nanoparticles (AuNPs) with size-controllable spacer polyethyleneglycol (PEG) to maintain an optimal distance to induce MEF. The sensor detects the target IgG with a concentration as low as 1 ng mL-1 within 8 minutes. The employment of the MEF into the dual-mode serological LFIA sensor shows a 1000-fold sensitivity improvement compared with that of colorimetric LFIAs. The proposed serological LFIA sensor was tested with 73 clinical samples, showing sensitivity, specificity, and accuracy of 95%, 100%, and 97%, respectively. In conclusion, the dual-mode serological LFIA has great potential for application in diagnosis and an epidemiological survey of vaccine efficacy and immunity status of individuals.

A lateral flow immunoassay method for the rapid detection of acetochlor and alachlor in vegetable oil by sensitivity enhancement by using dimethyl-β-cyclodextrin.

Acetochlor is an endocrine disruptor. The acetochlor residue is strongly lipophilic and can be enriched into products during the manufacturing process. In this study, we found that dimethyl-β-cyclodextrin (DM-β-CD) solution could decrease the apparent oil/water partition coefficient (Koil-w) of acetochlor and increase the sensitivity of fluorescence lateral flow immunoassay (LFIA) for acetochlor simultaneously. Based on this, a simple LFIA method for the determination of acetochlor and alachlor residues in vegetable oil was established. The detection process only involves vortex mixing of an oil sample and dimethyl-β-cyclodextrin solution in a 1 : 3 (V/V) ratio, loading the water phase onto the immunoassay strips and reading the results. Under optimized conditions, the LOD for acetochlor in oil was 3.53 ng g-1, and the working range was 12.03-2000.00 ng g-1. The recoveries of spiked samples ranged from 91.69% ± 1.12% to 112.23% ± 2.20%. Meanwhile, the cross reactivity for alachlor was 108.22%, while for other investigated acetochlor analogues it was less than 1%, and the recoveries of alachlor were from 92.90% ± 8.03% to 113.53% ± 3.40%, which indicate that this method can detect acetochlor and alachlor simultaneously. Compared with the traditional detection method, the pre-treatment process of the proposed method is "green" and simple, and can be applied to the on-site rapid detection of acetochlor and alachlor in vegetable oil and can provide inspiration for the detection of other lipophilic pollutants.

Development of receptor binding domain-based double-antigen sandwich lateral flow immunoassay for the detection and evaluation of SARS-CoV-2 neutralizing antibody in clinical sera samples compared with the conventional virus neutralization test

Vaccination is an effective strategy to fight COVID-19. However, the effectiveness of the vaccine varies among different populations in varying immune effects. Neutralizing antibody (NAb) level is an important indicator to evaluate the protective effect of immune response after vaccination. Lateral flow immunoassay (LFIA) is a rapid, safe and sensitivity detection method, which has great potential in the detection of SARS-CoV-2 NAb. In this study, a fluorescent beads-based lateral flow immunoassay (FBs-LFIA) and a latex beads-based LFIA (LBs-LFIA) using double antigen sandwich (DAS) strategy were established to detect NAbs in the serum of vaccinated people. The limit of detection (LoD) of the FBs-LFIA was 1.13 ng mL− 1 and the LBs-LFIA was 7.11 ng mL− 1. The two LFIAs were no cross-reactive with sera infected by other pathogenic bacteria. Furthermore, the two LFIAs showed a good performance in testing clinical samples. The sensitivity of FBs-LFIA and LBs-LFIA were 97.44% (95%CI: 93.15%–99.18%) and 98.29% (95%CI: 95.84%–99.37%), and the specificity were 98.28% (95%CI: 95.37%–99.45%) and 97.70% (95%CI: 94.82%–99.06%) compared with the conventional virus neutralization test (cVNT), respectively. Notably, the LBs-LFIA was also suitable for whole blood sample, requiring only 3 μL of whole blood, which provided the possibility to detect NAbs at home. To sum up, the two LFIAs based on double antigen sandwich established by us can rapidly, safely, sensitively and accurately detect SARS-CoV-2 NAb in human serum.

Development of fluorescent lateral flow immunoassay for SARS-CoV-2-specific IgM and IgG based on aggregation-induced emission carbon dots.

Understanding the dynamic changes in antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential for evaluating the effectiveness of the vaccine and the stage for the recovery of the COVID-19 disease. A rapid and accurate method for the detection of SARS-CoV-2-specific antibodies is still urgently needed. Here, we developed a novel fluorescent lateral flow immunoassay (LFA) platform for the detection of SARS-CoV-2-specific IgM and IgG by the aggregation-induced emission carbon dots conjugated with the SARS-CoV-2 spike protein (SSP). The aggregation-induced emission carbon dots (AIE-CDs) are one of the best prospect fluorescent probe materials for exhibiting high emission efficiency in both aggregate and solid states. The AIE-CDs were synthesized and displayed dual fluorescence emission, which provides a new perspective for the design of a high sensitivity testing system. In this work, the novel LFA platform adopted the AIE carbon dots, which are used to detect SARS-CoV-2-specific IgM and IgG conveniently. Furthermore, this sensor had a low LOD of 100 pg/ml. Therefore, this newly developed strategy has potential applications in the areas of public health for the advancement of clinical research.

Fluorescent nanodiamond-based spin-enhanced lateral flow immunoassay for detection of SARS-CoV-2 nucleocapsid protein and spike protein from different variants

SARS-CoV-2 viruses, responsible for the COVID-19 pandemic, continues to evolve into new mutations, which poses a significant threat to public health. Current testing methods have some limitations, such as long turnaround times, high costs, and professional laboratory requirements. In this report, the novel Spin-Enhanced Lateral Flow Immunoassay (SELFIA) platform and fluorescent nanodiamond (FND) reporter were utilized for the rapid detection of SARS-CoV-2 nucleocapsid and spike antigens from different variants, including wild-type (Wuhan-1), Alpha (B.1.1.7), Delta (B.1.617.2), and Omicron (B.1.1.529). The SARS-CoV-2 antibodies were conjugated with FND via nonspecific binding, enabling the detection of SARS-CoV-2 antigens via both direct and competitive SELFIA format. Direct SELFIA was performed by directly adding the SARS-CoV-2 antibodies-conjugated FND on the antigens-immobilized nitrocellulose (NC) membrane. Conversely, the SARS-CoV-2 antigen-containing sample was first incubated with the antibodies-conjugated FND, and then dropped on the antigen-immobilized NC membrane to carry out the competitive SELFIA. The results suggested that S44F anti-S IgG antibody can be efficiently used for the detection of wild-type, Alpha, Delta, and Omicron variants spike antigens. Findings were comparable in direct SELFIA, competitive SELFIA, and ELISA. A detection limit of 1.94, 0.77, 1.14, 1.91, and 1.68 ng/mL can be achieved for SARS-CoV-2 N protein, wild-type, Alpha, Delta, and Omicron S proteins, respectively, via competitive SELFIA assay. These results suggest that a direct SELFIA assay can be used for antibody/antigen pair screening in diagnosis development, while the competitive SELFIA assay can serve as an accurate quantitative diagnostic tool. The simplicity and rapidity of the SELFIA platform were demonstrated, which can be leveraged in the detection of other infectious diseases in the near future.

Quantum-dot-based sandwich lateral flow immunoassay for the rapid detection of shrimp major allergen tropomyosin

Tropomyosin (TM) has long been reckoned as the major allergen in shrimp is known to cause both food safety and public health concern all over the globe. In the present study, a simple, rapid, specific and accurate quantum-dot-based sandwich fluorescent lateral flow Immunoassay (LFIA) was developed for the detection of TM in processed foods. Fluorescent probes were prepared by EDC/NHS reaction of rabbit anti-TM polyclonal IgG with carboxylated quantum dots. Obtained results indicated that the visual detection limit (VDL) and the instrumental detection limit (IDL) of were 0.05 μg mL-1 and 0.01 μg mL-1, respectively. In addition, the detection time could be controlled within ten min. Furthermore, the established method showed no cross-reactivity with other species except shrimp. Moreover, the intra- and inter-assay coefficients of variation of the spiked samples were 8.87 %− 11.9 % and 7.75 %− 21.12 %. Besides, LFIA could detect 8 of 9 real food samples which were identified as TM-positive by the validated ELISA method. Additionally, 0.045 μg g-1 of incurred TM in model processed foods (roast fish fillet, boiled meatball and steamed meatball) also could be detected by the developed assay. These findings indicated that the LFIA developed in this research possess a great significance on the rapid and accurate detection of allergens in shrimp foodstuffs, related products and their production lines.

Hue Recognition Competitive Fluorescent Lateral Flow Immunoassay for Aflatoxin M1 Detection with Improved Visual and Quantitative Performance.

Immunological detection of small molecules in a point-of-care (POC) format is of great significance yet remains challenging for accurate visual discrimination and quantitative analysis. Here, we report a novel hue recognition competitive fluorescent lateral flow immunoassay (HCLFIA) strip that allows both visual and quantitative detection of aflatoxin M1 (AFM1). The HCLFIA strip works on the basis of the ratiometric change of emission, arising from the overlap of fluorescence signals of two nanocomposites tagged with probe antibodies and coated antigens. A visually discernible orange-red-to-green fluorescence color change allows the naked eye semiquantitative readout of AFM1 around the threshold concentration (0.05 ng mL-1), yielding a visible detection limit of 0.02 ng mL-1. Moreover, using a custom smartphone-based device and color chart analysis, ultrasensitive quantitative detection of AFM1 can be achieved with a low limit of detection at 0.0012 ng mL-1, which is considerably better than those of the previously reported colorimetric and fluorescent strips. The accuracy performed in spiked milk samples ranged from 97.91 to 113.12% with a coefficient of variation below 7.8%, showing good consistency with the results from isotope dilution liquid chromatography-tandem mass spectrometry. Thanks to the unique hue recognition scheme, the HCLFIA strip holds great potential for POC detection of small molecules.

Sensitive and simultaneous detection of ractopamine and salbutamol using multiplex lateral flow immunoassay based on polyethyleneimine-mediated SiO2@QDs nanocomposites: Comparison and application

The abuse of illegal additives poses a severe threat to human health. As such, it is of great significance to develop a simple, rapid and high-throughput analysis method for ensuring food safety from source to terminal. Herein, we proposed a multiplex fluorescent lateral flow immunoassay (LFIA) using the nanoassembly of silicon dioxide (SiO2) and quantum dots (QDs) as the advanced signal probe that can simultaneously detect ractopamine (RAC) and salbutamol (SAL) in swine urine and pork samples, and compared with other four conventional labels. The core–shell SiO2@QDs nanocomposites with strong luminescence, high stability, and abundant surface carboxyl groups were conjugated with antibodies to form high-performance SiO2@QDs immunoprobes, which improve the sensitivity and reliability of the LFIA. The developed SiO2@QDs-based LFIA achieved simultaneous detection of RAC and SAL in one strip within 13 min, with the limit of detection at 0.007 ng/mL and 0.032 ng/mL, respectively. The sensitivity of SiO2@QDs was superior to gold nanoparticles (AuNPs) and fluorescent microspheres (FMs), and exhibited comparative sensitivity with time-resolved microspheres (TRFMs), while overcoming the shortcomings of QDs that tend to aggregate. The recoveries in spiked swine urine and pork samples ranged from 73.7 to 111.0% with relative standard deviations between 4.7% and 15.5%. Good correlations were observed between the SiO2@QDs-based LFIA and commercial enzyme-linked immunosorbent assay for RAC (R2 = 0.936) and SAL (R2 = 0.979) detection. Briefly, the proposed method could be a promising screening on-site tool for convenient, rapid and sensitive detection of multiple illegal additives residues from the source to the terminal in food safety.

Development of a lateral flow immunoassay for rapid quantitation of carbendazim in agricultural products

Carbendazim (CBZ) is a systematic fungicide widely used in agriculture, and its residue issue not only affects trade of agricultural products but also causes potential risks to consumers. In this work, a lateral flow immunoassay based on time-resolved fluorescence microspheres (TRFMs) labeled monoclonal antibody (mAb) was developed for rapid quantitation of CBZ. Specifically, starting with the careful design and synthesis of hapten using 2-aminobenzimidazole and glutaric anhydride as reactants, a novel and specific mAb against CBZ was produced and characterized. Subsequently, using TRFMs as signal probe, a time resolved fluorescence lateral flow immunoassay (TRF-LFIA) was constructed through covalent coupling of mAbs and TRFMs. The developed TRF-LFIA could achieve rapid detection of CBZ within 10 min, and its applicability to the quantitation of CBZ in agricultural products (rice and tobacco) was evaluated. The limits of detection (LODs) in rice and tobacco were 0.41 ng/mL (0.012 mg/kg) and 0.56 ng/mL (0.017 mg/kg), respectively. The spiked recoveries in blank rice and tobacco were ranged from 82.0% to 113.0% with relative standard deviations of 2.0–11.8%. The quantitative results of CBZ in naturally incurred tobacco measured by TRF-LFIA were confirmed by liquid chromatography-tandem mass spectrometry, and the results were consistent. The developed TRF-LFIA could provide a sensitive, rapid and cost-effective method for on-site monitoring of CBZ in agricultural products.

Research on Rapid Detection Technology for β2-Agonists: Multi-Residue Fluorescence Immunochromatography Based on Dimeric Artificial Antigen.

To detect two types of β2-agonist residues at the same time, we coupled two haptens of clenbuterol (CLE) and ractopamine (RAC) to the same carrier protein through diazotization to prepare dimeric artificial antigen, and a fluorescent lateral flow immunoassay method based on europium nanoparticles (EuNP-FLFIA) was established by combining polyclonal antibodies with europium nanoparticles to form probes. Under optimized conditions, the EuNP-FLFIA could simultaneously detect eight aniline-type and one phenol-type β2-agonists, and the limits of detection (LOD) were 0.11–0.19 ng/mL and 0.12 ng/mL, respectively. The recovery rate of this method was 84.00–114.00%. This method was verified by liquid chromatography–tandem mass spectrometry (LC-MS/MS), and the test results were consistent (R2 > 0.98). Therefore, the method established in this study could be used as a high-throughput screening for the efficient and sensitive detection of β2-agonists in food.

Sensitive and simultaneous detection of multi-index lung cancer biomarkers by an NIR-Ⅱ fluorescence lateral-flow immunoassay platform

The simultaneous detection of multiple serum biomarkers of cancer with high sensitivity and point-of-care manner is of great significance for facile and early screening of cancers. In this work, the sensitivity of lateral-flow immunoassay (LFIA) platform was improved by two strategies. The NIR-Ⅱ emitting lead sulfide quantum dots (PbS QDs) were employed to replace common visible region fluorophores to reduce background interference from sample matrix. Meanwhile, numerous hydrophobic PbS QDs were concentrated and assembled within single dendritic scaffold via three-dimensional distribution manner to enhance the fluorescence intensity of individual colloidal label. The LFIA strips with multi-testing lines were performed to realize simultaneous diagnosis of carcino-embryonic antigen (CEA), cytokeratin 19 fragment (Cyfra21-1) and neuron-specific enolase (NSE). The multi-target LFIA could be completed within 12 min with precise quantitative results by a portable NIR-Ⅱ strip scanner. The analytical data illustrated wide linear detection ranges of 0.11–100 ng mL−1, 0.18–100 ng mL−1 and 0.28–100 ng mL−1 and limit of detection of 0.11, 0.18 and 0.28 ng mL−1 for CEA, Cyfra21-1 and NSE, respectively. The multi-target LFIA revealed minor cross-reactivity of three specific antibodies conjugated labels with non-specific cancer biomarkers and interfering proteins in human serum. For real serums of lung cancer patients and healthy persons, the combination detection of the three biomarkers exhibited an improved sensitivity up to 92.7%, which was significantly higher than any individual biomarker detection, with a satisfactory specificity of 92.0%. The multi-target LFIA platform with high sensitivity and specificity holds great significance for point-of-care and simultaneous diagnosis of multiple cancer biomarkers.

A novel time-resolved fluorescent lateral flow immunoassay for quantitative detection of the trauma brain injury biomarker-glial fibrillary acidic protein

A highly sensitive time-resolved fluorescence lateral flow immunoassay (TRF-LFIA) was developed to quantify glial fibrillary acidic protein (GFAP), a trauma brain injury (TBI) biomarker in blood, for the purpose of providing a diagnosis of mild brain injury.

A highly sensitive and quantitative time resolved fluorescent microspheres lateral flow immunoassay for streptomycin and dihydrostreptomycin in milk, honey, muscle, liver, and kidney

Streptomycin (STR) and dihydrostreptomycin (DHSTR) are clinically widely used in the prevention and treatment of animal diseases. Unreasonable use or abuse can easily cause adverse effects on human health. Thus, it is very necessary to establish a rapid detection method for STR and DHSTR in animal-derived foods. In this study, a time-resolved fluorescent microspheres lateral flow immunoassay (TRFM-LFIA) integrated with a portable fluorescence reader was developed for STR and DHSTR detection. The cut-off values of the TRFM-LFIA for STR and DHSTR in milk/honey/muscle/liver/kidney were both 30/15/80/25/60 μg kg−1, respectively, the limits of detection were 1.10/0.28/2.82/1.52/3.02, 0.75/0.23/1.76/1.21/2.35 μg kg−1, respectively, and the limits of quantitation were 3.62/0.93/9.31/5.02/9.96, 2.48/0.76/5.81/3.99/7.76 μg kg−1, respectively. The recoveries ranged from 80.0% to 120.1%, with coefficient of variation from 2.8% to 14.3%, respectively. The parallel experiment of 25 samples showed excellent correlation (R2 > 0.99) between ELISA kit and TRFM-LFIA. The sample pretreatment is very simple, and the results can be achieved in 8 min. This sensitive, simple, rapid and portable analysis strategy can provide universal technical support for the residue detection of veterinary drugs and even small molecular hazard factors.