Development of a new sensitive immunostrip assay based on mesoporous silica and colloidal Au nanoparticles

Home-Made Lateral Flow Test Strip Versus POC-CCA Assay for Detection of Active Schistosomiasis in Egypt

BACKGROUND

For years, the Kato-Katz (KK) technique has been considered the gold standard for diagnosing schistosomiasis. The aim of this study was to compare the effectiveness of our previously developed gold nanoparticle-based lateral flow test strip (AuNPs-LFTS) for diagnosing active Schistosoma mansoni with that of the commercially available point-of-care Circulating Cathodic Antigen detection (POC-CCA) kit.

METHODS

In this study, we collected sixty positive and twenty negative urine samples from patients in endemic hot spots in the Nile Delta, as well as from patients visiting the internal medicine clinic at Theodor Bilharz Research Institute (TBRI). We produced monoclonal antibodies (MAbs) against S. mansoni soluble egg antigen (SEA) from cloned hybridoma cells (4D/1D). These MAbs were conjugated with gold and mesoporous silica nanoparticles, and used to develop the LFTS.

RESULTS

The LFTS demonstrated a limit of detection (LoD) of 3 ng/ml. The sensitivity and specificity of the developed LFTS were found to be 96.7% and 95%, respectively, compared to 85% and 90% for the POC-CCA detection kit. The cases were divided into groups based on egg count in the stool, categorized as light, moderate, and heavy infections. The sensitivity of the LFTS in the group with light infection was higher than that of the POC-CCA. When using the KK technique (eggs per gram of stool sample [EPG]) as the reference test, the kappa value for the nano-based strips was 0.902, compared to 0.672 for the CCA strips, indicating an almost perfect agreement between KK and our developed LFTS.

CONCLUSION

These results confirm the reliability and effectiveness of the LFTS compared to commercially available kits for rapid, sensitive, and early diagnosis of schistosomiasis. However, it is recommended to conduct further assessments of the developed strip on a larger scale with a broader range of cases before considering its introduction to local or international markets.

Lateral Flow Assay: A Summary of Recent Progress for Improving Assay Performance

Lateral flow tests are one of the most important types of paper-based point-of-care (POCT) diagnostic tools. It shows great potential as an implement for improving the rapid screening and management of infections in global pandemics or other potential health disorders by using minimally expert staff in locations where no sophisticated laboratory services are accessible. They can detect different types of biomarkers in various biological samples and provide the results in a little time at a low price. An important challenge regarding conventional LFAs is increasing their sensitivity and specificity. There are two main approaches to increase sensitivity and specificity, including assay improvement and target enrichment. Assay improvement comprises the assay optimization and signal amplification techniques. In this study, a summarize of various sensitivity and specificity enhancement strategies with an objective evaluation are presented, such as detection element immobilization, capillary flow rate adjusting, label evolution, sample extraction and enrichment, etc. and also the key findings in improving the LFA performance and solving their limitations are discussed along with numerous examples.

High surface area nitrogen-functionalized Ni nanozymes for efficient peroxidase-like catalytic activity

Nitrogen-functionalization is an effective means of improving the catalytic performances of nanozymes. In the present work, plasma-assisted nitrogen modification of nanocolumnar Ni GLAD films was performed using an ammonia plasma, resulting in an improvement in the peroxidase-like catalytic performance of the porous, nanostructured Ni films. The plasma-treated nanozymes were characterized by TEM, SEM, XRD, and XPS, revealing a nitrogen-rich surface composition. Increased surface wettability was observed after ammonia plasma treatment, and the resulting nitrogen-functionalized Ni GLAD films presented dramatically enhanced peroxidase-like catalytic activity. The optimal time for plasma treatment was determined to be 120 s; when used to catalyze the oxidation of the colorimetric substrate TMB in the presence of H2O2, Ni films subjected to 120 s of plasma treatment yielded a much higher maximum reaction velocity (3.7⊆10-8 M/s vs. 2.3⊆10-8 M/s) and lower Michaelis-Menten coefficient (0.17 mM vs. 0.23 mM) than pristine Ni films with the same morphology. Additionally, we demonstrate the application of the nanozyme in a gravity-driven, continuous catalytic reaction device. Such a controllable plasma treatment strategy may open a new door toward surface-functionalized nanozymes with improved catalytic performance and potential applications in flow-driven point-of-care devices.

Point-of-care biosensors in medicine: a brief overview of our achievements in this field based on the conducted research in EMRI (endocrinology and metabolism research Institute of Tehran University of medical sciences) over the past fourteen years

The growing demand of diagnostic tools with enhanced analytical characteristics in term of sensitivity, selectivity, and low response time has encouraged researches to conduct their research towards development of point-of-care (POC) biosensors. POC diagnostic devices are powerful tools for detection, diagnosis, and monitoring of diseases at its initial stage. The above characteristics encouraged us to conduct active multidisciplinary and collaborative research oriented towards the design and development of POC sensing systems. Here, we present a brief overview of our recent achievement in the field of biomedical POC devices implemented in paper based microfluidic and screen printing electrodes and discuss the critical limitations that need to be surmounted to facilitate their translation into clinical practice in the future.

Highly sensitive antibody-aptamer sensor for vascular endothelial growth factor based on hybridization chain reaction and pH meter/indicator

Vascular endothelial growth factor (VEGF) is a crucial signaling protein for the tumor growth and metastasis, which is also acted as the biomarkers for various diseases. In this research, we fabricate an aptamer-antibody sensor for point-of-care test of VEGF. Firstly, target VEGF is captured by antibody immobilized on the microplate, and then binds with aptamer to form the sandwich structure. Next, with the assist of glucose oxidase (GOx)-functionalized ssDNAs, hybridization chain reaction occurs using the aptamer as the primer. Thus, GOx are greatly gathered on the microplate, which catalyzes the oxidization of glucose, leading to the pH change. As a result, the detect limit at a signal-to-noise was estimated to be 0.5pg/mL of target by pH meter, and 1.6pg/mL of VEGF was able to be distinguished by naked eyes. Meanwhile, this method has been used assay VEGF in the serum with the satisfactory results.

New analytical applications of gold nanoparticles as label in antibody based sensors

Gold nanoparticles (AuNPs) with optical and electrochemical distinctiveness as well as biocompatibility characteristics have proven to be powerful tools in nanomedicinal application. This review article discusses recent advances in the application of AuNPs as label in bioanalytical devices, especially electrochemical immunosensors, rapid and point-of-care (PoC) tests. A crucial assessment regarding implementation of different formats of antibodies allowing rapid and sensitive analysis of a range of analytes is also provided in this study. In addition to this, different approaches to minimize antibodies into Fab, scFv or even single-domain antibody fragments like VHHs will be reviewed. Given the high level of target specificity and affinity, such biomolecules are considered to be excellent elements for on-site or PoC analysis.

Development of an immunochromatographic assay based on carbon nanoparticles for the determination of the phytoregulator forchlorfenuron

Rapid analytical methods enabling the determination of diverse targets are essential in a number of research areas, from clinical diagnostics to feed and food quality and safety. Herein, the development of a quantitative immunochromatographic assay for the detection of the synthetic phytoregulator forchlorfenuron (CPPU) is described. The competitive lateral flow immunoassay (LFIA) was based on the immobilization onto a nitrocellulose membrane of an ovalbumin-CPPU conjugate (test line) and on the use of an immunodetection ligand consisting of carbon nanoparticles labeled with an anti-CPPU monoclonal antibody through interaction with a secondary antibody. The presence of CPPU in horticultural samples was visually interpreted by the decrease in the black signal intensity of the test line, according to the competitive character of the format. The quantitative determination of the analyte was easily performed by a two-step procedure consisting of flatbed scanning of the strips followed by computer-based image analysis of the pixel gray volumes of the test lines. Under optimized conditions, the immunochromatographic test afforded a limit of quantification in buffer of 89 ng/L. The accuracy of the strip test was assessed by the analysis of fruit samples with incurred residues, and the obtained results were compared with those derived from two reference methods, ELISA and HPLC. The LOQ of the CPPU-specific LFIA in kiwifruits and grapes was established at 33.4 μg/kg. The excellent analytical performance of the developed strip test demonstrates the potential of immunochromatographic assays for the quantitative monitoring of small organic molecules in complex matrices.