Development of a europium nanoparticles lateral flow immunoassay for NGAL detection in urine and diagnosis of acute kidney injury

Multiplexed Capillary-Flow Driven Immunoassay for Respiratory Illnesses

Multiplexed analysis in medical diagnostics is widely accepted as a more thorough and complete method compared to single-analyte detection. While analytical methods like polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) exist for multiplexed detection of biomarkers, they remain time-consuming and expensive. Lateral flow assays (LFAs) are an attractive option for point-of-care testing, and examples of multiplexed LFAs exist. However, these devices are limited by spatial resolution of test lines, large sample volume requirements, cross-reactivity, and poor sensitivity. Recent work has developed capillary-flow microfluidic ELISA platforms as a more sensitive alternative to LFAs; however, multiplexed detection on these types of devices has yet to be demonstrated. In the aftermath of the initial SARS-CoV-2 pandemic, the need for rapid, sensitive point-of-care devices has become ever clearer. Moving forward, devices that can distinguish between diseases with similar presenting symptoms would be the ideal home diagnostic. Here, the first example of a multiplexed capillary-flow immunoassay device for the simultaneous detection of multiple biomarkers is reported. From a single sample addition step, the reagents and washing steps required for two simultaneous ELISAs are delivered to spatially separated test strips. Visual results can be obtained in <15 min, and images captured with a smartphone can be analyzed for quantitative data. This device was used to distinguish between and quantify H1N1 hemagglutinin (HA) and SARS-CoV-2 nucleocapsid protein (N-protein). Using this device, analytical detection limits of 840 and 133 pg/mL were obtained for hemagglutinin and nucleocapsid protein, respectively. The presence of one target in the device did not increase the signal on the other test line, indicating no cross-reactivity between the assays. Additionally, simultaneous detection of both N-protein and HA was performed as well as simultaneous detection of N-protein and human C-reactive protein (CRP). Elevated levels of CRP in a patient infected with SARS-CoV-2 have been shown to correlate with more severe outcomes and a greater risk of death as well. To further expand on the simultaneous detection of two biomarkers, CRP and N-protein were detected simultaneously, and the presence of SARS-CoV-2 N-protein did not interfere with the detection of CRP when both targets were present in the sample.

A fluorescence-based immunochromatographic assay using quantum dot-encapsulated nanoparticles for the rapid and sensitive detection of fetuin-B

Coronary artery disease (CAD) is the leading cause of death worldwide. Earlier detection of CAD improves treatment outcomes and secondary prevention. The circulating fetuin-B protein is considered to be a promising biomarker for the early detection of CAD. However, a facile and reliable clinical test for fetuin-B is still lacking. Herein, we describe a reliable fluorescent biosensor for detecting fetuin-B in plasma that combines quantum dots-doped polystyrene nanoparticles with an immunochromatographic assay strip (QNPs-ICAS). The QNPs served as detection signals in the QNPs-ICAS sensor system, which was based on a double-antibody sandwich structure. Under optimum experimental conditions, the biosensor exhibited a broad linear range of 1-200 ng mL-1 and a low detection limit of 0.299 ng mL-1. Furthermore, the proposed immunosensor demonstrated high sensitivity, satisfactory selectivity, good reproducibility, and excellent recovery. Finally, the performance and applicability of our QNPs-based ICAS system were validated in clinical samples using a commercial ELISA kit with excellent correlations (r = 0.98451, n = 116). To conclude, the proposed sensor served as a rapid, sensitive, and accurate method for detecting fetuin-B in actual clinical samples, thereby demonstrating its potential for preliminary CAD screening and diagnosis.

Latest Trends in Lateral Flow Immunoassay (LFIA) Detection Labels and Conjugation Process

LFIA is one of the most successful analytical methods for various target molecules detection. As a recent example, LFIA tests have played an important role in mitigating the effects of the global pandemic with SARS-COV-2, due to their ability to rapidly detect infected individuals and stop further spreading of the virus. For this reason, researchers around the world have done tremendous efforts to improve their sensibility and specificity. The development of LFIA has many sensitive steps, but some of the most important ones are choosing the proper labeling probes, the functionalization method and the conjugation process. There are a series of labeling probes described in the specialized literature, such as gold nanoparticles (GNP), latex particles (LP), magnetic nanoparticles (MNP), quantum dots (QDs) and more recently carbon, silica and europium nanoparticles. The current review aims to present some of the most recent and promising methods for the functionalization of the labeling probes and the conjugation with biomolecules, such as antibodies and antigens. The last chapter is dedicated to a selection of conjugation protocols, applicable to various types of nanoparticles (GNPs, QDs, magnetic nanoparticles, carbon nanoparticles, silica and europium nanoparticles).

Colloidal silver-based lateral flow immunoassay for detection of profenofos pesticide residue in vegetables

A colloidal silver nanoparticle (AgNP)-based lateral flow immunoassay (LFIA) was evaluated in terms of the rapid detection of profenofos (PEO) pesticide residue in vegetables. Colloidal AgNPs, of a diameter of approximately 20 nm, were surface-modified with trisodium citrate dehydrate (TSC) in order to improve their stability and dispersion. An anti-profenofos polyclonal antibody (pAb) was successfully immobilized on the surface of the AgNPs by ionic interaction and characterized using UV-vis, SEM, TEM, FTIR and XPS analyses. Surface modification of Ag-pAb conjugates of varying pH, pAb content and cross-reactivity was employed to design and prepare labels for use in an LFIA to examine whether these factors affect the performance of the assay. The visible detection limit and optical detection limit of the PEO test strip were 0.20 and 0.01 ppm, respectively, in PEO standard solution. This assay showed no cross-reaction with omethoate, methamidophos or pyraclofos. Finally, the PEO test strip was effectively applied for the detection of PEO in liquid vegetables A and B, with optical detection limits of 0.09 and 0.075 ppm, respectively.