Development of membrane-based flow-through assay for detection of trypanosomosis in equines

A multirange paper-based analytical device for identifying low, moderate, and high P. aeruginosa bacterial loads in sputum samples

In this article we introduce a multirange analytical device that extends the dynamic range of nanoparticle-based immunoassays thanks to a multisensor design. Multirange devices contain low- and high-range sensors in the same analytical platform. The low-range sensor defines the limit of detection and quantifies low concentrated analytes, whereas the high-range sensor defines the upper limit of the dynamic range. A control sensor is also included for registering non-specific interactions. A device capable of distinguishing low, moderate, and high bacterial loads in sputum samples was developed to prove the concept of this approach. Using Pseudomonas aeruginosa as a model analyte, the multirange configuration extended the dynamic range 3 orders of magnitude while maintaining a limit of detection of 104 cells·mL-1. The control sensor was used to subtract matrix interferences, which decreased the number of false positives arising from non-specific interactions. The resulting analytical platform was able to correctly distinguish samples with an infection caused by the target pathogen from samples infected by another microorganism. It could also differentiate samples spiked with low, moderate, or high bacterial loads. The results shown here pave the way to using these devices for estimating the bacterial load in patients with chronic bronchial infection, which is a requirement to personalize the dosage of inhaled antibiotics.

Optimizing Effective Parameters to Enhance the Sensitivity of Vertical Flow Assay for Detection of Escherichia coli

Vertical flow immunoassays (VFIAs) are considered potential point-of-care testing (POCT) devices compared to lateral flow assays due to their ability to analyze a comparatively large sample volume and ease of multiplexing. However, VFIA devices are limited by low analytical sensitivity when coupled with a visual colorimetric signal. Herein, we carefully analyzed key parameters that accounted for the proper functionality of VFIA that can be modified to enhance the overall sensitivity of VFIA. In particular, we focused on improving the stability of conjugate pads impregnated with capture antibodies, maintaining a controlled flow rate to ensure higher analyte reactivity with capture antibodies, and enhancing the absorption efficiency. The results showed that air-drying of conjugate pads in the presence of 5% (w/v) lactose significantly improved the stability of antibodies during long-term storage. Integration of dissolvable polyvinyl alcohol (PVA) membrane of optimal concentration as a time-barrier film into the sensor delayed the flow of samples, thereby increasing the biorecognition interaction time between immunoreagents for the formation of immuno-complexes, which in turn led to higher sensitivity of the assay. Furthermore, the employment of an absorbent pad with higher water holding capacity significantly reduced the non-specific binding of immunocomplexes, thereby reducing the possibility of false-negative results.

Ten Years of Lateral Flow Immunoassay Technique Applications: Trends, Challenges and Future Perspectives

The Lateral Flow Immunoassay (LFIA) is by far one of the most successful analytical platforms to perform the on-site detection of target substances. LFIA can be considered as a sort of lab-in-a-hand and, together with other point-of-need tests, has represented a paradigm shift from sample-to-lab to lab-to-sample aiming to improve decision making and turnaround time. The features of LFIAs made them a very attractive tool in clinical diagnostic where they can improve patient care by enabling more prompt diagnosis and treatment decisions. The rapidity, simplicity, relative cost-effectiveness, and the possibility to be used by nonskilled personnel contributed to the wide acceptance of LFIAs. As a consequence, from the detection of molecules, organisms, and (bio)markers for clinical purposes, the LFIA application has been rapidly extended to other fields, including food and feed safety, veterinary medicine, environmental control, and many others. This review aims to provide readers with a 10-years overview of applications, outlining the trends for the main application fields and the relative compounded annual growth rates. Moreover, future perspectives and challenges are discussed.