Liposome-Enhanced Lateral-Flow Assays for Clinical Analyses

Abstract

Clinical and environmental analyses frequently necessitate rapid, simple, and inexpensive point-of-care or field tests. These semiquantitative tests may be later followed up by confirmatory laboratory-based assays, but provide an initial scenario assessment important for resource mobilization and threat confinement. Lateral-flow assays (LFAs) and dip-stick assays, which are typically antibody-based and yield a visually detectable signal, provide an assay format suiting these applications extremely well. Signal generation is commonly obtained through the use of colloidal gold or latex beads, which yield a colored band either directly proportional or inversely proportional to the concentration of the analyte of interest. Here, dye-encapsulating liposomes as a highly visible alternative are discussed. The semiquantitative LFA biosensor described in this chapter relies on a sandwich immunoassay for the detection of myoglobin in whole blood. After an acute myocardial infarction (AMI) event, several cardiac markers are released into the blood, the most common of which are troponin, creatine kinase MB, C-reactive protein, and myoglobin. Due to its early release, myoglobin has value as an indicator of a recent heart attack amongst conditions which present with similar symptoms and its lack of elevation can effectively rule out a heart attack (Brogan et al., Ann Emerg Med 24:665-671, 1994). The assay described within relies on sandwich complex formation between a membrane immobilized capture monoclonal antibody against myoglobin, a detector biotinylated monoclonal antibody against a different epitope on myoglobin, and streptavidin-conjugated visible dye (sulforhodamine B)-encapsulating liposomes to allow for signal generation.

Technical considerations to development of serological tests for SARS-CoV-2

“…With the implications of false results during COVID-19, to date SARS-CoV-2 serology tests irrespective of format have been carried out in centralized laboratories, though the first POC serology test received an EUA on 9/23/20 [ 41 ]. By contrast, assays such as ELISAs and microparticle-based immunoassays are designed to yield quantitative results in a laboratory setting [ [42] , [43] , [44] ]. Aside from submission to a centralized facility, sufficient sample numbers must be accumulated before these typically high-throughput analyses are run.…”

“…An absorbent pad is assembled on the distal end of the membrane to serve as a wick for fluids passing through the assembly. The assemblies are compiled with a user-optimized overlap of components (in our hands, 2 mm) using an adhesive backing to support and retain components, then cut into strips typically approximately 5 mm wide [ 42 ]. A key component of these assays is the housing in which they are subsequently encased.…”

Six decades of lateral flow immunoassay: from determining metabolic markers to diagnosing COVID-19

“…The materials listed above fully comply with these requirements; in addition, latex can be made in various colors and used in this form in multiplex systems [3] , [13] , [41] – [43] .…”

“…The modern multiplex LFIA formats are capable of detecting several analytes at a time in a single sample (for example, test systems for detecting narcotic drugs in urine). In this case, the system includes one pad for applying a sample, several (according to the number of tested substances) pads to release conjugate, containing specific antibodies to each of the target analytes, and the same number of test zones to readout the result [21] , [26] , [29] , [43] .…”

“…A noteworthy format of LFIA to detect increase in myoglobin concentration, based on a sandwich system, was proposed by К. Edwards with co-authors [43] . In the proposed system, immobilized antibodies conjugate with streptavidin and are detected with a specific fluorescent dye (sulforodamine B) encapsulated in liposomes, which facilitates signal generation [43] .…”