Semiquantitative, bar code version of immunochromatographic assay system for human serum albumin as model analyte

Abstract

An immunochromatographic assay system was devised that can express the concentration ranges of analyte (e.g., urinary human serum albumin) as distinct numbers of the ladder bar (bar coding) for semiquantitation. We constructed a model system consisting of five membrane pad strips partially superimposed in a length. Upon wicking of sample from the bottom, the medium dissolved two different biotinylated species, antibody to the analyte and conjugates of the antibody with colloidal gold, and antigen-antibody reactions took place in the hollow space of the glass fiber membrane. After eliminating unreacted biotinylated molecules at the next strip with an immobilized albumin, the immune complexes were transferred to the pad with streptavidin immobilized in a ladder bar pattern. Analytical conditions here were set for competition between the two biotinylated species for the streptavidin binding sites. The degree of such competition was proportional to the analyte concentration and, consequently, the bar signal number was elevated as the concentration increased. Under optimal conditions for sensitivity, the analytical system responded to the analyte doses at between 30 and 120 mg/dL by producing different bar codes within 5 min.

Lateral flow (immuno)assay: its strengths, weaknesses, opportunities and threats. A literature survey

“…Response at the test line (T) is dependent on the analyte concentration; response at the control line (C) indicates a proper flow through the membrane A response at the control line confirms a proper flow of the liquid through the strip. More test lines can be applied allowing for multianalyte testing [32][33][34][35][36] or for semiquantitative evaluation of the response [37,38].…”

“…Washing or pretest blocking will destroy these properties. However, in several publications preblocking the strips was mentioned [38,68,74].…”

“…When a more semiquantitative result is required, simple evaluation by spraying a series of lines of capture reagent with increasing concentration (comparable to a bar code) is sometimes sufficient [37,38]. A more extended format uses evaluation of the signal by a measuring device.…”

Nanoparticle-based lateral flow biosensors

“…One of the possible paths that the researchers could take to reach to this future is the development of paper-based biosensors, following the same principle as the immunochromatographic assays (IAs) (Lou et al, 1993;Cho and Paek, 2001;Lönnberg and Carlsson, 2001;Ho and Wauchope, 2002;Shyu et al, 2002): the separation of analytes which flow across a porous medium taking into account the specific interactions that occur between antigen and antibody, enzyme and substrate, or receptor and ligand. Paper is a simple, cheap, abundant and an easy-to-manufacture material that fulfils cost/efficient requirements in biosensing technology (Costa et al, 2014).…”

Aflatoxin Measurement and Analysis

“…Subsequently, a dipstick test determined microalbuminnuria in patients with hypertension (semi-) quantitively by comparing the colored singal with a standard color chart (Gerber, Johnston, & Alderman, 1998) such as with pH paper. However, the color indication of the assay is not self-confirmative, and may also show an error in matching intensity (Cho & Paek, 2001). According to the description above, although problems exist in two kinds of approaches, the detector-free methods seem to have more potential on-site application value considering convenience, low-cost and no interferences from instrument itself.…”