Authors:

Malina-Elena Cantemir

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About Paper:

Aptamers are single-stranded nucleic acid fragments designed to bind a molecular target with very high specificity, akin to antibodies. While the latter are frequently used in healthcare diagnostic devices, aptamers offer distinct advantages over antibodies in stability, choice of targets or cost and ease of synthesis. These properties pose aptamers as better candidates for biosensor applications than antibodies, especially for detecting targets which undergo frequent structural change due to high mutation rates, such as hemagglutinin (HA), a spike surface protein chiefly responsible for the infectivity of influenza A/B viruses. In this project, we report on progress made towards developing a colorimetric microfluidic paper-based analytical device (µ-PAD) by conducting initial optimization of HA detection in solution. Polystyrene beads decorated with gold nanoparticles (PS-AuNPs) were functionalized with aptamer RHA0385 which has broad specificity to HA proteins of different influenza strains. Detection relied on salt-induced microparticle aggregation which occurs when aptamers detach from the particles to bind their preferred targets, exposing particle surfaces to salt. Aggregation was marked by a transition from pink-red to purple, and quantitated spectrophotometrically. We identified ideal criteria relating to particle synthesis, salt type and concentration, and aptamer immobilization and surface blocking parameters. Ultimately, HA detection was conducted in Tris-EDTA buffer (pH 7.5) with 30 mM NaCl and presented in linear range of 0-100 µg/mL. The minimal HA concentration necessary for detection was observed as 5 µg/mL. These results suggest that further optimization of testing conditions is necessary to achieve lower limits of detection and improve assay sensitivity.

Source:

Purdue University / 2023

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Co-authors:

Malina-Elena Cantemir