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Fig. 3.3 Working principle of aptamer-gold nanoparticles (a) and Aptamer-Quantum dot-based
lateral flow (b) (Reprinted from [35] with permission from Elsevier)
In a comparative study, aptamer-based LFA was found to be superior over antibody
strip biosensor with respect to sensitivity and specificity. These results indicate the
potential of aptamer-based strip assays in rapid POCT for real field applications.
An aptamer-GNPs-based low cost, rapid and sensitive strip biosensor has also been
developed for the detection of circulating cancer cells (Ramos cells). This approach
was able to detect as low as 4000 cells without any visual aid. However, with the help
of strip reader, low end detection limit was improved to 800 cells in human blood
samples within 15 min [38]. This breakthrough offers a great opportunity to be used
for the diagnosis of blood cancer in resource-limited settings without compromising
the sensitivity and specificity.
Competitive format is preferred when compounds with low molecular weight
(e.g., haptens having only one epitope) are unable to bind aptamer or an antibody at
the same time.