Nanomaterial-based biosensors allow the detection of analytes with high sensitivity and adaptability. Moreover, the use of gold nanomaterials as signal transducers stands out because of their unique optical properties like high extinction coefficient. The functionalization of these nanostructures with aptamers adds important advantages, for instance, high selectivity, fast response and low cost. However, the low stability of large gold nanoparticles could limit the exploration of different morphologies and sizes.<br/><br/>In this study, the stability of gold nanotriangles (AuNT) in PBS was considerably improved via surface passivation with an amphiphilic polymer: polyvinylpyrrolidone (PVP). Then, it was shown that AuNT@PVP can be further functionalized with a hairpin CEA (carcinoembryonic antigen) aptamer biotinylated 3’-end and thiolated 5’-end (AuNT@PVP@Apt). The role of this hairpin aptamer in this sensor was studied as it was expected to interact with CEA inducing the opening of the hairpin structure to expose the biotin groups, which could then be tagged by streptavidin-functionalized small gold nanoparticles (AuNP@Strept, d &lt; 5 nm). Finally, the AuNP@Strept added to the samples were grown and the optical changes were measured via UV-Vis-NIR spectroscopy and correlated with the concentration of CEA. This study displays the challenges behind the design of this type of nanoaptasensor as well as a new possible detection mechanism involving the nanoparticle growth process.

Optical detection of carcinoembryonic antigen using PVP-stabilized nanoaptasensors and a controlled growth mechanism

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