Aptamer-based PDMS–gold nanoparticle composite as a platform for visual detection of biomolecules with silver enhancement

A sensitive colorimetric detection for biomolecules based on aptamer was described. Poly(dimethylsiloxane) (PDMS)–gold nanoparticles (AuNPs) composite film was used as a platform for immobilizing anti-target aptamer. PDMS–AuNPs composite film only covered with aptamer showed high inhibiting ability towards silver reduction, after target molecules were conjugated on the modified surface, the catalytic efficiency of AuNPs for silver reduction was increased. In this system, the darkness density of silver enhancement was applied for target quantitative measurement. Lysozyme and adenosine 5′-triphosphate (ATP) were tested as the models, quantitative measurements with imaging software or semiquantitative measurements with naked eyes were carried out in the range of 1 × 10−2–1 μg/mL and 1 × 10−4–1 × 103 μg/mL, the volume of reagent using in each assay is 15 μL or less. We speculated that aptamer-target conjugates’ inhibition ability for AuNPs’ catalytic efficiency toward silver reduction might come from charge and spatial effects. This study can offer a completely novel and relatively general approach for colorimetrical aptamer sensors with good analytical properties and potential applications. The sensor could be coupled with digital transmission of images for remote monitoring system in diagnosis, food control, and environmental analysis.