Colorimetric Aptasensor for Testosterone Detection Based on Aggregation of Gold Nanoparticles Induced by Cationic Surfactant

This paper proposes a colorimetric aptasensor for the detection of testosterone (TES) in environmental water, using TES-specific aptamer (apT5) as a sensing probe, gold nanoparticles (AuNPs) as indicator, and hexadecyltrimethylammonium bromide (CTAB) as inducer, respectively. Based on competition between TES and CTAB for apT5, the aptamer can form an aptamer–TES complex, leaving CTAB free to aggregate AuNPs in the presence of TES. Dispersed and aggregated AuNPs have different absorption wavelengths and the signal of absorption intensity is associated with the concentration of TES, so TES can be detected quantitatively based on the signal absorption intensity. This sensitive aptasensor for TES detection has a wide linear range (R = 0.998) from 1.91–800 nM and a limit of detection (LOD) of 1.91 nM. In addition, this aptasensor has high selectivity over some interferents. The method detects TES in tap water samples with recoveries in the range of 98.9–102.6 % (RSD ≤ 7.35 %). This biosensor presents a good and potential application to rapidly detect TES in actual environmental water samples.