Aptamer-based colorimetric biosensing of dopamine using unmodified gold nanoparticles

A simple, sensitive and selective colorimetric biosensor for the detection of dopamine (DA) was demonstrated with a 58-mer dopamine-binding aptamer (DBA) as recognition element and unmodified gold nanoparticles (AuNPs) as probes. Upon the addition of DA, the conformation of DBA would change from a random coil structure to a rigid tertiary structure like a pocket and this change has been demonstrated by circular dichroism spectroscopic experiments. Besides, the conformational change of DBA could facilitate salt-induced AuNP aggregation and lead to the color change of AuNPs from red to blue. The calibration modeling showed that the analytical linear range covered from 5.4 × 10−7 M to 5.4 × 10−6 M and the corresponding limit of detection (LOD) was 3.6 × 10−7 M. Some common interferents such as 3,4-dihydroxyphenylalanine (DOPA), catechol, epinephrine (EP), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and ascorbic acid (AA) showed no or just a little interference in the determination of DA.