Highly sensitive determination of dopamine by a turn-on fluorescent biosensor based on aptamer labeled carbon dots and nano-graphite

In this paper, a novel fluorescent biosensor based on DA aptamer labeled carbon dots (aptamer-CDs) and nano-graphite (NG) for the determination of dopamine (DA) was developed. In this system, aptamer-CDs were in charge of energy donor (fluorophor) and chemical recognition, while NG served as an energy acceptor. In the absence of DA, aptamer-CDs were adsorbed on the surface of NG through π-π stacking and hydrophobic interaction, which led to the fluorescence quenching of aptamer-CDs due to the surface energy transfer. When it was in presence, DA combined with its aptamer anchored on the surface of CDs to form specific globular chain structure which would detach from the surface of NG and thus the fluorescence intensity of aptamer-CDs was recovered. Under the optimal conditions, the fluorescence intensity of aptamer-CDs increased linearly with the increase of DA concentration in the range of 0.10–5.00   nM and the limit of detection was 0.055   nM. This method was successfully applied to the determination of DA in human urine samples with satisfactory results.