A novel label-free fluorescence aptasensor for dopamine detection based on an Exonuclease III- and SYBR Green I- aided amplification strategy

Abstract

A novel label-free fluorescence aptasensor was established for the detection of dopamine based on dopamine-triggered Exonuclease III- and SYBR Green I-assisted template DNA recycling and a decrease in fluorescence. SYBR Green I was selected as the fluorescent indicator; SYBR Green I fluoresces upon binding to double stranded DNA (dsDNA). The template DNA (tDNA) was designed to contain two regions: one complementary to the complementary strand (cDNA) and the other complementary to the aptamer. Various concentrations of dopamine automatically triggered the Exonuclease III restriction digestion to release SYBR Green I. Consequently, the fluorescence signal significantly decreased. Therefore, a method for detecting the dopamine concentration was established. Polyacrylamide gel electrophoresis was also used to confirm the feasibility of the developed sensor for detecting dopamine. Under optimal conditions, the variation in fluorescence was proportional to the concentration of dopamine in the range of 1.0 × 10-10 M to 10.0 × 10-9 M, with a detection limit of 8.0 × 10-11 M. The developed aptasensor showed good selectivity and was successfully applied to detect dopamine in mouse brain tissues. Due to its remarkable sensitivity and selectivity, the constructed fluorescence aptasensor was applicable not only for the routine detection of dopamine but also for diagnosing disease.