Label Free Fiber Optic Apta-Biosensor for <italic>In-Vitro</italic> Detection of Dopamine

Abstract

Dopamine (DA) analysis is complicated by the interference from other electrochemically active endogenous compounds present in the brain, including DA precursors and metabolites and other neurotransmitters (NT). Here, we report a simple, sensitive, and selective optical fiber biosensor for in vitro detection of the DA in the presence of other NT. It is composed of a 57-mer dopamine-binding aptamer (DBA) as recognition element and nonadiabatic tapered optical fiber as a probe. Upon the addition of DA, the conformation of DBA would change from a random coil structure to a rigid tertiary structure like a pocket. The conformational change of DBA leads to the refractive index change around the tapered fiber surface. Specific recognition of DA by the aptamer allowed a selective optical detection of DA within the physiologically relevant 0-10 μM range. The sensitivity of the Apta-Biosensor for concentration of the DA in the range of 0-1 μM and 1-10 μM with correlation coefficients (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) equal to 0.99 was 0.27 ± 0.05 and 0.08 ± 0.01 nm/μM, respectively. In addition, detection limit of the biosensor to DA in range from 0 to 1 μM and 1 to 10 μM was 37 and 125 nM, respectively. Some common interferents, such as epinephrine and ascorbic acid showed no or just a little interference in the determination of DA. In addition, the binding constant of the DA to DNA aptamer was determined.