From signal amplification to restrained background: Magnetic graphene oxide assisted homogeneous electrochemiluminescence aptasensor for highly sensitive detection of okadaic acid

Homogeneous electrochemical sensing is a modification-free approach, in which the biochemical reactions occur in a homogeneous solution rather than on a limited electrode interface. Homogeneous sensing strategies are high-efficient but yet suffer from high background signals, since the free indicators can diffuse upon the electrode to generate signals. In this work, a magnetic graphene oxide (M-GO) assisted homogeneous electrochemiluminescence (ECL) aptasensor was developed for the highly sensitive detection of okadaic acid (OA). The aptamer and Ru(bpy)32+ were adsorbed in M-GO to prepare the composite ECL probe. When the OA dissociated aptamer from M-GO, Ru(bpy)32+ was proportionally released from M-GO to generate the ECL signal. With the assistance of deoxyribonuclease I (DNase I), the cyclic dissociation and degradation of aptamers induced much more free Ru(bpy)32+ for signal amplification. But the unreleased Ru(bpy)32+ were still adsorbed in M-GO and magnetically separated. So the background signal was decreased, and the sensitivity was further improved. Results showed that the ECL intensity enhanced with the increasing logarithmic concentration of OA in the range of 0.01 ∼ 10.0 ng/mL, and the limit of detection was 4 pg/mL. The aptasensor illuminates a cost-effective approach for the highly sensitive detection of marine toxins.