Electrochemiluminescent immunoassay for neuron specific enolase by using amino-modified reduced graphene oxide loaded with N-doped carbon quantum dots

An ultrasensitive electrochemiluminescence based sandwich immunoassay is presented for determination of neuron specific enolase. The method uses silver-cysteine nanowires as the capture probe and a composite made of amino-modified reduced graphene oxide and nitrogen-doped carbon quantum dots as the signal probe. It was synthesized by covalent coupling of amino-modified reduced graphene oxide to the carboxy groups of nitrogen-doped carbon quantum dots. The nanowires possess a large specific surface and abundant functional groups which facilitate immobilizing the primary antibody (Ab₁). The amino-modified reduced graphene oxide is employed as a carrier for loading a large number of the quantum dots and secondary antibody (Ab₂). This increases the electrochemiluminescence intensity of quantum dots. Response to neuron specific enolase is linear in the 0.55 fg·mL⁻¹ to 5.5 ng·mL⁻¹ concentration range. It has a detection limit of 0.18 fg·mL⁻¹ (at S/N = 3). The relative standard deviation (for n = 6) is less than 2.9%. The assay is highly sensitive, reproducible, selective and stable.

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