Graphene-Orange II composite nanosheets with electroactive functions as label-free aptasensing platform for “signal-on” detection of protein

The combination of novel nanomaterials and biomolecule recognition units is promising in developing sensitive biosensors. This paper presents a facile approach for the preparation of water-soluble electroactive dye-Orange II functionalized graphene nanosheets (O-GNs). The successful attachment of Orange II on the surface of graphene nanosheets not only prevents the agglomeration of the as-formed graphene nanocomposite in aqueous media, but also endows graphene nanosheets with excellent electroactive property. Integrating the unique properties of the as-prepared O-GNs (high conductivity, high specific surface area and electroactive function) with high affinity and specificity of aptamer, a new label-free electrochemical biosensing concept is demonstrated for the “signal-on” detection of targets such as thrombin and lysozyme. The present O-GNs-based aptasensor exhibits good current response to the above proteins. The linear ranges for thrombin and lysozyme are 1.0×10−12–4.0×10−10 M and 5.0×10−12–7.0×10−10 M, with the detection limit of 3.5×10−13 M and 1.0×10−12 M, respectively. In contrast to the common laborious and expensive labeling approaches, the present O-GNs based aptasensing process is highly simple, cost-efficient and does not need labeling and modification of aptamers or introduce additional electrochemical probes.

► Orange II functionalized graphene nanosheets (O-GNs) were synthesized.
► O-GNs act as both enhanced material and in-situ probe for the electrochemical detection.
► Label-free aptasensing platform for “signal-on” detection of protein was proposed.
► The process is highly simple and does not need the introduction of additional electrochemical probes.