Graphene-encapsulated nanoparticle-based biosensor for the selective detection of cancer biomarkers.

Nanomaterials such as silicon nanowires (SiNWs), [ 1 , 2 ] carbon nanotubes (CNTs), [ 3–6 ] and graphene, [ 7,8 ] have gained much attention for use in electrical biosensors due to their nanoscopic and electrical properties. For instance, SiNWs and CNTs can be integrated into fi eld-effect transistors (FETs) to detect small amounts of target biomolecules with high sensitivity and selectivity by measuring electrical disturbances induced by the binding of these biomolecules to the surface of the nanostructure. [ 9,10 ] The detection of biomarker proteins with high sensitivity and selectivity is vital for the early diagnosis of many diseases including cancer and HIV. For this purpose, carbonbased nanomaterials such as CNTs and graphene have attracted signifi cant attention for fabricating highly sensitive FET-based biosensors. [ 6 , 8,9 , 11–15 ] In particular, the use of graphene in FETbased biosensors is becoming more and more appealing not only due to its unique properties, such as higher 2D electrical conductivity, superb mechanical fl exibility, large surface area, and high chemical and thermal stability, but also due to its ability to overcome the limitations of CNTs, such as variations in electrical properties of CNT-based devices and the limited surface area of CNTs. [ 16–24 ] Nevertheless, there have been only a few reports on the development of graphene FET-based biosensors, [ 14 , 25 ] and their potential as biosensors has not been fully explored. It is therefore critical to develop nanoscopic graphenebased biosensors that are simple in device structure, small in size, and allow label-free detection and real-time monitoring of biomarkers, all of which are essential criteria for biosensors. A key challenge in the above requirements is the achievement of both, well-organized 2D or 3D graphene structures, in microscopic and nanoscopic biosensing devices and well-defi ned bioconjugation chemistry on graphene.