Graphene in biosensing

JULY-AUGUST 2011 | VOLUME 14 | NUMBER 7-8 308 Graphene is a one-atom-thick material consisting of sp2-bonded carbon with a honeycomb structure. It resembles a large polyaromatic molecule of semi-infinite size1, 2. In the past five years, graphene-based nanomaterials have been the focus of a vast amount of attention. The interesting and exciting properties of single-layer graphene sheets, such as high mechanical strength3, high elasticity and thermal conductivity, demonstration of the room temperature quantum Hall effect, very high roomtemperature electron mobility2, tunable optical properties4,5, and a tunable band gap 6 have excited the scientific community especially in the areas of materials, physics, and chemistry. Different, but similarly fascinating properties are exhibited by double-, few-, and multilayer graphene. Because graphene is a conductive yet transparent material, with a low cost and low environmental impact, it is an ideal material for the construction of sensors and biosensor-based devices in various transduction modes, from electrical and electrochemical transduction to optical transduction. Biosensing is paramount for improving the quality of human life. Biosensors and biosensing protocols are able to detect a wide range of compounds, sensitively and selectively, with applications in security, health care for point-of-care analyses of diseases, and environmental safety. Here, we describe biosensors and biosensing systems employing graphene. Graphene is a zero-gap semiconductor material, which is electroactive and transparent. Because of its interesting properties, graphene has found its way into a wide variety of biosensing schemes. It has been used as a transducer in bio-field-effect transistors, electrochemical biosensors, impedance biosensors, electrochemiluminescence, and fluorescence biosensors, as well as biomolecular labels. In our review, we describe the application of graphene for enzymatic biosensing, DNA sensing, and immunosensing. We compare different techniques and present our views on the future development of the field.