On-Chip FRET Graphene Aptasensor.

We review the recent advances in the use of our originally developed on-chip graphene aptasensor to detect biologically important proteins, such as cancer markers. The detection mechanism, based on fluorescence resonance energy transfer (FRET), occurs at a graphene-biomolecule interface. In our system, the graphene surface is modified with a pyreneaptamer-dye probe. Pyrene functions as a linker to the graphene surface, the aptamer as a probe for selective protein recognition, and the dye as a fluorescence detection tag. Here, graphene behaves simultaneously as both an efficient acceptor for FRET over the entire visible region and as a strong adsorbate for single-stranded DNA (ssDNA), such as aptamers, via pi-pi interactions in the sp(2) domain. The system allows us to perform molecular detection on a solid surface, which is advantageous for realizing on-chip sensors. Such on-chip sensors allow parallel analysis systems, such as array sensors. This enables the quantitative comparison of different samples by forming a multichannel configuration and/or a micropattern with different probes. Moreover, detecting the target protein is possible simply by adding a sample of less than 1 mu L to the on-chip sensor; detection is completed in approximately 1 min. Aptasensors can be used for the detection ofmany different targets simply by replacing the aptamers. The simultaneous detection of multiple target molecules on a single chip using a 2 x 3 linear-array aptasensor was demonstrated here. Improved sensitivity was observed when a DNA spacer was in-corporated into the aptamer, demonstrating that the probe can be modified in interesting ways.