BioGraphING · Biomolecule Sensing with Graphene-Integrated Nanogaps

Biomolecule Sensing with Graphene-Integrated Nanogaps

In order to understand certain biological mechanisms, such as how genetic information can affect the development of a specific disease, it is key to develop a methodology that enables sensing of relevant biomolecules (e.g. DNA, proteins) at the single-molecule scale. Nanotechnology-based approaches to achieve these goals have made large strides in the last decade, and have shown unparalleled potential by enabling long-read, high-resolution sequencing without need for amplification and labeling. Among the most effective sequencing devices are nanopores and nanogaps, through which the biomolecules are transiently trapped, thereby causing a modulation of the ionic and tunnelling current respectively. In particular, electron tunnelling transport across a single-molecule junction is highly sensitive to the nature of the trapped molecule, rendering it a powerful tool for discriminating analytes with minor structural differences. The principle behind the strength of this approach is that biomolecules with different chemical composition have different local electronic densities of states that lead to a distinguishable tunnelling current. In BioGraphING, the researcher designed and developed the first graphene MCBJ platform to assess the viability of graphene electrodes as a biosensor technology that has the potential to open up high-resolution single-molecule protein fingerprinting to all. Graphene combines many of the requisites for an electrical sensor material: high conductivity, atomic thinness, flexibility, chemical inertness in air and liquid and mechanical strength, as well as compatibility with standard lithographic patterning techniques. In BioGraphING, the researcher developed a novel graphene-based technology that utilises the mechanically controlled break junction (MCBJs) technique. The MCBJ is conceptually simple: a suspended graphene bridge is positioned on a flexible metal substrate. Bending the substrate in a 3-point geometry causes the graphene to stretch and eventually break. The conductance at a fixed bias voltage is measured throughout the bending/breaking/remaking processes, giving detailed information of the structure-electronic property relationship. One- and two-dimensional histograms of conductance versus electrode displacement crucially allow mapping of the breaking dynamics in real-time and with statistical significance. The project was structured to achieve three objectives: O1. Demonstrating controlled nanogap formation in graphene MCBJs in air, vacuum and liquid. O2. Identifying molecular signatures from ‘reference’ molecules e.g. anthracene- or pyrene-funtionalized curcuminoids or oligo-phenylene-ethynylene (OPE3) molecules (i.e. π-π interactions with graphene), porphyrins w/o amine anchors (i.e. C-C and amine bonding with graphene respectively). O3. Demonstrating proof-of-concept peptide and protein fingerprinting using tunnelling currents.

Data: CORDIS, © European Union