Portable DNA sensor

Detection of changes in the transmission properties of light (electromagnetic radiation) forms the basis of optical tools from simple light microscopes to complicated nano-optical devices. Scientists are now well on their way to development of a lab-on-a-chip exploiting changes in transmission induced by the presence of a single DNA molecule.

With EU support of the project PLASBIORES, researchers are building on their robust technology for fabrication of integrated devices based on wafer-scale processes. These will lead them to production of a nanochannel equipped with a plasmonic nanoantenna on a microfluidic device for a revolutionary new way of sensing.

Exploiting direct imprint lithography, the team has fabricated multifunctional, multidimensional nanofluidic channels in a single step and in just a few minutes with no alignment necessary. They have also developed the technology to integrate plasmonic elements, specifically plasmonic nanoantennae consisting of gold-filled nanotriangles, also perfectly self-aligned with the nanochannels. Drilling four holes at the ends of the microchannels enables liquid access. The polymer device will then be bonded to a glass coverslip for characterisation.

Plasmonic nanoantennae are gaining a tremendous amount of interest, operating much like radio antennae but at higher frequencies. When light interacts with metal nanoparticles, in this case gold, it induces collective oscillations of the conduction electrons. These in turn can create useful effects. PLASBIORES researchers are exploiting the formation of high-intensity hot spots at the nanoparticle surface to detect single DNA molecules.

Researchers have tested both the nanochannels and the nanoantennae separately. The nanoantennae provided an amazing signal enhancement on the order of 104 when compared to a non-structured gold surface. Single DNA molecules were successfully fed into the nanochannels and stretched out via electrophoresis to a length 89 % of that predicted — one of the largest stretching factors in the literature for single molecules in nanochannels.

The preliminary results are extremely promising. This unique and portable device will have major impact on the field of medicine, particularly point-of-care applications. It will also enhance environmental monitoring and many other fields in which biological molecules are of interest.