NaTOS · Nanoscale Thermo Optical Sensing

Nanoscale Thermo Optical Sensing

Proteins, the engines that drive and regulate almost all processes in living organisms, come in many variations of shape and size. Nonetheless they are all made from a limited set of building blocks. In consequence their identification is difficult. Current identification techniques are all either marker based - meaning a spectroscopically or otherwise reliably identifiable label molecule must be tethered to the protein - or use substrates carrying special receptors that catch only the proteins of interest. Both routes involve time and personnel intensive chemical protocols and require precise knowledge of the analyte’s structure. Moreover, these methods do not recognize non-targeted molecules - a severe obstacle for the study of metabolic processes without a priori knowledge of all involved molecular species. This action aims to develop a novel biosensor, that does not rely on markers or analyte immobilization. It instead identifies free unmarked proteins by measuring the changes of their diffusive speed when exposed to a tuneable temperature gradient – the protein’s thermophoretic fingerprint. This sensor will be based on single plasmonic antennas that act as nanoscale detector and nanoscale heaters: Plasmonic antennas absorb and scatter light efficiently if excited with a frequency close to their resonance. This enables the creation of steep temperature gradients over a distances of few nanometers. Such gradients alter the diffusive speed and the local concentration of the proteins – a physical effect called thermophoresis. Both the average speed and the number of proteins in close proximity to the plasmonic antenna can be quantified by observing the changes in its scattering intensity induced by the proteins’ movement. Since thermophoresis is shape and charge dependent even proteins of equal size and mass can be discerned via their thermophoretic fingerprints. The fundamental technical basis of the action has been established. Namely the detection of small freely diffusing analyte's with diameters on the nanometer scale. It turned out that the device can recognize analytes on a single entity basis and such was more sensitive than initially planned.

Data: CORDIS, © European Union