Correlography of randomly scattered surface plasmons for quantitative biology

Lead Research Organisation: Imperial College London
Department Name: Dept of Physics


Life is a highly complex system that, despite an ever-growing pool of research is still poorly understood. Advances in the life sciences, enabled by constant innovation in experimental techniques, fuel an increasingly higher quality of life through drug development, rapid diagnostics and improved healthcare. Fuller understanding of the science of life, however, requires the temporal dynamics of biological processes to be monitored and the characteristics of single molecule to be quantitatively analysed. Light is an invaluable tool in the quest to reach this goal. More recently, coupled electronic-optical oscillations in metal nanostructures and films, simply known as plasmons, have also played an increasingly important role, allowing stronger light-matter interactions and strong field confinement. "Plasmon speckle" patterns, which are strongly spatially fluctuating fields, arise when many plasmons randomly interfere with each other. Such speckle patterns can be formed at metal interfaces due to scattering from inherent surface roughness or bound nanoparticles. Through the cumulative effect of multiple interfering plasmons, plasmon speckle possesses an extreme sensitivity to the local environment and the scattering configuration, which is further enhanced when plasmons scatter many times.
This project will explore principles by which biosensing, i.e. detection of biomolecules, can be achieved by measuring changes in the plasmon speckle. For example, binding of individual biomolecules, can manifest as large step-like changes in the correlation of optical speckle patterns resulting from inelastic plasmon scattering. Moreover, dynamic biological processes, such as molecular reactions or conformational changes, cause plasmon speckle to fluctuate in time in a way that strongly depends on the molecular properties, interaction kinetics and local trapping forces, providing a powerful route to studying particle size, mobility and binding dynamics. The core focus of this project is thus to establish correlation based techniques, akin to dynamic light scattering, on a surface plasmon based sensor.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509486/1 30/09/2016 30/03/2022
1992728 Studentship EP/N509486/1 30/09/2017 29/09/2021 Joel Berk
Description Via the interaction of light with a metal surface, a light wave confined to the surface of the metal called a surface plasmon polariton can be formed. By studying the pattern of light scattered by rough metal surface features and an analyte particle near the surface, we have developed an algorithm to detect and track the analyte particle. We have verified the algorithm with simulations and it has been found to work in conditions where light is scattered once before leaving the metal surface. In addition, we have shown that the algorithm can be sensitive enough to detect/track small biomolecules such as single proteins or viruses. We are currently working on studying the situation where light is scattered many times before leaving the surface, and whether this regime is more sensitive than the single scattering case.
Exploitation Route It is hoped the methods we propose for tracking can be developed into an easily manufactured biosensor, similar to the widely used and commercially available SPR sensors, but with greater sensitivity down to the single molecule level and with the potential to track a molecule near the surface. In addition, the algorithms we have suggested may be able to be further generalised to retrieving information from a random light scattering environment, whether this be for biological studies and imaging, or other fields which use scattered light as a signal to study objects (for example atmospheric physics).
Sectors Agriculture, Food and Drink,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

Description Single particle tracking with SPP speckle 
Organisation Yonsei University
Country Korea, Republic of 
Sector Academic/University 
PI Contribution We provide theoretical model, numerical simulations, initial research idea and data analysis.
Collaborator Contribution Our partners are providing experimental measurements using their bespoke SPP setup.
Impact Research is still on-going. Initial data looks promising, but better data still currently needed.
Start Year 2019