I am interested in the potential of interferometric scattering microscopy to uncover the hidden dynamics of biology at the nanoscale, in particular, in exploring what we can learn about membrane organization and cellular function. I am also excited to develop nanofluidic tools to facilitate novel investigations into single-cell biology via advanced optical microscopies.
High-precision protein-tracking with interferometric scattering microscopy
Richard W. Taylor, Cornelia Holler, Reza Gholami Mahmoodabadi, Michelle Küppers, Houman Mirzaalian Dastjerdi, Vasily Zaburdaev, Alexandra Schambony, Vahid Sandoghdar
Frontiers in Cell and Developmental Biology
The mobility of proteins and lipids within the cell, sculpted oftentimes by the organisation of the membrane, reveals a great wealth of information on the function and interaction of these molecules as well as the membrane itself. Single particle tracking has proven to be a vital tool to study the mobility of individual molecules and unravel details of their behaviour. Interferometric scattering (iSCAT) microscopy is an emerging technique well suited for visualising the diffusion of gold nanoparticle-labelled membrane proteins to a spatial and temporal resolution beyond the means of traditional fluorescent labels. We discuss the applicability of interferometric single particle tracking (iSPT) microscopy to investigate the minutia in the motion of a protein through measurements visualising the mobility of the epidermal growth factor receptor in various biological scenarios on the live cell.
Point spread function in interferometric scattering microscopy (iSCAT). Part I: aberrations in defocusing and axial localization
Reza Gholami Mahmoodabadi, Richard W. Taylor, Martin Kaller, Susann Spindler, Mahdi Mazaheri, Kiarash Kasaian, Vahid Sandoghdar
Interferometric scattering (iSCAT) microscopy is an emerging label-free technique optimized for the sensitive detection of nano-matter. Previous iSCAT studies have approximated the point spread function in iSCAT by a Gaussian intensity distribution. However, recent efforts to track the mobility of nanoparticles in challenging speckle environments and over extended axial ranges has necessitated a quantitative description of the interferometric point spread function (iPSF). We present a robust vectorial diffraction model for the iPSF in tandem with experimental measurements and rigorous FDTD simulations. We examine the iPSF under various imaging scenarios to understand how aberrations due to the experimental configuration encode information about the nanoparticle. We show that the lateral shape of the iPSF can be used to achieve nanometric three-dimensional localization over an extended axial range on the order of 10 µm either by means of a fit to an analytical model or calibration-free unsupervised machine learning. Our results have immediate implications for three-dimensional single particle tracking in complex scattering media.
Interferometric Scattering (iSCAT) Microscopy & Related Techniques
Richard W. Taylor, Vahid Sandoghdar
Label-Free Super-Resolution Microscopy
Interferometric scattering (iSCAT) microscopy is a powerful tool for label-free sensitive detection and imaging of nanoparticles to high spatiotemporal resolution. As it was born out of detection principles central to conventional microscopy, we begin by surveying the historical development of the microscope to examine how the exciting possibility for interferometric scattering microscopy with sensitivities sufficient to observe single molecules has become a reality. We discuss the theory of interferometric detection and also issues relevant to achieving a high detection sensitivity and speed. A showcase of numerous applications and avenues of novel research across various disciplines that iSCAT microscopy has opened up is also presented.
Interferometric Scattering Microscopy: Seeing Single Nanoparticles and Molecules via Rayleigh Scattering
Fluorescence microscopy has been the workhorse for investigating optical phenomena at the nanometer scale but this approach confronts several fundamental limits. As a result, there have been a growing number of activities toward the development of fluorescent-free imaging methods. In this Mini Review, we demonstrate that elastic scattering, the most ubiquitous and oldest optical contrast mechanism, offers excellent opportunities for sensitive detection and imaging of nanoparticles and molecules at very high spatiotemporal resolution. We present interferometric scattering (iSCAT) microscopy as the method of choice, explain its theoretical foundation, discuss its experimental nuances, elaborate on its deep connection to bright-field imaging and other established microscopies, and discuss its promise as well as challenges. A showcase of numerous applications and avenues made possible by iSCAT demonstrates its rapidly growing impact on various disciplines concerned with nanoscopic phenomena.
Interferometric scattering microscopy reveals microsecond nanoscopic protein motion on a live cell membrane
Richard W. Taylor, Reza Gholami Mahmoodabadi, Verena Rauschenberger, Andreas Giessl, Alexandra Schambony, Vahid Sandoghdar
Much of the biological functions of a cell are dictated by the intricate motion of proteins within its membrane over a spatial range of nanometers to tens of micrometers and time intervals of microseconds to minutes. While this rich parameter space is not accessible to fluorescence microscopy, it can be within reach of interferometric scattering (iSCAT) particle tracking. Being sensitive even to single unlabeled proteins, however, iSCAT is easily accompanied by a large speckle-like background, which poses a substantial challenge for its application to cellular imaging. Here, we show that these difficulties can be overcome and demonstrate tracking of transmembrane epidermal growth factor receptors (EGFR) with nanometer precision in all three dimensions at up to microsecond speeds and tens of minutes duration. We provide unprecedented examples of nanoscale motion and confinement in ubiquitous processes such as diffusion in the plasma membrane, transport on filopodia, and endocytosis.
Visualization of lipids and proteins at high spatial and temporal
resolution via interferometric scattering (iSCAT) microscopy
Susann Spindler, Jens Ehrig, Katharina König, Tristan Nowak, Marek Piliarik, Hannah E. Stein, Richard W. Taylor, Elisabeth Garanger, Sebastien Lecommandoux, et al.
Journal of Physics D - Applied Physics
Microscopy based on the interferometric detection of light scattered from nanoparticles (iSCAT) was introduced in our laboratory more than a decade ago. In this work, we present various capabilities of iSCAT for biological studies by discussing a selection of our recent results. In particular, we show tracking of lipid molecules in supported lipid bilayers (SLBs), tracking of gold nanoparticles with diameters as small as 5 nm and at frame rates close to 1 MHz, 3D tracking of Tat peptide-coated nanoparticles on giant unilamellar vesicles (GUVs), imaging the formation of lipid bilayers, sensing single unlabelled proteins and tracking their motion under electric fields, as well as challenges of studying live cell membranes. These studies set the ground for future quantitative research on dynamic biophysical processes at the nanometer scale.
I was born in the United Kingdom where I completed my graduate studies, gaining a Masters (1st, Hons) in Physics from the University of Birmingham in 2009. Thereafter I completed my doctoral studies in 2013 in the Nanophotonics group of Prof. Jeremy J. Baumberg at the University of Cambridge. The subject of my doctoral work was ‘On the sub-nm plasmonics of gold nanoparticles clusters’, which led to a patent for ‘Plasmonic junctions for surface-enhanced spectroscopy’. In 2013 I joined the group of Prof. Sandoghdar to develop interferometric scattering microscopy for application to live cells, becoming a Humboldt Postdoctoral fellow in 2015. In addition to research activities, I also enjoy aiding efforts for scientific outreach, and I also co-organised the first international workshop on interferometric scattering microscopy in 2020.
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