We asked Sergey Alexandrov, lead author of the STARSTEM publication Spatial frequency domain correlation mapping optical coherence tomography for nanoscale structural characterization about their recent Applied Physics Letters Journal article. Here is Sergey’s interview:

What were you aiming to find out in this publication?

Development of the new technologies for visualization of the sub-micron structure with nanoscale sensitivity to structural changes.

Why does this research need to be done?

For both the fundamental study of biological processes and early diagnosis of pathological processes, information about nanoscale tissue structure is crucial. Furthermore, it is becoming increasingly evident that 2D biology often does not translate into the real 3D situation. The research is motivated by current needs of optical science and technology for biomedical and other applications and is devoted to an important fundamental problem: investigation of new possibilities to detect the structural changes within 3D objects without labels by providing nanoscale sensitivity to structural alterations. One of the most appreciated and fast developed techniques for 3D biomedical imaging is optical coherence tomography (OCT), but resolution and sensitivity to structural alterations is typically limited to microscale. Proposed approach permits to dramatically improve sensitivity to structural changes, up to nanoscale, using just single frame.

Describe the methods chosen.

Label free non-contact optical imaging technologies have been developed. The ability to detect nano-scale structural changes has been demonstrated using different phantoms and human skin in vivo. Healthy volunteer was involved in this study.

What is the intended impact and how can others use the research?

According to the STARSTEM project these techniques will be used to detect changes in cell morphologies and extracellular vesicles at the nanometer scale; to investigate the potential of imaging of extracellular vesicle-mediated disease responses; for nanosensitive detection of tissue responses to disease.

What are the next steps?

  • Experiments to perform nanosensitive detection of tissue responses to disease.
  • Further development of these optical technologies.


sf-cmOCT images of the human finger in vivo: (a) before and (b) during occlusion, with examples of the axial spatial frequency profiles between consecutive frames. (c) Frequency distribution of correlation coefficients within the yellow region of interest before (red) and during (green) occlusion with the corresponding mean values.

Related research.

  1. Alexandrov, P. M. McNamara, N. Das, Y. Zhou, G. Lynch, J. Hogan, and M. Leahy “Spatial frequency domain correlation mapping optical coherence tomography for nanoscale structural characterization”. Appl. Phys. Lett. 2019, v.115, N12, 121105. https://doi.org/10.1063/1.5110459.
  2. Alexandrov, N. Das, J. McGrath, P. Owens, C. J. R. Sheppard, F. Boccafoschi, C. Giannini, T. Sibillano, H. Subhash, and M. Leahy. “Label free ultra-sensitive imaging with sub-diffraction spatial resolution”. 21st International Conference on Transparent Optical Networks ICTON, July 9-13, 2019 Angers, France, Invited, IEEE-Xplore Proceedings 2019 Fr.A6.3, pp.1-4. https://ieeexplore.ieee.org/xpl/conhome/1000766/all-proceedings

You can find out more about the publication and download the full text over on our publications page.