Tropical Journal of Pharmaceutical Research

Original Research Article | OPEN ACCESS

Microscopic imaging ellipsometry of submicron-scale bacterial cells

Mai Ibrahim Khaleel^1-3, Yu-Da Chen^1-3, Ching-Hang Chien^1-3, Yia-Chung Chang¹

¹Research Center for Applied Sciences, Academia Sinica, Taipei, 11529; ²Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Tsing Hua University; ³Department of Engineering and System Science, National Tsing Hua University, Hsinchu, 30013, Taiwan.

For correspondence:- Yia-Chung Chang Email: yiachang@gate.sinica.edu.tw

Accepted: 23 October 2017 Published: 30 November 2017

Citation: Khaleel MI, Chen Y, Chien C, Chang Y. Microscopic imaging ellipsometry of submicron-scale bacterial cells. Trop J Pharm Res 2017; 16(11):2713-2725 doi: 10.4314/tjpr.v16i11.20

© 2017 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..

Abstract

Purpose: To demonstrate the power of microscopic imaging ellipsometry (MIE) to identify submicron-scale bacterial cells and track their surface topology variation.

Methods: Microscopic imaging ellipsometry with rotating compensator configuration was used to measure the ellipsometric spectra for dried submicron-scale Streptococcus mutans cells cultured on gold (Au) film for wavelengths (λ) in the visible range (λ = 490 – 710) nm. The ellipsometry characteristic images, Psi (Ψ), Delta (Δ), p- and s- polarized reflectance (Ip and Is), and reflectance difference image (RDI) for a chain of two and four dried cells, were collected for a series of different objective planes (near the focal plane) for λ = 600nm.

Results: The results show that by adjusting the position of objective planes (POP) to achieve the best focus, it was possible to identify cells smaller than 1 µm and observe their diffraction patterns in Ψ and Δ images. It was observed that Δ spectra and images were particularly sensitive to POP, while Ψ spectra and images for dried S. mutans cells were rather insensitive to POP.

Conclusion: MIE is a sensitive non-optical technique that can be used to image biological systems without the need for labeling of molecules

Keywords: Objective plane, Imaging ellipsometry, Submicron-scale bacterial cells, Streptococcus mutans, Biosensing, Focal plane