Eur. Phys. J. Plus (2014) 129: 116
https://doi.org/10.1140/epjp/i2014-14116-1

Regular Article

Determination of the complex refractive index of cell cultures by reflectance spectrometry

¹ National Institute of Research and Development for Optoelectronics INOE 2000, Mǎgurele, Romania
² “Horia Hulubei” National Institute of Physics and Nuclear Engineering IFIN-HH, Mǎgurele, Romania
³ Physical Medicine and Balneoclimatology, National Institute of Rehabilitation, Bucharest, Romania

^* e-mail: antoninacalin@yahoo.com

Received: 26 February 2014
Accepted: 24 April 2014
Published online: 12 June 2014

Abstract

In this paper we propose a new approach to using reflectance spectrometry in connection with the Kramers-Kronig analysis for the determination of the complex refractive index of biological cells. Applying this procedure, the real and imaginary parts of the refractive index (refractive index and extinction coefficient) can be simultaneously determined. The accuracy of this procedure in the determination of the refractive index and extinction coefficient of culture media proved to be comparable with spectroscopic ellipsometry. Applying this procedure on the human umbilical vein endothelial cells (HUVEC), the results obtained from time-series measurements showed significant changes in the complex refractive index of cell cultures within 72h, the most important increases for both real and imaginary parts of the refractive index being recorded in the first 24h, when synthesis processes are happening. Thus, the analysis of the time-dependent changes in the complex refractive index provides information about the frequencies of the modifications that occur on both organizational structure and cells composition during the cell cycle. In conclusion, the combination of reflectance spectrometry with the Kramers-Kronig analysis is a feasible way to determine the complex refractive index of biological cells and to assess the events taking place during the cell cycle.