Spectral oscillations in backscattering of light from a biological cell

TL;DR

This paper investigates the origins of beat-like signals in light backscattering from biological cells, identifying the cell nucleus as a primary source and using Mie theory simulations to analyze the spectral oscillations.

Contribution

It demonstrates that spectral oscillations in backscattering are caused by cellular structures like the nucleus and organelles, with simulations confirming the beat-like patterns.

Findings

Backscattering exhibits beat-like spectral patterns.

High frequency oscillations are due to single scattering.

Multiple scattering contributes to slowly varying oscillations.

Abstract

Possible origins of the experimentally observed beat-like signal in elastic light backscattering from an epithelial biological cell are identified. The source of the beat-like signal is most likely the cellular nucleus, which is a spheroidal particle with an optically sharp edge, low relative index of refraction, and a size parameter in the resonant range; another possible source is an agglomeration of cell organelles of a similar size. Using Mie theory computer simulations for a dielectric sphere with biological nucleus-like parameters, we have shown that backscattering as a function of size parameter has a beat-like pattern. The high frequency periodic oscillation is the single scattering contribution, while multiple scattering events give slowly varying oscillatory contributions. With increasing contrast, the backscattering signal changes from a pure sinusoid to that of a beat signal. The beat-like pattern in scattering from a low contrast particle does not depend on any particular features of the sphere; a similar pattern is observable in scattering from star-like non-spherical objects with a sharp optical contrast and smooth shape; in this case, the high frequency of oscillations depends on the object orientation relative to incident light