Non-disruptive Supercontinuum based scattering analyses of cartilage and collagen before and after apoptosis and necrosis

Abstract

We demonstrate a method to determine the angular- and spectral-resolved scattering properties in the second optical window (1100 nm to 1350 nm) which enabled the characterization of biological nano- and microscaled cell structures. The nanosecond pulses of a spectrally filtered IR enhanced supercontinuum (SC) light source were captured time-resolved to depress background and minimize disruptive effects of the biological cells. The scattering characteristics of biological nano- and micro-scaled cell structures were recorded spectrally- and angle-resolved, the scattered portion of the light after the sample was recorded in a time-resolved manner at defined angles and wavelength. A spectrally filtered and collimated SC light source was used. The scattering results of cellular structures at defined wavelengths were compared to calculations treating the structures as ideal spherical particles. The scattering characteristics of a monolayer of human chondrocytes and mouse fibroblast cells were measured in a standard cell culture plate. Because of the size and distribution of the scattering structures, Mi scattering was assumed and analyzed using a Fourier transform-based approach. The final result was the development of a contamination-free method to study pathological changes in cell cultures, apoptosis or necrosis. In order to record the state of the cells without losing experimental information, the Principal Component Analysis (PCA) method was applied in addition to Fourier analysis, which allows the dimensionality of complex data to be reduced. The method was investigated to evaluate it for an automated acquisition of cell states. The system was tested to detect structural changes of human chondrocytes and L292 mouse fibroblasts before and after poisoning with staurosporin and Triton X100.