Comparison of Subcellular Nanoparticle Size Distributions Across Cell Types with Light Transmission Spectroscopy

The cellular cytoplasm is a complex environment with a wide breadth of both size and concentration of particles, making a comprehensive survey of the subcellular structures interesting and difficult. Using LTS, we measure optical extinction spectra over a wavelength range of ~220-1000 nm, then apply Mie Theory to obtain particle size distributions (PSD). We present improvements to previous spinach cell PSDs, as well as those of new cell types and a comparison of healthy and cancer cells. With a combination of advanced filtration and quantitative LTS (a method of obtaining the concentration directly from the magnitude of the absorption peaks in the extinction spectra), we have improved the measurement of particles <100 nm, allowing the accurate assessment of PSDs over a wide size range: from ~5 nm to 3000nm. These PSDs reveal a power law dependence of particle concentration, N(D), with diameter, D, where N(D) α D^-α across cell types. We discuss values obtained for α and an in-depth comparison to literature for studies of both isolated subcellular structures and PSDs of other natural systems. We discuss modeling the cell as a self-similar system of spheres on many size scales, with the goal to enrich our understanding of the fundamental nature of particle packing in the cytoplasm.