Soft x-ray microimaging of whole wet cells

Citation

Gilbert, John Richard (1992) Soft x-ray microimaging of whole wet cells. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/prbh-5m08. https://resolver.caltech.edu/CaltechTHESIS:09072011-074554399

Abstract

We have produced images of whole wet tissue culture cells with the Stony Brook/BNL scanning transmission x-ray microscope (STXM). For fixed cells we have taken images at theoretical resolutions of ~50-75nm, and in practice have measured FWHM of features down to near lOOnm, without any exotic processing. For un-fixed (i.e., initially live) cells we have imaged with 100nm pixels and measured features down to 250nm.

We have developed, tested and used a wet cell for maintaining fixed or live cells on the STXM stage during imaging. Our design of the wet cell and the culture substrates that go with it make the STXM compatible with almost all standard systems for surface adherent tissue culture.

We have made measurements of radiation damage to STXM images due to the process of imaging. The damage we see in the STXM is mass loss from the sample. Our measurements give two principal results. One, the damage caused by absorption of radiation in fixed cells is a linear loss of x-ray absorbing mass with cumulative energy absorbed. Two, the measured value for the slope of that linear relationship is found to be α =-0.78±0.35 in units of [C atom equivalent absorption] per [eV absorbed]. These observations allow us to model several different aspects of the imaging of fixed tissue.

We have also produced a pair of carbon and oxygen mass distribution maps of a fixed chick fibroblast that shows some differences in composition among sub-micron features. This pair of maps is the result of taking x-ray transmission images at two different wavelengths, and decomposing that data into carbon and oxygen mass maps.

Our results on radiation damage suggest that the STXM may not be able to do much better than 50nm resolution on unprotected tissue culture cells. Both the ability of the STXM to measure the radiation hardness α and its ability to produce elemental decompositions suggest that the best feature of the STXM may be its ability to provide novel types of quantitative analysis of whole wet samples at high resolution.

Thesis Files