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Electron Microscopy, Structural Analysis, Diffraction, Microscopy, Microfabrication
Abstract:
One of the biggest challenges in life sciences is to investigate chemical and biological reactions as they occur under natural conditions with sufficient spatiotemporal resolution to fully reveal the structure-function correlation. As a more general aspect in science, the aim has been to watch atomic motions as they occur. In biochemistry, natural environment refers to solution. An ultimate method to be implemented for this purpose is lacking for electrons mainly due to the difficulties in sample preparation and probe source design.
In this thesis, we focused on improving sample preparation methods for conventional transmission electron microscopy (CTEM) and femtosecond electron diffraction (FED) in solution phase. Silicon based micro- and nanofabrication techniques are used to manufacture the current generation of nanofluidic cells and developed new methods to improve its effectiveness regarding the spatial resolution with electrons. This device is used for mainly two different systems with in-liquid TEM in this thesis work. We used a no-flow version of the nanofluidic cell first to investigate DNA hybridization dynamics in solution. Secondly, we imaged cancer cells in situ with TEM to investigate their morphology differentiation and oligonucleotide bound gold nanoparticle uptake for potential use in targeted drug delivery.
The behavior of the nanofluidic cell windows in high vacuum has been characterized for different window lateral dimensions using custom designed thin-film interferometer. We can measure the sample cell thickness interferometrically and associate it with the obtained spatial resolution in TEM. The obtained results have importance for developing more advanced nanofluidic cells for both real space imaging and diffraction with electrons.
The nanofluidic cell was used first time for electron diffraction from liquid water in the course of this thesis. We used a differential pressure method to control the thickness of the liquid layer in flow cell allowing in situ sample exchange.
The obtained results highlight the potential of the nanofluidic cell to study molecular dynamics in solution in femtosecond time scale with ultra-fast stroboscopic techniques.
