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Title: Developing scanning ion conductance microscopy (SICM) for nanoscale force and topographic characterisation of live cells
Author: Johnson, N. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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Scanning Ion Conductance Microscopy (SICM) uses a scanning nanopipette to obtain high resolution, non-contact images of soft surfaces such as live cells under physiologically relevant conditions. Ion current flowing through the tip aperture is used as a feedback control signal to maintain a constant tip-sample separation. This thesis details recent efforts to improve the mechanical stability of the instrument, develop new software algorithms for scanning control, and create new techniques for mechanical characterization. These advances have led to reduced imaging time, improved spatial resolution, and the ability to image increasingly challenging samples. In addition to improved imaging, SICM was extended to controllably apply and release pressure near a surface. A known hydrostatic pressure can be generated at the pipette tip and the sample’s response followed using SICM distance feedback control. In this fashion the cells were deformed, the pressure released, and their response to zero applied pressure monitored. This new pressure application method was first automated and calibrated on oil droplets. It was then used to investigate the mechanical properties of live osteoblasts and the contribution of the underlying cell cytoskeleton to the measured response. A second pressure application technique was developed to improve the lateral resolution. At very small pipette-sample separations (less than the typical SICM control distance) the micropipette exerts a force due to the high electric field at the pipette tip. This force can be used to deform cells with >100 nm lateral resolution and can rapidly map the mechanical characteristics. In fact, it was possible to observe the cytoskeleton beneath the osteoblast cell membrane. To conclude, cellular topography and dynamics studies were conducted on live T-cells, sperm cells, and viral entry events. These experiments further demonstrated the capabilities of the improved SICM and the new pressure application techniques.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available