Scanning Ion Conductance Microscopy In Biological Studies

By Author: Park Systems
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Scanning ion conductance microscopes (SICM) enable high-resolution imaging of the sample surface. This type of microscope has been developed over two decades and has become useful in biological studies, which allows the surface topography of live cells. Scanning ion conductance microscopes have allowed researchers to localize proteins and ion channels in nanostructures at surface level.

The scanning ion conductance microscope was developed in 1989 at the University of California and is specifically designed for scanning nonconductive and soft materials, which are in an electrolyte solution, offering sum micrometer resolutions.
The microscope does not make direct contact with the sample, preserving the sample.

The scanning ion conductance microscope comprises a glass micropipette probe, a micromanipulator, and an amplifier. It also relies on an inverted microscope. The micropipette has a very small opening, which is filled with electrolytes and lowered into the bath which holds the sample. A voltage is then applied across the electrolyte through two electrodes, one in the bath and one inside the pipette. ...
... The ion conductance reduces as the tip of the micropipette gets close to the sample surface. Changes in the current are then measured by the amplifier, sending signals back to the controller, ensuring distance is maintained between the tip and sample surface. The tip follows the path of the surface topography, recording it and converting it to useful images.

In DC or direct current mode, there is continuous feedback as the pipette moves up and down, as it scans the sample surface. It does have poor sensitivity and resolution but does not cause damage to the sample. AC, or alternating current, the mode detects changes in the AC amplitude, controlling the feedback and modulating the tip distance from the sample surface. This is more sensitive than DC mode, allowing the probe to work a few nanometers from the surface of the sample. The AC ionic current can also be recorded during the scan. DC and AC modes are suitable for samples with smooth surfaces.

Approach retract scanning mode (ARS) is also called backstep. The hopping mode relies on the ion current being recorded as the pipette moves vertically, approaching and retracting from the surface of the sample. It does not rely on continuous feedback or raster scanning patterns. As the nanopipette gets close to the surface, it measures the height and selected imaging points, it retracts back to a safe distance before it moves to the next imaging point.

Electron microscopes make it possible to get high-resolution images on biological samples. The samples need to be fixed before any experiments are carried out. On the other hand, scanning ion conductance microscopes can reveal the dynamics and morphology of live cells at a nanometer scale. These microscopes can be used to monitor cell movement and volume, while delivering mechanical and chemical stimulations to cellular nanostructures and cells, even guiding cell growth.

Hopping mode or ARS has made it easier to research a range of samples, including hair cells in high resolution. The scanning ion conductance microscope has been used to investigate rental epithelial cells and more.

Scanning ion conductance microscopes combine simultaneous confocal fluorescent imaging, which allows researchers to study the relationship between cell surface membranes and proteins or nanoparticles in live and fixed samples. It performs at enough resolution on living cells to provide quality images. This type of microscopy has grown in biological studies.

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