Auger architectomics

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The NanoSAM microscope

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Yeast cells viewed with the Auger-architectomics technique

Auger-architectomics

Auger-architectomics is a scientific technique that allows biologists, working in the field of nano-technology, to slice open the cells of living organisms in order to view and assess their internal workings. Using argon gas etching to open the cells, and an electron microscope to create a three-dimensional view, researchers can harness this technique to track how cells perform their functions. This is most importantly used to assess how cells react to medication, for instance in the field of cancer research.

It was first discovered in 2010 by Prof Lodewyk Kock and his team working in the biotechnology department at the University of the Free State in South Africa .

The technique was adapted from Nano Scanning Auger Microscopy (NanoSAM), used by physical scientists to study the surface structures of, for instance, semi-conductors, ie. metal and inanimate materials. The innovation developed by the University scientists was to adapt this nanotechnology to work also on biological samples and thereby better understand processes within living cells.

Originally designed to observe yeast cells in order to find out more about how they manufactured the gas that causes bread to rise, the scientists discovered that the process could also be used in observing other living cells. In 2012 the technique was successfully applied to human cell tissue.

History:

The project was started ab initio at the UFS by the Kock-Group in 1982, with the major inputs and breakthroughs occurring between 2007 and 2012. The initial aim was to explore novel lipid biochemical routes, thereby exposing lipids with unique functions in yeasts, and developing new taxonomic systems based on lipid composition. This naturally unfolded into the development of the anti-mitochondrial antifungal assay (3A system) where yeast pigmented sexual stages (sensors) are used as indicators to screen compounds for anti-mitochondrial activity. (Mitochondria are the cell’s main power producers, they provide the energy that powers the cell. Anti-mitochondrial activity is activity that destroys the power plant of a cell and allows it to die). Drugs aimed at selectively switching off the powerhouse of the cell, therefore, might find application in combating various diseases such as fungal infections and cancer. Auger-architectomics - which opens up individual cells in order to scan them - is a vital part of assessing the effectiveness of such drugs. It is crucial to be able to see inside a single cell in order to see if that single cell can be powered down with targeted treatment.

Using the experience that had been gained during the development of the 3A system since 1982, the UFS scientists felt there was a need to analyse the system in more detail. As a result, they adapted the nanotechnology used to scan the properties of metals in physics, and applied it to cells. The result was a combination of the three methods of Auger atom electron physics, electron microscopy and Argon etching - a nanotechnique new and unique to biology and medicine which had never before been attempted on biological material.

The main challenge in applying the technology to biological material was to ‘invent’ a sample preparation procedure that would ensure that the atom and 3D structure remained stable while Argon nano-etching occurred. During the NanoSAM SEM visualisation, an electron beam at 25kV is used instead of the normal 5kV SEM. Sample fixation and dehydration methods had to be developed and optimised to fit NanoSAM without creating sample distortions. Dehydration regimes based on alcohol extraction procedures were installed and optimized, while fixation using various fixatives was included. Electron conductivity of samples throughout Argon etching was assured by optimized gold sputtering.

The Kock Group at the University combined three methods: Auger atom electron physics coupled to scanning electron microscopy (SEM), added to Argon-etching of biological cell structure in order to create a new field of cell exploration. It exposed a new world in 3D and element composition architecture. Dubbed Auger-architectomics, it was used to expose and map structurally and chemically new cell inclusions, ie. gas bubbles (“lungs”) inside eukaryotic cells. This is an entirely new field of biological research and a new type of imaging nanotechnology.

How does Auger-architectomics work?

Firstly, the biological sample is plated with gold in order to stabilise the outer structure and make it electron conductive. (Gold has been found to have different properties on a nano-scale and it is capable of binding to biological material.) It is then scanned in SEM mode (i) and the surface visually enlarged. (ii) Auger atom electron physics are applied and selected areas on the sample surface beamed with electrons. The incident beam ejects an electron in the inner orbital of the atom leaving an open space. This is filled by an electron from an outer orbital by relaxation. Energy is released causing the ejection of an electron from the outer orbital. This electron is called the Auger electron. The amount of energy that is released is measured by Auger electron spectroscopy (AES) and used to identify the atom and its intensity. Similarly the surface area can be screened by an electron beam eventually yielding Auger electrons that are mapped showing the distribution of atoms in different colours covering a surface area of predetermined size (iii). The previously screened surface of the sample is etched with Argon at, for example, 27nm/min exposing a new surface of the sample that is then again analysed as described above. In this way a 3-dimensional image of the whole cell is visualised in SEM as well as element composition architecture.

Advancement of science:

This process in nanotechnology led to the discovery of gas bubbles inside yeasts. This is considered a paradigm shift since naked gas bubbles are not expected inside any type of cell due to structured water in the cytoplasm. This was exposed at a depth of 945 nm (after mining with Argon at 27 nm/min etching for 35 min) in a fluconazole treated bubble-like sensor of the yeast Nadsonia. Figure 2d (from ref. 1) shows a C:O intensity ratio of exactly C:O =1:2 indicating CO2 inside this bubble. This figure clearly shows a drastic decrease in carbon intensity as mining proceeds through the sensor thereby further mapping the bubble architecture, chemically. This observation played a crucial role in the discovery of gas bubbles in yeasts and to follow metal based nanomedicine in diseased cells. This is the only technology known at present that can accomplish this type of nano-analysis on biological material.

Use in medicine: Nano-technology developments in medicine allow micro-doses of drugs and therapies to be delivered directly to infected cells, instead of bombing cells wholesale and killing off healthy cells. Gold at a nano-level has the ability to bind to certain types of biological material, which means that certain types of cells can be targeted. The technique of Auger-architectomics may be used to map the success or otherwise of targeted drug delivery by analysing cells.