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The micro-ion beam is speeding up

A new device at the PTB’s micro-ion beam facility allows irradiating several hundred cells individually per second. The procedure is thus about ten times faster than previously. It can now be efficiently used to investigate radiation damage mechanisms in individual cells. Understanding the damage mechanisms is important for dosimetry in the low-dose range.

Measured activation of protein p53 in cell nuclei as a measure of the radiation damage: red means high, green: low activation. The cells marked with an X had been irradiated.

The radiation experiments on living cells are performed in cooperation with institutes in the field of radiobiological research. An important subject of the investigations is the so-called bystander effect, which refers to the occurrence of a measurable effect on a non-radiated cell when a neighbouring cell was irradiated.

To make irradiations faster and more precise an electrostatic deflection unit has been added to PTB’s micro-ion beam facility. The unit can deflect the beam within a millisecond with micrometer accuracy. Time-consuming mechanical positioning of each individual cell can thus be omitted. Now it is possible to irradiate several hundred cells per second individually. Including all preparative steps, the experimental throughput could be increased to up to 50 000 cells per hour, i.e. it could be increased tenfold. The position accuracy could also be slightly improved: Deflection of the beam now only shows an uncertainty of approx. 0.5 µm, half the amount hitherto achieved with mechanical positioning.

The second important contribution to an increase in efficiency was the extension of the cell recognition software. With the aid of a newly developed module for the quantification of protein colouring one can now investigate which processes take place in a cell at a given moment in time. There are, for example, proteins which are required to repair DNA inherent in the cell or which indicate the beginning of the programmed cell death (apaptosis). To investigate the bystander effect it is important that the radiated and non-radiated cells are found on the same carrier (by using the position data stored and reference positions). Then, activation of the protein p53, – a fast indicator of a stress condition of the cell –, is measured with a CCD camera. Correlation with the radiation information then furnishes information about the communication path of the bystander effect.