Mass spectrometry traditionally requires material to be extracted in bulk from samples, at the expense of information about the complex spatial relationships of the individual components. However, to understand physiology at the ‘micro/nano’ scale, a more sophisticated approach is essential. NanoSIMS (nanoscale secondary ion mass spectrometry) is an ion microprobe which combines high spatial resolution (50-100 nm) and high sensitivity. NanoSIMS is particularly well-suited to isotopic and elemental imaging, allowing the simultaneous detection of seven ion species with high mass resolution.
We will describe how combining stable isotope labelling with NanoSIMS allows us to directly visualise the distribution of labelled components within an experimental system, without changing the system's chemical nature.For example, 15N and 13C labels are commonly used in biological systems (nutrient tracking, drug delivery), however, there is potential for addition of any other stable isotope of interest (e.g. 34S,41K, 44Ca, 57Fe). Furthermore, isotopic labels can be conjugated to specific antibodies to identify proteins, or to oligonucleotides to identify specific species of bacteria.
NanoSIMS also allows interrogation of systems without addition of isotope tracers. For microbial ecology applications, this may be of use to investigate spatial partioning of more exotic elements – including those at very low concentrations. We anticipate applications in contaminated land rehabilitation as well as bio-prospecting.