Paper BI-TuM1
Gas Cluster Ion Beams for Improved Biological Imaging with ToF-SIMS

Tuesday, December 13, 2016, 8:00 am, Room Milo

The quest for improved molecular signal levels in imaging secondary ion mass spectrometry has been a long one. As the nature of the primary ion beam used to sputter the surface has a direct influence on the species detected there has been a long history of research in this area. The latest ion beam technology of SIMS is based on gas cluster ions, introduced by Matsuo and co-workers. These beams are routinely used for sample etching and cleaning in SIMS and XPS instruments but are not normally employed as analysis beams in SIMS instruments due to challenges associated with fast pulsing, focusing and low analyte ionisation efficiencies.

The use of a higher energy (40 keV) gas cluster ion beam (GCIB) on a J105 ToF-SIMS instrument (Ionoptika Ltd), where fast beam pulsing is not required for good spectral quality, offers great benefits for biological analysis.

Comparison of signal levels on rodent brain between the 40 keV GCIB and equivalent energy C₆₀ shows a 30-50× increase in secondary ion yield for intact lipids while spot sizes of approximately 2 µm have been achieved.

The application of this system for the imaging of animal and human tissue samples in cardiovascular and breast cancer research will be presented. Lipid changes following surgically induced infarction in mouse hearts have been imaged with distinct differences detected between the infarcted and healthy regions of the tissue along with specific lipid signals associated with the interface between the 2 regions. Breast cancer biopsy tissue has been imaged and the lipid distributions studied in the tumour and surrounding stroma. Changes in the abundance of lipids arising from modification of dietary fatty acids versus de novo synthesised lipids shed new light onto lipogenesis processes in the tumour microenvironment.