Analytical figures of merit for a novel tissue imaging system
A novel laser-ablation sample introduction system has been developed for the Fluidigm® Helios™ mass cytometer to enable highly multiplexed imaging of biological samples. Herein, we report on the analytical figures of merit for this system using a slide, coated uniformly with a metal-doped PMMA film, as a test sample. The system is based on the use of a fifth harmonic Nd–YAG laser focused to a spot size of 1 micrometer or less. A fast wash-out ablation chamber provides resolution of individual plumes when operated at a 100 Hz or 200 Hz laser repetition frequency. The system exhibits a linear response to metal concentration in the sample over 4 orders of magnitude. The variation of signals generated for 1 micrometer diameter pixels is ≤15% RSD. Pixel-to-pixel sample contamination due to redeposition of the ablated material is approximately 0.6%. The variation of the ablated crater diameter with laser energy is also explored, demonstrating a linear behaviour over a limited range of laser energies.