We report a new laser ablation technique employing a pulsed 2 940 nm laser and a simple ablation cell for digital mapping biomarkers in tissues using metal nanoparticle tags. Unlike the conventional laser ablation systems, where nanoparticles are ablated, we can desorb intact nanoparticles and count them. The method is demonstrated by monitoring proliferating cells in 3D aggregates of human colorectal carcinoma cells. Precise counting of the tags in each pixel generates sharp distribution maps of a proliferation biomarker in the tissue. A mass spectrometer detects up to 83% nanoparticles of a selected element with a single particle detection limit. Advantageously, the desorption of nanoparticles from regions outside the tissue is strongly suppressed.
The authors gratefully acknowledge the financial support of the Czech Science Foundation (18-16583S and 21-12262S), Masaryk University, Brno, Czech Republic (MUNI/A/1325/2021), European Regional Development Fund - Project ENOCH (CZ.02.1.01/0.0/16_019/0000868) and the project National Institute for Cancer Research (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the European Union - Next Generation EU.
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