Micro-Sampling of Biological Tissue by Substrate-Mediated Laser Ablation: Toward Spatially-Resolved Proteomics at µm Scale
Abstract
Since the pioneering works of R. Caprioli in 1997, conventional mass spectrometry imaging (MSI) tools resulting
from Matrix-Assisted Laser Desorption/Ionization (MALDI) is widely used in various fields of -omics research (e.g.
lipidomics, proteomics, metabolomics...) because of its high spatial resolution and detection sensitivity. However, due
to the inherent complexity of the biological tissue it has certain limitations. One of the major drawbacks of the
technique is the limited capability of detecting and identifying minority compounds, notably proteins, directly on
tissue. Various strategies have been developed to overcome this issue. All require a micro-sampling step. Different
techniques have been specifically applied for this purpose like laser capture microdissection, liquid extraction or
parafilm assisted microdissection (PAM) [1]. However, the spatial resolution of these techniques is typically about
1mm and it is a real challenge to develop a tool with a sufficient yield to reduce the size of the sampled area.
We have explored the potential of a new micro-sampling technique based on an indirect substrate-mediated laser
ablation (SMLA) mechanism which permits the use of low deposited energy while preserving the biological content.
Taking advantage of this effect, analyses of micro-sampled tissue was performed, demonstrating the identification of
significant number of proteins [2]. Furthermore, SMLA was confronted to PAM in order to show its efficiency. Our
objective is now to increase the spatial resolution up to µm scale. This requires the characterization of the SMLA
mechanism to optimize the ablation yields. We present here recent advances in this field including systematic studies
taking into account the physico-chemical parameters of various substrates who highlights the role of the ablation of
the substrate in the SMLA mechanism [3] and the study of the plume dynamic by shadowgraphy used to improve the
capture yield of the ablated material.