Studies
on complex biological phenomena often combine two or more
imaging techniques to collect high-quality comprehensive data directly
in situ
, preserving the biological context. Mass spectrometry
imaging (MSI) and vibrational spectroscopy imaging (VSI) complement
each other in terms of spatial resolution and molecular information.
In the past decade, several combinations of such multimodal strategies
arose in research fields as diverse as microbiology, cancer, and forensics,
overcoming many challenges toward the unification of these techniques.
Here we focus on presenting the advantages and challenges of multimodal
imaging from the point of view of studying biological samples as well
as giving a perspective on the upcoming trends regarding this topic.
The latest efforts in the field are discussed, highlighting the purpose
of the technique for clinical applications.
Imaging techniques based on mass spectrometry or spectroscopy methods inform in situ about the chemical composition of biological tissues or organisms, but they are sometimes limited by their specificity, sensitivity, or spatial resolution. Multimodal imaging addresses these limitations by combining several imaging modalities; however, measuring the same sample with the same preparation using multiple imaging techniques is still uncommon due to the incompatibility between substrates, sample preparation protocols, and data formats. We present a multimodal imaging approach that employs a gold-coated nanostructured silicon substrate to couple surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) and surface-enhanced Raman spectroscopy (SERS). Our approach integrates both imaging modalities by using the same substrate, sample preparation, and data analysis software on the same sample, allowing the coregistration of both images. We transferred molecules from clean fingertips and fingertips covered with plasticine modeling clay onto our nanostructure and analyzed their chemical composition and distribution by SALDI-MS and SERS. Multimodal analysis located the traces of plasticine on fingermarks and provided chemical information on the composition of the clay. Our multimodal approach effectively combines the advantages of mass spectrometry and vibrational spectroscopy with the signal enhancing abilities of our nanostructured substrate.
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