Chemical Images on Fingerprints Revealed with Mass Spectrometry

Andrea Carrà,Luigi Falciola,Lavinia Morosi,Enrico Davoli,Giuseppe Cappelletti

doi:10.3390/app11125624

Abstract

Commercially available UV-adsorbent TiO2 nanoparticles were used to assist laser/desorption ionization in the course of matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Titanium nano-powders proved extremely stable and efficient for small molecule ionization, with negligible background noise in the low mass region (m/z < 500 Da). Validation steps were carried out, assessing detection limits and comparing the results to those of the established DESI/Orbitrap technique. The new analytical method was used to reveal the molecular distribution of endogenous (lipids) and exogenous (analgesics and antipyretics) compounds in latent finger marks (LFMs). The detection limits of endogenous fatty acids and small molecules such as caffeine were in the range of fmol/mm2 on LFMs. The technique separated overlapping latent finger marks, exploiting the differences in lipid expression of human skin. Finally, the method was used to prove contact between skin and objects contaminated by different substances, such as credit cards and paper clips, with chemical images that maintain the shape of the objects on the LFM.

Highlights

In recent decades, there have been many efforts to develop new analytical techniques for localizing and mapping trace compounds in biological samples
We developed a new method based on matrix-assisted laser desorption ionization (MALDI)-Mass spectrometry imaging (MSI), starting with commercially available TiO2 nanoparticles (Evonik P25)
All our experimental evidence indicated that commercially available P25 nanoparticles assist the ionization of small molecules in MSI experiments

Summary

Introduction

There have been many efforts to develop new analytical techniques for localizing and mapping trace compounds in biological samples. Mass spectrometry imaging (MSI) is one method of choice because it measures the chemical composition of a sample point by point. In 1967, Liebl [1] reported the first MSI experiment regarding the characterization of some inorganic materials. The combination of a laser probe with a time-of-flight (TOF) mass spectrometer was proposed by Hillenkamp et al [2], exploiting the potential of the technique for organic materials. Karas et al [3] and Tanaka et al [4] reported that some specific UV-adsorbent compounds (matrix) can assist laser ionization, leading to a more efficient and versatile

Methods

Results

Conclusion