History of hair analysis by mass spectrometry imaging

In conventional forensic science, blood and urine have been used for drug testing. However, hair has recently attracted attention as a new source of biological information in this milieu. Drugs and biomolecules taken up by the hair from the capillaries of the scalp are retained in the hair without being degraded by enzymes, migrating toward the tip of the hair as the hair grows at a constant rate. As a result, drug residues are stored in the hair in chronological order. In recent years, mass spectrometry imaging (MSI) has been developed to visualize the history of drug use in hair samples, making use of this unique property. Advances in this drug testing technique are expected to create a powerful deterrent for drug abuse and doping. In this paper, we introduce the history of hair research using MSI and the evolution of instruments, matrices, and methods.