Detection of morphine and opioids in fingernails: immunohistochemical analysis and confirmation with ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry

This study aimed to investigate the detection of morphine in fingernails from forensic autopsies using immunohistochemistry (IHC), with confirmation by ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS). A primary antibody specific to morphine and a secondary antibody conjugated to horseradish peroxidase (HRP) was used. IHC on specimens of Subjects A and B (both drug addicts) resulted in the detection of morphine on a cell layer of the nail plate matrix. UHPLC-HRMS and GC-MS analysis showed that Subject A had a morphine concentration of 0.35 ng/mg in the fingernail and 472 ng/mL in the blood, while Subject B reached 1.23 ng/mg in the fingernail and 360 ng/ml in the blood. Most of those matrices were positive for codeine, methadone, EDDP, and 6-MAM. The use of IHC in Subject C (a former addict) showed no positivity for morphine in the fingernail, while the UHPLC-HRMS analysis confirmed its absence in the fingernail and blood. Additionally, an analysis of the scalp or pubic hair of the subjects was carried out using UHPLC-HRMS. The results suggest that IHC can be used to establish the site of accumulation of morphine in the nail matrix; for postmortem diagnosis; and that basic substances can be detected by UHPLC-HRMS. There are no previous studies on the use of IHC as a technique for forensic purposes in unconventional matrices, such as nails.