Non-invasive Raman biomarkers for monitoring fentanyl-induced neurotoxicity in human microglia

Abstract

Fentanyl is a highly potent analgesic, but its abuse can result in physical dependency and addiction, which increases the risk for overdose and death. Fentanyl’s higher lipophilicity results in its increased accumulation in the brain, leading to increased central nervous system (CNS) cytotoxicity and microglial dysfunction, and, ultimately, cell apoptosis/cell death, which causes significant neurocognitive impairment in patients who abuse fentanyl. Monitoring cell apoptosis in human microglia non-invasively using Raman spectral analysis allows detection of chemical changes/protein content within microglia during various stages of cell apoptosis. The goal of this study was to examine the fentanyl-induced spectral changes using Raman spectroscopy, to detect underlying biochemical changes in microglia undergoing apoptosis. Our results indicate that fentanyl treatment of microglia caused significant changes in several lipid moieties, which were attributed to a pro-inflammatory response and increased oxidative stress, as reflected by increased levels of reactive oxygen species, singlet oxygen ( ¹ O ₂ ), and decreased intracellular Ca ²⁺ in response to higher fentanyl concentration. Fentanyl-induced increase in mitochondrial membrane potential signals increased cellular stress, culminating in impending apoptosis. The ability to non-invasively monitor the fentanyl-induced apoptosis in human microglia using Raman spectral analysis allows observation of chemical changes within the microglia and helps highlight mechanisms that underlie fentanyl-induced neurotoxicity.