Activity-Based Concept to Screen Biological Matrices for Opiates and (Synthetic) Opioids

Abstract

Abstract BACKGROUND Detection of new highly potent synthetic opioids is challenging as new compounds enter the market. Here we present a novel screening method for the detection of opiates and (synthetic) opioids based on their activity. METHODS A cell-based system was set up in which activation of the μ-opioid receptor (MOR) led to recruitment of β-arrestin 2, resulting in functional complementation of a split NanoLuc luciferase and allowing readout via bioluminescence. Assay performance was evaluated on 107 postmortem blood samples. Blood (500 μL) was extracted via solid-phase extraction. Following evaporation and reconstitution in 100 μL of Opti-MEM® I, 20 μL was analyzed in the bioassay. RESULTS In 8 samples containing synthetic opioids, in which no positive signal was obtained in the bioassay, quadrupole time-of-flight mass spectrometry revealed the MOR antagonist naloxone, which can prevent receptor activation. Hence, further evaluation did not include these samples. For U-47700 (74.5–547 ng/mL) and furanyl fentanyl (<1–38.8 ng/mL), detection was 100% (8/8) for U-47700 and 95% (21/22) for furanyl fentanyl. An analytical specificity of 93% (55/59) was obtained for the opioid negatives. From an additional 10 samples found to contain other opioids, 5 were correctly scored positive. Nondetection in 5 cases could be explained by very low concentrations (<1 ng/mL alfentanil/sufentanil) or presence of inactive enantiomers. CONCLUSIONS The MOR reporter assay allows rapid identification of opioid activity in blood. Although the cooccurrence of opioid antagonists is currently a limitation, the bioassay's high detection capability, specificity, and untargeted nature may render it a useful first-line screening tool to investigate potential opioid intoxications.