Synthetic cannabinoids are a class of new psychoactive substances which can bind to CB₁ and CB₂ receptors in the human body with hundreds of times stronger binding affinity than tetrahydrocannabinol (THC) and cannabidiol (CBD), the active components of plant cannabis. Their widespread abuse has raised significant health and social concerns due to severe toxicity and addiction.

Currently, the detection methods of synthetic cannabinoids primarily rely on large-scale analytical instruments such as high-performance liquid chromatography-mass spectrometry (HPLC-MS), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). Compared to these instrumental methods, visualized detection techniques (such as colorimetry and fluorescence) offer advantages in sensitivity, response time, and ease of outcome interpretation, making them more suitable for on-site detection. However, there is currently no available visualized detection method for MDMB-CA type synthetic cannabinoids, remaining a significant research gap in this area.

To address this challenge, Xinjiang Key Laboratory of Trace Chemical Substances Sensing, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, has developed an innovative zinc(II)-enhanced excimer fluorescence probe. Upon the conjugation modulation and metal-bridging strategy, the probe achieved highly specific recognition of MDMB-CA type synthetic cannabinoids based on multiple non-covalent interactions. Through theoretical analysis, the team elucidated the optical response mechanism, revealing that the ratiometric fluorescence emission was due to the transformation from the excimer emission to fluorescence resonance energy transfer (FRET)-based emission.

Experimental results demonstrate that the probe can specifically detect multiple MDMB-CA-type synthetic cannabinoids within 5 seconds and are not affected by the presence of 14 potential interfering substances. Furthermore, the team develop a portable detection chip by incorporating both extraction and enrichment functions, enabling accurate detection of synthetic cannabinoids in complex sample matrices such as e-cigarette oil and tobacco leaves. Additionally, the probe can be used to detect synthetic cannabinoids and the corresponding metabolites in urine samples.

This study establishes a novel excimer fluorescence probe based on the conjugation modulation and metal-bridging strategy, providing a new approach for the detection and identification of synthetic cannabinoids. Beyond advancing synthetic cannabinoid detection, the research also contributes to the development of sensing probes and offers new insights for accurately detecting structurally diverse and weakly reactive chemical substances. This progress was published in Angewandte Chemie International Edition entitled as "Zinc(II)-Enhanced Excimer Probe for Recognition of MDMB-CA Synthetic Cannabinoids." This work was supported by the Key Research and Development Program of Xinjiang and Tianshan Innovation Team Plan.

Figure：Zinc-Enhanced Excimer Probe for Synthetic Cannabinoid Detection

(Image by the group of Prof. Dou Xincun)