Tetrahydrocannabinol Sensing in Complex Biofluid with Portable Raman Spectrometer Using Diatomaceous SERS Substrates

Abstract

Using thin-layer chromatography in tandem with surface-enhanced Raman spectroscopy (TLC-SERS) and tetrahydrocannabinol (THC) sensing in complex biological fluids is successfully conducted with a portable Raman spectrometer. Both THC and THC metabolites are detected from the biofluid of marijuana-users as biomarkers for identifying cannabis exposure. In this article, ultra-sensitive SERS substrates based on diatomaceous earth integrated with gold nanoparticles (Au NPs) were employed to detect trace levels of cannabis biomarkers in saliva. Strong characteristic THC and THC metabolite SERS peaks at 1601 and 1681 cm−1 were obtained despite the moderate interference of biological molecules native to saliva. Urine samples were also analyzed, but they required TLC separation of THC from the urine sample to eliminate the strong influence of urea and other organic molecules. TLC separation of THC from the urine was performed by porous microfluidic channel devices using diatomaceous earth as the stationary phase. The experimental results showed clear separation between urea and THC, and strong THC SERS characteristic peaks. Principal component analysis (PCA) was used to analyze the SERS spectra collected from various THC samples. The spectra in the principal component space were well clustered for each sample type and share very similar scores in the main principal component (PC1), which can serve as the benchmark for THC sensing from complex SERS spectra. Therefore, we proved that portable Raman spectrometers can enable an on-site sensing capability using diatomaceous SERS substrates to detect THC in real biological solutions. This portable THC sensing technology will play pivotal roles in forensic analysis, medical diagnosis, and public health.

Methods in Raman spectroscopy for saliva studies – a review

“…Raman-saliva studies in illicit compounds show high sensitivity using SERS-based sensing, comfortably outperforming the 10 s ng/mL range cutoff for many illicit drugs as recommended by the US Substance Abuse and Mental Health Services Administration (SAMHSA). [146,147] Sivashanmugan et al [148] have analyzed saliva in a Raman study on cannabis users, acquiring samples 15 min after the established use. Similarly, in a study on methamphetamine, Qu et al [100] successfully acquire 20 saliva samples for SERS analysis from actual methamphetamine addicts from the Residential Drug Treatment Center of Beijing You-An Hospital, reporting discrimination between these and the saliva analysis of 20 non-addicted subjects.…”

Photonics of human saliva: potential optical methods for the screening of abnormal health conditions and infections

“…Trace level detection of THC from saliva was reported using hybrid plasmonic biosilica nanomaterials by depositing silver nanoparticles (Ag NPs) into diatom photonic, where the band at 1621 cm −1 due to the O-C=O stretching in THC, could be observed (Sivashanmugan et al 2019a , b ). The group have extended the study and developed diatomaceous SERS substrates based protocol and detected THC using a portable device (Sivashanmugan et al 2019a , b ). Optoplasmonic materials are of high interest in SERS substrate fabrication due to their unique properties of comprising both photonic and plasmonic elements.…”

Recent progress of microfluidics in surface‐enhanced Raman spectroscopic analysis

“…They are offline SERS detection after separation [104,105], online detection through SERS-active nanoparticle external injection [106], and online detection using a microchip device having built-in SERS substrate [42,47,49]. Wang's group [104,105] prepared microfluidic diatomite analytical devices by spin-coating and tape-stripping stationary phase of liquid chromatography on glass slide. A thin-layer chromatographic separation was progressed after spotting sample solution on reservoir and immersing bottom F I G U R E 5 Microfluidic electrophoresis-SERS device: (A) channel network, (B) junction for AgNPs addition, and (C) sampling cross (reprinted from Ref.…”