THC (tetrahydrocannabinol) is one of the two psychoactive cannabinoids in cannabis, the other being CBD (cannabidiol). This article covers how electrochemical sensors are used to detect THC concentrations.
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What is THC?
While CBD is increasingly becoming legalized due to its reported health benefits and the fact that, on its own, it is not considered a narcotic drug, products containing THC remain illegal in many states and countries due to its psychoactive effects.
Once ingested, THC interacts with the endocannabinoid receptor system, inducing a wide range of physiological and psychological effects. For example, THC is known to stimulate the release of dopamine, causing euphoria. It also impacts the hippocampus, the area of the brain implicated in forming new memories, distorting short-term memory processing. Other effects of THC include hallucinations, delusions, psychomotor impairment, and in severe cases, it can induce relapse in schizophrenic symptoms.
Despite some of its risks, cannabis has become legalized in a number of states for medicinal purposes due to the impact of THC on the endocannabinoid system. An increasing number of studies have focussed on this system as a potential target for various pathological conditions, particularly cancer, for which studies have shown cannabinoids to have anticancer potential.
Why is it Important to Detect THC?
Perhaps the most important application of THC detection is within research. The medicinal and recreational use of cannabis has been legalized in Canada and many states of the US, with others poised to follow in their footsteps. Research into the potential benefits of the drug has become a hot topic, with new potential benefits of the drug emerging all the time, along with the list of diseases it may be able to treat or provide relief for.
However, we still do not fully understand the full effects of cannabis on the body. To date, there are over 60 unique cannabinoids within cannabis and it remains unclear how each of these influences the human body. To understand more about cannabis, to ensure that it is safely used and that its potential as a therapeutic agent can be realized, research into one of its most prominent cannabinoids, THC, is vital. Therefore, methods that accurately and reliably detect THC are of utmost importance.
Additionally, as cannabis becomes legalized across the globe, it is important to fully understand the effects of THC on a person’s competency behind the wheel. This research will be crucial to informing legislation on driving while under the influence of the substance. Again, platforms that detect THC will be fundamental to this research. Also, THC detection is important for law enforcement to detect if someone has been driving while under the influence of THC.
Finally, CBD products have become increasingly popular around the world as, for the most part, CBD products are legal as long as they do not contain THC (in the US, CBD products must contain no more than 0.3% THC). Therefore, THC tracing is essential in the growing CBD market to ensure the safety and consistency of its products.
Detecting THC with Electrochemical Sensors
The current standard method of detecting THC within a human subject is by collecting a blood sample and analyzing it with chromatography joint with mass spectrometry. The process is complex, requires trained members of staff, and is costly and time-consuming. The current method is not suitable for roadside testing and it increases the cost of research. These limitations of THC detection were sought to be overcome by US scientists, who published their novel method of THC detection in the American Chemical Society Sensors in 2019.
The team proposes a platform that uses electrochemical sensors that are portable (therefore suitable for roadside testing), non-invasive (therefore, the time-consuming collection of biological samples by trained staff is not required), fast and relatively low-cost, overcoming the limitations of current THC detection methods.
The publication outlines how electrochemical sensors prove to be a highly sensitive analytical tool in this scenario. Electrochemical sensors also have the additional benefit of lending themselves to miniaturization.
What are Electrochemical Sensors and How Do They Work?
Electrochemical sensors are devices that use electrodes as a transducer element in the presence of an analyte. They provide real-time information about the composition of a sample, and have become increasingly important in the analysis of biological samples. Electrochemical sensors work via the principles of potentiometric, amperometric, or conductivity measurements. The substance that the sensor is designed to detect instructs which principles the sensor design will follow.
Already, electrochemical sensors have been successful in numerous biomedical applications, such as the detection of blood gases, electrolytes, metabolites, DNA and antibodies.
Advancements in Electrochemical Sensors Used to Trace THC
As discussed above, a novel platform for analyzing trace THC in human samples has recently been developed by a research team at Oregon State University. The platform uses electrochemical sensors to detect trace THC in human plasma and saliva via Surface-enhanced Raman scattering (SERS). The key to developing this method was utilizing silver nanoparticles within the SERS-active substrate.
Additionally, recent research has shown wearable THC detectors may be possible in the near future. Scientists in San Diego recently developed a wearable voltammetric THC sensor and an amperometric enzymatic alcohol sensor that simultaneously detects THC and alcohol. The advancement may be promising for roadside testing and drivers’ self-assessment before driving.
Overall, there will likely be several novel, electrochemical sensor-based platforms emerging for the testing of trace THC in the coming years. These innovations will serve to protect the public and make THC consumption safer.
References and Further Reading
Amini, K., Sepehrifard, A., Valinasabpouri, A., Safruk, J., Angelone, D. and de Campos Lourenco, T., 2022. Recent advances in electrochemical sensor technologies for THC detection—a narrative review. Journal of Cannabis Research, 4(1). https://jcannabisresearch.biomedcentral.com/articles/10.1186/s42238-022-00122-3#Sec2
Atakan, Z., 2012. Cannabis, a complex plant: different compounds and different effects on individuals. Therapeutic Advances in Psychopharmacology, 2(6), pp.241-254. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3736954/
Sivashanmugan, K., Squire, K., Tan, A., Zhao, Y., Kraai, J., Rorrer, G. and Wang, A., 2019. Trace Detection of Tetrahydrocannabinol in Body Fluid via Surface-Enhanced Raman Scattering and Principal Component Analysis. ACS Sensors, 4(4), pp.1109-1117. https://pubs.acs.org/doi/abs/10.1021/acssensors.9b00476
Mishra, R., Sempionatto, J., Li, Z., Brown, C., Galdino, N., Shah, R., Liu, S., Hubble, L., Bagot, K., Tapert, S. and Wang, J., 2020. Simultaneous detection of salivary Δ9-tetrahydrocannabinol and alcohol using a Wearable Electrochemical Ring Sensor. Talanta, 211, p.120757. https://www.sciencedirect.com/science/article/pii/S0039914020300485#!
Zou, S. and Kumar, U., 2018. Cannabinoid Receptors and the Endocannabinoid System: Signaling and Function in the Central Nervous System. International Journal of Molecular Sciences, 19(3), p.833. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5877694/