Tetrahydrocannabinol (THC) is one of the therapeutic compounds in the cannabis plant. Rapid and simple THC detection is essential, whether it be in human bodily fluids, in field or lab samples. This article focuses on the biosensor technologies that are used to detect THC.
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What is Tetrahydrocannabinol (THC)?
The main psychoactive component of cannabis, tetrahydrocannabinol (THC), affects the endocannabinoid system in the brain.
Its agonism on cannabinoid receptors affects the levels of numerous neurotransmitters (e.g., norepinephrine and norepinephrine), which are linked to THC's influence on conscious perception and mood.
A small amount of THC offers medicinal benefits, primarily as a neuroprotective and anti-inflammatory agent. Cannabidiol (CBD) combined with THC, such as Nabiximols, has been demonstrated as an effective pain reliever for cancer patients. In contrast, a high concentration of THC can be addictive and psychoactive.
Importance of THC Detection
THC must be detected quickly and easily in human bodily fluids and breath, as well as laboratory and field samples.
Accurate detection offers information on how THC affects the human body and its potential medical uses, and directs cannabis farmers in identifying the many stages of the plant's development in the field. It also aids researchers in the laboratory in ensuring the efficacy of their products, determining their potency, and better understanding their manufacturing procedures.
The importance of tetrahydrocannabinol detection in forensic investigation cannot be underestimated. Since there is no roadside driving under the influence (DUI) test for assessing cannabis impairment, the value resides in the rapid identification of the psychoactive substance THC.
Drawbacks of Traditional Detection Methods
To accurately detect THC and CBD in biofluids, lab-based techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC), mass spectrometry (MS), enzyme-linked immunosorbent assay (ELISA), and capillary electrophoresis (CE) are often employed.
The drawbacks of these methods include low limits of detection (LOD), and high sensitivity, high costs, the requirement of skilled personnel, and time-consuming measurements.
Electrochemical Sensors for THC Detection
Electrochemical sensors, which translate chemical, physical, or biological variables into measurable electrical signals, have drawn a lot of attention for the purpose of detecting THC and CBD to get around the drawbacks of conventional techniques. This is attributed to their rapid and selective detection, lower LOD, and high specificity.
The sensors are affordable, simple to construct, and portable due to their smaller size. They do not require trained workers to operate. In addition, sensors and microelectronic parts can be integrated for real-time monitoring.
Affinity Biosensor for THC Detection
THC can be identified in bodily fluids, like saliva and blood, within three to six hours following consumption and may remain in the human system for many days. Salivary THC levels are associated with blood THC levels, which makes it a non-invasive method for fast THC testing.
There have been many reports of THC being electrochemically detected in saliva samples. Electrochemical affinity biosensors provide an attractive choice for quick THC analysis due to their portability and technological simplicity.
How Does Affinity Biosensor Work?
Affinity biosensors detect biomarkers using a recognition element that particularly binds the targeted biomarker. A measurable signal output relating to the concentration of the biomarker of interest is then produced as the outcome of the chemical reaction between the recognition element and the targeted biomarker.
Home-kit lateral flow assays for THC already exist; however, for maintaining a reliable measurement, these tests need highly precise sample amounts, cautious reagent handling by personnel, and often lengthy waiting periods for results.
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Recent Development: Affinity Biosensor for Rapid THC Detection in Saliva
A recent study on electrochemical biosensor for detecting THC published in the journal “scientific reports” highlights the fabrication of a novel affinity biosensor that uses nonfaradaic electrochemical impedance spectroscopy (EIS) to identify BSA-THC hapten in specimens of human saliva.
Affinity biosensing applies a chemical reaction between the target THC and a THC-specific antibody to provide a signal output proportional to the amount of the THC biomarker.
The sensor measured THC in less than a minute and with great sensitivity and specificity across a wide range of patients and their specimens. It had a smaller detection limit of 100 pg/ml and a dynamic linear range of 100 pg/ml - 100 ng/ml in human saliva.
The stability and electrochemical behavior of the THC immunoassay in various salivary pH buffers were investigated using the zeta potential method.
Stevenson et al. established consistent and dose-dependent biosensing in fluctuating salivary pH levels. To determine the level of THC in human saliva, a binary classification system with a high overall performance (AUC = 0.95) was also used.
This biosensor, when combined with low-power electronic components and a portable saliva swab, can improve the testing procedure, eliminate the requirement for sample preparation, and reduce wait time because it does not rely on slow diffusion-limited processes.
Commercial Use of Biosensors to Detect THC
The THC-detecting biosensors can be used in an array of applications, including law enforcement (roadside DUI testing), aviation and airports, manufacturing and industrial facilities, cannabis research, medicinal applications, nuclear power plants, clinics and hospitals, prisons and detention facilities, etc.
Cannabis Sensors is a designer and manufacturer of biosensors for detecting THC and CBD in the liquid, air, and other mediums. Cannsense9, Vitreousense, Cannabisense, and Aurasense sensors are available from this company.
Challenges with Affinity Biosensor Technology
The main obstacles that these sensors face are nonspecific contact and interference from compounds and organisms in the matrix. Another challenge in this field is the unique requirements for storing sensors that have been modified with antibodies and proteins.
Future Outlook
Researchers from all around the world are putting a lot of effort into designing portable, rapid and user-friendly THC detection devices for use in a variety of applications, including roadside drug testing, cannabis crop appraisal, and cannabis quality assurance.
The recent research studies presented here show that electrochemical sensors have significant promise for application in this area. The main issue that the scientific community must now resolve is the development of biosensors with the least amount of nonspecific interactions and matrix interference. Developing long-lasting and reusable sensors is an area worth exploring.
References and Further Reading
Stevenson, H., et al. (2019) A Rapid Response Electrochemical Biosensor for Detecting Thc In Saliva. Scientific Reports, 9(1), pp.1–11.
Electrochemical Sensors to Trace THC [Online]. [cited 2023 Sep 5]. Available at: https://www.azosensors.com/article.aspx?ArticleID=2655
Mishra, R. K., et al. (2020) Simultaneous detection of salivary Δ9-tetrahydrocannabinol and alcohol using a Wearable Electrochemical Ring Sensor. Talanta, 211.
Amini, K., et al. (2022) Recent advances in electrochemical sensor technologies for THC detection—a narrative review. Journal of Cannabis Research, 4(1).
Pazuki, D., et al. (2023) Nanomaterials-Based Electrochemical Δ9-THC and CBD Sensors for Chronic Pain. Biosensors, 13(3), p.384.
the Technology [Online]. [cited 2023 Sep 5]. Available at: https://cannabisensor.com/?page_id=107
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