Nanomaterials-Based Electrochemical Δ9-THC and CBD Sensors for Chronic Pain

Abstract

Chronic pain is now included in the designation of chronic diseases, such as cancer, diabetes, and cardiovascular disease, which can impair quality of life and are major causes of death and disability worldwide. Pain can be treated using cannabinoids such as Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) due to their wide range of therapeutic benefits, particularly as sedatives, analgesics, neuroprotective agents, or anti-cancer medicines. While little is known about the pharmacokinetics of these compounds, there is increasing interest in the scientific understanding of the benefits and clinical applications of cannabinoids. In this review, we study the use of nanomaterial-based electrochemical sensing for detecting Δ9-THC and CBD. We investigate how nanomaterials can be functionalized to obtain highly sensitive and selective electrochemical sensors for detecting Δ9-THC and CBD. Additionally, we discuss the impacts of sensor pretreatment at fixed potentials and physiochemical parameters of the sensing medium, such as pH, on the electrochemical performance of Δ9-THC and CBD sensors. We believe this review will serve as a guideline for developing Δ9-THC and CBD electrochemical sensors for point-of-care applications.

Keywords: cancer painkiller; cannabinoids; chronic diseases; electrochemical sensing; functionalization; nanomaterials.

Figure 1

Chemical structures of (A) ${\mathsf{\Delta }}^9$-tetrahydrocannabinol $({\mathsf{\Delta }}^9$-THC) and (B) cannabidiol (CBD). Irreversible oxidation of ${\mathsf{\Delta }}^9$-THC: (C) before and (D) after deprotonation. Reprinted and adapted with permission from ref. [5]. Copyright 2020 American Chemical Society.

Figure 2

(A): DPV signals of Sonogel-Carbon-PEDOT electrodes for 19.1 µM CBD at different pH: acetic or acetate buffer (AB) with pH 4.0, phosphate buffer (PB) with pH 7.0, and boric or borate buffer (BB) with pH 10.0. (B): A comparison between DPV signals of Sonogel-Carbon-PEDOT electrodes for 19.1 µM CBD in BB, acetonitrile (ACN):BB (15:85), and ethanol (EtOH):BB (15:85). (C): Calibration curve and DPV signals of Sonogel-Carbon-PEDOT electrodes at different CBD concentrations. Reprinted and adapted with permission from ref. [8]. Copyright 2020 Elsevier.

Figure 3

(a) Three major parts of the device, including the PVC sheet (substrate), modified screen printed electrodes (detection part), and chromatographic paper (separation part). (b) Functionalization process for modifying graphene ink with 1.25% cobalt phthalocyanine (CoPc) and printing Ag or AgCl ink on the substrate for fabricating reference electrode. (c) The device after mounting the detection part and (d) the separation part on the PVC sheet. (e) Different methanol concentrations in hexane and their influence on the amount of retardation factors (${\mathit{R}}_{\mathit{f}}$) of CBD (black spots), ${\mathsf{\Delta }}^9$-THC (red spots) in the mobile phase, and DPV signals. The calibration curves of (f)${\mathsf{\Delta }}^9$-THC and (g) CBD were obtained from CoPc modified-screen printed graphene electrode (CoPc/SPGE) in 0.1 M PBS with pH 7.0. Reprinted and adapted with permission from ref. [7]. Copyright 2022 Elsevier.

Figure 4

(a): The leaf-like sensor configuration, including dual working electrodes with the same counter electrode (C.E.) and reference electrode (R.E.). (b): Wearable electrochemical ring sensor. (c): The case, electronic board, and sensing system. Reprinted and adapted from ref. [45]. Copyright 2020 Elsevier.

Figure 5

ΔI as a function of i: ${\mathsf{\Delta }}^9$-THC, ii: caffeine, and iii: acetaminophen utilizing (a): carbon beads/MIPs electrode and (b): CNT/MIP electrode. Reprinted and adapted with permission from ref. [50]. Copyright 2019 Elsevier.

Figure 6

(A): CV responses from mag–MIP/Gr–UiO66/SPE at different CBD concentrations and (B): the linear relationship between peak current and CBD concentration. Reprinted and adapted from ref. [52]. Copyright 2022 Multidisciplinary Digital Publishing Institute (MDPI).