An indirect competitive ELISA assay using fragment antigen-binding (Fab) antibody for the quantitative detection of delta-9-tetrahydrocannabinol from Cannabis sativa L.

Delta-9-tetrahydrocannabinol (THC) is one of the cannabinoid metabolites present in Cannabis sativa. Currently, cannabis is an ingredient in foods, cosmetics, and medicinal products. Many countries control cannabis and THC for illegal or under-regulation products. This study focused on development of recombinant antibodies specific to THC, and their application of analytical methods using enzyme-linked immunosorbent assay (ELISA) techniques. Conjugation of THC with bovine serum albumin or ovalbumin was performed using Mannich and N,N'-carbonyldiimidazole reactions. The recombinant antibody was expressed from Escherichia coli in form of fragmented antigen-binding (Fab) antibody. Antigen-conjugates and Fab were performed using ELISA-based analytical method and validated method for sensitivity, accuracy, and precision. The developed Fab in this study demonstrates high specificity for detection of THC. The analytical range was between 0.78 and 25 µg/mL, with limit of detection of 0.59 µg/mL. Accuracy ranged from 98.15-108.97%, with intra- and inter-assay % relative standard deviation of 2.15-8.03 and 1.83-8.45%, respectively. Parameters for method validation, including accuracy and precision, were within acceptable limits which are comparable to modified HPLC method from previous study. The approach demonstrated outstanding sensitivity and specificity for analysis of THC in cannabis extracts, suggesting it to be suitable for the quantitative assessment of THC in variety of products.