Enhancing the Performance of Colorimetric Aptasensor for the Detection of ∆9-THC by Pyrrolidinyl Peptide Nucleic Acid

Δ9-Tetrahydrocannabinol (Δ9-THC) is the primary psychoactive component that is found in cannabis. Taking large doses of the psychoactive chemicals may lead to acute psychosis, including hallucinations, delusions, and a loss of a sense of personal identity. In this study, a gold-nanoparticles-based colorimetric aptasensor for the detection of Δ9-THC was successfully developed. The detection principle is different from previously reported systems by employing a short positively charged pyrrolidinyl peptide nucleic acid (acpcPNA) to prevent the folding of the free aptamer thereby exposing a single-stranded region that can bind and stabilize the gold nanoparticles. In the presence of Δ9-THC, the target became bound to the aptamer, induced its conformational change, and released the PNA probe. The released positively charged PNA probes effectively induced the aggregation of the gold nanoparticles, resulting in the color change from wine red to blue. The change in color can be detected visually or quantitated by measuring the ratio of the absorbances at 670 nm and 520 nm (A670/A520). No color change was observed in the absence of the PNA probe. Under the optimal conditions, the method provided a linearity range from 0.5 μM to 2.5 μM of Δ9-THC, and the limit of detection was 0.44 μM. Furthermore, this aptasensor exhibited high selectivity as it only responded to Δ9-THC, compared with other cannabinoids, allowing accurate detection of Δ9-THC