Rapid Testing of Δ9-Tetrahydrocannabinol and Its Metabolite On-Site Using a Label-Free Ratiometric Fluorescence Assay on a Smartphone

Abstract

Excessive consumption of Δ9-tetrahydrocannabinol (THC) severely endangers human health and has raised public safety concerns. However, its quantification by readily rapid tools with simplicity and low cost is still challenging. Herein, we found that a G-rich THC aptamer (THC1.2) can tightly bind to thioflavin T (ThT) with strong fluorescence, which would be specifically quenched in the presence of THC. Based on that, a label-free ratiometric fluorescent sensor for the sensing of THC and its metabolite (THC-COOH) based on THC1.2/ThT as a color emitter and red CdTe quantum dots as reference fluorescence was constructed. Notably, a transition of the fluorescent color of the ratiometric probe from green to red can be instantly observed upon the increased concentration of THC and THC-COOH. Furthermore, a portable smartphone-based fluorescence device integrated with a self-programmed Python program was fabricated and used to accomplish on-site monitoring of THC and THC-COOH within 5 min. Under optimized conditions, this ratiometric fluorescent sensor allowed for an instant response toward THC and its metabolite with considerable limits of detection of 97 and 254 nM, respectively. The established sensor has been successfully applied to urine and saliva samples and exhibited satisfactory recoveries (88–116%). This ratiometric fluorescent sensor can be used for the simultaneous detection of THC and THC-COOH with the advantages of rapidness, low cost, ease of operation, and portability, providing a promising strategy for on-site detection and facilitating law enforcement regulation and roadside control of THC.

Portable and Rapid Fluorescence Turn-On Detection of Total Pepsin in Saliva Based on Strong Electrostatic Interactions

“…At present, the acquisition of fluorescence results usually depends on the collection of light intensity by laboratory fluorescence instruments, which severely limits its practical application in on-site analysis. To realize the on-site detection of pepsin, a portable and miniaturized fluorescence capture device was further fabricated. ,, Here, we designed and fabricated a smartphone-based portable color device that can analyze and quantify the fluorescence of the sample (Figure a). The device consists of a 3D-printed shell and an internal structure, and the signal is read by taking photos with a smartphone (see Figure S7 for detailed dimensions).…”

“…To realize the on-site detection of pepsin, a portable and miniaturized fluorescence capture device was further fabricated. 18,19,40 Here, we designed and fabricated a smartphone-based portable color device that can analyze and quantify the fluorescence of the sample (Figure 3a). The device consists of a 3D-printed shell and an internal structure, and the signal is read by taking photos with a smartphone (see Figure S7 for detailed dimensions).…”

“…To date, the commonly used analytical methods, such as enzyme-linked immunosorbent assays, electrochemical immunosensors, spectrophotometry, and molecularly imprinted analysis, have been reported to detect pepsin. − However, these approaches are limited in their use for rapid on-site analysis because they typically require complex experimental procedures. Fluorescent sensors have been widely used, retaining the advantages of high sensitivity and rapid response. − Recently, strategies based on pepsin digestion resulting in fluorescence quenching of protein-coated fluorescent dyes or nanomaterials have been reported for pepsin detection. − Interestingly, the isoelectric point (pI) of pepsin is quite low, and it has the strongest activity at around pH 2.0 . The activity of pepsin is decreased or even inactivated as the pH increased .…”

Highly Selective and Portable Fluorescence Turn-On Detection of Sc3+ in Ore and Water Based on Strong Lewis Acid–Base Coordination

“…In recent years, simple and rapid testing strategies such as fluorescence, colorimetry, and potentiometry have gained favor but still suffered from poor selectivity and long response time. Fluorescence technology is known for its high sensitivity and low background, and the fluorescence approach offers many possibilities for developing portable sensors combined with 3D printing technology. − Additionally, portable smartphone-based fluorescence sensing platforms offer multiple advantages for real-time monitoring of environmental samples and can be combined with machine learning to reduce labor costs. − Calcein (CL), a remarkable coordination reagent and indicator that belongs to the family of amino poly­(carboxylic acid) ligands of fluorescein, was widely designed as sensing protocols for anions, cations, , molecules, , and biomarkers . However, the quenching fluorescence of CL at acidic pH and poor selectivity limit its broad applications in various fields.…”

Point-of-Care Platform Based on Solid-Phase Fluorescence Filter Effect for Urinary Iodine Testing in Children and Pregnant Women

“…The solid-phase fluorescence filter effect (SPFFE) is a nonradiative energy transfer phenomenon that occurs between a solid-phase absorber and a solid-phase fluorophore, which can be achieved by the solid-phase IFE sensor. Besides, the target reacted with the IFE system via the headspace sampling way can alleviate the interference of the liquid matrix toward the fluorophore by the absorber and act as an enrichment. , In addition, ratiometric fluorescence generates different colors with characteristic hues rather than changes in color brightness, which reduces the environmental interference and enables sensitive detection of analytes. − …”