Sensor Platform with a Custom‐tailored Aptamer for Diagnosis of Synthetic Cannabinoids

Abstract

Synthetic cannabinoids (SCs) are the large group of abused drugs and detection of them is still a challenge. Hence, new methods for analysis of SCs are being investigated. We aimed to develop a novel system for selective analysis of SCs. First, various custom‐tailored aptamers against the target SCs were selected through GO‐SELEX process. Toggling between different SC analytes during successive rounds of selection was performed to generate cross‐reactive aptamers. Then, the amino‐capped aptamers were synthesized and easily attached to the cysteamine‐covered gold electrodes. Analytical parameters and selectivity of the aptasensors were compared by using electrochemical techniques. After comparison of the analytical features and selectivity towards target analytes, one of the aptamers designated as Apta‐1 was chosen for further measurements. The aptasensor was tested by using differential pulse voltammetry technique against JWH‐018 (5‐pentanoic acid), selected as a model for SCs. The linearity and limit of detection were determined as 0.01–1.0 ng/mL and 0.036 ng/mL. Finally, sample application in synthetic urine samples was successfully performed with standard addition method, as confirmed by LC‐QTOF/MS. JWH‐018 (4‐hydroxypentyl), JWH‐073 (3‐hydroxybutyl), JWH‐250 (5‐hidroxypentyl) and HU‐210 were used to test the selectivity of the aptasensor and the system was shown to recognize all these SCs. Also other illegal drugs did not significantly interfere with the signal responses.

Laser‐scribed Graphene Electrodes as an Electrochemical Immunosensing Platform for Cancer Biomarker ‘eIF3d’

“…6 Peaks were observed in C 1s spectra. Peak at 284.17 eV was shown pure graphitic sites [36], while peak at 284.78 eV was shown C−C or C=C binding [37]. Peak at 285.3 eV was indicated the presence of hydrocarbons in PBA [38].…”

Screening and Evaluation of Thiamethoxam Aptamer Based on Pressurized GO-SELEX and Its Sensor Application

“…As shown in Figure 2A, after adding GO and the target in the incubation system at the ratio of 5000:1, free target still existed in the solution. Based on the previous report [21] and cost, 500:1 was used as the mass ratio of GO/target. GO-SELEX was suitable for screening the aptamers of targets which cannot be absorbed by GO.…”

“…Since different lengths of ssDNA show different binding kinetics on the GO surface [24], the GO/ssDNA mass ratio was optimized before GO-SELEX experiments, enabling GO to fully adsorb ssDNA. Commonly, the GO/ssDNA quality ratio was between 500:1 and 1000:1 [21,25], allowing the ssDNA concentration to reach the baseline level. In Figure 2B, the nucleic acid concentration was seen to decrease with the increase of GO/ssDNA, and at the mass ratio of 500:1, the DNA content in the solution reached the first equilibrium point, indicating that this concentration reached the baseline level, consistent with previous studies [21].…”

“…Commonly, the GO/ssDNA quality ratio was between 500:1 and 1000:1 [21,25], allowing the ssDNA concentration to reach the baseline level. In Figure 2B, the nucleic acid concentration was seen to decrease with the increase of GO/ssDNA, and at the mass ratio of 500:1, the DNA content in the solution reached the first equilibrium point, indicating that this concentration reached the baseline level, consistent with previous studies [21]. At GO/ssDNA mass ratio was between 500:1~4000:1, although the nucleic acid concentration could reach the baseline level, there was still free ssDNA not bound to the target, which would become non-specific enrichment sequences and existed in each round of the library, thus affecting the screening efficiency.…”

“…In this paper, we aimed to screen a thiamethoxam aptamer based on pressurized GO-SELEX and test the applicability of its sensor in thiamethoxam detection. Specifically, based on previous studies [21,22], aptamers of small pesticide molecular target of thiamethoxam were obtained by raising the additional amount of GO by an order of magnitude, and analyzed the impact of increased screening pressure on screening results. After 15 rounds of screening, an innovative capture method was set up to evaluate the affinity of the aptamer libraries of each round.…”