Search Results (3)

Ochratoxin A (OTA) is a mycotoxin widely found in foodstuffs such as cereal grains. It greatly threatens human health owing to its strong toxicity and high stability. Aptasensors have emerged as promising tools for the analysis of small molecule contaminants. Nucleic-acid-based signal amplification enables detectable signals to be obtained from aptasensors. However, this strategy often requires the use of complex primers or multiple enzymes, entailing problems such as complex system instability. Herein, we propose a fluorescent aptasensor for the ultrasensitive detection of OTA in cereal products, with signal amplification through RecJ_f exonuclease-assisted target recycling. The aptamer/fluorescein-labeled complementary DNA (cDNA-FAM) duplex was effectively used as the target-recognition unit as well as the potential substrate for RecJ_f exonuclease cleavage. When the target invaded the aptamer-cDNA-FAM duplex to release cDNA-FAM, RecJ_f exonuclease could cleave the aptamer bonded with the target and release the target. Thus, the target-triggered cleavage cycling would continuously generate cDNA-FAM as a signaling group, specifically amplifying the response signal. The proposed exonuclease-assisted fluorescent aptasensor exhibited a good linear relationship with OTA concentration in the range from 1 pg/mL to 10 ng/mL with an ultralow limit of detection (6.2 ng/kg of cereal). The analytical method showed that recoveries of the cereal samples ranged from 83.7 to 109.3% with a repeatability relative standard deviation below 8%. Importantly, the proposed strategy is expected to become a common detection model because it can be adapted for other targets by replacing the aptamer. Thus, this model can guide the development of facile approaches for point-of-care testing applications. Full article

Graphene oxide (GO) is widely used in sensors. The detection of proteins based on bare GO has been developed; however, the detection sensitivity needs to be improved. In this paper, a novel GO-DNA sensor for thrombin detection was developed using an aptamer linked to the surface of GO. Polyethylene glycol (PEG) was further used to prevent thrombin from nonspecific adsorption and to improve the sensitivity of the sensor for detection of thrombin. In order to improve the limit of detection for thrombin, we developed a GO and RecJf exonuclease co-assisted signal amplification strategy, and a detection limit of 24.35 fM for thrombin was achieved using this strategy. The results show that it is a promising method in analytical applications. Full article

In this study, we developed an aptamer-based fluorescent sensing platform for the detection of ochratoxin A (OTA) based on RecJ_f exonuclease-assisted signal amplification and interaction between graphene oxide (GO) and the OTA aptamer (OTA-apt). After optimizing the experimental conditions, the present aptamer-based sensing system can exhibit excellent fluorescent response in the OTA assay, with a limit of detection of 0.07 ng/mL. In addition to signal amplification, this strategy is also highly specific for other interfering toxins. Furthermore, this aptasensor can be reliably used for assessing red wine samples spiked with different OTA concentrations (2.4, 6 and 20 ng/mL). The proposed assay plays an important role in the field of food safety and can be transformed for detecting other toxins by replacing the sequence that recognizes the aptamer. Full article