Lei Zheng

Ultrasensitive one-step rapid detection of ochratoxin A by the folding-based electrochemical aptasensor

A one-step electrochemical aptasensor using the thiol- and methylene blue- (MB-) dual-labeled aptamer modified gold electrode for determination of ochratoxin A (OTA) was presented in this research. The aptamer against OTA was covalently immobilized on the surface of the electrode by the self-assembly effect and used as recognition probes for OTA detection by the binding induced folding of the aptamer. Under the optimal conditions, the developed electrochemical aptasensor demonstrated a wide linear range from 0.1 pg mL(-1) to 1000 pg mL(-1) with the limit of detection (LOD) of 0.095 pg mL(-1), which was an extraordinary sensitivity compared with other common methods for OTA detection. Moreover, as a practical application, this proposed electrochemical aptasensor was used to monitor the OTA level in red wine samples without any special pretreatment and with satisfactory results obtained. Study results showed that this electrochemical aptasensor could be a potential useful platform for on-site OTA measurement in real complex samples.

One-step signal amplified lateral flow strip biosensor for ultrasensitive and on-site detection of bisphenol A (BPA) in aqueous samples

A one-step signal amplified lateral flow strip (LFS) biosensor has been developed for ultrasensitive and on-site visual detection of bisphenol A (BPA). This signal amplified LFS was based on the dual labeling using different-sized gold nanoparticles (Duo-LFS). This Duo-LFS could achieve BPA detection with 0.5 ng/mL as the visual sensitivity by naked eye observation and with 0.076 ng/mL as the limit of detection (LOD) for semi-quantitative detection by software analysis, which is at least 10-fold improvement of the sensitivity of traditional LFS based methods. This one-step signal amplified lateral flow strip biosensor and related signal enhancement method could be adopted as a potential generous technique for all LFS-based detection methods.

Chronic bisphenol A exposure alters behaviors of zebrafish (Danio rerio).

The adult zebrafish (Danio rerio) were exposed to treated-effluent concentration of bisphenol A (BPA) or 17β-estradiol (E2) for 6 months to evaluate their effects on behavioral characteristics: motor behavior, aggression, group preference, novel tank test and light/dark preference. E2 exposure evidently dampened fish locomotor activity, while BPA exposure had no marked effect. Interestingly, BPA-exposed fish reduced their aggressive behavior compared with control or E2. Both BPA and E2 exposure induced a significant decrease in group preference, as well as a weaker adaptability to new environment, exhibiting lower latency to reach the top, more entries to the top, longer time spent in the top, fewer frequent freezing, and fewer erratic movements. Furthermore, the circadian rhythmicity of light/dark preference was altered by either BPA or E2 exposure. Our results suggest that chronic exposure of treated-effluent concentration BPA or E2 induced various behavioral anomalies in adult fish and enhanced ecological risk to wildlife.

Ultrasensitive and rapid screening of mercury(II) ions by dual labeling colorimetric method in aqueous samples and applications in mercury-poisoned animal tissues.

Rapid and ultrasensitive detection of trace heavy metal mercury(II) ions (Hg(2+)) are of significant importance due to the induced serious risks for environment and human health. This presented article reports the gold nanoparticle-based dual labeling colorimetric method (Dual-COLO) for ultrasensitive and rapid detection of Hg(2+) using the specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) as recognition system and the dual labeling strategy for signal amplification. Both qualitative and quantitative detections of Hg(2+) are achieved successfully in aqueous samples. More importantly, the achieved detection limit of 0.005 ng mL(-1) (0.025 nM) without any instruments is very competitive to other rapid detection methods even ICP-MS based methods. This Dual-COLO method is also applied directly for real water sample monitoring and, more importantly, applied in analysis of mercury poisoned animal tissues and body fluidic samples, indicating a potentially powerful and promising tool for environmental monitoring and food safety control.

Real-time detection of Cu(II) with PEDOT:PSS based organic electrochemical transistors

Copper is an essential element in the environment and the human body, but at the same time, exposure to high concentrations of Cu2+ ions will potentially lead to acute toxicity and various neurodegenerative diseases. Thus, it is of great significance for the development of highly sensitive and selective strategies for the detection of Cu2+ ions. Here, we report a highly efficient poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) based organic electrochemical transistor (OECT) sensor, for real-time Cu2+ ions detection. The detection limit of the OECT device is as low as 100 nM, far beyond the sensitivity required for practical uses. The detection mechanism may base on the chemical reactivity of Cu2+ ions oxiding the PEDOT:PSS in solution both in absence and presence of the base potential. The OECT devices also exhibit excellent selective response to Cu2+ ions rather than other metal ions. Finally, we also demonstrate the determination of Cu2+ ions in tap water with the OECT Cu2+ sensor. Considering the high sensitivity and selectivity, as well as the real-time and low cost features of our Cu2+ OECT sensor, it is ideal for portable and disposable applications for environment monitoring and public health.

Detection of Bisphenol A Using DNA-Functionalized Graphene Field Effect Transistors Integrated in Microfluidic Systems

Bisphenol A (BPA) detection has attracted much attention recently for its importance to food safety and environment. The DNA-functionalized solution-gated graphene transistors are integrated in microfluidic systems and used for recycling detections of BPA for the first time. In the presence of BPA, both single- and double-stranded DNA molecules are detached and released from the graphene surface in aqueous solutions, leading to the change of device electrical performance. The channel currents of the devices change monotonically with the concentration of BPA. Moreover, the devices modified with double-stranded DNA are more sensitive to BPA and show the detection limit down to 10 ng/mL. The highly sensitive label-free BPA sensors are expected to be used for convenient BPA detections in many applications.