In vivo tracing of endogenous salicylic acids as the biomarkers for evaluating the toxicity of nano-TiO2 to plants.

Currently, nano-titanium dioxide (nTiO2) is considered an emerging environmental contaminant. Bottlenecked by the traditional destructive and lethal sampling methods, nTiO2's effect in living plants is poorly investigated. Here, in vivo tracing of endogenous salicylic acids at regular intervals was performed by using solid phase microextraction (SPME) technique for evaluating the effects of nTiO2 on plants. By planting aloe in soil containing varying amounts of nTiO2, the titanium (Ti) element accumulated in the leaves to concentrations and then reached the maximum of 1.1 ± 0.4 µg/g after nTiO2 exceeding 0.1 g/kg. The levels of salicylic acid (SA) and acetylsalicylic acid (ASA) were up-regulated upon the exposure to nTiO2, while were positively correlated to the contents of Ti. Moreover, the increased malondialdehyde, decreased total superoxide dismutase and fluctuated glutathione along with the addition of nTiO2 demonstrated the oxidative stress caused by nTiO2. Meanwhile, apparent growth indicators including leaf elongation, plant fresh weight and root development were influenced, which further confirmed the toxicity of nTiO2 imparted on aloe. This study presents the possibility of using salicylic acids as biomarkers for revealing the toxicity of nTiO2 on plants in addition to the other biomarkers and biomass data, and the in vivo SPME technique is powerful for their monitoring.

Development of an on-site detection approach for rapid and highly sensitive determination of persistent organic pollutants in real aquatic environment.

Analysis of organic pollutants is usually accomplished in centralized laboratories. However, the time-delayed and time-consuming process is insufficient and risky for precisely detection due to the contamination of vials, the losses of analytes during transportation and storage. Herein, a rapid and highly sensitive on-site detection approach was developed without using any vials by coupling an on-site pre-equilibrium solid phase microextraction (SPME) sampling method with a portable gas chromatography mass spectrometer (portable GC-MS), for the determination of three families of persistent organic pollutants (polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons). Based on sampling-rate (SR) calibration method, the concentrations of target analytes in aquatic systems could be easily determined. Limits of detection (LODs) in the low parts-per-tillion levels (≤5.25 ng·L-1) were obtained for most of the investigated analytes with a total analysis time only ∼30 min. The proposed on-site detection approach was then successfully applied in the determination of persistent organic pollutants in real aquatic environment. A comparable result obtained by liquid extraction (LE) equipped with laboratorial GC-MS demonstrated the accuracy of the on-site detection method. In general, this study demonstrated a rapid and highly sensitive on-site approach, avoiding any risks of contamination during sampling and analysis, for determination of POPs as well as the potential applications for other organic pollutants in aquatic phase.

Determination of four salicylic acids in aloe by in vivo solid phase microextraction coupling with liquid chromatography-photodiode array detection.

In recent years, great concerns have been raised about salicylic acid (SA) and its derivatives as plant regulators. Therefore, precise determination of the distribution of SAs in the living plants is necessary for not only fundamental researches but also the regulating mechanisms. In this study, a custom-made solid phase microextraction (SPME) fiber based on diallyl dimethyl ammonium chloride-assembled graphene oxide-coated C18 composite (C18@GO@PDDA) was proposed for in vivo detection of salicylic acid, acetylsalicylic acid (ASA), 4-methyl salicylic acid（4-SA）and 3-methyl salicylic acid (3-SA) in aloe plants. Under the optimized conditions, the analytical performance evaluated in homogenized aloe plant tissues exhibited low detection limits (1.8-2.8 µg g-1), wide linear ranges (10-5000 µg g-1), and satisfactory reproducibility (relative standard deviations less than 8.4% and 9.3% for inter-fiber and intra-fiber assays, respectively). Under cadmium stress, the developed method was applied for the in vivo tracing of four salicylic acids in aloe plants. A 48-h in vivo tracing revealed that salicylic acids were involved in the pathway of cadmium stress tolerance. To our best knowledge, it is the first effort to realize the in vivo analysis of SA and its derivatives in plants, and it has a made a great step forward in the area of plant hormone analysis.

Boronate Affinity-Molecularly Imprinted Biocompatible Probe: An Alternative for Specific Glucose Monitoring.

A biocompatible probe for specific glucose recognition is based on photoinitiated boronate affinity-molecular imprinted polymers (BA-MIPs). The unique pre-self-assembly between glucose and boronic acids creates glucose-specific memory cavities in the BA-MIPs coating. As a result, the binding constant toward glucose was enhanced by three orders of magnitude. The BA-MIPs probe was applied to glucose determination in serum and urine and implanted into plant tissues for low-destructive and long-term in vivo continuous glucose monitoring.

A novel probe based on phenylboronic acid functionalized carbon nanotubes for ultrasensitive carbohydrate determination in biofluids and semi-solid biotissues.

Carbohydrates are known to be involved in a wide range of biological and pathological processes. However, due to the presence of multiple hydroxyl groups, carbohydrate recognition is a particular challenge. Herein, we reported an ultrasensitive solid-phase microextraction (SPME) probe based on phenylboronic acid (PBA) functionalized carbon nanotubes (CNTs) for direct in vitro or in vivo recognition of carbohydrates in biofluids as well as semi-solid biotissues. The coating of the proposed probe possessed a 3D interconnected porous architecture formed by the stacking of CNTs. As a result, the binding capacity toward carbohydrates was excellent. The proposed approach was demonstrated to be much superior to most carbohydrate sensors, including higher sensitivity, wider linear range, and excellent qualitative ability in multi-carbohydrate systems. Thus, this approach opens up new avenues for the facile and efficient recognition of carbohydrates for important applications such as glycomics.