Overexpression of the homoterpene synthase gene, OsCYP92C21, increases emissions of volatiles mediating tritrophic interactions in rice.

Plant defence homoterpenes can be used to attract pest natural enemies. However, the biosynthetic pathway of homoterpenes is still unknown in rice, and the practical application of such indirect defence systems suffers from inherent limitations due to their low emissions from plants. Here, we demonstrated that the protein OsCYP92C21 is responsible for homoterpene biosynthesis in rice. We also revealed that the ability of rice to produce homoterpenes is dependent on the subcellular precursor pools. By increasing the precursor pools through specifically subcellular targeting expression, genetic transformation and genetic introgression, we significantly enhanced homoterpene biosynthesis in rice. The final introgressed GM rice plants exhibited higher homoterpene emissions than the wild type rice and the highest homoterpene emission reported so far for such GM plants even without the induction of herbivore attack. As a result, these GM rice plants demonstrated strong attractiveness to the parasitic wasp Cotesia chilonis. This study discovered the homoterpene biosynthesis pathway in rice, and lays the foundation for the utilisation of plant indirect defence mechanism in the "push-pull" strategy of integrated pest management through increasing precursor pools in the subcellular compartments and overexpressing homoterpene synthase by genetic transformation.

Biomolecule-free, selective detection of o-diphenol and its derivatives with WS2/TiO2-based photoelectrochemical platform.

Herein, a novel photoelectrochemical platform with WS2/TiO2 composites as optoelectronic materials was designed for selective detection of o-diphenol and its derivatives without any biomolecule auxiliary. First, catechol was chosen as a model compound for the discrimination from resorcinol and hydroquinone; then several o-diphenol derivatives such as dopamine, caffeic acid, and catechin were also detected by employing this proposed photoelectrochemical sensor. Finally, the mechanism of such a selective detection has been elaborately explored. The excellent selectivity and high sensitivity should be attributed to two aspects: (i) chelate effect of adjacent double oxygen atoms in the o-diphenol with the Ti(IV) surface site to form a five/six-atom ring structure, which is considered as the key point for distinction and selective detection. (ii) This selected WS2/TiO2 composites with proper band level between WS2 and TiO2, which could make the photogenerated electron and hole easily separated and results in great improvement of sensitivity. By employing such a photoelectrochemical platform, practical samples including commercial clinic drugs and human urine samples have been successfully performed for dopamine detection. This biomolecule-free WS2/TiO2 based photoelectrochemical platform demonstrates excellent stability, reproducibility, remarkably convenient, and cost-effective advantages, as well as low detection limit (e.g., 0.32 µmol L(-1) for dopamine). It holds great promise to be applied for detection of o-diphenol kind species in environment and food fields.

Engineered photoelectrochemical platform for rational global antioxidant capacity evaluation based on ultrasensitive sulfonated graphene-TiO2 nanohybrid.

Dietary antioxidants as health promoters for human beings have attracted much attention and triggered tremendous efforts in evaluation of the antioxidant capacity. Unfortunately, no versatile detection system has been designed to date. Due to the possible synergistic effect among antioxidant components in a diversified system, to isolate and quantify an individual antioxidant via a chromatography approach limits the scope for global antioxidant activity assay. Quality inspections with a spectroscopy strategy to any colored food are far from satisfactory. Herein, a photoelectrochemical (PEC) platform with an ultrasensitive titanium dioxide decorated sulfonated graphene (SGE-TiO2) based transducer was introduced for antioxidant monitoring. Under an open circuit potential (zero potential), with extraordinary response, excellent reproducibility and stability, this PEC sensor could be successfully applied for rational analysis of the global antioxidant capacity. Such a highly efficient strategy showed advantages such as simplicity, convenience, high sensitivity and universality, which were also applicable to the detection of colored system. Moreover, the PEC sensor could be employed for practical evaluation of antioxidant capacity of teas. The concerned mechanism was further proposed and adequately discussed. This straightforward yet powerful approach provides a general format for dietary antioxidant assessment in foodstuff industries.

Tailoring heterostructured Bi2MoO6/Bi2S3 nanobelts for highly selective photoelectrochemical analysis of gallic acid at drug level.

Along with continuous growing widespread adulterations of botanical drugs, the necessity for drug quality monitoring has become more popular than ever. Considering that antioxidants are widely found in natural plant pharmaceuticals, gallic acid (GA) is often regarded as the reference standard to make sure whether these are up to grade as guided by Chinese Pharmacopeia. Herein, a novel Bi2MoO6/Bi2S3 photoelectrochemical sensor has been successfully involved toward selective GA analysis to supervise drug quality, in which γ-Bi2MoO6 nanobelts were treated as template nanocrystal and scaffold. Such Bi2S3 accommodated in Bi2MoO6 nanobelts render platform with excellent light-harvesting capability, selectivity and reproducibility. Concerned mechanism was in-depth pursued through theoretical computation and morphology speculation, inferring that two aspects mainly contribute to the findings: (1) engineering particular structure brings about surface dangling bonds, which raises the likelihood of electrostatic interaction with opposite charges; (2) appending Bi2S3 to the Bi2MoO6 nanobelts acted as a new avenue to mediate photoelectrochemical behavior, nearly devoid of interference effect. Our work opens up broad possibilities for finely distinguishing different antioxidants. As the extension of this simple and valid strategy, photoelectrochemistry will become a potent backing for quality guaranty in drug field, which offers an entry into ensuring good consistency in batch production.

Design of two electrode system for detection of antioxidant capacity with photoelectrochemical platform.

Recently, a flow photoelectrochemical cell has been first developed and applied to assay global antioxidant capacity in our group. Yet, shortcomings of liquid reference electrode such as sample contaminations from the leaking of the reference solution, mechanically fragile, temperature and light sensitivity, etc. are significant restrictions for integration and miniaturization of photoelectrochemical sensing instruments, which have greatly limited their practical applications. Bearing these problems, in this work a novel two electrode flow photoelectron-chemical system (two-EPCS) has been developed for detection of antioxidant capacity. It is noteworthy that the electrochemical modulation-free mode (detection at the potential of 0.0V) is performed, which has greatly simplified the analysis process and will result in significant simplifications of the instrument integrations. During the sample analysis, both standard antioxidants and commercial beverages were detected. Results evaluated from the two-EPCS are well agreed with those of the traditional three-EPCS at low potentials. By unloading of the reference electrode, it is of great convenience to design a novel photoelectrochemical microfluidic chip based on the two-EPCS, which has also been successfully applied for antioxidant capacity assay. It is satisfactory that comparable detection concentration range and sensitivity were accomplished by applying the microfluidic chip technique. Moreover, the two-EPCS is verified to be a universal platform which does not depend on selected optoelectronic materials but pervasive for general photocatalysts. Such a two-EPCS should be considered as a feasible alternative to the three-EPCS, which will become a promising candidate for industrial and commercial photoelectrochemical sensing instrument integrations in the future.

The fluorescence detection of glutathione by ∙OH radicals' elimination with catalyst of MoS2/rGO under full spectrum visible light irradiation.

In this study, a new method for the detection of glutathione (GSH) was designed based on the ∙OH radicals' elimination system due to the reducing ability of GSH for the first time. Fluorescence method with terephthalic acid (TA) as the probe was employed for the quantification of ∙OH radicals' production and elimination. Experimental conditions of ∙OH radicals' production were optimized in detail, and ∙OH radicals were found to be efficiently produced by the excellent catalysis performance of MoS2/rGO under full spectrum visible light irradiation. The introduction of GSH make fluorescent intensity decrease due to the elimination of ∙OH radicals. For the present fluorescence based GSH sensor, a wide detection range of 60.0-700.0 µM and excellent selectivity have been achieved. Furthermore, it has been successfully employed for the determination of GSH in commercial drug tablets and human serum.

Photoelectrochemical device based on Mo-doped BiVO4 enables smart analysis of the global antioxidant capacity in food.

For a healthy diet, which is an extension of a high quality lifestyle, tremendous attention has been focused on using antioxidant capacity indicators for food inspections and health guides. Although photoelectrochemical transducers have broadened our horizons for global antioxidant activity analysis, a growing body of foods and beverages needs to be quantified in the visible region and the necessary photoelectrochemical instrumentalization is still in its infancy. Generally, BiVO4 is considered as an ideal starting material for antioxidant surveillance under visible light irradiation. However, it is subjected to unsatisfied charge collection and utilization in practical applications. Herein, we studied the effects of successive molybdenum substitution of vanadium on the photocatalytic behavior of BiMo x V(1-x)O4 under visible light illumination. A superior photocurrent density was obtained for BiMo0.015V0.985O4 due to the flower-like architecture and favorable crystalline form. At the same time, this superhybrid BiMo0.015V0.985O4 composite successfully acted as a sensing unit in a photoelectrochemical platform for antioxidant capacity evaluation in foodstuffs. The related mechanism was further unearthed and discussed in-depth. Such a straightforward yet cogent principle was also applied to our integrated device for the "smart" analysis of the global antioxidant capacity, whereby collected data can be treated as a nutritive value index for routine quality control in the food industry. On the basis of this achievement, it is anticipated that mobile app-based quantitative antioxidant capacity detection will soon be realized.