Decoding early stress signaling waves in living plants using nanosensor multiplexing.

Increased exposure to environmental stresses due to climate change have adversely affected plant growth and productivity. Upon stress, plants activate a signaling cascade, involving multiple molecules like H2O2, and plant hormones such as salicylic acid (SA) leading to resistance or stress adaptation. However, the temporal ordering and composition of the resulting cascade remains largely unknown. In this study we developed a nanosensor for SA and multiplexed it with H2O2 nanosensor for simultaneous monitoring of stress-induced H2O2 and SA signals when Brassica rapa subsp. Chinensis (Pak choi) plants were subjected to distinct stress treatments, namely light, heat, pathogen stress and mechanical wounding. Nanosensors reported distinct dynamics and temporal wave characteristics of H2O2 and SA generation for each stress. Based on these temporal insights, we have formulated a biochemical kinetic model that suggests the early H2O2 waveform encodes information specific to each stress type. These results demonstrate that sensor multiplexing can reveal stress signaling mechanisms in plants, aiding in developing climate-resilient crops and pre-symptomatic stress diagnoses.

Single-Crystal 2D Covalent Organic Frameworks for Plant Biotechnology.

Molecules chemically synthesized as periodic two-dimensional (2D) frameworks via covalent bonds can form some of the highest-surface area and -charge density particles possible. There is significant potential for applications such as nanocarriers in life sciences if biocompatibility can be achieved; however, significant synthetic challenges remain in avoiding kinetic traps from disordered linking during 2D polymerization of compatible monomers, resulting in isotropic polycrystals without a long-range order. Here, we establish thermodynamic control over dynamic control on the 2D polymerization process of biocompatible imine monomers by minimizing the surface energy of nuclei. As a result, polycrystal, mesocrystal, and single-crystal 2D covalent organic frameworks (COFs) are obtained. We achieve COF single crystals by exfoliation and minification methods, forming high-surface area nanoflakes that can be dispersed in aqueous medium with biocompatible cationic polymers. We find that these 2D COF nanoflakes with high surface area are excellent plant cell nanocarriers that can load bioactive cargos, such as the plant hormone abscisic acid (ABA) via electrostatic attraction, and deliver them into the cytoplasm of intact living plants, traversing through the cell wall and cell membrane due to their 2D geometry. This synthetic route to high-surface area COF nanoflakes has promise for life science applications including plant biotechnology.

Design of Biodegradable, Climate-Specific Packaging Materials That Sense Food Spoilage and Extend Shelf Life.

The AgriFood systems in tropical climates are under strain due to a rapid increase in human population and extreme environmental conditions that limit the efficacy of packaging technologies to extend food shelf life and guarantee food safety. To address these challenges, we rationally designed biodegradable packaging materials that sense spoilage and prevent molding. We nanofabricated the interface of 2D covalent organic frameworks (COFs) to reinforce silk fibroin (SF) and obtain biodegradable membranes with augmented mechanical properties and that displayed an immediate colorimetric response (within 1 s) to food spoilage, using packaged poultry as an example. Loading COF with antimicrobial hexanal also mitigated biotic spoilage in high-temperature and -humidity conditions, resulting in a four-order of magnitude decrease in the total amount of mold growth in soybeans packaged in silk-COF, when compared to cling film (i.e., polyethylene). Together, the integration of sensing, structural reinforcement, and antimicrobial agent delivery within a biodegradable nanocomposite framework defines climate-specific packaging materials that can decrease food waste and enhance food safety.

Growth inhibition of human liver carcinoma HepG2 cells and α-glucosidase inhibitory activity of Murdannia bracteata (C.B. Clarke) Kuntze ex J.K. Morton extracts.

ETHNOPHARMACOLOGICAL RELEVANCE: The juice of the entire fresh herb and infusion of dried sample of Murdannia bracteata are consumed to treat liver cancer and diabetes in Malaysia. However, no scientific evidence of these bioactivities has been reported. MATERIALS AND METHODS: To verify the therapeutic potentials of sequential extracts and infusion of this plant by determining its cytotoxicity against human liver carcinoma HepG2 cells and α-glucosidase inhibitory activity. The cytotoxic activities of the extracts against HepG2 were determined using a methylene blue assay, and an α-glucosidase inhibitory assay was used to assess anti-diabetic activity. The molecular basis of the anti-hepatocellular carcinoma activity of the most active extract was determined using RT-PCR. Chemical profiling of the most active extract was performed using GC-MS and UPLC analyses. RESULTS: The results obtained from the cytotoxic screening revealed the dose-dependent growth inhibition of the HepG2 cells by only the hexane extract, with an EC50 value of 37.17±1.00 µg/ml. The HepG2 cell death was found to be apoptotic in nature and based on the significant biphasic induction of caspase-3, suggesting that the extract inhibited cell growth through a caspase-3-dependent pathway. The hexane extract also displayed α-glucosidase inhibitory activity, with an EC50 of 117.04±2.34 µg/ml. GC-MS analysis revealed that α-tocopherol was the major volatile compound in the hexane extract, and two phenolics (apigenin and caffeic acid derivatives) were detected using UPLC. CONCLUSIONS: Based on various published reports, it could be suggested that α-tocopherol and apigenin derivatives might be involved in the apoptosis-based cytotoxicity of the active extract of this plant against HepG2 carcinoma cells. The effects of this plant in the treatment of diabetes can be related to the presence of α-glucosidase inhibitors, such as the caffeic acid derivative identified in the active extract.