Gas-Responsive and Gas-Releasing Polymer Assemblies.

In order to explore the unique physiological roles of gas signaling molecules and gasotransmitters in vivo, chemists have engineered a variety of gas-responsive polymers that can monitor their changes in cellular milieu, and gas-releasing polymers that can orchestrate the release of gases. These have advanced their potential applications in the field of bio-imaging, nanodelivery, and theranostics. Since these polymers are of different chain structures and properties, the morphology of their assemblies will manifest distinct transitions after responding to gas or releasing gas. In this review, we summarize the fundamental design rationale of gas-responsive and gas-releasing polymers in structure and their controlled transition in self-assembled morphology and function, as well as present some perspectives in this prosperous field. Emerging challenges faced for the future research are also discussed.

Cage-by-cage supramolecular polymerization via panel-decorated triphenylphosphine organic cage.

Significant efforts have been dedicated to designing porous organic cage compounds with geometric complexity and topological diversity. However, the use of these cage molecules as premade building units for constructing infinite cage-based superstructures remains unexplored. Here, we report the use of a panel-decorated phosphine organic cage as a special monomer to achieve supramolecular polymerization, resulting in cage-by-cage noncovalent polymers through the synergy of metal-coordination and intercageπ-πdimerization. At a monomer concentration of 122 mM, the average degree of polymerization reaches 17, corresponding to a molecular weight of 26 kDa. The obtained cage-based supramolecular polymers can further hierarchically self-assemble into vesicular morphologies or one-dimensional nanofiber architectures. Selective control over the cosolvents can regulate their structural hierarchy and assembled morphology. This approach paves a new way for the construction of cage-based hierarchical assemblies and materials.

Reshaping Membrane Polymorphism of Polymer Vesicles through Dynamic Gas Exchange.

The quest for a universal method to shape the vesicular morphology in dynamic and diversified manners is a challenging topic of cell mimicry. Here we present a simple gas exchange strategy that can direct the deformation movements of polymer vesicles. Such vesicles are assembled by a class of gas-based dynamic polymers, where CO2 connects between the frustrated Lewis pair via dynamic gas-bridged bonds. Use of other competitive gases (N2O, SO2, or C2H4) to in situ exchange the CO2 linkages can change the polymer structure and drive the membrane to proceed with three fundamental movements, including membrane stretching, membrane incurvation, and membrane protrusion, thus remolding the shapes of polymersomes. The choices of gas types, concentrations, and combinations are crucial to adjusting the vesicle evolution, local change of membrane curvature, and anisotropic geometrical transformation. This will become a generalized strategy to control the vesicular polymorphism and deformable behavior.

Water stress enhances expression of genes encoding plastid terminal oxidase and key components of chlororespiration and alternative respiration in soybean seedlings.

Plastid terminal oxidase (PTOX) is a plastid-localized plastoquinone (PQ) oxidase in plants. It functions as the terminal oxidase of chlororespiration, and has the potential ability to regulate the redox state of the PQ pool. Expression of the PTOX gene was up-regulated in soybean seedlings after exposure to water deficit stress for 6 h. Concomitantly expression of the NDH-H gene, encoding a component of the NADPH dehydrogenase (NDH) complex which is a key component of both chlororespiration and NDH-dependent cyclic electron transfer (CET), was also up-regulated. Transcript levels of the proton gradient regulation (PGR5) gene, which encodes an essential component of the PGR5-dependent CET, were not affected by water stress, while the expression of the alternative oxidase (AOX1) gene, which encodes a terminal oxidase of alternative respiration in mitochondria, was also up-regulated under water stress. Therefore, our results indicate that water stress induced the up-regulation of genes encoding key components of chlororespiration and alternative respiration. Transcript levels of the AOX1 gene began to increase in response to water stress before those of PTOX suggesting that alternative respiration may react faster to water stress than chlororespiration.

Nonlinear amplification of nano bowl surface concavity on the critical response threshold to biosignals.

Polymer nanoparticles that can sharply sense and detect biological signals in cells are promising candidates for biomedical and theranostic nanomaterials. However, the response ability of current polymer assemblies poorly matches the requirement of trace concentration level (10-6 ~ 10-9 mol/L) of cellular biosignals due to their linear signal input-to-function output mode, which impedes their practical applications in vivo. Here we report a kind of nanobowl system with pH-tunable invaginated morphology that can nonlinearly amplify the response abilities toward biosignals by modulating the surface concavity. Compared to conventional spherical nanoparticles, nonspherical nanobowls with a specific concave structure reduce the critical response threshold of polymers by up to 5 orders of magnitude, from millimole to nanomole level, covering most of biosignal concentration windows. Moreover, we find that this nonlinear signal gain effect is originated from the collective impact of a single signal on transitioning the polymer chain aggregation state of individual assemblies, rather than just altering a certain unit or chain. This nonlinear signal-to-response mechanism is potential to solve the tricky problems of probing and sensing endogenous signals with trace physiological concentration.

Polythionoester Vesicle: An Efficient Polymeric Platform for Tuning H2S Release.

Hydrogen sulfide (H2S) serves as a key gaseous regulator that not only directs many physiological activities, but also manifests therapeutic benefits to many diseases. Developing H2S vehicle platforms for its local delivery and long-acting release is important to achieve target gas therapy. Most of the known H2S-donating polymers contain labile thioester scaffolds within their structures that suffer from the issue of low gas releasing efficiency. Here we present the use of thionoester, a constitutional isomer of thioester, as the functional unit to build a structural platform of cysteine-triggered H2S donor polymer, polythionoester. Simple exchange of the sulfur and oxygen positions in the carbonyl sulfide scaffold makes the polythionoesters undergo a distinct mechanism of H2S production, which can largely improve the gas-releasing efficiency (>80%). Moreover, the thionoester-containing block copolymers can self-assemble into vesicles in an aqueous media. We discover that control over the size effect can adjust the vesicle disassembly rate and gas-releasing kinetics. A tunable half-life of H2S generation (2.6-9.8 h) can be accessed by tailoring the vesicle dimension. This allows such polymersomes to be potential as a gas nanodelivery system for long-lasting gas therapeutics.

Salivary microRNAs as promising biomarkers for detection of esophageal cancer.

BACKGROUND AND PURPOSE: Tissue microRNAs (miRNAs) can detect cancers and predict prognosis. Several recent studies reported that tissue, plasma, and saliva miRNAs share similar expression profiles. In this study, we investigated the discriminatory power of salivary miRNAs (including whole saliva and saliva supernatant) for detection of esophageal cancer. MATERIALS AND METHODS: By Agilent microarray, six deregulated miRNAs from whole saliva samples from seven patients with esophageal cancer and three healthy controls were selected. The six selected miRNAs were subjected to validation of their expression levels by RT-qPCR using both whole saliva and saliva supernatant samples from an independent set of 39 patients with esophageal cancer and 19 healthy controls. RESULTS: Six miRNAs (miR-10b*, miR-144, miR-21, miR-451, miR-486-5p, and miR-634) were identified as targets by Agilent microarray. After validation by RT-qPCR, miR-10b*, miR-144, and miR-451 in whole saliva and miR-10b*, miR-144, miR-21, and miR-451 in saliva supernatant were significantly upregulated in patients, with sensitivities of 89.7, 92.3, 84.6, 79.5, 43.6, 89.7, and 51.3% and specificities of 57.9, 47.4, 57.9%, 57.9, 89.5, 47.4, and 84.2%, respectively. CONCLUSIONS: We found distinctive miRNAs for esophageal cancer in both whole saliva and saliva supernatant. These miRNAs possess discriminatory power for detection of esophageal cancer. Because saliva collection is noninvasive and convenient, salivary miRNAs show great promise as biomarkers for detection of esophageal cancer in areas at high risk.