A Review of Biodegradable Plastics: Chemistry, Applications, Properties, and Future Research Needs.

Environmental concerns over waste plastics' effect on the environment are leading to the creation of biodegradable plastics. Biodegradable plastics may serve as a promising approach to manage the issue of environmental accumulation of plastic waste in the ocean and soil. Biodegradable plastics are the type of polymers that can be degraded by microorganisms into small molecules (e.g., H2O, CO2, and CH4). However, there are misconceptions surrounding biodegradable plastics. For example, the term "biodegradable" on product labeling can be misconstrued by the public to imply that the product will degrade under any environmental conditions. Such misleading information leads to consumer encouragement of excessive consumption of certain goods and increased littering of products labeled as "biodegradable". This review not only provides a comprehensive overview of the state-of-the-art biodegradable plastics but also clarifies the definitions and various terms associated with biodegradable plastics, including oxo-degradable plastics, enzyme-mediated plastics, and biodegradation agents. Analytical techniques and standard test methods to evaluate the biodegradability of polymeric materials in alignment with international standards are summarized. The review summarizes the properties and industrial applications of previously developed biodegradable plastics and then discusses how biomass-derived monomers can create new types of biodegradable polymers by utilizing their unique chemical properties from oxygen-containing functional groups. The terminology and methodologies covered in the paper provide a perspective on directions for the design of new biodegradable polymers that possess not only advanced performance for practical applications but also environmental benefits.

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.

Cyanine Polymersomes Inbreathe Gas Signaling Molecule: SO2 -Driven Bilayer Tubular Deformation for Transmembrane Traffic Regulation.

Fabricating nanoscale assemblies that can respond to gas signaling molecules has emerged as a field of growing interest owing to their unique biomedical applications in gas-guided delivery and gas therapeutics. Yet, among a variety of endogenous gaseous biosignals, exploiting sulfur dioxide (SO2 ) as a cue for controllable self-assembly remains elusive, despite its crucial two-sided roles both in physiology and pathology. Here we show a SO2 -responsive polymersome system assembled from a novel class of cyanine-containing block copolymers. By intake of SO2 gas, the tautomerism of cyanine drives such vesicles to continuously deform, and change into long nanotubes through axial stretching and anisotropic extrusion of the membranes. Unexpectedly, during this order-to-order phase transition, their membranes manifest well SO2 -dose-dependent permselectivity, which allows the cargos of different sizes loaded therein to be selectively transferred across the bilayers. This study would inspire us to better understand and mimic the function of gas signaling molecules in shifting biomembrane shape and managing transmembrane traffic.

Sporadic hand, foot, and mouth disease cases associated with non-C4 enterovirus 71 strains in Xiamen, China, from 2009 to 2018.

Enterovirus 71 (EV71) has caused large hand, foot, and mouth disease (HFMD) epidemics among young children, and EV71 infection is the leading cause of severe HFMD cases and deaths. In mainland China, the prevalence and risk factors of non-C4 EV71 strains are still unclear. In this study, we monitored non-C4 strains over a 10-year HFMD epidemiological surveillance period in Xiamen. The 5'UTR and VP1 coding region of EV71 strains were amplified by RT-nested PCR and sequenced. Thirty-two non-C4 EV71 strains were identified during 2009-2018. This study provides important information about the prevalence of EV71 in China that will be applicable for development of vaccines and diagnostic reagents as well as establishment of policies for HFMD prevention and control.

CO2 -Strengthened Double-Cross-Linked Polymer Gels from Frustrated Lewis Pair Networks.

Conventional thermosets consisting of polymer networks with robust and irreversible chemical linkages are incapable of reshaping or reprocessing once formed. In contrast, reversible non-covalent crosslinks can impart structurally flexible and reconfigurable feature to the networks, but at the expense of certain mechanical strength. The integration of fixed covalent bonds and noncovalent bonds into these materials can usually attain enhanced mechanical properties and meanwhile provide dynamic and adaptable functions, such as responsive and healing ability to external stimuli. Here a double-cross-linked frustrated Lewis pair network (FLPN) is developed through a specific three-component reaction among triarylborane, triarylphosphine, and CO2 , which is composed of permanent chemical crosslinks and dynamic CO2 gas-bridged connections. The amount of CO2 added can regulate the density of supramolecular node in such FLPN, so as to control the strength and toughness of the gel material. Moreover, the broken gel can be rapidly healed by CO2 stimulus through the reconstruction of dynamic covalent network. This study will inspire a new way to create gas-based smart materials by incorporating frustrated Lewis pair chemistry into traditional gel system.

808 nm Near-Infrared Light-Triggered Payload Release from Green Light-Responsive Donor-Acceptor Stenhouse Adducts Polymer-Coated Upconversion Nanoparticles.

Owing to deep activation in biotissues and enhanced targeting efficiency, developing photoresponsive polymer-upconversion nanoparticles (PP-UCNPs) nanovectors has witnessed rapid growth in the past decade. However, up to date, all developed nanovectors require high-order photon processes to initiate the release of cargos. The photodamage caused by high-power near-infrared laser light may be a critical obstacle to their clinical application. Here, for the first time, by leveraging absorption-emission spectral matching between donor-acceptor Stenhouse adducts (DASA) PP and UCNPs (λex , 808 nm) in the green region (≈530 nm), the designed nanovector is capable of releasing cargos at a low-power 808 nm excitation (0.2 W). Considering the high molar absorptivity, biobenign, and synthetic tunability of DASA, DASA PP can be utilized as an up-and-coming candidate to design and synthesize the next generation of upconversion nanovectors without photodamage.

Challenges of the establishment of rubber-based agroforestry systems: Decreases in the diversity and abundance of ground arthropods.

The global land area devoted to rubber plantations has now reached 13 million hectares, and the further expansion of these rubber plantations at the expense of tropical forests will have significant adverse effects on the ecological environment. Rubber-based agroforestry systems are considered a preferable approach for ameliorating the ecological environment. Many researchers have focused on the positive effects of rubber-based agroforestry systems on the ecological environment, while ignoring the risks involved in the establishment of rubber-based agroforestry systems. The present study investigated the effects of different-aged rubber-based agroforestry systems on the abundance and diversity of ground arthropods. It has been observed that the abundance and taxon richness of ground arthropods generally showed no difference when comparing young and mature rubber plantations. The rubber-based agroforestry systems significantly decreased the understory vegetation species, along with the abundance and taxon richness of ground arthropods compared to the same aged-rubber monoculture plantations. In addition, the change in the abundance and taxon richness of ground arthropods was greatly affected by the understory vegetation species and soil temperature. The abundance and taxon richness of ground arthropods decreased with the decrease in number of species of understory vegetation. The study results indicate that the establishment of rubber-based agroforestry systems have adversely affected the abundance and richness of ground arthropods to an extant greater than expected. Therefore, single, large rubber-based agroforestry systems are not recommended, and the intercropping of rubber and rubber-based agroforestry systems must be designed to promote the migration of ground arthropods between different systems.

Hydrogen Polysulfide Biosignal-Responsive Polymersomes as a Nanoplatform for Distinguishing Intracellular Reactive Sulfur Species (RSS).

Reactive sulfur species (RSS) are a family of crucial biosignals for regulating cell processes. Among these, hydrogen polysulfide (H2 Sn , n ≥ 2) is a hallmark of tumor suppressor activation and regarded as the actual regulator to mediate sulfur-related biology. However, high effective recognition of intracellular H2 Sn is insurmountable due to its extremely low concentration and the disturbance of RSS analogues. Here an H2 Sn -responsive macromolecule that can distinguish H2 Sn from intracellular RSS through polymer degradation in ultrasensitive and highly selective manner is reported. This kind of polymers can further self-assemble into vesicular nanostructure. Upon cell uptake, they can be function as "all-in-one" H2 Sn -nanoplatforms, in order to fulfill multiple ambitious tasks including monitoring the H2 Sn biosynthetic pathways, unraveling the puzzles of H2 Sn -mediated cellular events, and conducting H2 Sn pathological milieu-specific drug delivery.

Epidemiologic and etiologic characteristics of hand, foot, and mouth disease in Chongqing, China between 2010 and 2013.

Hand, foot, and mouth disease (HFMD) has become very common in children, with widespread occurrence across China. The aim of this study was to investigate the epidemiologic and etiologic characteristics of HFMD, including etiologic variations in Chongqing, China. An epidemiologic investigation was based on 3,472 patients who presented with HFMD manifestations and were admitted at the Children's Hospital of Chongqing Medical University between 2010 and 2013. Fecal specimens from 830 patients were analyzed by nested RT-PCR to identify the enterovirus pathogens, and the molecular characterization of HFMD was illustrated by phylogenetic tree analysis. The results of this study indicate that the peak of the HFMD epidemic in Chongqing between 2010 and 2013 occurred between April and July each year. The median age of onset was 2.24 years old, and children under the age of five accounted for 96.4% of all the HFMD cases; the male-to-female ratio was 1.89:1. Enterovirus 71 accounted for a major proportion of the isolated strains every year, including the majority (74%) of severe cases. However, the proportion of Coxsackie A (CV-A) 6 infections increased from 2.11% in 2010 to 16.36% in 2013, while the proportion of CV-A16 infections decreased from 31.23% in 2010 to 4.67% in 2013. Molecular epidemiologic study showed that all enterovirus 71 strains belonged to subgenotype C4a, whereas all CV-A16 strains belonged to genotype B1, including subgenotype B1a and subgenotype B1b.

Triterpenoid-Based Self-Healing Supramolecular Polymer Hydrogels Formed by Host-Guest Interactions.

Pentacyclic triterpenoids, a class of naturally bioactive products having multiple functional groups, unique chiral centers, rigid skeletons, and good biocompatibility, are ideal building blocks for fabricating versatile supramolecular structures. In this research, the natural pentacyclic triterpenoid glycyrrhetinic acid (GA) was used as a guest molecule for ß-cyclodextrin (ß-CD) to form a GA/ß-CD (1:1) inclusion complex. By means of GA and ß-CD pendant groups in N,N'-dimethylacrylamide copolymers, a supramolecular polymer hydrogel can be physically cross-linked by host-guest interactions between GA and ß-CD moieties. Moreover, self-healing of this hydrogel was observed and confirmed by step-strain rheological measurements, whereby the maximum storage modulus occurred at a [GA]/[ß-CD] molar ratio of 1:1. Additionally, these polymers displayed outstanding biocompatibility. The introduction of a natural pentacyclic triterpenoid into a hydrogel system not only provides a biocompatible guest-host complementary GA/ß-CD pair, but also makes this hydrogel an attractive candidate for tissue engineering.

CO2-stimulated diversiform deformations of polymer assemblies.

Use of a given physiological stimulus to delicately deform polymer assemblies is a challenging topic. Here we develop synthetic block copolymers to construct a series of CO2-sensitive self-assembled nanostructures that can simulate controllable deformations of the organelles in different ways. By controlling the CO2 stimulation levels, one can modulate the size, shape, and morphology of the polymer aggregates, which is conducive to understanding the stimuli-triggered dynamic reshaping process of polymer assemblies in aqueous solution.

Polymeric microtubules that breathe: CO2 -driven polymer controlled-self-assembly and shape transformation.

Tubular breathing motion: Polymer tubules self-assembled from a gas-sensitive triblock copolymer can undergo shape evolution. A sequence from microtubes through submicroscopic vesicles to nanosized spherical micelles is modulated by CO2 stimulation levels.

Facile and efficient fabrication of photoresponsive microgels via thiol-Michael addition.

A photoresponsive microgel is designed by the combination of a noncovalent assembly strategy with a covalent cross-linking method. End-functionalized poly(ethylene glycol) with azobenzene [(PEG-(Azo)(2))] was mixed with acrylate-modified ß-CD (ß-CD-MAA) to form photoresponsive inclusion complex through host-guest interaction. The above photoresponsive complex was cross-linked by thiol-functionalized PEG (PEG-dithiol) via Michael addition click reaction. The photoreversibility of resulted microgel was studied by TEM, UV-Vis spectroscopy, and (1)H NMR measurements. The characterization results indicated that the reversible size changes of the microgel could be achieved by alternative UV-Vis irradiations with good repeatability.

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.

Phase diagrams guide synthesis of highly ordered intermetallic electrocatalysts: separating alloying and ordering stages.

Supported platinum intermetallic compound catalysts have attracted considerable attention owing to their remarkable activities and durability for the oxygen reduction reaction in proton-exchange membrane fuel cells. However, the synthesis of highly ordered intermetallic compound catalysts remains a challenge owing to the limited understanding of their formation mechanism under high-temperature conditions. In this study, we perform in-situ high-temperature X-ray diffraction studies to investigate the structural evolution in the impregnation synthesis of carbon-supported intermetallic catalysts. We identify the phase-transition-temperature (TPT)-dependent evolution process that involve concurrent (for alloys with high TPT) or separate (for alloys with low TPT) alloying/ordering stages. Accordingly, we realize the synthesis of highly ordered intermetallic catalysts by adopting a separate annealing protocol with a high-temperature alloying stage and a low-temperature ordering stage, which display a high mass activity of 0.96 A mgPt-1 at 0.9 V in H2-O2 fuel cells and a remarkable durability.

Voltage-responsive vesicles based on orthogonal assembly of two homopolymers.

Two end-decorated homopolymers, poly(styrene)-beta-cyclodextrin (PS-beta-CD) and poly(ethylene oxide)-ferrocene (PEO-Fc), can orthogonally self-assemble into a supramolecular diblock copolymer (PS-beta-CD/PEO-Fc) in aqueous solutions based on the terminal host-guest interactions. These assemblies can further form supramolecular vesicles, and their assembly and disassembly behaviors can be reversibly switched by voltage through the reversible association and disassociation of the middle supramolecular connection. The vesicles possess an unprecedented property that their assembly or disassembly speed can be controlled by the applied voltage strength. Luminescence spectroscopy demonstrates that the vesicles act as nanocapsules carrying molecules within their hollow cavities and that the external voltage strength accurately regulates the drug release time.

Cellulose-based dual graft molecular brushes as potential drug nanocarriers: stimulus-responsive micelles, self-assembled phase transition behavior, and tunable crystalline morphologies.

Well-defined cellulose-based dual graft molecular brushes, composed of ethyl cellulose-graft-poly(N,N-dimethylaminoethyl methacrylate)-graft-poly(epsilon-caprolactone) (EC-g-PDMAEMA-g-PCL), have been prepared by ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Unlike other brush copolymers, the new molecular brushes show some unique physicochemical properties and multifunction due to their unique topological structures. These biocompatible copolymers self-assembled to micelles in aqueous solution. Upon pH change, the single micelles further assembled into micellar aggregates. As a result, the micelles in aqueous media could act as excellent drug nanocarriers for controlled drug release. The crystallinity and crystal morphology of the copolymers can be controlled to a certain extent by varying the length of the side chains, which may exert strong spacial restriction and, hence, affect the crystal structures.

An emerging and expanding clade accounts for the persistent outbreak of Coxsackievirus A6-associated hand, foot, and mouth disease in China since 2013.

Enterovirus (EV)-A71 and Coxsackievirus (CV)-A16 have historically been the major pathogens of hand, foot, and mouth disease (HMFD) in China; however, CV-A6， which had previously received little attention, became the predominant pathogen in 2013, and has remained one of the common pathogens since then. In this work, we conducted a molecular epidemiology study of CV-A6-associated HFMD in Xiamen from 2009 to 2015. The data showed CV-A6 pandemics had a certain periodicity rather than occurring randomly. Evolution analysis based on near-complete VP1 nucleotide sequences showed subgenotype D5 lineage 4 strains account for the persistent outbreak of CV-A6-associated HFMD in China since 2013. Alignment analysis revealed eight candidate amino acid substitutions in VP1, which may provide useful information for the research of CV-A6 virulence enhancement. This study contributed to elucidating the circulation patterns and genetic characteristics of CV-A6 in China; however, further surveillance and intervention in CV-A6 epidemics is recommended.

[Preparation and properties of Talpha1 loaded injectable sustained release microspheres].

To prepare thymosin alpha-1 (Talpha) loaded injectable sustained release microspheres and to evaluate its release behavior, bioactivities in vitro as well as its pharmacodynamics in vivo, Talpha1 loaded microspheres was prepared with poly ( lactic-co-glycolic acid) (PLGA) as carrier material by double emulsion (W/O/W) method. Physical and chemical properties of microspheres, such as mean diameter, The release behavior and its influencing factors were morphology and drug loading were evaluated. evaluated by HPLC determination. The bioactivity of Talpha1 in the course of encapsulation process and in vitro release ware evaluated by CCK-8 method. The ratio of CD4+/CD8+ in blood was determined with flow cytometry and the pharmacodynamics of Ta, loaded microspheres was evaluated by the change of CD4+/ CD8+. Microspheres with good shape and dispersive quality were prepared. The drug entrapment efficiency of two optimizing prescriptions containing 5% NaCl and 10% glucose as outer water phase were 87. 8% and 90. 2% , respectively. The cumulated release in one month is up to 90%. The bioactivity of Talpha was conserved with glucose as outer water phase, but in the course of in vitro release, the specific activity of Talpha in the microspheres decreased a little. Talpha microspheres can increase significantly the immunity of immuno-suppressed rats. Talpha can be encapsulated in injectable microspheres to yield one-month continuous release when using biodegradable polymers PLGA as carrier material, and this technique will have a favorable perspective in the near future.