Effects of antibiotics and heavy metals on denitrification in shallow eutrophic lakes.

Antibiotic and heavy metal residues in shallow lakes caused by aquaculture and human activities such as sewage discharge have attracted much attention and public concern. However, mechanisms by which these environmental pollutants affect the microorganism-mediated biogeochemical cycle are unknown. This study focused on the effects of antibiotics, heavy metal, and antibiotic resistance genes (ARGs) on denitrification in shallow lakes. The results showed that antibiotics and metal elements had inhibitory effects on denitrification, whereas AGRs exhibited stimulating effects. Specifically, the enrofloxacin concentration showed a significant negative correlation with the copy number of denitrifying bacteria, whereas the copy number of the ARGs sulI, sulII, and tetG showed significant positive correlations. In addition, tetG was closely related to the community structure of nirS-type denitrifiers, and nirS-type denitrifiers were significantly correlated with the potential denitrification rate (PDR). Furthermore, the ARGs sulI, sulII, and tetG were positively correlated with PDR (P < 0.05). By contrast, the metal elements arsenic, manganese, cobalt, and antimony were negatively correlated with the copy number of denitrifying bacteria. Arsenic was significantly correlated with the community composition of nirK-type denitrifiers, but nirK-type denitrifiers did not show a significant correlation with the PDR. This work extends our understanding of the effects of antibiotics and heavy metals on denitrification, but further studies are needed to determine the interaction effects of pollutants.

Fluorescent polymer cubosomes and hexosomes with aggregation-induced emission.

Fluorescent polymer cubosomes and hexosomes with aggregation-induced emission (AIE) were prepared from amphiphilic block copolymers PEG-b-PTPEMA where the hydrophobic block PTPEMA was a polymethacrylate with tetraphenylethene (TPE) as the AIE side group. Four highly asymmetric block copolymers with hydrophilic block weight ratio f PEG ≤ 20% were synthesized. Cubosomes and hexosomes with strong fluorescence emission were obtained by nanoprecipitation of polymers with f PEG < 9% in dioxane/water and THF/water systems. Their ordered internal structures were studied by electron microscopy (cryo-EM, SEM and TEM) and the X-ray scattering technique (SAXS). To elucidate the formation mechanisms of these inverted colloids, other parameters influencing the morphologies, like the water content during self-assembly and the organic solvent composition, were also investigated. This study not only inspires people to design novel building blocks for the preparation of functional cubosomes and hexosomes, but also presents the first AIE fluorescent polymer cubosome and hexosome with potential applications in bio-related fields.

Light-Gated Nano-Porous Capsules from Stereoisomer-Directed Self-Assemblies.

Structuring pores into stable membrane and controlling their opening is extremely useful for applications that require nanopores as channels for material exchange and transportation. In this work, nanoporous vesicles with aggregation-induced emission (AIE) properties were developed from the amphiphilic polymer PEG550-TPE-Chol, in which the hydrophobic part is composed of a tetraphenylethene (TPE) group and a cholesterol moiety and the hydrophilic block is a poly(ethylene glycol) (PEG, Mn = 550 Da). Two stereoisomers, trans-PEG550-TPE-Chol and cis-PEG550-TPE-Chol, were successfully synthesized. These thermally stable stereoisomers showed distinct self-assembly behavior in water: trans-PEG550-TPE-Chol formed classical vesicles, while cis-PEG550-TPE-Chol self-assembled into cylindrical micelles. Interestingly, trans/cis mixtures of PEG550-TPE-Chol (trans/cis = 60/40), either naturally synthesized without isomers' separation during the synthesis or intentionally mixed using trans- and cis-isomers, constructed perforated vesicles with nanopores. Moreover, under the illumination of high intensity UV light (365 nm, 15 mW/cm2), the classical vesicles of trans-PEG550-TPE-Chol were perforated by its cis counterparts generated from the trans-cis photoisomerization, while the cylindrical micelles of cis-PEG550-TPE-Chol interweaved to form meshes and nanoporous membranes due to the trans-isomers produced by cis-trans photoisomerization. All of these assemblies in water emitted bright cyan fluorescence under UV light, while their constituent molecules were not fluorescent when solubilized in organic solvent. The AIE fluorescent normal vesicles and nanoporous vesicles may find potential applications in biotechnology as light-gated delivery vehicles and capsules with nanochannels for material exchange.

CO2 -Activated Reversible Transition between Polymersomes and Micelles with AIE Fluorescence.

Fluorescent polymersomes with both aggregation-induced emission (AIE) and CO2 -responsive properties were developed from amphiphilic block copolymer PEG-b-P(DEAEMA-co-TPEMA) in which the hydrophobic block was a copolymer made of tetraphenylethene functionalized methacrylate (TPEMA) and 2-(diethylamino)ethyl methacrylate (DEAEMA) with unspecified sequence arrangement. Four block copolymers with different DEAEMA/TPEMA and hydrophilic/hydrophobic ratios were synthesized, and bright AIE polymersomes were prepared by nanoprecipitation in THF/water and dioxane/water systems. Polymersomes of PEG45 -b-P(DEAEMA36 -co-TPEMA6 ) were chosen to study the CO2 -responsive property. Upon CO2 bubbling vesicles transformed to small spherical micelles, and upon Ar bubbling micelles returned to vesicles with the presence of a few intermediate morphologies. These polymersomes might have promising applications as sensors, nanoreactors, or controlled release systems.

Nematicidal amide alkaloids from the seeds of Clausena lansium.

Five new amide alkaloids (1-3, 5-6) were isolated from the seeds of Clausena lansium together with one new natural product (4) and four known analogues (7-10). The structures of the new amide alkaloids were elucidated based on a comprehensive spectroscopic data analysis including 1D and 2D NMR as well as HRESIMS, and by comparison with the literature. The bioactivity results showed that compound 8 expressed potent nematicidal activity against Panagrellus redivevus, with IC50 value of 0.12 mM, while compounds 3 and 5 presented moderate nematicidal activity with IC50 values of 2.75 and 3.93 mM, respectively (abamectin as the positive control with IC50 value of 1.05 mM).

Fluorescent Polymersomes with Aggregation-Induced Emission.

Fluorescent polymersomes are interesting systems for cell/tissue imaging and in vivo study of drug distribution and delivery. We report on bright fluorescent polymersomes with aggregation-induced emission self-assembled by a series of tetraphenylethylene (TPE)-containing amphiphilic biodegradable block copolymers, where the hydrophilic block is a polyethylene glycol and hydrophobic block is a TPE-substituted trimethylenecarbonate polymer P(TPE-TMC). Their self-assemblies in water were prepared by nanoprecipitation using dioxane or tetrahydrofuran as co-solvent, and the self-assembling processes were studied in detail by cryo-electron microscopy, dynamic light scattering, and spectrofluorometer. The polymersomes are formed via the closure of bilayer lamellae self-assembled first by amphiphilic block copolymers. The polymersome membrane affords a nanosize bright fluorescent system with self-assembly induced emission in the thickness scale of 10-15 nm. The control of the whole size of polymersome is achieved by the choice of co-solvent for self-assembling and by the design of a suitable hydrophilic/hydrophobic ratio of block copolymers. These polymersomes can be potentially used as a stable fluorescent tool to monitor the transportation and distribution of drugs and bioconjugates in living cells.

Dual-responsive shape memory hydrogels with novel thermoplasticity based on a hydrophobically modified polyampholyte.

Shape memory hydrogels offer the ability to recover their permanent shape from temporarily trapped shapes without application of external forces. Here, we report a novel dual-responsive shape memory hydrogel with characteristic thermoplasticity. The water-insoluble hydrogel is prepared by simple ternary copolymerization of acrylamide (AM) and acrylic acid (AA) with low amounts of a cationic surfmer, in the absence of organic crosslinkers. Through either ionic/complex binding of carboxyl groups via trivalent cations or salt-dependent hydrophobic association, the hydrogel can memorize a temporary shape successfully, which recovers its permanent form in the presence of a reducing agent or deionized water. Besides, the unique thermoplasticity of the hydrophobic polyampholyte hydrogel allows the change of its permanent shape upon heating and the fixation after cooling, which is in strong contrast to the conventional chemically cross-linked shape memory hydrogels. This fascinating feature undoubtedly enriches the shape memory hydrogel systems. Thus, we believe that the facile strategy could provide new opportunities with regard to the design and practical application of stimulus-responsive hydrogel systems.

Preparation of anion-exchangeable polymer vesicles through the self-assembly of hyperbranched polymeric ionic liquids.

This work reports the self-assembly of anion-exchangeable vesicles from an amphiphilic hyperbranched polymeric ionic liquid (HBPIL). By a simple one-step anion exchange with methyl orange, the obtained HBPILs could self-assemble into pH-indicative and colorful vesicles in water with color changes directly visible to the naked eye in response to solution pH. In addition, by another step of anion exchange with bovine serum albumin (BSA), the BSA-coated vesicles could also be readily prepared.