Light-Gating Crystalline Porous Covalent Organic Frameworks.

We report light gating in synthetic one-dimensional nanochannels of stable crystalline porous covalent organic frameworks. The frameworks consist of 2D hexagonal skeletons that are extended over the x-y plane and stacked along the z-direction to create dense yet aligned 1D mesoporous channels. The pores are designed to be photoadaptable by covalently integrating tetrafluoro-substituted azobenzene units onto edges, which protrude from walls and offer light-gating machinery confined in the channels. The implanted tetrafluoroazobenzene units are thermally stable yet highly sensitive to visible light to induce photoisomerization between the E and Z forms. Remarkably, photoisomerization induces drastic changes in intrapore polarity as well as pore shape and size, which exert profound effects on the molecular adsorption of a broad spectrum of compounds, ranging from inorganic iodine to organic dyes, drugs, and enzymes. Unexpectedly, the systems respond rapidly to visible lights to gate the molecular release of drugs and enzymes. Photoadaptable covalent organic frameworks with reversibly convertible pores offer a platform for constructing light-gating porous materials and tailorable delivery systems, remotely controlled by visible lights.

Photoresponsive Covalent Organic Frameworks: Visible-Light Controlled Conversion of Porous Structures and Its Impacts.

Covalent organic frameworks are a novel class of crystalline porous polymers that enable molecular design of extended polygonal skeletons to attain well-defined porous structures. However, construction of a framework that allows remote control of pores remains a challenge. Here we report a strategy that merges covalent, noncovalent, and photo chemistries to design photoresponsive frameworks with reversibly and remotely controllable pores. We developed a topology-guided multicomponent polycondensation system that integrates protruded tetrafluoroazobenzene units as photoresponsive sites on pore walls at predesigned densities, so that a series of crystalline porous frameworks with the same backbone can be constructed to develop a broad spectrum of pores ranging from mesopores to micropores. Distinct from conventional azobenzene-based systems, the tetrafluoroazobenzene frameworks are highly sensitive to visible lights to undergo high-rate isomerization. The photoisomerization exerts profound effects on pore size, shape, number, and environment, as well as molecular uptake and release, rendering the system able to convert and switch pores reversibly and remotely with visible lights. Our results open a way to a novel class of smart porous materials with pore structures and functions that are convertible and manageable with visible lights.

Phototransformation of phosphite induced by zinc oxide nanoparticles (ZnO NPs) in aquatic environments.

Phosphite, an essential component in the biogeochemical phosphorus cycle, may make significant contributions to the bioavailable phosphorus pool as well as water eutrophication. However, to date, the potential impacts of coexisting photochemically active substances on the environmental fate and transformation of phosphite in aquatic environments have been sparsely elucidated. In the present study, the effect of zinc oxide nanoparticles (ZnO NPs), a widely distributed photocatalyst in aquatic environments, on phosphite phototransformation under simulated solar irradiation was systematically investigated. The physicochemical characteristics of the pristine and reacted ZnO NPs were thoroughly characterized. The results showed that the presence of ZnO NPs induced the indirect phototransformation of phosphite to phosphate, and the reaction rate increased with increasing ZnO NPs concentration. Through experiments with quenching and trapping free radicals, it was proved that photogenerated reactive oxygen species (ROS), such as hydroxyl radical (•OH), superoxide anion (O2•-), and singlet oxygen (1O2), made substantial contributions to phosphite phototransformation. In addition, the influencing factors such as initial phosphite concentration, pH, water matrixes (Cl-, F-, Br-, SO42-, NO3-, NO2-, HCO3-, humic acid (HA) and citric acid (CA)) were investigated. The component of generated precipitates after the phosphite phototransformation induced by ZnO NPs was still dominated by ZnO NPs, while the presence of amorphous Zn3(PO4)2 was identified. This work explored ZnO NPs-mediated phosphite phototransformation processes, indicating that nanophotocatalysts released into aquatic environments such as ZnO NPs may function as photosensitizers to play a beneficial role in the transformation of phosphite to phosphate, thereby potentially mitigating the toxicity of phosphite to aquatic organisms while exacerbating eutrophication. The findings of this study provide a novel insight into the comprehensive assessment of the environmental fate, potential ecological risk, and biogeochemical behaviors of phosphite in natural aquatic environments under the condition of combined pollution.

Light-induced dynamic RGD pattern for sequential modulation of macrophage phenotypes.

Due to the critical roles of macrophage in immune response and tissue repair, harnessing macrophage phenotypes dynamically to match the tissue healing process on demand attracted many attentions. Although there have developed many advanced platforms with dynamic features for cell manipulation, few studies have designed a dynamic chemical pattern to sequentially polarize macrophage phenotypes and meet the immune requirements at various tissue repair stages. Here, we propose a novel strategy for spatiotemporal manipulation of macrophage phenotypes by a UV-induced dynamic Arg-Gly-Asp (RGD) pattern. By employing a photo-patterning technique and the specific interaction between cyclodextrin (CD) and azobenzene-RGD (Azo-RGD), we prepared a polyethylene glycol-dithiol/polyethylene glycol-norbornene (PEG-SH/PEG-Nor) hydrogel with dynamic RGD-patterned surface. After irradiation with 365-nm UV light, the homogeneous RGD surface was transformed to the RGD-patterned surface which induced morphological transformation of macrophages from round to elongated and subsequent phenotypic transition from pro-inflammation to anti-inflammation. The mechanism of phenotypic polarization induced by RGD pattern was proved to be related to Rho-associated protein kinase 2 (ROCK2). Sequential modulation of macrophage phenotypes by the dynamic RGD-patterned surface provides a remote and non-invasive strategy to manipulate immune reactions and achieve optimized healing outcomes.

The efficient biomineralization and adsorption of cadmium (Cd2+) using secretory organo-biominerals (SOBs) produced by screened Alcaligenes faecalis K2.

Cadmium-contaminated wastewater has attracted increasing concerns due to its non-biodegradable properties and high toxicity. To explore eco-friendly and economically feasible strategies, the screened Alcaligenes faecalis K2 were employed for the biomineralization and recovery of Cd2+ from wastewater while producing considerable secretory organo-biominerals (SOBs) as bioadsorbents. At 75 mg/L Cd2+ exposure, 85.5% of Cd2+ was removed by K2, 43.0% of which was fixed in the granular SOBs. SOBs were convenient for separating from the solution. The adsorption capacity of granular sorbent made from SOBs was verified to be greater than 77.1 mg/g. Practically, 89.5% of 75 mg/L of Cd2+ could be stably removed while ereK2 continuously generated SOBs in a moving-bed biofilm reactor (MBBR). To sum up, the production of bioadsorbents can be achieved by K2, while removing Cd with live microorganisms, which was conducive to making full use of materials and improving Cd removal efficiency.

High levels of microplastic pollution in aquaculture water of fish ponds in the Pearl River Estuary of Guangzhou, China.

Microplastics (MPs) have caused great concern worldwide recently due to their ubiquity in the aquatic environment. The current knowledge on the occurrence of MPs in aquaculture fish ponds in a typical estuary system remains meagre. This study investigated the abundance and characteristics (shape, color, size and composition) of MPs in aquaculture water and pond influents in the Pearl River Estuary of Guangzhou, China, using an improved separation method. The bulk sampling and improved separation method by the combination of ethanol and polyaluminum chloride (PAC) significantly increased the MP separation efficiency, especially for particles with size less than <333 µm. The investigation results showed that MPs were detected in all water samples of fish ponds at two experimental stations with abundances of 10.3-60.5 particles/L (S1) and 33.0-87.5 particles/L (S2), respectively. Moreover, the average abundance of MPs in aquaculture water (42.1 particles/L) exhibited higher value than that in pond influents (32.1 particles/L). Most of MPs were colored and fibrous in appearance. MPs with the size range of <1000 µm (56.3-87.7%) prevailed in aquaculture water. MPs with size <333 µm that usually ignored in most studies were detected with percentage of 43.7% at S1station and 33.2% at S2 station, respectively. The small-sized MPs (<100 µm) in aquaculture water (23.7% at S1 station and 14.6% at S2 station) were more abundant than those in pond influents (7.2% at S1 station and 2.5% at S2 station). The main composition of MPs was polypropylene (PP) and polyethylene (PE). These findings indicated a high level of MP pollution in aquaculture fish ponds. The MPs originated from the Pearl River Estuary were accumulated in aquaculture fish ponds. This study provides an insight into MP pollution in aquaculture fish ponds at a typical estuarine system and highlights the load of MPs in the pond influents.

Near-Infrared-Triggered Dynamic Surface Topography for Sequential Modulation of Macrophage Phenotypes.

Immune response is critical to tissue repair. Designing biomaterials with immunomodulatory functions has become a promising strategy to facilitate tissue repair. Considering the key roles of macrophages in tissue repair and the significance of the balance of M1 and M2, smart biomaterials, which can harness macrophage phenotypes dynamically to match the tissue healing process on demand, have attracted a lot of attention to be set apart from the traditional anti-inflammatory biomaterials. Here, we prepare a gold nanorod-contained shape memory polycaprolactone film with dynamic surface topography, which has the ability to be transformed from flat to microgrooved under near-infrared (NIR) irradiation. Based on the close relationships between the morphologies and the phenotypes of macrophages, the NIR-triggered surface transformation induces the elongation of macrophages, and consequently the upregulated expressions of arginase-1 and IL-10 in vitro, indicating the change of macrophage phenotypes. The sequential modulation of macrophage phenotypes by dynamic surface topography is further confirmed in an in vivo implantation test. The healing-matched modulation of macrophage phenotypes by dynamic surface topography without the stimuli of cytokines offers an effective and noninvasive strategy to manipulate tissue regenerative immune reactions to achieve optimized healing outcomes.