Regulation of mitochondrial network architecture and function in mesenchymal stem cells by micropatterned surfaces.

Mitochondrial network architecture, which is closely related to mitochondrial function, is mechanically sensitive and regulated by multiple stimuli. However, the effects of microtopographic cues on mitochondria remain poorly defined. Herein, polycaprolactone (PCL) surfaces were used as models to investigate how micropatterns regulate mitochondrial network architecture and function in rat adipose-derived stem cells (rASCs). It was found that large pit (LP)-induced rASCs to form larger and more complex mitochondrial networks. Consistently, the expression of key genes related to mitochondrial dynamics revealed that mitochondrial fusion (MFN1 and MFN2) and midzone fission (DRP1 and MFF) were increased in rASCs on LP. In contrast, the middle pit (MP)-enhanced mitochondrial biogenesis, as evidenced by the larger mitochondrial area and higher expression of PGC-1. Both LP and MP promoted ATP production in rASCs. It is likely that LP increased ATP levels through modulating mitochondrial network architecture while MP stimulated mitochondria biogenesis to do so. Our study clarified the regulation of micropatterned surfaces on mitochondria, highlighting the potential of LP and MP as a simple platform to stimulate mitochondria and the subsequent cellular function of MSCs.

Nitrogen-containing wastewater fuel cells for total nitrogen removal and energy recovery based on Cl•/ClO• oxidation of ammonia nitrogen.

The excess nitrogen discharge into water bodies has resulted in extensive water pollution and human health risks, which has become a critical global issue. Moreover, nitrogenous wastewater contains considerable chemical energy contributed by organic pollutants and nitrogenous compounds. Therefore, the treatment of various kinds of nitrogen-containing wastewater for nitrogen removal and energy recovery is of significance. Biological methode and advanced oxidation processes (AOPs) are the main methods for nitrogen removal. However, biological treatment is easily inhibited by high-salinity, high ammonia nitrogen (NH3-N/NH4+-N), nitrite and toxic organics in wastewater, which limits its application. AOPs mainly induce in situ generation of highly reactive species, such as hydroxyl radical (HO•), sulfate radical (SO4•-) and chlorine radicals (Cl•, ClO•, Cl2•-), for nitrogen removal. Nevertheless, HO• shows low reactivity and N2 selectivity towards NH3-N/NH4+-N oxidation, and SO4•- also demonstrates unsatisfactory NH3-N/NH4+-N removal. It has been shown that Cl•/ClO• can efficiently remove NH3-N/NH4+-N with high N2 selectivity. The generation of Cl•/ClO• can be triggered by various techniques, among which the PEC technique shows great potential due to its higher efficiency for Cl•/ClO• generation and eco-friendly approach for pollutants degradation and energy recovery by utilizing solar energy. Cl•/ClO• oxidation of NH3-N/NH4+-N and nitrate nitrogen (NO3--N) reduction can be strengthened through the design of photoanode and cathode materials, respectively. Coupling with this two pathways, an exhaustive total nitrogen (TN) removal system is designed for complete TN removal. When introducing the mechanism into photocatalytic fuel cells (PFCs), the concept of nitrogen-containing wastewater fuel cells (NFCs) is proposed to treat several typical types of nitrogen-containing wastewater, achieving high-efficiency TN removal, organics degradation, toxic chlorate control, and energy recovery simultaneously. Recent research progress in this field is reviewed, summarized and discussed, and in-depth perspectives are proposed, providing new ideas for the resource treatment of nitrogen-containing wastewater.

Efficient ammonia removal and toxic chlorate control by using BiVO4/WO3 heterojunction photoanode in a self-driven PEC-chlorine system.

The efficient removal of ammonia is a difficult issue in wastewater treatment because ammonia is easily converted to nitrate instead of N2. The oxidation of ammonia by chlorine radical (Cl) is recognized as an effective method. However, the massive generation of toxic byproducts chlorate and nitrate pose great risk for its practical application due to the excessive oxidation capacity of hydroxyl radical. Herein, we propose a novel method to selectively generate Cl for efficient ammonia removal using BiVO4/WO3 photoanode in a self-driven photoelectrocatalytic (PEC) system. Cl was predominantly produced by regulating the valence band edge of WO3 though modifying BiVO4, which tuned the moderate oxidative force of hole to reduce OH generation and thereby inhibited the formation of chlorate and nitrate. The self-driven ammonia degradation was achieved by employing BiVO4/WO3 and Si photovoltaic cells as composite photoanodes to improve light-absorption and electron-hole separation, thus enhancing Cl production. These results showed that 10 mg L-1 of ammonia-N was completely removed (99.3 %) in 120 min with 80.1 % of total nitrogen removal. Toxic byproducts chlorate and nitrate were inhibited by 79.3 % and 31 %, respectively, compared to WO3. This work provides new insights to develop efficient, energy-saving and environment-friendly method for ammonia pollution treatment.

Novel 3D Pd-Cu(OH)2/CF cathode for rapid reduction of nitrate-N and simultaneous total nitrogen removal from wastewater.

Removal of NO3- is a challenging problem in wastewater treatment. Electrocatalysis shows a great potential to remove NO3- but selectively converting NO3- to N2 is facing a low efficiency. Here, a novel 3D Pd-Cu(OH)2/CF cathode based electrocatalytic (EC) system was proposed that can rapidly and selectively convert NO3- to NH4+, and further convert to N2 simultaneously. The special designs for the system include: Cu(OH)2 nanowires were firstly grown on copper foam (CF) with excellent conductivity that features high specific surface area in enhancing NO3- absorption and conversion to NO2-. Then, palladium (Pd) with a superior photons activation capacity was doped on the Cu(OH)2 nanowires to promote the reduction of NO2- to NH4+. Then NH4+ was quickly oxidized into N2 by active chlorine. Finally, total nitrogen (TN) could easily be removed completely via above exhaustive cycle reactions. The 3D Pd-Cu(OH)2/CF cathode exhibits a 98.8 % conversion of NO3- to NH4+ in 45 min with the reported highest removal rate of 0.017 cm-2 min-1, which is 19.4 times higher than that of CF. The converted NH4+ was finally exhaustively oxidized to N2 with a 98.7 % of TN removal in 60 min.

Efficient SO2 Removal and Highly Synergistic H2O2 Production Based on a Novel Dual-Function Photoelectrocatalytic System.

The direct conversion of SO2 to SO3 is rather difficult for flue gas desulfurization due to its inert dynamic with high reaction activation energy, and the absorption by wet limestone-gypsum also needs the forced oxidation of O2 to oxidize sulfite to sulfate, which is necessary for additional aeration. Here, we propose a method to remove SO2 with highly synergistic H2O2 production based on a novel dual-function photoelectrocatalytic (PEC) system in which the jointed spontaneous reaction of desulfurization and H2O2 production was integrated instead of nonspontaneous reaction of O2 to H2O2. SO2 was absorbed by alkali liquor then oxidized quickly into SO42- by a nanorod α-Fe2O3 photoanode, which possessed high alkali corrosion resistance and electron transport properties. H2O2 was produced simultaneously in the cathode chamber on a gas diffusion electrode and was remarkably boosted by the conversion reaction of SO32- to SO42- in the anode chamber in which the released chemical energy was effectively used to increase H2O2. The photocurrent density increased by 40% up to 1.2 mA·cm-2, and the H2O2 evolution rate achieved 58.8 µmol·L-1·h-1·cm-2 with the synergistic treatment of SO2, which is about five times than that without SO2. This proposed PEC cell system offers a cost-effective and environmental-benign approach for dual purpose of flue gas desulfurization and simultaneous high-valued H2O2 production.

Comparative study on nitrogen removal and functional genes response between surface flow constructed wetland and floating treatment wetland planted with Iris pseudacorus.

Excessive nitrogen accumulated from wastewater with low C/N ratio is a new threat to water ecosystem. In this study, surface flow constructed wetland (SFCW) and floating treatment wetland (FTW) planted with Iris pseudacorus were set in parallel for nitrogen removal. The nitrogen removal efficiencies and pathways, as well as the abundance and functional diversities of the microbial community, were investigated. The results demonstrated that SFCW generally had better nitrogen removal performance than FTW did over four seasons. The average total nitrogen removal efficiency was 66.0% and 43.8% in SFCW and FTW, respectively. The plant uptake played a vital role in nitrogen reduction, which accounted for 29.3% and 7.7% of the total removed nitrogen in SFCW and FTW, respectively. A combination of high-throughput sequencing and quantitative polymerase chain reaction analysis revealed that the two wetland systems had complete nitrogen cycling, and the narG gene was the dominant nitrogen-transformation functional gene in both systems. More abundant denitrifying genes in SFCW than in FTW were also responsible for higher removal capacity of nitrogen. The results suggest that the planting pattern of wetland vegetation has an important impact on nitrogen removal efficiency by influencing the plant absorption and the development of microbial communities.