Chitosan oligosaccharide-functionalized nano-prodrug for cascade chemotherapy through oxidative stress amplification.

Redox nanoparticles have been extensively developed for chemotherapy. However, the intracellular oxidative stress induced by constant aberrant glutathione (GSH), reactive oxygen species (ROS) and gamma-glutamyl transpeptidase (GGT) homeostasis remains the primary cause of evading tumor apoptosis. Herein, an oxidative stress-amplification strategy was designed using a pH-GSH-H2O2-GGT sensitive nano-prodrug for precise synergistic chemotherapy. The disulfide bond- conjugated doxorubicin prodrug (DOX-ss) was constructed as a GSH-scavenger. Then, phenylboronic acid (PBA), DOX-ss and poly (γ-glutamic acid) (γ-PGA) were successively conjugated using chitosan oligosaccharide (COS) to obtain the nano-prodrug PBA-COS-ss-DOX/γ-PGA. The PBA-COS-ss-DOX/γ-PGA prodrug could tightly attach to the polymer chain segment by atom transfer radical polymerization. Simultaneously, the drug interacted relatively weakly with the polymer by encapsulating ionic crosslinkers in DOX@PBA-COS/γ-PGA. The disulfide bond of the DOX-ss prodrug as a GSH-scavenger could be activated using overexpressed GSH to release DOX. Particularly, PBA-COS-ss-DOX/γ-PGA could prevent premature drug leakage and facilitate DOX delivery by GGT-targeting and intracellular H2O2-cleavable linker in human hepatocellular carcinoma (HepG2) cells. Concurrently, the nano-prodrug induced strong oxidative stress and tumor cell apoptosis. Collectively, the pH-GSH-H2O2-GGT responsive nano-prodrug shows potential for synergistic tumor therapy.

Zero-valent iron enhanced methane production of anaerobic digestion by reinforcing microbial electron bifurcation coupled with direct inter-species electron transfer.

Zero-valent iron (ZVI) can facilitate methanogens of anaerobic digestion (AD). However, the impact of ZVI on the micro-energetic strategies of AD microorganisms remains uncertain. This study aimed to elucidate the development of an energy conservation model involving direct interspecies electron transfer (DIET) and electron bifurcate (EB) by using four types of ZVI. Overall, the ZVI addition resulted in a substantial increase in methane production (1.26 to 2.18 times higher), and the effect of boron (B) doped ZVI was particularly pronounced. The underlying mechanism may be the formation of energy harvest pathway related to DIET. In detail, B-doped ZVI could enhance its interfacial binding to cytochrome c. Decreased polar solvation energy from 20.473 to 1.509 kJ/mol is beneficial for electron transfer, thereby augmenting the flavin-bounded Cytc activity and DIET process. Besides, ZVI-enhanced EB enzyme activity like HdrA2B2C2-MvhAGD could improve the EB process, which can couple with DIET for electron transfer and energy conservation. Energy analysis based on EB-coupled DIET metabolism pathways demonstrated that the ATP saved in this coupled model theoretically line in 0.25 to 0.5 mol ATP/mol substrate. Overall, this study offers valuable insights into microbial energetic strategies pertaining to the utilization of conductive materials, with the target of enhancing methane recovery efficiency from organic waste.

Comparative research on the pipe-soil frictional resistances of circular and rectangular pipe sections during trenchless pipe jacking.

Pipe jacking is a trenchless construction method to achieve forward tunneling and efficient construction of underground structure simultaneously without extensive surface excavation. In the process of pipe jacking construction, the jacking force provided by the hydraulic jacking equipment must overcome the frontal resistance of the cutter head and the frictional resistance between the pipe sections and formation at the same time. In particular, the pipe-soil frictional resistance increases with the increases of jacking distance, buried depth, pipe diameter and the complexity of jacking trajectory. Therefore, it is very important to correctly estimate jacking force in trenchless jacking engineering practice for the smooth implementation of pipe jacking, operation risk and comprehensive cost control. Firstly, the stress states of jacking circular and rectangular pipe sections in the soil are analyzed, and the key influencing factors of their pipe-soil frictional resistance are obtained respectively. Then, the pipe-soil frictional resistance of jacking the circular and rectangular pipe sections with the same external surface area in the dry sandy soil and coal granular layer are tested separately by using the self-developed multifunctional experimental apparatus during trenchless pipe jacking. The results show that the pipe-soil frictional resistances of jacking circular and rectangular pipe sections in the coal granular layer are always smaller than that in the sandy soil under the same experimental conditions, and the corresponding fitting calculation equation of pipe-soil frictional resistances are obtained respectively. Meanwhile, the modified calculation methods of the above pipe-soil frictional resistances are proposed respectively based on the relationship between the lateral pressure coefficient K and the buried depth of pipe section H. Moreover, the disturbed area of soil in the upper part of jacking circular pipe section presents an arc distribution, while the disturbed area of soil in the upper part of jacking rectangular pipe section presents a slightly concave distribution. Due to the different disturbance conditions of soil around the pipe section, the lateral pressure coefficient K should be corrected in the calculation equations of pipe-soil frictional resistance of jacking circular and rectangular pipe sections based on the discrete element numerical simulation analysis by EDEM software. Finally, the pipe-soil frictional resistances obtained by different methods in the sandy soil are compared and analyzed. The calculated values of the modified theoretical calculation method are very close to the experimental test values, while the other methods are smaller than the experimental test values, which makes the rationality of the modified theoretical calculation method of pipe-soil frictional resistance is verified, and some suggestions are also put forward for the value of some coefficients in the relevant empirical estimation equations. The above research achievements systematically compared the states of pipe-soil frictional resistances of jacking circular and rectangular pipe sections based on different research methods, especially for the correct evaluation of jacking force during trenchless pipe jacking, they could provide some valuable references and effective guidance for the subsequent research, engineering practice and further development of trenchless pipe jacking technology.

Electronic Bifurcation: A New Perspective on Fe Bio-Utilization in Anaerobic Digestion of Lactate.

Anaerobic microorganisms use flavin/quinone-based electronic bifurcation (EB) to gain a survival advantage at the thermodynamic limits. However, the contribution of EB to microscopic energy and productivity in the anaerobic digestion (AD) system is unknown. This study demonstrates for the first time that under limited substrate conditions, Fe-driven EB in AD leads to a 40% increase in specific methane production and contributes to 25% ATP accumulation, by analyzing the concentration of EB enzymes such as Etf-Ldh, HdrA2B2C2, and Fd, NADH and actual Gibbs free-energy changes. Differential pulse voltammetry and electron respiratory chain inhibition experiments detected that iron enhanced electron transport in EB by accelerating the activity of flavin, Fe-S clusters, and quinone groups. Other microbial and enzyme genes with EB potential closely related to iron transport have also been found in metagenomes. The potential of EB to accumulate energy and enhance productivity in AD systems was investigated, and metabolic pathways were proposed in the study.

Novel Role of Hematite in Anaerobic Digestion: Manipulating Membrane-Bound Electron Transport Chain by the Construction of Biological Capacitors with Humic Acid.

Humic acid (HA) has attracted much attention for its electron-competitive effect of quinone groups on anaerobic methanogenesis. This study analyzed the biological "capacitor" to determine how it might effectively reduce electron competition. As biological capacitor-producing additives, three semiconductive materials, including magnetite, hematite, and goethite, were selected. The results showed that hematite and magnetite could significantly alleviate the inhibited methanogenesis caused by the HA model compound anthraquinone-2,6-disulfonate (AQDS). The electrons flowing to methane in hematite-AQDS, magnetite-AQDS, control, sole-AQDS, and goethite-AQDS groups accounted for 81.24, 77.12, 75.42, 70.55, and 56.32% of the total produced electrons, respectively. Hematite addition significantly accelerated the methane production rate (18.97%) compared with sole-AQDS. Electrochemical investigation showed that AQDS might have its oxidation potential reduced by adsorbing on hematite, which results in an energy band bending for hematite and the formation of a biological capacitor. The biological capacitor's integrated electric field helps with the transfer of electrons from reduced AQDS to anaerobic consortia via bulk hematite. Metagenomic and metaproteomic sequencing analyses revealed that the ferredoxin and Mph-reducing hydrogenase in hematite addition increased by 7.16 and 21.91%, respectively, compared to sole-AQDS addition. Accordingly, this research suggested that AH2QDS may re-transfer electrons to methanogens via the biological capacitor and the membrane's Mph-reducing hydrogenase, thus lowering the HA electron competition.

Regulation strategy, bioactivity, and physical property of plant and microbial polysaccharides based on molecular weight.

Structural features affect the bioactivity, physical property, and application of plant and microbial polysaccharides. However, an indistinct structure-function relationship limits the production, preparation, and utilization of plant and microbial polysaccharides. Molecular weight is an easily regulated structural feature that affects the bioactivity and physical property of plant and microbial polysaccharides, and plant and microbial polysaccharides with a specific molecular weight are important for exerting their bioactivity and physical property. Therefore, this review summarized the regulation strategies of molecular weight via metabolic regulation; physical, chemical, and enzymic degradations; and the influence of molecular weight on the bioactivity and physical property of plant and microbial polysaccharides. Moreover, further problems and suggestions must be paid attention to during regulation, and the molecular weight of plant and microbial polysaccharides must be analyzed. The present work will promote the production, preparation, utilization, and investigation of the structure-function relationship of plant and microbial polysaccharides based on their molecular weight.

The bio-chemical cycle of iron and the function induced by ZVI addition in anaerobic digestion: A review.

Zero-valent iron (ZVI) is known to be an additive in facilitating waste treatment and improving biogas production in anaerobic digestion (AD) systems. This review concentrates on the chemical cycle of iron as well as the function of the iron cycle in the removal of four kinds of pollutants: organic carbon, nitrogen, sulphur and phosphorus, which are commonly encountered in waste treatment. In recent studies, the addition of ZVI to an AD system promoted the in-situ production of CH4 from CO2, enabling carbon capture through biotechnology. Additionally, using iron-carbon microbial electrolytic cells in AD systems in order to accelerate electron transport, as well as specific pollutant degradation mechanisms, are illustrated in the present study. Particularly, the main factors affecting the removal efficiency of contaminants in a ZVI-AD system such as pH, VFA/ Alkalinity (ALK), oxidation-reduction potential and particle size are reviewed. According to the above characteristics, combined with technical model and economic analyses, an AD system based on ZVI was considered to be an economical, efficient and carbon-neutral pollutant treatment technology. Accordingly, Iron-based AD is suggested to be a promising and sustainable approach orientated to a circular economy, which may be applied to many waste treatments fields.

Highly sensitive and thermal stable CO gas sensor based on SnO2 modified by SiO2.

Effects of surface chemical modification with SiO2 on the thermal stability and CO gas-sensing properties of SnO2 were investigated. The SiO2 on the SnO2 surface effectively inhibits the nanocrystal growth of SnO2. The average size of modified SnO2 sintered at 600 degrees C is 5.8 nm. The gas sensitivity to CO was found to be markedly enhanced by the surface chemical modification. The CO gas as low as 5 ppm can be effectively detected by the modified SnO2-based sensors. At the same time, the modified SnO2-based sensor has excellent selectivity to CO, fast response and recovery properties.