The two-step strategy for enhancing the specific activity and thermostability of alginate lyase AlyG2 with mechanism for improved thermostability.

To overcome the trade-off challenge encountered in the engineering of alginate lyase AlyG2 from Seonamhaeicola algicola Gy8T and to expand its potential industrial applications, we devised a two-step strategy encompassing activity enhancement followed by thermal stability engineering. To enhance the specific activity of efficient AlyG2, we strategically substituted residues with bulky steric hindrance proximal to the active pocket with glycine or alanine. This led to the generation of three promising positive mutants, with particular emphasis on the T91S mutant, exhibiting a 1.91-fold specific activity compared to the wild type. To mitigate the poor thermal stability of T91S, mutants with negative ΔΔG values in the thermal flexibility region were screened out. Notably, the S72Ya mutant not only displayed 17.96 % further increase in specific activity but also exhibited improved stability compared to T91S, manifesting as a remarkable 30.97 % increase in relative activity following a 1-hour incubation at 42 °C. Furthermore, enhanced kinetic stability was observed. To gain deeper insights into the mechanism underlying the enhanced thermostability of the S72Ya mutant, we conducted molecular dynamics simulations, principal component analysis (PCA), dynamic cross-correlation map (DCCM), and free energy landscape (FEL) analysis. The results unveiled a reduction in the flexibility of the surface loop, a stronger correlation dynamic and a narrower motion subspace in S72Ya system, along with the formation of more stable hydrogen bonds. Collectively, our findings suggest amino acids substitutions resulting in smaller side chains proximate to the active site can positively impact enzyme activity, while reducing the flexibility of surface loops emerges as a pivotal factor in conferring thermal stability. These insights offer valuable guidance and a framework for the engineering of other enzyme types.

[TFEB activator 1 enhances autophagic degradation of oligomeric amyloid-ß in microglia].

The purpose of the study was to investigate the mechanism of TFEB activator 1 (TA1) improving the autophagic degradation of oligomeric amyloid-ß (oAß) in microglia, and to explore the therapeutic effect of TA1 on an in vitro model of microglia in Alzheimer's disease (AD). Primary microglia were exposed to 1 µmol/L oAß for 0, 3, 12, and 24 h respectively to construct the in vitro model of microglia in AD. In order to explore the therapeutic effect of TA1, primary microglia were co-treated with 1 µmol/L oAß and 1 µmol/L TA1 for 12 h. To determine the autophagy flux, the above cells were further treated with 100 nmol/L Bafilomycin A1 for 1 h before fixation. Fluorescent probes were used to detect the endocytosis or degradation of oAß1-42 by microglia. The autophagic flux was determined by infection of lentivirus mCherry-EGFP-LC3. The nuclear TFEB intensity, the autophagosomes number, and the colocalization ratio of oAß1-42 with lysosome-associated membrane protein 1 (LAMP1) or microtubule-associated protein light chain 3 (LC3), were detected by immunofluorescence assay. Expressions of autophagy-related-genes, including Lamp1, Atg5, and Map1lc3b, were detected by qRT-PCR. Results showed that prolonged oAß exposure inhibited the endocytosis and degradation of oAß by microglia. Meanwhile, the number of autophagosomes and autophagy flux in microglia decreased after 12 h of oAß treatment. We further found that the nuclear expression of autophagy regulator TFEB decreased after 12 h of oAß exposure, resulting in the decrease of autophagy genes, thus leading to the damage of autophagic degradation of oAß. Therefore, long-term oAß exposure was considered to construct the in vitro model of microglia in AD. After TA1 treatment, the nuclear expression of TFEB in cells was obviously upregulated. TA1 treatment upregulated the expressions of autophagy-related genes, leading to the recovery of autophagy flux. TA1 also recovered the endocytosis and degradation of oAß by microglia. In conclusion, TA1 could improve oAß clearance by microglia in AD by upregulating microglial TFEB-mediated autophagy, suggesting TA1 as a potential therapeutic drug for AD.

Ln3+ Induced Thermally Activated Delayed Fluorescence of Chiral Heterometallic Clusters Ln2Ag28.

A series of TADF-active compounds: 0D chiral Ln-Ag(I) clusters L-/D-Ln2Ag28-0D (Ln = Eu/Gd) and 2D chiral Ln-Ag(I) cluster-based frameworks L-/D-Ln2Ag28-2D (Ln = Gd) has been synthesized. Atomic-level structural analysis showed that the chiral Ag(I) cluster units {Ag14S12} in L-/D-Ln2Ag28-0D and L-/D-Ln2Ag28-2D exhibited similar configurations, linked by varying numbers of [Ln(H2O)x]3+ (x = 6 for 0D, x = 3 for 2D) to form the final target compounds. Temperature-dependent emission spectra and decay lifetimes measurement demonstrated the presence of TADF in L-Ln2Ag28-0D (Ln = Eu/Gd) and L-Gd2Ag28-2D. Experimentally, the remarkable TADF properties primarily originated from {Ag14S12} moieties in these compounds. Notably, {Ag14S12} in L-Eu2Ag28-0D and L-Gd2Ag28-2D displayed higher promote fluorescence rate and shorter TADF decay times than L-Gd2Ag28-0D. Combined with theoretical calculations, it was determined that the TADF behaviors of {Ag14S12} cluster units were induced by 4f perturbation of Ln3+ ions. Specially, while maintaining ΔE(S1-T1) small enough, it can significantly increase k(S1→S0) and reduce TADF decay time by adjusting the type or number of Ln3+ ions, thus achieving the purpose of improving TADF for cluster-based luminescent materials.

Discovery of indole-2-one derivatives as BRD4 (BD1) selective inhibitors.

Bromodomain protein 4 (BRD4) is a member of the BET family, and its overexpression is closely associated with the development of many tumors. Inhibition of BRD4 shows great therapeutic potential in anti-tumor, and pan-BRD4 inhibitors show adverse effects of dose limiting toxicity and thrombocytopenia in clinical trials. To improve clinical effects and reduce side effects, more efforts have focused on seeking selective inhibitors of BD1 or BD2. Herein, a series of indole-2-one derivatives were designed and synthesized through docking-guided optimization to find BRD4-BD1 selective inhibitors, and their BRD4 inhibitory and antiproliferation activities were evaluated. Among them, compound 21r had potent BRD4 inhibitory activity (the IC50 values of 41 nM and 313 nM in BD1 and BD2 domain), excellent anti-proliferation (the IC50 values of 4.64 ± 0.30 µM, 0.78 ± 0.03 µM, 5.57 ± 1.03 µM against HL-60, MV-4-11 and HT-29 cells), and displayed low toxicity against normal cell GES-1 cells. Further studies revealed that 21r inhibited proliferation by decreasing the expression of proto-oncogene c-Myc, blocking cell cycle in G0/G1 phase, and inducing apoptosis in MV-4-11 cells in a dose-dependent manner. All the results showed that compound 21r was a potent BRD4 inhibitor with BD1 selectivity, which had potential in treatment of leukemia.

Silver Nanoparticles Encapped by Dihydromyricetin: Optimization of Green Synthesis, Characterization, Toxicity, and Anti-MRSA Infection Activities for Zebrafish (Danio rerio).

To achieve the environmentally friendly and rapid green synthesis of efficient and stable AgNPs for drug-resistant bacterial infection, this study optimized the green synthesis process of silver nanoparticles (AgNPs) using Dihydromyricetin (DMY). Then, we assessed the impact of AgNPs on zebrafish embryo development, as well as their therapeutic efficacy on zebrafish infected with Methicillin-resistant Staphylococcus aureus (MRSA). Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) analyses revealed that AgNPs possessed an average size of 23.6 nm, a polymer dispersity index (PDI) of 0.197 ± 0.0196, and a zeta potential of -18.1 ± 1.18 mV. Compared to other published green synthesis products, the optimized DMY-AgNPs exhibited smaller sizes, narrower size distributions, and enhanced stability. Furthermore, the minimum concentration of DMY-AgNPs required to affect zebrafish hatching and survival was determined to be 25.0 µg/mL, indicating the low toxicity of DMY-AgNPs. Following a 5-day feeding regimen with DMY-AgNP-containing food, significant improvements were observed in the recovery of the gills, intestines, and livers in MRSA-infected zebrafish. These results suggested that optimized DMY-AgNPs hold promise for application in aquacultures and offer potential for further clinical use against drug-resistant bacteria.

Large language model for horizontal transfer of resistance gene: From resistance gene prevalence detection to plasmid conjugation rate evaluation.

The burgeoning issue of plasmid-mediated resistance genes (ARGs) dissemination poses a significant threat to environmental integrity. However, the prediction of ARGs prevalence is overlooked, especially for emerging ARGs that are potentially evolving gene exchange hotspot. Here, we explored to classify plasmid or chromosome sequences and detect resistance gene prevalence by using DNABERT. Initially, the DNABERT fine-tuned in plasmid and chromosome sequences followed by multilayer perceptron (MLP) classifier could achieve 0.764 AUC (Area under curve) on external datasets across 23 genera, outperforming 0.02 AUC than traditional statistic-based model. Furthermore, Escherichia, Pseudomonas single genera based model were also be trained to explore its predict performance to ARGs prevalence detection. By integrating K-mer frequency attributes, our model could boost the performance to predict the prevalence of ARGs in an external dataset in Escherichia with 0.0281-0.0615 AUC and Pseudomonas with 0.0196-0.0928 AUC. Finally, we established a random forest model aimed at forecasting the relative conjugation transfer rate of plasmids with 0.7956 AUC, drawing on data from existing literature. It identifies the plasmid's repression status, cellular density, and temperature as the most important factors influencing transfer frequency. With these two models combined, they provide useful reference for quick and low-cost integrated evaluation of resistance gene transfer, accelerating the process of computer-assisted quantitative risk assessment of ARGs transfer in environmental field.

Andrias Davidianus Mucus-Based Bioadhesive with Enhanced Adhesion and Wound Healing Properties.

The skin secretion of Andrias davidianus (SSAD) is a novel biological adhesive raw material under development. This material exhibits robust adhesion while maintaining the flexibility of the wound. It also has the potential for large-scale production, making it promising for practical application explore. Hence, in-depth research on methods to fine-tune SSAD properties is of great importance to promote its practical applications. Herein, we aim to enhance the adhesive and healing properties of SSAD by incorporating functional components. To achieve this goal, we selected 3,4-dihydroxy-l-phenylalanine and vaccarin as the functional components and mixed them with SSAD, resulting in a new bioadhesive, namely, a formulation termed "enhanced SSAD" (ESSAD). We found that the ESSAD exhibited superior adhesive properties, and its adhesive strength was improved compared with the SSAD. Moreover, ESSAD demonstrated a remarkable ability to promote wound healing. This study presents an SSAD-based bioadhesive formulation with enhanced properties, affirming the feasibility of developing SSAD-based adhesive materials with excellent performance and providing new evidence for the application of SSAD. This study also aims to show that SSAD can be mixed with other substances, and addition of effective components to SSAD can be studied to further adjust or improve its performance.

1H-Indazoles derivatives targeting PI3K/AKT/mTOR pathway: Synthesis, anti-tumor effect and molecular mechanism.

The PI3K/AKT/mTOR signaling pathway is one of the most common abnormal activation pathways in tumor cells, and has associated with multiple functions such as tumor cell growth, proliferation, migration, invasion, and tumor angiogenesis. Here, a series of 3-amino-1H-indazole derivatives were synthesized, and their antiproliferative activities against HT-29, MCF-7, A-549, HepG2 and HGC-27 cells were evaluated. Among them, W24 exhibited the broad-spectrum antiproliferative activity against four cancer cells with IC50 values of 0.43-3.88 µM. Mechanism studies revealed that W24 inhibited proliferation by affecting the DNA synthesis, induced G2/M cell cycle arrest and apoptosis by regulating Cyclin B1, BAD and Bcl-xL, meanwhile induced the change of intracellular ROS and mitochondrial membrane potential in HGC-27 cells. Moreover, W24 inhibited the migration and invasion of HGC-27 cells by decreasing EMT pathway related proteins and reducing the mRNA expression levels of Snail, Slug and HIF-1α. Furthermore, W24 displayed low tissue toxicity profile and good pharmacokinetic properties in vivo. Therefore, 3-amino-1H-indazole derivatives might serve as a new scaffold for the development of PI3K/AKT/mTOR inhibitor and anti-gastric cancer reagent.

Design, synthesis, and biological evaluation of quinoxalinone derivatives as potent BRD4 inhibitors.

The bromodomain-containing protein 4 (BRD4) has gained growing interest as an effective drug target for the treatment of hepatocellular carcinoma (HCC). Herein, we designed and synthesized a series of quinoxalinone derivatives as BRD4 inhibitors via scaffold hopping. The representative compound X9 showed potent BRD4 inhibitory activity (with IC50 = 82.3 nM), and preferable antiproliferative activity against HepG2 cells (with IC50 = 1.13 ± 0.07 µM), as well as less toxicity against GES-1 cells (with IC50 = 57.24 ± 5.46 µM). Furthermore, compound X9 dose-dependently inhibited colony formation and blocked the migration of HepG2 cells by down-regulating the expression of Snail and MMP-9 while up-regulating the E-cadherin and Occludin. Besides, compound X9 efficiently down-regulated the expression of c-Myc in HepG2 cells, induced apoptosis, and arrested at G0/G1 phase. In total, quinoxalinone was a potential core as BRD4 inhibitor and compound X9 might be effective for liver cancer therapy.

Amyloid Protein Cross-Seeding Provides a New Perspective on Multiple Diseases In Vivo.

Amyloid protein cross-seeding is a peculiar phenomenon of cross-spreading among different diseases. Unlike traditional infectious ones, diseases caused by amyloid protein cross-seeding are spread by misfolded proteins instead of pathogens. As a consequence of the interactions among misfolded heterologous proteins or polypeptides, amyloid protein cross-seeding is considered to be the crucial cause of overlapping pathological transmission between various protein misfolding disorders (PMDs) in multiple tissues and cells. Here, we briefly review the phenomenon of cross-seeding among amyloid proteins. As an interesting example worth mentioning, the potential links between the novel coronavirus pneumonia (COVID-19) and some neurodegenerative diseases might be related to the amyloid protein cross-seeding, thus may cause an undesirable trend in the incidence of PMDs around the world. We then summarize the theoretical models as well as the experimental techniques for studying amyloid protein cross-seeding. Finally, we conclude with an outlook on the challenges and opportunities for basic research in this field. Cross-seeding of amyloid opens up a new perspective in our understanding of the process of amyloidogenesis, which is crucial for the development of new treatments for diseases. It is therefore valuable but still challenging to explore the cross-seeding system of amyloid protein as well as to reveal the structural basis and the intricate processes.

Discovery of novel VEGFR-2-PROTAC degraders based on the localization of lysine residues via recruiting VHL for the treatment of gastric cancer.

VEGFR-2 is an attractive therapeutic target for antitumor drug research by blocking tumor angiogenesis and PROTAC provides a new technology for targeted protein knockout. Herein, a library of novel VEGFR-2-PROTAC degraders were rationally designed and synthesized based on the Lys residue region on the surface of VEGFR-2 protein using protein structure-based drug design strategy. Among them, P7 exhibited preferable antitumor activity against HGC-27 cells and less toxic to human normal HUVEC, HEK293T and GES-1 cells in vitro, as well as the potent degradation activity of VEGFR-2 protein in HGC-27 cells (DC50: 0.084 ± 0.04 µM, Dmax: 73.7%) and HUVEC cells (DC50: 0.51 ± 0.10 µM, Dmax: 76.6%). Additionally, P7 degraded VEGFR-2 protein by the formation of ternary complex and the ubiquitin proteasome pathway in HGC-27 cells. Furthermore, P7 shortened the half-life of VEGFR-2 protein synthesis and had no inhibitory effect on the expression of VEGFR-2 mRNA in HGC-27 cells. Moreover, P7 inhibited the colony formation, migration and invasion of HGC-27 cells in a time- and dose-dependent manner, and meanwhile induced G2/M phase cycle arrest and apoptosis. All the results demonstrated that P7 could be as a promising VEGFR-2-PROTAC degrader for gastric cancer therapy.

Enhanced methane production in anaerobic digestion: A critical review on regulation based on electron transfer.

Anaerobic digestion (AD) is a potential bioprocess for waste biomass utilization and energy conservation. Various iron/carbon-based CMs (e.g., magnetite, biochar, granular activated carbon (GAC), graphite and zero valent iron (ZVI)) have been supplemented in anaerobic digestors to improve AD performance. Generally, the supplementation of CMs has shown to improve methane production, shorten lag phase and alleviate environmental stress because they could serve as electron conduits and promote direct interspecies electron transfer (DIET). However, the CMs dosage varied greatly in previous studies and CMs wash out remains a challenge for its application in full-scale plants. Future work is recommended to standardize the CMs dosage and recover/reuse the CMs. Moreover, additional evidence is required to verify the electrotrophs involved in DIET.

A Versatile Hydrophilic and Antifouling Coating Based on Dopamine Modified Four-Arm Polyethylene Glycol by One-Step Synthesis Method.

A versatile hydrophilic and antifouling coating was designed and prepared based on catechol-modified four-arm polyethylene glycol. The dopamine (DA) molecules were grafted onto the end of the four-arm polyethylene glycol carboxyl (4A-PEG-COOH) through the amidation reaction, which was proven by 1H NMR and FTIR analysis, assisting the strong adhesion of PEG on the surface of various types of materials, including metallic, inorganic, and polymeric materials. The reduction of the water contact angle and the bacteria-repellent and protein-repellent effects indicated that the coating had good hydrophilicity and antifouling performance. Raman spectroscopy analysis demonstrated the affinity between the polymeric surface and water, which further confirmed the hydrophilicity of the coating. Finally, in vitro cytotoxicity assay demonstrated good biocompatibility of the coating layer.

[Nuclear respiratory factor 1 mediates LPS-induced acute lung injury through NF-κB].

The purpose of this paper was to study the transcriptional regulation of nuclear respiratory factor 1 (NRF1) on nuclear factor kappa B (NF-κB), a key molecule in lipopolysaccharide (LPS)-induced lung epithelial inflammation, and to clarify the mechanism of NRF1-mediated inflammatory response in lung epithelial cells. In vivo, male BALB/c mice were treated with NRF1 siRNA, followed with LPS (4 mg/kg) or 0.9% saline through respiratory tract, and sacrificed 48 h later. Expression levels of NRF1, NF-κB p65 and its target genes were detected by Western blot and real-time PCR. Nuclear translocation of NRF1 or p65 was measured by immunofluorescent technique. In vitro, L132 cells were transfected with NRF1 siRNA or treated with BAY 11-7082 (5 µmol/L) for 24 h, followed with treatment of 1 mg/L LPS for 6 h. Cells were lysed for detections of NRF1, NF-κB p65 and its target genes as well as the binding sites of NRF1 on RELA (encoding NF-κB p65) promoter by chromatin immunoprecipitation assay (ChIP). Results showed that LPS stimulated NRF1 and NF-κB p65. Pro-inflammatory factors including interleukin-1ß (IL-1ß) and IL-6 were significantly increased both in vivo and in vitro. Obvious nuclear translocations of NRF1 and p65 were observed in LPS-stimulated lung tissue. Silencing NRF1 resulted in a decrease of p65 and its target genes both in vivo and in vitro. In addition, BAY 11-7082, an inhibitor of NF-κB, significantly repressed the inflammatory responses induced by LPS without affecting NRF1 expression. Furthermore, it was proved that NRF1 had three binding sites on RELA promoter region. In summary, NRF1 is involved in LPS-mediated acute lung injury through the transcriptional regulation on NF-κB p65.

Polyvinylamine with moderate binding affinity as a highly effective vehicle for RNA delivery.

Polymeric carriers for RNA therapy offer potential advantages in terms of low immunogenicity, promoting modifiability and accelerating intracellular transport. However, balancing high transfection efficacy with low toxicity remains challenging with polymer-based vehicles; indeed, polyethyleneimine (PEI) remains the "gold standard" polymer for this purpose despite its significant toxicity limitations. Herein, we demonstrate the potential of polyvinylamine (PVAm), a commodity high-charge cationic polymer used in the papermaking industry and has similar structure with PEI, as an alternative carrier for RNA delivery. High levels of transfection of normal, tumor, and stem cells with a variety of RNA cargoes including small interfering RNA (siRNA), microRNA (miRNA), and recombinant RNA can be achieved in vitro under the proper complex conditions. While, both the anti-tumor effect achieved in a xenograft osteosarcoma model and lipid-lowering activity observed in a hyperlipidemia mice indicate the potential for highly effective in vivo activity. Of note, both the transfection efficiency and the cytotoxicity of PVAm compare more favorably with those of PEI, with PVAm offering the additional advantages of simpler purification and significantly lower cost. In addition, the mechanism for the difference in transfection efficiency between PVAm and PEI is explored by molecular docking as well as analyzing the process of association and dissociation between polymers (PVAm and PEI) and nucleic acids. Our research provides a novel, non-toxic, and cost-effective carrier candidate for next generation RNA therapy, and elucidates the potential mechanism of PVAm for its efficient delivery of RNA.

Enhancement of methane production from waste activated sludge using hybrid microbial electrolysis cells-anaerobic digestion (MEC-AD) process - A review.

Hybrid microbial electrolysis cells-anaerobic digestion (MEC-AD) was proved to increase methane productivity and methane yield of waste activated sludge (WAS) by establishing direct interspecies electron transfer method and enriching functional microorganisms. This review first summarized the pretreatment methods of WAS for MEC-AD and then reviewed the reactor configurations, operation parameters, and the economic benefit of MEC-AD. Furthermore, the enhancement mechanisms of MEC-AD were reviewed based on the analysis of thermodynamics and microbial community. It was found that the decrease of hydrogen partial pressure due to the hydrogenotrophic methanogens enriched in cathodic biofilm and direct interspecies electron transfer between exoelectrogens and anode were the core mechanisms for improving acidogenesis, acetogenesis, and methanogenesis. Finally, the potentially technological issues that need to be addressed to increase energy efficiency in large-scale MEC-AD processes were discussed.

Formation of ß-Lactoglobulin Self-Assemblies via Liquid-Liquid Phase Separation for Applications beyond the Biological Functions.

Proteins are like miracle machines, playing important roles in living organisms. They perform vital biofunctions by further combining together and/or with other biomacromolecules to form assemblies or condensates such as membraneless organelles. Therefore, studying the self-assembly of biomacromolecules is of fundamental importance. In addition to their biological activities, protein assemblies also exhibit extra properties that enable them to achieve applications beyond their original functions. Herein, this study showed that in the presence of monosaccharides, ethylene glycols, and amino acids, ß-lactoglobulin (ß-LG) can form assemblies with specific structures, which were highly reproducible. The mechanism of the assembly process was studied through multi-scale observations and theoretical analysis, and it was found that the assembling all started from the formation of solute-rich liquid droplets via liquid-liquid phase separation (LLPS). These droplets then combined together to form condensates with elaborate structures, and the condensates finally evolved to form assemblies with various morphologies. Such a mechanism of the assembly is valuable for studying the assembly processes that frequently occur in living organisms. Detailed studies concerning the properties and applications of the obtained ß-LG assemblies showed that the assemblies exhibited significantly better performances than the protein itself in terms of autofluorescence, antioxidant activity, and metal ion absorption, which indicates broad applications of these assemblies in bioimaging, biodetection, biodiagnosis, health maintenance, and pollution treatment. This study revealed that biomacromolecules, especially proteins, can be assembled via LLPS, and some unexpected application potentials could be found beyond their original biological functions.

A novel selective probe for detecting glutathione from other biothiols based on the concept of Fluorescence Fusion.

Biological thiols importantly regulate the intracellular redox activity and metabolic level, but many of the developed probes for biothiols are facing difficulty in effectively distinguishing GSH from Cys/Hcy due to the similarity in mechanism. In this work, despite the previous pattern of "Logic Gate", we reported the concept of "Fluorescence Fusion" for the first time to achieve only one excitation-emission process. The exploited the probe, MZ-NBD, could quickly measure GSH in 10 min with a large Stokes shift (130 nm). Though the reacting mechanism was similar, only GSH could cause the "Fluorescence Fusion" with only one strong fluorescence response while Cys/Hcy caused two peaks. Adjusting the excitation wavelength could hardly split the fused peak into two. Though image recognition by artificial intelligence could easily distinguish the patterns of peaks, here we used the signal-treating method to realize the high selectivity towards GSH. Moreover, MZ-NBD could be utilized for rapid detection of GSH in living MCF-7 cells, which was more suitable for GSH than using the "Logic Gate" strategy. More than introducing a novel probe with the new concept, this work was meaningful as the linker of traditional reaction-based fluorescent probes and potential image recognition by artificial intelligence, thus led to various future researches in inter-disciplines.

Bimetallic MOFs-derived coral-like Ag-Mo2C/C interwoven nanorods for amperometric detection of hydrogen peroxide.

Coral-like Ag-Mo2C/C-I and blocky Ag-Mo2C/C-II composites were obtained from one-step in situ calcination of [Ag(HL)3(Mo8O26)]n·nH2O [L: N-(pyridin-3-ylmethyl) pyridine-2-amine] under N2/H2 and N2 atmospheres, respectively. The coral-like morphology of Ag-Mo2C/C-I is composed of interwoven nanorods embedded with small particles, and the nano-aggregate of Ag-Mo2C/C-II is formed by cross-linkage of irregular nanoparticles. The above composites are decorated on glassy carbon electrode (GCE) drop by drop to generate two enzyme-free electrochemical sensors (Ag-Mo2C/C/GCE) for amperometric detection of H2O2. In particular, the coral-like Ag-Mo2C/C-I/GCE sensor possesses rapid response (1.2 s), high sensitivity (466.2 µA·mM-1·cm-2), and low detection limit (25 nM) towards trace H2O2 and has wide linear range (0.08 µM~4.67 mM) and good stability. All these sensing performances are superior to Ag-Mo2C/C-II/GCE, indicating that the calcining atmosphere has an important influence on microstructure and electrochemical properties. The excellent electrochemical H2O2 sensing performance of Ag-Mo2C/C-I/GCE sensor is mainly attributed to the synergism of unique microstructure, platinum-like electron structure of Mo2C, strong interaction between Mo and Ag, as well as the increased active sites and conductivity caused by co-doped Ag and carbon. Furthermore, this sensor has been successfully applied to the detection of H2O2 in human serum sample, contact lens solution, and commercial disinfector, demonstrating the potential in related fields of environment and biology. Graphical abstract.

The underlying mechanism of enhanced methane production using microbial electrolysis cell assisted anaerobic digestion (MEC-AD) of proteins.

Anaerobic digestion (AD) is a promising technology capable of converting waste matter into bio-energy. Recent studies have reported that microbial electrolysis cell assisted anaerobic digestion (MEC-AD) is an effective system for methane production from organic waste, via enhanced electron transfer. However, little is known about the effects of applied voltage on the AD of proteins. Herein, the mechanism of MEC-AD on protein digestion was investigated using varying concentrations of bovine serum albumin (BSA) as the protein substrate (500 mg/L, 4 g/L, and 20 g/L BSA). Experimental results showed that the applied voltage can not only enhance the methane production rate from 23.8% to 45.6% at low and medium organic loading (BSA concentration of 500 mg/L and 4 g/L), but also improve the methanogenesis efficiency increased by 225.4% at high BSA concentration (20 g/L) with the applied voltage of 0.6 V compared to that with open circuit. Mechanism explorations revealed that the applied voltage significantly enhanced the acidogenesis and methanogenesis processes in the AD of proteins. Microbial community characterization showed that with the applied voltage, the abundance of fermentative bacteria increased by 46.7 % at the anode, while, the abundance of Methanobacterium at the cathode increased from 10.4 to 84.3%, indicating the methanogenesis pathway transformed from acetoclastic to hydrogenotrophic. External circuit electron transfer calculations demonstrated that only 10% of the produced methane could be attributed to direct interspecies electron transfer (DIET). From a thermodynamic perspective, the applied external voltage led to a reduction in the cathodic potential to -0.9 V, which is beneficial for enhanced methane production via mediated interspecies electron transfer (MIET) by enrichment of hydrogenotrophic methanogens. The findings reported here reveal the previously unrecognized contribution of proteins to MEC-AD, while also furthering our understanding of the role of applied voltage in the MEC-AD process.