Advanced Palladium Nanosheet-Enhanced Phototherapy for Treating Wound Infection Caused by Multidrug-Resistant Bacteria.

With the increasing spread of multidrug-resistant (MDR) bacteria worldwide, it is needed to develop antibiotics-alternative strategies for the treatment of bacterial infections. This work develops a multifunctional single-component palladium nanosheet (PdNS) with broad-spectrum and highly effective bactericidal activity against MDR bacteria. PdNS exerts its endogenous nanoknife (mechanical cutting) effect and peroxidase-like activity independent of light. Under near-infrared region (NIR) light irradiation, PdNS exhibits photothermal effect to produce local heat and meanwhile possesses photodynamic effect to generate 1O2; notably, PdNS has catalase-like activity-dependent extra photodynamic effect upon H2O2 addition. PdNS+H2O2+NIR employs a collectively synergistic mechanism of nanoknife effect, peroxidase/catalase-like catalytic activity, photothermal effect, and photodynamic effect for bacterial killing. PdNS+H2O2+NIR causes compensatory elevated phospholipid biosynthesis, disordered energy metabolism, increased cellular ROS levels and excessive oxidative stress, and inhibited nucleic acid synthesis in bacteria. In mice, PdNS+H2O2+NIR gives >92.7% bactericidal rates at infected wounds and almost the full recovery of infected wounds, and it leads to extensive down-regulation of proinflammatory pathways and comprehensive up-regulation of wound healing pathways, conferring elevated inflammation resolution and meanwhile accelerated wound repair. PdNS+H2O2+NIR represents a highly efficient nanoplatform for photoenhanced treatment of superficial infections.

Dynamics of fermentation quality, bacterial communities, and fermentation weight loss during fermentation of sweet sorghum silage.

BACKGROUND: Sweet sorghum is used mainly as an energy crop and feed crop in arid and semiarid regions, and ensiling is a satisfactory method for preserving high-quality sweet sorghum. The aim of this study was to reveal the dynamics of the fermentation quality, bacterial communities, and fermentation weight loss (FWL) of sweet sorghum silage during fermentation. METHODS: Sweet sorghum was harvested at the first inflorescence spikelet stage and ensiled without (CK) or with lactic acid bacterial (LAB) additives (L). After ensiling, samples were collected on days 0, 1, 3, 5, 15, 40, and 100 to assess the fermentation quality, bacterial communities, and FWL. RESULTS: For CK and L, on day 1, the pH was 5.77 and 5.57, respectively, and the lactic acid (LA) was 1.30 and 2.81 g/kg dry matter (DM), respectively. Compared with CK, L had a lower pH and higher LA from days 1 to 5 (P < 0.05), a lower FWL from days 5 to 100 (P < 0.05), and a greater abundance of Lactiplantibacillus from days 1 to 15 (P < 0.05). The main bacterial genera were Leuconostoc and Weissella in CK and Lactiplantibacillus, Leuconostoc, and Weissella in L on day 1; Lactiplantibacillus in all silages from days 3 to 40; and Lactiplantibacillus and Lentilactobacillus in all silages on day 100. CONCLUSIONS: Sweet sorghum silage fermented relatively slowly during the first day. Moreover, inoculation with LAB accelerated fermentation and optimized bacterial communities during the initial fermentation phase. Inoculation with LAB also reduced the silage FWL, and the LAB succession relay occurred in the silage throughout the fermentation process.

Impact of Additives and Packing Density on Fermentation Weight Loss, Microbial Diversity, and Fermentation Quality of Rape Straw Silage.

To investigate the effects of the combined addition of Lactiplantibacillus plantarum and sucrose on the fermentation weight loss (FWL), fermentation quality, and microbial community structure of ensiled rape straw under varying packing density conditions. After harvesting, the rapeseed straw was collected, cut into 1-2 cm pieces, and sprayed with sterile water to adjust the moisture content to 60%. The straw was then divided into two groups: one treated with additives (1 × 105 CFU/g fresh material of Lactiplantibacillus plantarum and 10 kg/t fresh material of sucrose), and the other sprayed with an equivalent amount of sterile water as the control (CK). The treated materials were thoroughly mixed and packed into silos at densities of 450, 500, and 550 kg/m3. FWL was recorded on days 1, 3, 6, 15, 20, and 45 of fermentation. On day 45, the samples were analyzed for fermentation quality, microbial counts, and microbial diversity. FWL increased significantly (p < 0.05) in both the treated (LS) and control groups during fermentation. The LS group showed higher lactic acid (LA) levels (p < 0.05) and lower ammonia nitrogen levels (p < 0.05) compared to CK. The CK group had significantly higher (p < 0.05) counts of Coliforms and lower bacterial counts (p < 0.05) than LS. The dominant genera in the silage were Xanthomonas, Lactiplantibacillus plantarum, and Lentilactobacillus. In the LS group, the relative abundances of Lactiplantibacillus plantarum and Lentilactobacillus ranged from 16.93% to 20.43% and 15.63% to 27.46%, respectively, with their combined abundance being higher than in CK. At a packing density of 500 kg/m3, the relative abundances of Lactiplantibacillus plantarum and Lentilactobacillus in the LS group were significantly higher (p < 0.05) than in CK. Increasing packing density and applying additives to rape straw silage effectively reduced FWL, improved fermentation quality, boosted the relative abundance of beneficial lactic acid bacteria, and decreased the presence of undesirable bacteria such as Enterobacter and Bacillus.

Treatment of Acute Wound Infections by Degradable Polymer Nanoparticle with a Synergistic Photothermal and Chemodynamic Strategy.

Mild-heat photothermal antibacterial therapy avoids heat-induced damage to normal tissues but causes bacterial tolerance. The use of photothermal therapy in synergy with chemodynamic therapy is expected to address this issue. Herein, two pseudo-conjugated polymers PM123 with photothermal units and PFc with ferrocene (Fc) units are designed to co-assemble with DSPE-mPEG2000 into nanoparticle NPM123/Fc. NPM123/Fc under 1064 nm laser irradiation (NPM123/Fc+NIR-II) generates mild heat and additionally more toxic ∙OH from endogenous H2O2, displaying a strong synergistic photothermal and chemodynamic effect. NPM123/Fc+NIR-II gives >90% inhibition rates against MDR ESKAPE pathogens in vitro. Metabolomics analysis unveils that NPM123/Fc+NIR-II induces bacterial metabolic dysregulation including inhibited nucleic acid synthesis, disordered energy metabolism, enhanced oxidative stress, and elevated DNA damage. Further, NPM123/Fc+NIR-II possesses >90% bacteriostatic rates at infected wounds in mice, resulting in almost full recovery of infected wounds. Immunodetection and transcriptomics assays disclose that the therapeutic effect is mainly dependent on the inhibition of inflammatory reactions and the promotion of wound healing. What is more, thioketal bonds in NPM123/Fc are susceptible to ROS, making it degradable with highly favorable biosafety in vitro and in vivo. NPM123/Fc+NIR-II with a unique synergistic antibacterial strategy would be much less prone to select bacterial resistance and represent a promising antibiotics-alternative anti-infective measure.

Genomic epidemiology and heterogeneity of Providencia and their blaNDM-1-carrying plasmids.

Providencia as an opportunistic pathogen can cause serious infection, and moreover the emergence of multi-drug-resistant Providencia strains poses a potentially life-threatening risk to public health. However, a comprehensive genomic study to reveal the population structure and dissemination of Providencia is still lacking. In this study, we conducted a genomic epidemiology analysis on the 580 global sequenced Providencia isolates, including 257 ones sequenced in this study (42 ones were fully sequenced). We established a genome sequence-based species classification scheme for Providencia, redefining the conventional 11 Providencia species into seven genocomplexes that were further divided into 18 genospecies, providing an extensively updated reference for Providencia species discrimination based on the largest Providencia genome dataset to date. We then dissected the profile of antimicrobial resistance genes and the prevalence of multi-drug-resistant Providencia strains among these genocomplexes/genospecies, disclosing the presence of diverse and abundant antimicrobial resistance genes and high resistance ratios against multiple classes of drugs in Providencia. We further dissected the genetic basis for the spread of blaNDM-1 in Providencia. blaNDM-1 genes were mainly carried by five incompatible (Inc) groups of plasmids: IncC, IncW, IncpPROV114-NR, IncpCHS4.1-3, and IncpPrY2001, and the last three were newly designated in this study. By tracking the spread of blaNDM-1-carrying plasmids, IncC, IncpPROV114-NR, IncpCHS4.1-3, and IncpPrY2001 plasmids were found to be highly involved in parallel horizontal transfer or vertical clonal expansion of blaNDM-1 among Providencia. Overall, our study provided a comprehensive genomic view of species differentiation, antimicrobial resistance prevalence, and plasmid-mediated blaNDM-1 dissemination in Providencia.

Community Synergy of Lactic Acid Bacteria and Cleaner Fermentation of Oat Silage Prepared with a Multispecies Microbial Inoculant.

To investigate community synergy of lactic acid bacteria (LAB) and cleaner fermentation of oat silage, oat silages were prepared with or without (control) commercial LAB inoculants LI1 (containing Lactiplantibacillus plantarum, Lentilactobacillus buchneri, Lacticaseibacillus paracasei, and Pediococcus acidilactici) and LI2 (containing Lactiplantibacillus plantarum and Lentilactobacillus buchneri). The microbial community, LAB synergy, and cleaner fermentation were analyzed at 1, 3, 6, 15, 35, and 90 days of ensiling. The LAB inoculant improved fermentation quality, with significantly (P < 0.05) lower pH, ammonia nitrogen content, and gas production and higher lactic acid and acetic acid contents than those of the control. Enterobacteriaceae was the main bacterial community in early stage of fermentation, which utilizes sugar to produce CO2 gas, causing dry matter (DM) and energy loss. As fermentation progressed, the microbial diversity decreased, and the microbial community shifted from Gram-negative to Gram-positive bacteria. The inoculation of multispecies LAB displayed community synergy; Pediococcus acidilactici formed a dominant community in the early stage of fermentation, which produced an acid and anaerobic environment for the subsequent growth of Lentilactobacillus and Lacticaseibacillus species, thus forming a LAB-dominated microbial community. The predicted functional profile indicated that the silage inoculated with LI1 enhanced the carbohydrate metabolism pathway but inhibited the amino acid metabolism pathway, which played a role in promoting faster lactic acid production, reducing the decomposition of protein to ammonia nitrogen, and improving the fermentation quality of silage. Therefore, oat silage can be processed to high-quality and cleaner fermented feed by using an LAB inoculant, and LI1 showed better efficiency than LI2. IMPORTANCE Oat natural silage is rich in Enterobacteriaceae, increasing gas production and fermentation loss. Lactic acid bacteria interact synergistically to form a dominant community during ensiling. Pediococci grow vigorously in the early stage of fermentation and create an anaerobic environment. Lactobacilli inhibit the harmful microorganisms and result in cleaner fermentation of oat silage.

Chondrogenic Differentiation of Adipose-Derived Stromal Cells Induced by Decellularized Cartilage Matrix/Silk Fibroin Secondary Crosslinking Hydrogel Scaffolds with a Three-Dimensional Microstructure.

Finding an ideal scaffold is always an important issue in the field of cartilage tissue engineering. Both decellularized extracellular matrix and silk fibroin have been used as natural biomaterials for tissue regeneration. In this study, a secondary crosslinking method of γ irradiation and ethanol induction was used to prepare decellularized cartilage extracellular matrix and silk fibroin (dECM-SF) hydrogels with biological activity. Furthermore, the dECM-SF hydrogels were cast in custom-designed molds to produce a three-dimensional multi-channeled structure to improve internal connectivity. The adipose-derived stromal cells (ADSC) were seeded on the scaffolds, cultured in vitro for 2 weeks, and implanted in vivo for another 4 and 12 weeks. The double crosslinked dECM-SF hydrogels exhibited an excellent pore structure after lyophilization. The multi-channeled hydrogel scaffold presents higher water absorption ability, surface wettability, and no cytotoxicity. The addition of dECM and a channeled structure could promote chondrogenic differentiation of ADSC and engineered cartilage formation, confirmed by H&E, safranin O staining, type II collagen immunostaining, and qPCR assay. In conclusion, the hydrogel scaffold fabricated by the secondary crosslinking method has good plasticity and can be used as a scaffold for cartilage tissue engineering. The multi-channeled dECM-SF hydrogel scaffolds possess a chondrogenic induction activity that promotes engineered cartilage regeneration of ADSC in vivo.

Quantitative T2 mapping monitoring the maturation of engineered elastic cartilage in a rabbit model.

BACKGROUND: Cartilage tissue engineering provides a promising approach to reconstruct craniofacial defects, and a noninvasive method is needed to assess its effectiveness. Although magnetic resonance imaging (MRI) has been used to evaluate articular cartilage in vivo, few studies focused on its feasibility in monitoring engineered elastic cartilage (EC). METHODS: Auricular cartilage, silk fibroin (SF) scaffold, and EC consisting of rabbit auricular chondrocytes and SF scaffold were transplanted subcutaneously into the rabbit back. In eight weeks after transplantation, grafts were imaged by MRI using PROSET, PDW VISTA SPAIR, 3D T2 VISTA, 2D MIXED T2 Multislice, and SAG TE multiecho sequences, followed by histological examination and biochemical analysis. Statistical analyses were performed to identify the association between T2 values and biochemical indicator values of EC. RESULTS: In vivo imaging shows that 2D MIXED T2 Multislice sequence (T2 mapping) clearly distinguished the native cartilage, engineered cartilage and fibrous tissue. T2 values showed high correlations with cartilage-specific biochemical parameters at different time points, especially the elastic cartilage specific protein elastin (ELN, r= -0.939, P < 0.001). CONCLUSION: Quantitative T2 mapping can effectively detect the in vivo maturity of engineered elastic cartilage after subcutaneously transplantation. This study would promote the clinical application of MRI T2 mapping in monitoring engineered elastic cartilage in the repair of craniofacial defects.

Fermentation weight loss, fermentation quality, and bacterial community of ensiling of sweet sorghum with lactic acid bacteria at different silo densities.

Sweet sorghum is an important forage in arid and semi-arid climatic regions. This study aimed to reveal the fermentation weight loss (FWL), fermentation quality, and bacterial community of ensiling of sweet sorghum with lactic acid bacteria LAB; (Lactiplantibacillus plantarum and Lentilactobacillus buchneri) at different silo densities. For this study, sweet sorghum was harvested at the first spikelet of inflorescence stage and ensiled without or with LAB (CK or L) in polyethylene laboratory-scale silos (diameter, 20 cm; height, 30 cm) at densities of 650 (CK_650 and L_650), 700 (CK_700 and L_700), and 750 kg/m3 (CK_750 and L_750), respectively. The FWL, fermentation quality, microbial counts, and bacterial community of the silage were assessed after 100 days of ensiling. L_750 had a lower FWL than CK_650, _700, and _750 after 100 days of ensiling (P < 0.005), and the FWL was affected by silo density and inoculating LAB (P < 0.005). All silages had low pH (<4.0) and ammonia nitrogen content (<50 g/kg total nitrogen) and did not contain propionic and butyric acids; moreover, inoculating LAB increased lactic and acetic acids (P < 0.005). Bacterial communities in inoculated and uninoculated silages were clustered together, respectively, and clearly separated from each other. The total abundance of Lactiplantibacillus and Lentilactobacillus in fresh forage was <1%. Lactiplantibacillus had the highest abundance in all silages (from 71.39 to 93.27%), followed by Lentilactobacillus (from 3.59 to 27.63%). Inoculating LAB increased the abundance of Lentilactobacillus in each silo density (P < 0.005) and decreased Lactiplantibacillus in the silage in densities of 700 and 750 kg/m3 (P < 0.005); moreover, increasing silo density decreased Lactiplantibacillus abundance and increased Lentilactobacillus abundance in inoculated silages (P < 0.005). Overall, sweet sorghum silage showed satisfactory fermentation quality, with a density of no <650 kg/m3, and inoculating LAB improved fermentation quality and reduced FWL. Lactiplantibacillus and Lentilactobacillus presented as minor taxa in fresh sweet sorghum and dominated the bacterial community of all silages. Inoculating LAB was the main factor affecting the bacterial community of sweet sorghum silage. Moreover, inoculating LAB and increasing silo density can contribute to the decreasing Lactiplantibacillus abundance and increasing Lentilactobacillus abundance.

Fermentation quality, bacterial community, and aerobic stability of ensiling Leymus chinensis with lactic acid bacteria or/and water after long-term storage.

Leymus chinensis is a major forage resource for herbivores on typical steppe and meadow steppes in Northern China. This study aimed to reveal the fermentation quality, bacterial community, and aerobic stability of L. chinensis silage treated with lactic acid bacteria or/and water after long-term storage. Leymus chinensis was harvested at the heading stage and ensiled with lactic acid bacteria [LAB, 2.00 ml/kg fresh weight (FW) of LAB, L], water (100 ml/kg FW of distilled water, W), or a combination of both [2.00 ml/kg fresh weight (FW) of LAB and 100 ml/kg FW of distilled water, LW] in polyethylene laboratory-scale silos (diameter, 20 cm; height, 30 cm) at a density of 650 kg/m3. As a control silage (CK), untreated L. chinensis silage was also assessed. The samples were taken at 0 day of opening after 300 days of ensiling (CK_0d, L_0d, W_0d, and LW_0d) and at 10 days of opening (CK_10d, L_10d, W_10d, and LW_10d). The fermentation quality, microbial counts, bacterial community, and aerobic stability of the silage were assessed. The CK_0d contained higher pH and aerobic bacteria count, and lower LA and BC concentrations than L_0d, W_0d, and LW_0d (p < 0.05), and the LAB and yeasts were only detected in CK at 0 day of opening. Lactobacillus had the most abundance among bacterial genera in all silages at 0 day of opening. Just CK had 2°C above the ambient temperature during aerobic exposure (at 224 h). During aerobic exposure, the pH and microbial counts in CK increased (p < 0.05), and Lactobacillus in L and LW had decreasing abundance (p < 0.05). The CK_10d had higher pH and microbial counts, and lower lactic acid and buffering capacity than L_10d, W_10d, and LW_10d (p < 0.05). At 10 days of opening, the coliforms and yeasts were just detected in CK, and Lactobacillus also had the most abundance among bacterial genera in all silages at 10 days of opening. Overall, inoculating LAB and adding water improved the fermentation quality and the aerobic exposure of L. chinensis silage after long-term storage. The activities of coliforms and yeasts during aerobic exposure contributed to the aerobic deterioration of L. chinensis silage without any treating. Lactobacillus dominated the bacterial communities of all silage at 0 and 10 days of opening. During aerobic exposure, the abundance of Lactobacillus reduced in L. chinensis silage treated with LAB or water.

Spatiotemporal evolution of seismicity during the cyclic operation of the Hutubi underground gas storage, Xinjiang, China.

Underground gas storages (UGSs) are important large-scale industrial facilities used to bridge the gap between natural gas consumption and supply. The cyclic operation of the UGS may alter the subsurface stresses and local seismicity. We examined seismicity around the Hutubi UGS from 2011 to 2019 using the matched filter technique (MFT) and double-difference location methods. More than 1300 earthquakes were detected with seismicity around the UGS showing a remarkable increase since the start of its operation and showing a clear correlation to seasonal gas production. About 684 detected earthquakes were located, most of them occurred within 6 km of the reservoir. The events can be grouped into two clusters. Both clusters initiated around the gas pressure boundary. The first cluster extinct after the first injection period. While the second cluster diffused upward along a pre-existing fault. We speculate that strain localization caused by non-uniform gas injection contributes to the initiation of seismicity clusters around the UGS, and the trapped crude oil/gas played an important role in the migration of the second surge. The revealed seismicity pattern contributes to a better understanding of the mechanism of induced seismic events and emphasizes the importance of seismic monitoring in the UGS region.

Effects of Pyroligneous Acid on Diversity and Dynamics of Antibiotic Resistance Genes in Alfalfa Silage.

Antibiotic resistance genes (ARGs) are recognized as contaminants due to their potential risk for human and environment. The aim of the present study is to investigate the effects of pyroligneous acid (PA), a waste of biochar production, on fermentation characteristics, diversity, and dynamics of ARGs during ensiling of alfalfa using metagenomic analysis. The results indicated that PA decreased (P < 0.05) dry matter loss, pH value, gas production, coliform bacteria count, protease activity, and nonprotein-N, ammonia-N, and butyric acid contents and increased (P < 0.05) lactic acid content during ensiling. During fermentation, Bacteria, Firmicutes, and Lactobacillus were the most abundant at kingdom, phylum, and genus levels, respectively. Pyroligneous acid reduced the relative abundance of Bacteria and Firmicutes and increased that of Lactobacillus. The detected ARGs belonged to 36 drug classes, including mainly macrolides, tetracycline, lincosamides, and phenicol. These types of ARGs decreased during fermentation and were further reduced by PA. These types of ARGs were positively correlated (P < 0.05) with fermentation parameters like pH value and ammonia-N content and with bacterial communities. At the genus level, the top several drug classes, including macrolide, tetracycline, lincosamide, phenicol, oxazolidinone, streptogramin, pleuromutilin, and glycopeptide, were positively correlated with Staphylococcus, Streptococcus, Listeria, Bacillus, Klebsiella, Clostridium, and Enterobacter, the potential hosts of ARGs. Overall, ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community composition. Ensiling could be a feasible way to mitigate ARGs in forages. The addition of PA could not only improve fermentation quality but also reduce ARG pollution of alfalfa silage. IMPORTANCE Antibiotic resistance genes (ARGs) are considered environmental pollutants posing a potential human health risk. Silage is an important and traditional feed, mainly for ruminants. ARGs in silages might influence the diversity and distribution of ARGs in animal intestinal and feces and then the manure and the manured soil. However, the diversity and dynamics of ARGs in silage during fermentation are still unknown. We ensiled alfalfa, one of the most widely used forages, with or without pyroligneous acid (PA), which was proved to have the ability to reduce ARGs in soils. The results showed that ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community. The majority of ARGs in alfalfa silage reduced during fermentation. The addition of PA could improve silage quality and reduce ARG pollution in alfalfa silage. This study can provide useful information for understanding and controlling ARG pollution in animal production.

Bacterial Community and Fermentation Quality of Ensiling Alfalfa With Commercial Lactic Acid Bacterial Additives.

The aim of this study was to determine the effects of six common commercial lactic acid bacteria (LAB) additives [A1, Lactobacillus plantarum, L. buchneri, and Enterococcus faecalis; A2, L. plantarum and L. casei; A3, L. plantarum and L. buchneri; A4, L. plantarum, L. buchneri, L. casei, and Pediococcus acidilactici; A5, L. plantarum (producing feruloyl esterase); and A6, L. buchneri, P. acidilactici, ß-glucanase, and xylanase] on the bacterial community and fermentation quality of alfalfa silage. Alfalfa was harvested at the squaring stage, wilted in the field for 24 h, and ensiled without any additives (Control) or with A1, A2, A3, A4, A5, or A6. Microbial counts, bacterial community, fermentation parameters, and nutritional composition were determined after ensiling for 90 days. The total abundance of LAB genera on alfalfa pre-ensiling was 0.38% in bacterial community. The abundances of Lactobacillus, Enterococcus, and Pediococcus in the Control silage were 42.18, 40.18, and 8.09% of abundance, respectively. The abundances of Lactobacillus in A1-, A2-, A3-, A4-, and A5-treatments were 89.32, 92.93, 92.87, 81.12, and 80.44%, respectively. The abundances of Pediococcus and Lactobacillus in A6-treatment were 70.14 and 24.86%, respectively. Compared with Control silage, LAB-treated silage had lower pH and less ammonia nitrogen and water-soluble carbohydrates concentrations (p < 0.05). Further, the A5- and A6-treatments contained lower neutral detergent fiber, acid detergent fiber, and hemicellulose than other treatments (p < 0.05). Overall, LAB genera were presented as minor taxa in alfalfa pre-ensiling and as dominant taxa in alfalfa silage. Adding LAB additives improved the fermentation quality and altered the bacterial community of alfalfa silage. The main bacterial genera in Control silage were Lactobacillus, Enterococcus, and Pediococcus. Lactobacillus dominated the bacterial communities of A1-, A2-, A3-, A4-, and A5-treatments, while Pediococcus and Lactobacillus were dominant bacterial genera in A6-treatment. Inoculating A5 and A6 degraded the fiber in alfalfa silage. It is necessary to ensile alfalfa with LAB inoculants.

Degradable Pseudo Conjugated Polymer Nanoparticles with NIR-II Photothermal Effect and Cationic Quaternary Phosphonium Structural Bacteriostasis for Anti-Infection Therapy.

Photothermal therapy based on conjugated polymers represents a promising antibacterial strategy but still possesses notable limitations. Herein, degradable pseudo conjugated polymers (PCPs) containing photothermal molecular backbones and reactive oxygen species (ROS)-sensitive thioketal bonds are designed. Triphenylphosphine (PPh3 ) is introduced into PCPs to generate phosphonium-based PCPs (pPCPs), which further assembled with hyaluronic acid into pPCP nanoparticles (pPCP-NPs). pPCP-NPs with quaternary phosphonium cations selectively anchor on and destroy bacterial cell membranes through electrostatic action. Under 1064 nm laser irradiation, pPCP-NPs (pPCP-NPs/+L) produce near-infrared-II (NIR-II) photothermal antibacterial effect, thereby killing bacteria in a sustained manner. pPCP-NPs are readily degraded upon ROS abundant at infection sites, therefore exhibiting enough biosafety. pPCP-NPs/+L display an almost 100% bacterial inhibition rate in vitro and resultin a nearly complete recovery of bacteria-induced mouse wounds. A further metabolomics analysis denotes that pPCP-NPs/+L work in a concerted way to induce bacterial DNA damage, inhibit bacterial carbon/nitrogen utilization and amino acid/nucleotide synthesis. Taken together, degradable pPCP-NPs with both NIR-II photothermal effect and cationic phosphonium structural bacteriostasis provide a new avenue for antibiotics-alternative anti-infection therapy.

Cryo-self-assembled silk fibroin sponge as a biodegradable platform for enzyme-responsive delivery of exosomes.

Although advances in protein assembly preparation have provided a new platform for drug delivery during tissue engineering, achieving long-term controlled exosome delivery remains a significant challenge. Diffusion-dominated exosome release using protein hydrogels results in burst release of exosomes. Here, a fibroin-based cryo-sponge was developed to provide controlled exosome release. Fibroin chains can self-assemble into silk I structures under ice-cold conditions when annealed above the glass transition temperature. Exosome release is enzyme-responsive, with rates primarily determined by enzymatic degradation of the scaffolds. In vivo experiments have demonstrated that exosomes remain in undigested sponge material for two months, superior to their retention in fibrin glue, a commonly used biomaterial in clinical practice. Fibroin cryo-sponges were implanted subcutaneously in nude mice. The exosome-containing sponge group exhibited better neovascularization and tissue ingrowth effects, demonstrating the efficacy of this exosome-encapsulating strategy by realizing sustained release and maintaining exosome bioactivity. These silk fibroin cryo-sponges containing exosomes provide a new platform for future studies of exosome therapy.

YfiF, an unknown protein, affects initiation timing of chromosome replication in Escherichia coli.

The Escherichia coli YfiF protein is functionally unknown, being predicted as a transfer RNA/ribosomal RNA (tRNA/rRNA) methyltransferase. We find that absence of the yfiF gene delays initiation of chromosome replication and the delay is reversed by ectopic expression of YfiF, whereas excess YfiF causes an early initiation. A slight decrease in both cell size and number of origin per mass is observed in ΔyfiF cells. YfiF does not genetically interact with replication proteins such as DnaA, DnaB, and DnaC. Interestingly, YfiF is associated with ribosome modulation factor (RMF), hibernation promotion factor (HPF), and the tRNA methyltransferase TrmL. Defects in replication initiation of Δrmf, Δhpf, and ΔtrmL can be rescued by overexpression of YfiF, indicating that YfiF is functionally identical to RMF, HPF, and TrmL in terms of replication initiation. Also, YfiF interacts with the rRNA methyltransferase RsmC. Moreover, the total amount of proteins and DnaA content per cell decreases or increases in the absence of YfiF or the presence of excess YfiF. These facts suggest that YfiF is a ribosomal dormancy-like factor, affecting ribosome function. Thus, we propose that YfiF is involved in the correct timing of chromosome replication by changing the DnaA content per cell as a result of affecting ribosome function.

Identification of tick-borne pathogens by metagenomic next-generation sequencing in Dermacentor nuttalli and Ixodes persulcatus in Inner Mongolia, China.

BACKGROUND: Hard ticks act as arthropod vectors in the transmission of human and animal pathogens and are widely distributed in northern China. The aim of this study is to screen the important tick-borne pathogens (TBPs) carried by hard ticks in Inner Mongolia using metagenomic next-generation sequencing (mNGS) and to estimate the risk of human infection imposed by tick bites. METHODS: The adult Dermacentor nuttalli (n = 203) and Ixodes persulcatus (n = 36) ticks feeding on cattle were collected. The pooled DNA samples prepared from these ticks were sequenced as the templates for mNGS to survey the presence of TBPs at the genus level. Individual tick DNA samples were detected by genus--specific or group-specific nested polymerase chain reaction (PCR) of these TBPs and combined with DNA sequencing assay to confirm the results of mNGS. RESULTS: R. raoultii (45.32%, 92/203), Candidatus R. tarasevichiae (5.42%, 11/203), Anaplasma sp. Mongolia (26.60%, 54/203), Coxiella-like endosymbiont (CLE) (53.69%, 109/203), and Babesia venatorum (7.88%, 16/203) were detected in D. nuttalli, while R. raoultii (30.56%, 11/36), Anaplasma sp. Mongolia (27.80%, 10/36), and CLE (27.80%, 10/36) were detected in I. persulcatus. The double- and triple-pathogen/endosymbiont co-infections were detected in 40.39% of D. nuttalli and 13.89% of I. persulcatus, respectively. The dual co-infection with R. raoultii and CLE (14.29%, 29/203) and triple co-infection with R. raoultii, Anaplasma sp. Mongolia, and CLE (13.79%, 28/203) were most frequent in D. nuttalli. CONCLUSIONS: This study provides insight into the microbial diversity of D. nuttalli and I. persulcatus in Inner Mongolia, China, reporting for the first time that Candidatus R. tarasevichiae had been found in D. nuttalli in China, and for the first time in the world that Anaplasma sp. Mongolia has been detected in I. persulcatus. This study proves that various vertically transmitted pathogens co-inhabit D. nuttalli and I. persulcatus, and indicates that cattle in Inner Mongolia are exposed to several TBPs.

Stepwise Cross-Linking of Fibroin and Hyaluronic for 3D Printing Flexible Scaffolds with Tunable Mechanical Properties.

The development of 3D printing techniques has provided a promising platform to study tissue engineering and mechanobiology; however, the pursuit of printability limits the possibility of tailoring scaffolds' mechanical properties. The brittleness of those scaffolds also hinders potential clinical application. To overcome these drawbacks, a double-network ink composed of only natural biomaterials is developed. A shear-thinning hydrogel made of silk fibroin (SF) and methacrylated hyaluronic acid (MAHA) presents a high mechanical modulus with a low concentration of macromers. The physical cross-linking due to protein folding further increases the strength of the scaffolds. The proposed SF/MAHA scaffold exhibits a storage modulus 10 times greater than that of methacrylated gelatin scaffold, along with better flexibility and biodegradation. The synergistic effect between fibroin and hyaluronic allows us to tailor the mechanical strength of scaffolds without compromising their printability. The hierarchy porous structure of the SF/MAHA scaffolds offers a better spatial microenvironment for the migration and proliferation of cells compared to gelatin scaffolds. For the first time, this strategy achieves 3D printing of natural biomaterials with controlled mechanical characteristics by manipulating the cross-linking of peptide chains. The design of such ductile scaffolds with hydrolysis resistance provides a new platform for the mechanobiology research. It also shows promise in the tissue engineering of musculoskeletal system where structural strength is needed.

Digestion degree is a key factor to regulate the printability of pure tendon decellularized extracellular matrix bio-ink in extrusion-based 3D cell printing.

Improving the printability of pure, decellularized extracellular matrix (dECM) bio-ink without altering its physiological components has been a challenge in three-dimensional (3D) cell printing. To improve the printability of the bio-ink, we first investigated the digestion process of the powdered dECM material obtained from porcine tendons. We manifested the digestion process of tendon derived dECM powders, which includes dissolution, gelatinization and solubilization. After a short dissolution period (around 10 min), we observed a 'High viscosity slurry' status (3 h) of the dECM precursors, i.e. the gelatinization process, followed by the solubilization processes, i.e. a 'Medium viscosity slurry' period (12 h) and a 'Low viscosity slurry' period (72 h). The 'Medium viscosity slurry' status of the dECM bio-ink was inhomogeneous and could not be extruded out from the barrel after the pH value was neutralized to 7.4. Although the 'Low viscosity slurry' status of the dECM bio-ink has been reported to be extrudable, it has poor printability. This study explores the printability of the 'High viscosity slurry' status of the dECM bio-ink, which has not been addressed thus far. The results demonstrate that this less digested status of the dECM bio-ink yields higher shape fidelity and stacking accuracy than the traditional over-digested status of the dECM bio-ink; this indicates better printability of this less digested dECM bio-ink. We compared the performance of the two bio-inks using cell viability tests for 3D cell printing. Bone marrow mesenchymal stem cells derived from rats was printed using the 'High viscosity slurry' status of the dECM bio-ink, yielding high cellular viability lasting for 7 d after printing. Thus, the 'High viscosity slurry' status of tendon dECM bio-ink can be utilized to fabricate complicated 3D organoid structures; it also shows promise for applications such as regenerative medicine and biomimetic tissue engineering.

Biomechanically, structurally and functionally meticulously tailored polycaprolactone/silk fibroin scaffold for meniscus regeneration.

Meniscus deficiency, the most common and refractory disease in human knee joints, often progresses to osteoarthritis (OA) due to abnormal biomechanical distribution and articular cartilage abrasion. However, due to its anisotropic spatial architecture, complex biomechanical microenvironment, and limited vascularity, meniscus repair remains a challenge for clinicians and researchers worldwide. In this study, we developed a 3D printing-based biomimetic and composite tissue-engineered meniscus scaffold consisting of polycaprolactone (PCL)/silk fibroin (SF) with extraordinary biomechanical properties and biocompatibility. We hypothesized that the meticulously tailored composite scaffold could enhance meniscus regeneration and cartilage protection. Methods: The physical property of the scaffold was characterized by scanning electron microscopy (SEM) observation, degradation test, frictional force of interface assessment, biomechanical testing, and fourier transform infrared (FTIR) spectroscopy analysis. To verify the biocompatibility of the scaffold, the viability, morphology, proliferation, differentiation, and extracellular matrix (ECM) production of synovium-derived mesenchymal stem cell (SMSC) on the scaffolds were assessed by LIVE/DEAD staining, alamarBlue assay, ELISA analysis, and qRT-PCR. The recruitment ability of SMSC was tested by dual labeling with CD29 and CD90 by confocal microscope at 1 week after implantation. The functionalized hybrid scaffold was then implanted into the meniscus defects on rabbit knee joint for meniscus regeneration, comparing with the Blank group (no scaffold) and PS group. The regenerated meniscus tissue was evaluated by histological and immunohistochemistry staining, and biomechanical test. Macroscopic and histological scoring was performed to assess the outcome of meniscus regeneration and cartilage protection in vivo. Results: The combination of SF and PCL could greatly balance the biomechanical properties and degradation rate to match the native meniscus. SF sponge, characterized by fine elasticity and low interfacial shear force, enhanced energy absorption capacity of the meniscus and improved chondroprotection. The SMSC-specific affinity peptide (LTHPRWP; L7) was conjugated to the scaffold to further increase the recruitment and retention of endogenous SMSCs. This meticulously tailored scaffold displayed superior biomechanics, structure, and function, creating a favorable microenvironment for SMSC proliferation, differentiation, and extracellular matrix (ECM) production. After 24 weeks of implantation, the histological assessment, biochemical contents, and biomechanical properties demonstrated that the polycaprolactone/silk fibroin-L7 (PS-L7) group was close to the native meniscus group, showing significantly better cartilage protection than the PS group. Conclusion: This tissue engineering scaffold could greatly strengthen meniscus regeneration and chondroprotection. Compared with traditional cell-based therapies, the meniscus tissue engineering approach with advantages of one-step operation and reduced cost has a promising potential for future clinical and translational studies.