Neonatal IL-4 Over-Exposure is Accompanied by Macrophage Accumulation in Dura Mater After Instant Anti-inflammatory Cytokine Response in CSF.

Multiple studies have shown that clinical events resulting into neonatal IL-4 over-exposure, such as asthma in early life and food allergy, were associated with brain damage and that the neuroinflammation induced by them might lead to cognitive impairments, anxiety-/depressive-like behaviors. IL-4 is the most major elevated cytokine in periphery when these clinical events occur and peripheral IL-4 level positively correlates with the severity of those events. Our previous studies have verified that neonatal IL-4 over-exposure induced a delayed neuroinflammatory damage in rodents, which might have adverse implications for brain development and cognition. Neuroinflammation in brain parenchyma is often accompanied by changes in CSF cytokines levels. However, whether the cytokines levels in CSF change after neonatal IL-4 over-exposure is unknown. Here, we found a delayed pro-inflammatory cytokines response (higher IL-6, IL-1ß and, TNF levels) in both hippocampus and CSF after an instant anti-inflammatory cytokine response in IL-4 over-exposed rats. Moreover, the pro-inflammatory cytokines response appeared earlier in CSF than in hippocampus. The level of each of the pro-inflammatory cytokines in CSF positively correlated with that in hippocampus at the age of postnatal day 42. More microglia numbers/activation and higher M-CSF level in the hippocampus in IL-4 over-exposed rats were also observed. Furthermore, there were more macrophages with inflammatory activation in dural mater of IL-4 over-exposed rats. In sum, neonatal IL-4 over-exposure in rats induces delayed inflammation in CSF, suggesting CSF examination may serve as a potential method in predicting delayed neuroinflammation in brain following neonatal IL-4 over-exposure.

Genome Sequence Resource of Cladosporium velox Strain C4 Causing Cotton Boll Disease in Xinjiang, China.

Cladosporium spp., as one of the largest and most heterogeneous genera of hyphomycetes, are widely distributed worldwide. This genus is usually adaptable to a wide variety of extreme environments. However, only 11 genomes of Cladosporium genus have been publicly released. From 2017, we found for the first time that Cladosporium velox could cause cotton boll disease and lead to stiffness and cracking boll in Xinjiang, China. Herein, we provide a high-quality reference genome for the C. velox strain C4 isolated from cotton boll in Xinjiang, China. The genome size and encoding gene number of the C. velox strain C4 and C. cucumerinum strain CCNX2, which was recently released and caused the cucumber scab, showed minor differences. This resource will contribute to future research that aims to elucidate the genetic basis of C. velox pathogenicity and could expand our knowledge of Cladosporium spp. genomic characteristics that will be valuable for the development of Cladosporium disease control measures.

[Di'ao Xinxuekang alleviates non-alcoholic steatohepatitis in mice by up-regulating Nrf2/HO-1 signaling pathway].

The present study investigated the therapeutic effect and mechanism of Di'ao Xinxuekang(DXXK) on non-alcoholic steatohepatitis(NASH) in mice. Sixty-five C57 BL/6 J mice were randomly divided into a normal group and an experimental group for model induction with the high-fat diet for 16 weeks. Then the mice in the experimental group were randomly divided into a model group, an atorvastatin group(4 mg·kg~(-1)·d~(-1)), and high-(200 mg·kg~(-1)·d~(-1)), medium-(60 mg·kg~(-1)·d~(-1)), and low-dose(20 mg·kg~(-1)·d~(-1)) DXXK groups, with 10 mice in each group. Drugs were administered by gavage for eight weeks. Serum lipid, liver lipid, serum alanine aminotransferase(ALT), aspartate aminotransferase(AST), malondialdehyde(MDA), superoxide dismutase(SOD), and glutathione reductase(GSH-Px) were determined. Interleukin-1ß(IL-1ß) and tumor necrosis factor-α(TNF-α) were measured by enzyme-linked immunosorbent assay(ELISA). The liver index was calculated. The liver pathological change and lipid accumulation were observed by HE and oil red O staining. The liver ultrastructure was observed by the transmission electron microscope. The mRNA and protein expression of nuclear factor-erythroid 2 related factor 2(Nrf2) and heme oxygenase-1(HO-1) was detected by real-time fluorescence-based quantitative PCR and Western blot, respectively. The results showed that compared with the normal group, the model group displayed serum lipid and liver lipid metabolism disorders, elevated transaminase, lipid deposition, steatosis, and inflammation, suggesting that the NASH model in mice was properly induced. Compared with the model group, the DXXK groups showed decreased serum lipid, liver lipid, ALT, AST, MDA, IL-1ß, and TNF-α, increased SOD and GSH-Px, alleviated hepatic steatosis, ballooning, and inflammation, and up-regulated Nrf2 and HO-1 gene and protein expression. In conclusion, DXXK can significantly alleviate NASH in mice, which is related to the inhibition of oxidative stress and inflammatory damage by up-regulating the Nrf2/HO-1 signaling pathway.

[Regulatory effect of Di'ao Xinxuekang on TLR4/MyD88/NF-κB signaling pathway in atherosclerotic rats].

The aim of this paper was to observe the effect of Di'ao Xinxuekang(DXXK) on TLR4/MyD88/NF-κB signaling pathway in atherosclerotic rats, and to explore its anti-atherosclerotic mechanism. Sixty SD rats were randomly divided into normal group, model group, atorvastatin group(4.0 mg·kg~(-1)), and DXXK groups(100, 30, 10 mg·kg~(-1)), with 10 rats in each group. The atherosclerosis model was induced by high fat diet plus vitamin D_2. Experimental drugs were administered intragastrically once daily for 8 weeks starting from the 9 th week. Biochemical analyzers were used to detect levels of triglyceride(TG), total cholesterol(TC), low-density lipoprotein cholesterol(LDL-C) and high-density lipoprotein cholesterol(HDL-C) in blood lipid. The levels of serum tumor necrosis factor(TNF)-α, interleukin(IL)-6 and IL-1ß were detected by ELISA. Pathological changes of aortic tissues were observed by using Sudan Ⅳ and HE staining. The mRNA and protein expressions of TLR4, MyD88 and NF-κB p65 in aortic tissues were detected by RT-PCR and Western blot, respectively. As compared with the model group, TC, TG, and LDL-C levels in serum were significantly decreased, HDL-C content was significantly increased, and levels of TNF-α, IL-6, and IL-1ß in serum were significantly decreased in atorvastatin group and DXXK high and middle dose groups. Aortic lesions in atorvastatin group and DXXK group were significantly improved, and the mRNA and protein expressions of TLR4, MyD88, NF-κB p65 in the aorta were decreased. DXXK has a preventive and therapeutic effect on atherosclerosis in rats, and its mechanism may be related to inhibiting inflammatory reaction by regulating TLR4/MyD88/NF-κB signal transduction, thereby inhibiting the progression of atherosclerosis.

Pretreatment of Grape Seed Proanthocyanidin Extract Exerts Neuroprotective Effect in Murine Model of Neonatal Hypoxic-ischemic Brain Injury by Its Antiapoptotic Property.

Grape seed proanthocyanidin extract (GSPE), an active component extracted from the grape, has been reported to demonstrate antioxidant, anti-inflammatory, anticancer, and antiapoptosis effects. However, little is known about the role of GSPE on neonatal hypoxic-ischemic (HI) brain injury. The aim of this study was to evaluate the neuroprotective effect of GSPE pretreatment on neonatal HI brain injury in mice. A modified Rice-Vannucci method was performed to induce neonatal HI brain injury in the 7-day-old mouse pups pretreated with GSPE or vehicle. The infarct volumes were determined by TTC staining. TUNEL staining was used to detect cells apoptosis, and the expressions of apoptosis-related proteins: bax, bcl2, and cleaved caspase-3 were assayed by Western blot. Behavioral tests were also conducted to assess the functional recovery after injury. We showed that the brain damage and neurobehavioral outcomes improvement was observed in GSPE pretreated group. GSPE was proved to suppress apoptosis through inhibition of bax and cleaved caspase-3 expression. It demonstrates that GSPE could alleviate brain damage maybe through its antiapoptotic activity in a neonatal HI brain injury model, and GSPE has the potential to be a new drug for effective prevention of this disorder.

Crude glycerol from biodiesel as a carbon source for production of a recombinant highly thermostable ß-mannanase by Pichia pastoris.

OBJECTIVE: To explore an efficient use of crude glycerol for the production of a highly thermostable ß-mannanase (ReTMan26) by Pichia pastoris X33. RESULTS: Cell growth was significantly inhibited by 4 and 6% (w/v) crude glycerol in 250 ml shake-flasks and in 5 l bioreactor batch cultures, respectively, but not affected by pure glycerol at the same concentrations. For further study, the impact of various impurities in crude glycerol on the cell growth of, and ReTMan26 production by, Pichia pastoris was investigated. Salts and methanol did not exert an inhibitory effect, but ≥ 0.2% and 0.3% (w/v) soap in shake-flask and bioreactor cultures, respectively, inhibited fermentation. Under identical conditions, the biomass and ReTMan26 activity produced by high-cell-density fermentation using 5% crude glycerol (glycerol at 80%, w/w) were slightly higher than those using 4% (w/v) pure glycerol. CONCLUSIONS: Non-pretreated ≤ 5% (w/v) crude glycerol could be effectively utilized for industrial production of ReTMan26, and the total production costs using crude glycerol were ~ 4.2% lower than those using pure glycerol.

Xylose fermentation efficiency and inhibitor tolerance of the recombinant industrial Saccharomyces cerevisiae strain NAPX37.

Industrial yeast strains with good xylose fermentation ability and inhibitor tolerance are important for economical lignocellulosic bioethanol production. The flocculating industrial Saccharomyces cerevisiae strain NAPX37, harboring the xylose reductase-xylitol dehydrogenase (XR-XDH)-based xylose metabolic pathway, displayed efficient xylose fermentation during batch and continuous fermentation. During batch fermentation, the xylose consumption rates at the first 36 h were similar (1.37 g/L/h) when the initial xylose concentrations were 50 and 75 g/L, indicating that xylose fermentation was not inhibited even when the xylose concentration was as high as 75 g/L. The presence of glucose, at concentrations of up to 25 g/L, did not affect xylose consumption rate at the first 36 h. Strain NAPX37 showed stable xylose fermentation capacity during continuous ethanol fermentation using xylose as the sole sugar, for almost 1 year. Fermentation remained stable at a dilution rate of 0.05/h, even though the xylose concentration in the feed was as high as 100 g/L. Aeration rate, xylose concentration, and MgSO4 concentration were found to affect xylose consumption and ethanol yield. When the xylose concentration in the feed was 75 g/L, a high xylose consumption rate of 6.62 g/L/h and an ethanol yield of 0.394 were achieved under an aeration rate of 0.1 vvm, dilution rate of 0.1/h, and 5 mM MgSO4. In addition, strain NAPX37 exhibited good tolerance to inhibitors such as weak acids, furans, and phenolics during xylose fermentation. These findings indicate that strain NAPX37 is a promising candidate for application in the industrial production of lignocellulosic bioethanol.

[Aggregation Behavior of Collagen-Based Surfactant Molecules in Aqueous Solutions Based on Synchronization Fluorescence Spectrum Technology].

Due to the intrinsic fluorescence characteristic of tyrosine (Tyr) and phenylalanine (Phe), synchronization fluorescence spectrum technology which adopted the constant wavelength difference (Δλ = 15 nm) was selected to investigate the effects of collagen-based surfactant (CBS) concentration, pH, NaCt concentration and temperature on the aggregation state of CBS molecules in aqueous solutions. Meanwhile, temperature-dependent two-dimensional (2D) synchronization fluorescence correlation analyses was used to investigate the variation order of Tyr and Phe residues in CBS molecules with the change of temperature. The results showed that the characteristic absorption peaks located at 261 and 282 nm were attributed to Phe and Tyr, respectively. With the increase of CBS concentration, the amount of Phe and Tyr residues increased gradually which resulted in the increase of aggregate degree of CBS molecules and then led to the increase of fluorescence intensity. When the pH value (pH 5.0) of CBS solutions was close to the isoelectric point of CBS, the aggregate degree of CBS molecules increased due to the increase of the hydrophobic interaction and the formation ability of hydrogen bond. Additionally, with the increase of NaCl concentration, the repulsion force for inter/intra-molecules of CBS decreased, which helped to improve the aggregation behavior of CBS molecules. However, with the increase of temperature, the aggregation state of CBS was changed to be monomolecular state, and then resulted in the decrease of the fluorescence intensity gradually due to the quenching, the denaturation and the decrease of hydrogen bond formation ability. Furthermore, temperature-dependent 2D synchronization fluorescence correlation spectroscopy demonstrated that at lower temperature (10-40 degrees C), the aggregate state of CBS changed to be loose state and then Phe residues located in the inside of the aggregate varied before Tyr residues; while in the heating process of 45-70 degrees C, the monomolecular state of CBS changed to be random coil conformation, the separation distance between Tyr residues increased and the hydrogen bond formation ability reduced strongly, which led to Tyr residues changed before Phe residues.

Effects on Spatial Cognition and Nociceptive Behavior Following Peripheral Nerve Injury in Rats with Lesion of the Striatal Marginal Division Induced by Kainic Acid.

Neuropathic pain and cognitive deficit are frequently comorbidity in clinical, but their underlying correlation and mechanisms remain unclear. Here, we utilized a combined rat model including kainic acid (KA) injection into bilateral striatal marginal division and chronic constriction nerve injury (CCI). PET/CT scans revealed that the SUVmax of KA rats was significantly decreased when compared to naive and saline rats. In contrast to the naive and saline rats, KA rats had longer latencies in locating the hidden platform on day 4, 5 in Morris water maze task. Thermal hyperalgesia and mechanical allodynia of KA rats were alleviated following CCI. Immunostaining results showed that substance P was markedly increased within ipsilateral spinal cord dorsal horn of KA rats after CCI, especially on the post-operative day 14. By means of real-time PCR, the up-regulation of GluR within ipsilateral spinal cord dorsal horn was observed in all KA and CCI rats. PKCγ, IL-6 and NF-κB were up-regulated in both CCI rats when compared to naive and their respective sham rats. These results suggest that cognitive impairment of rats altered the pain behaviors, and these intracellular regulators play crucial roles in the process of neuropathic pain.

Influence on the physicochemical properties of fish collagen gels using self-assembly and simultaneous cross-linking with the N-hydroxysuccinimide adipic acid derivative.

Collagen gels from Southern catfish (Silurus meridionalis Chen) skins were prepared via the self-assembly of collagen molecules and simultaneous cross-linking with the N-hydroxysuccinimide adipic acid derivative (NHS-AA). The doses of NHS-AA were converted to [NHS-AA]/[NH2] ratios (0.025-1.6, calculated by the [active ester group] of NHS-AA and [ε-NH2] of lysine and hydroxylysine residues of collagen). When the ratio < 0.05, collagen gels were formed by collagen molecule self-assembly, resulting in the opalescent appearance of collagen gels and the characteristic D-periodicity of partial collagen fibrils, the collagen gel ([NHS-AA]/[NH2] = 0.05) displayed a small increase in denaturation temperature (Td, 42.8 °C), remaining weight (12.59%), specific water content (SWC 233.7) and elastic modulus (G' 128.4 Pa) compared with uncross-linked collagen gel (39.1 °C, 9.12%, 222.4 and 85.4 Pa, respectively). As the ratio > 0.05, disappearance of D-periodicity and a gradual change in appearance from opalescent to transparent suggested that the inhibition of NHS-AA in the self-assembly of collagen molecules was more obvious. As a result, the collagen gel ([NHS-AA]/[NH2] = 0.2) had the lowest Td (35.8 °C), remaining weight (7.96%), SWC (130.9) and G' (31.9 Pa). When the ratio was 1.6, the collagen molecule self-assembly was markedly suppressed and the formation of collagen gel was predominantly via the covalent cross-linking bonds which led to the transparent appearance, and the maximum values of Td (47.0 °C), remaining weight (45.92%) and G' (420.7 Pa) of collagen gel. These results indicated that collagen gels with different properties can be prepared using different NHS-AA doses.

[Effect of temperature on the aggregation behavior of collagen solution by two-dimensional synchronous fluorescence correlation spectroscopy].

The synchronous fluorescence spectroscopy and two dimensional correlation analysis method were applied to study the aggregation behavior of acid-soluble collagen solutions (0.2, 0.4 and 1.6 mg x mL(-1)) during the heating process of 10-70 degrees C. It was found that the fluorescence excited at 292 and 282 nm (delta lamda=9 nm) belongs to the tyrosine (Tyr) residues which participate in forming hydrogen bonds or not, respectively. The two dimensional correlation analysis with the temperature varying showed that with the temperature increased (10-30 degrees C) hydrogen bonds among collagen molecular with Tyr residues formed in the 0.2 mg x mL(-1) collagen solution, while the higher aggregations of collagen molecular and hydrophobic micro-domains appeared in the 0.4 and 1.6 mg x mL(-1) collagen solutions. With approaching the denatured temperature of collagen (36-38 degrees C), the hydrophobic micro-domain and aggregates seemed to be broken in the 0.4 and 1.6 mg x mL(-1) collagen solutions, however the hydrogen bonds in the 0.2 mg x mL(-1) were stable. Above the denaturation temperature of collagen, the triple-helix structure of collagen molecular in solution of each concentration tended to be loose. In the heating process of 45-70 degrees C, this trend was more obvious.

Physicochemical properties of collagen solutions cross-linked by glutaraldehyde.

The physicochemical properties of collagen solutions (5 mg/ml) cross-linked by various amounts of glutaraldehyde (GTA) [GTA/collagen (w/w) = 0-0.5] under acidic condition (pH 4.00) were examined. Based on the results of the determination of residual amino group content, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, dynamic rheological measurements, differential scanning calorimetry and atomic force microscopy (AFM), it was proved that the collagen solutions possessed strikingly different physicochemical properties depending on the amount of GTA. At low GTA amounts [GTA/collagen (w/w) ≤ 0.1], the residual amino group contents of the cross-linked collagens decreased largely from 100% to 32.76%, accompanied by an increase in the molecular weight. Additionally, increases of the fiber diameter and the values of G', G″ and η* were measured, while the thermal denaturation temperature (Td) did not change visibly and the fluidity of collagen samples was still retained with increasing the GTA amount. When the ratio of GTA to collagen exceeded 0.1, although the residual amino group content only decreased by ~8.2%, the cross-linked collagen solution [GTA/collagen (w/w) = 0.3] displayed a clear loss of flow and a sudden rise (~2.0 °C) of the Td value compared to the uncross-linked collagen solution, probably illustrating that the collagen solution was converted into a gel with mature network structure-containing nuclei observed in AFM image. It was conjectured that the physicochemical properties of the collagen solutions might be in connection with the cross-linking between collagen molecules from the same aggregate or different aggregates.

A bioactive composite sponge based on biomimetic collagen fibril and oxidized alginate for noncompressible hemorrhage and wound healing.

The study focuses on developing a bioactive shape memory sponge to address the urgent demand for short-term rapid hemostasis and long-term wound healing in noncompressible hemorrhage cases. A composite sponge was created by spontaneously generating pores and double cross-linking under mild conditions using biomimetic collagen fibril (BCF) and oxidized alginate (OA) as natural backbone, combined with an inert calcium source (Ca) from CaCO3-GDL slow gelation mechanism. The optimized BCF/OACa (5/5) sponge efficiently absorbed blood after compression and recovered to its original state within 11.2 ± 1.3 s, achieving physical hemostatic mechanism. The composite sponge accelerated physiological coagulation by promoting platelet adhesion and activation through BCF, as well as enhancing endogenous and exogenous hemostatic pathways by Ca2+. Compared to commercial PVA expanding hemostatic sponge, the composite sponge reduced bleeding volume and shortened hemostasis time in rat liver injury pick and perforation wound models. Additionally, it stimulated fibroblast migration and differentiation, thus promoting wound healing. It is biodegradable with low inflammatory response and promotes granulation tissue regeneration. In conclusion, this biocomposite sponge provides multiple hemostatic pathways and biochemical support for wound healing, is biologically safe and easy to fabricate, process and use, with significant potential for clinical translation and application.

A high-strength collagen-based antimicrobial film grafted with ε-polylysine fabrication by riboflavin-mediated ultraviolet irradiation for pork preservation.

In this study, a UV-cured collagen-based film (C-P-H film) with high mechanical strength and antimicrobial properties was developed by riboflavin-mediated ultraviolet irradiation of collagen solution containing histidine-modified ε-polylysine. Fourier transform infrared analysis indicated that covalent cross-linking was formed between the collagen molecule and the histidine-grafted ε-polylysine. Compared with the pure collagen film, the C-P-H film containing 5 wt% histidine-modified ε-polylysine showed higher tensile strength (145.98 MPa), higher thermal denaturation temperature (76.5 °C), lower water vapor permeability (5.54 × 10-11 g m-1 s-1 Pa) and excellent antimicrobial activities against Escherichia coli and Staphylococcus aureus. In addition, the wrapping of the C-P-H film effectively inhibited bacterial growth of pork during storage time, successfully prolonging the shelf-life of pork by approximately 4 days compared to that of plastic wrap. These results suggested that collagen-based film grafted with histidine-modified ε-polylysine via riboflavin-mediated ultraviolet irradiation process had a great potential for pork preservation.

Landscape of m6A RNA methylation regulators in liver cancer and its therapeutic implications.

Liver cancer remains as the third leading cause of cancer-related death globally as of 2020. Despite the significant progress made in the field of liver cancer treatment, there is still a lack of effective therapies in patients with advanced cancer and the molecular mechanisms underlying liver cancer progression remain largely elusive. N6-methyladenosine (m6A) modification, as the most prevalent and abundant internal RNA modification in eukaryotic RNAs, plays an essential role in regulating RNA metabolism including RNA splicing, stability, translation, degradation. To date, there is mounting evidence showing that m6A dysregulation is closely associated with the onset and development of many tumors including hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (ICC) and hepatoblastoma (HB). In this review, we summarize the last research progress regarding the functions of m6A-related regulators in liver cancer and its underlying mechanisms. Additionally, we also discuss the therapeutic applications of m6A-based inhibitors in liver cancer treatment.

Efficient biosynthesis of transglutaminase in Streptomyces mobaraensis via systematic engineering strategies.

Transglutaminases (TGases) have been widely used in food, pharmaceutical, biotechnology, and other industries because of their ability to catalyze deamidation, acyl transfer, and crosslinking reactions between Ƴ-carboxamide groups of peptides or protein-bound glutamine and the Ɛ-amino group of lysine. In this study, we demonstrated an efficient systematic engineering strategy to enhance the synthesis of TGase in a recombinant Streptomyces mobaraensis smL2020 strain in a 1000-L fermentor. Briefly, the enzymatic properties of the TGase TGL2020 from S. mobaraensis smL2020 and TGase TGLD from S. mobaraensis smLD were compared to obtain the TGase TGLD with perfected characteristics for heterologous expression in a recombinant S. mobaraensis smL2020ΔTG without the gene tgL 2020. Through multiple engineering strategies, including promoter engineering, optimizing the signal peptides and recombination sites, and increasing copies of the expression cassettes, the final TGLD activity in the recombinant S. mobaraensis smL2020ΔTG: (PL2020-spL2020-protgLD-tgLD)2 (tgL2020and BT1) reached 56.43 U/mL and 63.18 U/mL in shake flask and 1000-L fermentor, respectively, which was the highest reported to date. With the improvement of expression level, the application scope of TGLD in the food industry will continue to expand. Moreover, the genetic stability of the recombinant strain maintained at more than 20 generations. These findings proved the feasibility of multiple systematic engineering strategies in synthetic biology and provided an emerging solution to improve biosynthesis of industrial enzymes.

LexA, an SOS response repressor, activates TGase synthesis in Streptomyces mobaraensis.

Transglutaminase (EC 2.3.2.13, TGase), an enzyme that catalyzes the formation of covalent cross-links between protein or peptide molecules, plays a critical role in commercial food processing, medicine, and textiles. TGase from Streptomyces is the sole commercial enzyme preparation for cross-linking proteins. In this study, we revealed that the SOS response repressor protein LexA in Streptomyces mobaraensis not only triggers morphological development but also enhances TGase synthesis. The absence of lexA significantly diminished TGase production and sporulation. Although LexA does not bind directly to the promoter region of the TGase gene, it indirectly stimulates transcription of the tga gene, which encodes TGase. Furthermore, LexA directly enhances the expression of genes associated with protein synthesis and transcription factors, thus favorably influencing TGase synthesis at both the transcriptional and posttranscriptional levels. Moreover, LexA activates four crucial genes involved in morphological differentiation, promoting spore maturation. Overall, our findings suggest that LexA plays a dual role as a master regulator of the SOS response and a significant contributor to TGase regulation and certain aspects of secondary metabolism, offering insights into the cellular functions of LexA and facilitating the strategic engineering of TGase overproducers.

Development of a pH-sensitive film based on collagen/chitosan/ZnO nanoparticles and mulberry extract for pork freshness monitoring.

pH-sensitive films based on collagen, chitosan, ZnO-nanoparticles and mulberry extract (CC/ZnO/ME) were developed to monitor pork freshness. Fourier transform infrared analysis revealed that collagen, chitosan, ZnO-nanoparticles and ME interacted via hydrogen bonds. The UV-vis light barrier ability of CC/ZnO/ME film was gradually enhanced as increasing ME content from 0.5 to 2.0 % wt. Compared with CC film, the mechanical strength and DPPH radical free scavenging rate of the CC/ZnO/ME film had increased by 13.84 MPa and 58.74 %, respectively. CC/ZnO/ME1 and CC/ZnO/ME2 films exhibited better pH-sensitivity than CC/ZnO/ME3 film, with color visibly changing from red to blue/green in different buffer solutions (pH 3-12). When monitoring the freshness of pork stored at 4℃, the color of CC/ZnO/ME2 film changed from deep purple to blue when TVB-N content exceeded the maximum permissible limit (15 mg/100 g) on 6th day.

Development of composite film based on collagen and phenolic acid-grafted chitosan for food packaging.

Collagen, a fibrous protein with triple-helical structure, is a good film-forming substrate for food packaging films because collagen films show advantages of biodegradability, high mechanical strength and good water resistance. However, collagen films lack functional activities, which may limit their applications in the field of active packaging. In this work, phenolic acid-grafted-chitosan was blended with collagen to improve the antioxidant and antimicrobial activities of collagen films. Gallic acid (GA), ferulic acid (FA) and caffeic acid (CA) were respectively grafted onto chitosan, and the physical properties and functional activities of the collagen/phenolic acids-g-chitosan (CGC, CFC and CCC) films were compared. The prepared films presented varying degrees of yellow color, and exhibited significantly improved UV light blocking capacity, antioxidant and antimicrobial properties due to the function of phenolic acid. Moreover, compared with collagen/chitosan (CC) film, CGC, CFC and CCC films showed higher mechanical strength (69.08-73.79 MPa), higher thermal denaturation temperature (69.4-71.2 °C), and lower water vapor permeability values (2.64-2.98 × 10-12 g m-1 s-1 Pa-1). The properties of collagen/ phenolic acids-g-chitosan films were greatly affected by the type of phenolic acid grafted. CGC film had the best antioxidant property as well as the best mechanical property, thermostability, UV light and water vapor blocking capacity.

An antibacterial and healing-promoting collagen fibril constructed by the simultaneous strategy of fibril reconstitution and ε-polylysine anchoring for infected wound repair.

The development of antibacterial dressings has attracted much attention to address the disordered wound healing caused by bacterial infection. Constructing dressings that have desirable antibacterial activity and could promote wound healing is important for infected wound repair. Inspired by the role of the key regulator collagen fibrils with D-periodic functional domains in the physiological wound healing process, we developed an antibacterial and wound healing-promoting collagen fibril with a structure highly similar to natural collagen in ECM and inherent antibacterial activity by the simultaneous strategy of fibril reconstitution and the antibacterial agent ε-polylysine (ε-PL) anchoring. Accompanied by the fibrillogenesis of collagen molecules, the anchorage of ε-PL into collagen fibrils was actualized through the formation of the covalent bond catalyzed by transglutaminase (TGase) between ε-PL and collagen. The collagen fibril possessed natural D-periodicity and achieved 20% ε-PL graft yield by co-assembling collagen/ε-PL mediated by 25 U g-1 TGase, which showed a satisfactory proliferation of L929 fibroblasts and sustained inhibition rates above 90% against E. coli and S. aureus. The rat S. aureus-infected dermal wound model further demonstrated that the reconstituted antibacterial collagen fibril visibly promoted re-epithelialization, new collagen deposition, and angiogenesis by down-regulating the inflammatory-relative gene IL-6 and up-regulating the relative activity factor expression of CD31, achieving accelerated infected wound healing with 61.89% ± 3.96% wound closure on postoperative day 7 and full closure on day 14.