Metabolic engineering of Escherichia coli for the production of (R)-α-lipoic acid.

OBJECTIVE: To increase the production of (R)-α-lipoic acid directly from octanoic acid using engineered Escherichia coli with the regeneration of S-adenosylmethionine. RESULTS: The biosynthesis of (R)-α-lipoic acid (LA) in E. coli BL21(DE3) is improved by co-expression of lipoate-protein ligase A (LplA) from E. coli MG1655 and lipoate synthase (LipA) from Vibrio vulnificus. The engineered strain produces 20.99 µg l-1 of LA in shake flask cultures. The titers of LA are increased to 169.28 µg l-1 after the optimization of the medium components and fermentation conditions. We find that the [4Fe-4S] cluster is important for the activity of LipA and co-expression of iscSUA promotes the regeneration of the [4Fe-4S] cluster and leads to the highest LA titer of 589.30 µg l-1. CONCLUSION: The method described here can be widely applied for the biosynthesis of (R)-α-lipoic acid and other metabolites.

Using CIVT-SELEX to Select Aptamers as Genetic Parts to Regulate Gene Circuits in a Cell-Free System.

The complexity of genetic circuits has not seen a significant increase over the last decades, even with the rapid development of synthetic biology tools. One of the bottlenecks is the limited number of orthogonal transcription factor-operator pairs. Researchers have tried to use aptamer-ligand pairs as genetic parts to regulate transcription. However, most aptamers selected using traditional methods cannot be directly applied in gene circuits for transcriptional regulation. To that end, we report a new method called CIVT-SELEX to select DNA aptamers that can not only bind to macromolecule ligands but also undergo significant conformational changes, thus affecting transcription. The single-stranded DNA library with affinity to our example ligand human thrombin protein is first selected and enriched. Then, these ssDNAs are inserted into a genetic circuit and tested in the in vitro transcription screening to obtain the ones with significant inhibitory effects on downstream gene transcription when thrombins are present. These aptamer-thrombin pairs can inhibit the transcription of downstream genes, demonstrating the feasibility and robustness of their use as genetic parts in both linear DNAs and plasmids. We believe that this method can be applied to select aptamers of any target ligands and vastly expand the genetic part library for transcriptional regulation.

Hierarchical Fluid Interface Enables Spatiotemporal Regulation of Ligand Distribution to Increase Kinetics and Thermodynamics of Interfacial Binding Reaction.

In nature, regulation of the spatiotemporal distribution of interfacial receptors and ligands leads to optimum binding kinetics and thermodynamics of receptor-ligand binding reactions within interfaces. Inspired by this, we report a hierarchical fluid interface (HieFluidFace) to regulate the spatiotemporal distribution of interfacial ligands to increase the rate and thermodynamic favorability of interfacial binding reactions. Each aptamer-functionalized gold nanoparticle, termed spherical aptamer (SAPT), is anchored on a supported lipid bilayer without fluidity, like an "island", and is surrounded by many fluorescent aptamers (FAPTs) with free fluidity, like "rafts". Such ligand "island-rafts" model provides a large reactive cross-section for rapid binding to cellular receptors. The synergistic multivalency of SAPTs and FAPTs improves interfacial affinity for tight capture. Moreover, FAPTs accumulate at binding sites to bind to cellular receptors with clustered fluorescence to "lighten" cells for direct identification. Thus, HieFluidFace in a microfluidic chip achieves high-performance capture and identification of circulating tumor cells from clinical samples, providing a new paradigm to optimize the kinetics and thermodynamics of interfacial binding reactions.

Visible spectrophotometric assay for characterization of ω-transaminases.

Omega-transaminases (ω-TAs) have attracted considerable interest for their use in asymmetric synthesis of chiral amines with a high degree of optical purity and yield. The rapid evaluation of the characteristics of newly identified or engineered ω-TAs is important for industrial applications. In this study, a visible spectrophotometric assay was developed for rapid quantitative determination of ω-TA activities based on the transamination of 2-(4-nitrophenyl)ethan-1-amine to generate a red product (E)-N-(4-nitrophenethyl)-2-(4-nitrophenyl)ethen-1-amine. After various co-solvents were evaluated, dimethyl sulfoxide (DMSO) was considered optimal because the red product exhibits good solubility and retains its original color. The red product dissolved in DMSO has its highest absorbance at 465 nm, and its concentration has a good linear relationship with the absorbance. A spectrophotometric assay was established and validated using conventional HPLC analysis (<10% divergence). This method was then used to characterize an ω-TA from thermophilic Geobacillus thermoleovorans and an ω-TA obtained from the metagenome of a soda lake. The results demonstrated that ω-transaminase enzymatic properties could be characterized simply, rapidly, and at low cost, using this newly established visible spectrophotometric assay method.

Safety assessment of desaminotyrosine: Acute, subchronic oral toxicity, and its effects on intestinal microbiota in rats.

In this work, the acute and subchronic toxicities of desaminotyrosine (DAT) by oral administration in SD rats and its effects on the intestinal microflora were investigated. The acute toxicity test showed that DAT is a low-toxic substance with a LD50 of 3129 mg/kg. The subchronic toxicity test showed that DAT has no toxicity at a low dose (125 mg/kg/day). However, DAT exhibited obvious toxicities to food intake, liver, kidney, and lung at higher dose (250 mg/kg/day and 500 mg/kg/day). DAT inhibited the food intake of rats in a dose-dependent manner. Serum biochemical analysis showed that DAT can increase the serum glucose level of rats. Fecal microbiota analysis showed that DAT treatment can significantly change the intestinal microflora of rats, the dose of 125 mg/kg/day has the most significant effect on the diversity of intestinal microbiota. In daily application, the side effects caused by DAT might be gastrointestinal irritation, weight loss, liver or kidney injury, and blood sugar elevation. Based on our study, the no-observed-adverse-effect level (NOAEL) of DAT is 125 mg/kg BW/day for rats.

Fluidic Multivalent Membrane Nanointerface Enables Synergetic Enrichment of Circulating Tumor Cells with High Efficiency and Viability.

The ubiquitous biomembrane interface, with its dynamic lateral fluidity, allows membrane-bound components to rearrange and localize for high-affinity multivalent ligand-receptor interactions in diverse life activities. Inspired by this, we herein engineered a fluidic multivalent nanointerface by decorating a microfluidic chip with aptamer-functionalized leukocyte membrane nanovesicles for high-performance isolation of circulating tumor cells (CTCs). This fluidic biomimetic nanointerface with active recruitment-binding afforded significant affinity enhancement by 4 orders of magnitude, exhibiting 7-fold higher capture efficiency compared to a monovalent aptamer functionalized-chip in blood. Meanwhile, this soft nanointerface inherited the biological benefits of a natural biomembrane, minimizing background blood cell adsorption and maintaining excellent CTC viability (97.6%). Using the chip, CTCs were successfully detected in all cancer patient samples tested (17/17), suggesting the high potential of this fluidity-enhanced multivalent binding strategy in clinical applications. We expect this bioengineered interface strategy will lead to the design of innovative biomimetic platforms in the biomedical field by leveraging natural cell-cell interaction with a natural biomaterial.

[Cloning, expression, directed evolution in vitro and structural simulation of ß-glycosidase from Bacillus subtilis].

OBJECTIVE: To further study physiological functions and structure of ß-glycosidase, we cloned the bglC gene of Bacillus subtilis and expressed it in E. coli BL21 (DE3), followed by the characterization and structural simulation of the enzyme. METHODS: We amplified the bglC gene and transferred it into E. coli BL21 (DE3), then we obtained a mutant with higher hydrolytic activity by directed evolution. After purifying the enzymes through a nickel-nitrilotriacetic acid agarose column, we characterized the wild-type and mutant enzymes. By means of CD spectrum, Native-PAGE and protein 3-D structure modeling, we analyzed the higher structure of the ß-glycosidase. RESULTS: We got one mutant enzyme BS-GLY_M1 (A242T/T385A/S425L) with improved hydrolytic activity by directed evolution and screening. The specific activity of wild-type enzyme was 9.7 U/mg, with optimum temperature at 60 degrees C and optimum pH at 7.0. The specific activity of BS-GLY_M1 was 17. 1U/mg, with optimum temperature at 55 degrees C and optimum pH at 7.0. Moreover, the half-life time of the mutant enzyme at 55 degrees C was 3.5 h, 2 h longer than that of wild-type enzyme. Furthermore, the catalytic efficiency (K(m)/K(cat)) of BS-GLY_M1 on the substrates 4-nitrophenyl-ß-galactoside, lactose, and arbutin improved obviously. The polymer forms of the enzyme under the native conditions were of dimer and tetramer, but the dimer was the most probable functional unit. Result of structural simulation also showed slight changes occurred in the tertiary structure of the mutant enzyme, which may be the main reason for the enhanced thermal stability and catalytic efficiency of BS-GLY _M1. [ CONCLUSION: ß-glycosidase from Bacillus subtilis could be expressed in E. coli BL21 (DE3), meanwhile its hydrolysis efficiency could be further improved by directed evolution.

Biomimetic injectable and bilayered hydrogel scaffold based on collagen and chondroitin sulfate for the repair of osteochondral defects.

The simultaneous regeneration of articular cartilage and subchondral bone is a major challenge. Bioinspired scaffolds with distinct regions resembling stratified anatomical architecture provide a potential strategy for osteochondral defect repair. Here, we report the development of an injectable and bilayered hydrogel scaffold with a strong interface binding force. In this bilayer hydrogel, composed of carbonyl hydrazide grafted collagen (COL-CDH) and oxidized chondroitin sulfate (OCS), which are derivatives of osteochondral tissue components, in combination with poly (ethylene glycol) diacrylate (PEGDA), functions as a cartilage layer; while zinc-doped hydroxyapatite acts as a subchondral bone layer that is based on the cartilage layer. The strong interface between the two layers involves dynamic amide bonds formed between COL-CDH and OCS, and permanent CC bonds formed by PEGDA radical reactions. This bilayer hydrogel can be used to inoculate adipose mesenchymal stem cells which can then differentiate into chondrocytes and osteoblasts, secreting glycosaminoglycan, and promoting calcium deposition. This accelerates the regeneration of cartilage and subchondral bone. Micro-CT and tissue staining revealed an increase in the amount of bone present in new subchondral bone, and new tissues with a structure similar to normal cartilage. This study therefore demonstrates that injectable bilayer hydrogels are a promising scaffold for repairing osteochondral defects.

Rubropunctatin-silver composite nanoliposomes for eradicating Helicobacter pylori in vitro and in vivo.

Helicobacter pylori (H. pylori) is a major factor in peptic ulcer disease and gastric cancer, and its infection rate is rising globally. The efficacy of traditional antibiotic treatment is less effective, mainly due to bacterial biofilms and the formation of antibiotic resistance. In addition, H. pylori colonizes the gastrointestinal epithelium covered by mucus layers, the drug must penetrate the double barrier of mucus layer and biofilm to reach the infection site and kill H. pylori. The ethanol injection method was used to synthesize nanoliposomes (EPI/R-AgNPs@RHL/PC) with a mixed lipid layer containing rhamnolipids (RHL) and phosphatidylcholine (PC) as a carrier, loaded with the urease inhibitor epiberberine (EPI) and the antimicrobial agent rubropunctatin silver nanoparticles (R-AgNPs). EPI/R-AgNPs@RHL/PC had the appropriate size, negative charge, and acid sensitivity to penetrate mucin-rich mucus layers and achieve acid-responsive drug release. In vitro experiments demonstrated that EPI/R-AgNPs@RHL/PC exhibited good antibacterial activity, effectively inhibited urease activity, removed the mature H. pylori biofilm, and inhibited biofilm regeneration. In vivo antibacterial tests showed that EPI/R-AgNPs@RHL/PC exhibited excellent activity in eradicating H. pylori and protecting the mucosa compared to the traditional clinical triple therapy, providing a new idea for the treatment of H. pylori infection.

Chitosan nonwoven fabric composited calcium alginate and adenosine diphosphate as a hemostatic bandage for acute bleeding wounds.

Acute bleeding following accidental injury is a leading cause of mortality. However, conventional hemostatic bandages impede wound healing by inducing excessive blood loss, dehydration, and adherence to granulation tissue. Strategies such as incorporating active hemostatic agents and implementing chemical modifications can augment the properties of these bandages. Nevertheless, the presence of remote thrombosis and initiators may pose risks to human health. Here, a hemostatic bandage was developed by physically combined chitosan nonwoven fabric, calcium alginate sponge, and adenosine diphosphate. The presented hemostatic bandage not only exhibits active and passive mechanisms for promoting clotting but also demonstrates excellent mechanical properties, breathability, ease of removal without causing damage to the wound bed or surrounding tissues, as well as maintaining an optimal moist environment conducive to wound healing. In vitro evaluation results indicated that the hemostatic bandage possesses favorable cytocompatibility with low levels of hemolysis. Furthermore, it effectively aggregates various blood cells while activating platelets synergistically to promote both extrinsic and intrinsic coagulation pathways. In an in vivo rat model study involving liver laceration and femoral artery injury scenarios, our developed hemostatic bandage demonstrated rapid clot formation capabilities along with reduced blood loss compared to commercially available fabrics.

Electrospun Biomimetic Periosteum Capable of Controlled Release of Multiple Agents for Programmed Promoting Bone Regeneration.

The effective repair of large bone defects remains a major challenge due to its limited self-healing capacity. Inspired by the structure and function of the natural periosteum, an electrospun biomimetic periosteum is constructed to programmatically promote bone regeneration using natural bone healing mechanisms. The biomimetic periosteum is composed of a bilayer with an asymmetric structure in which an aligned electrospun poly(ε-caprolactone)/gelatin/deferoxamine (PCL/GEL/DFO) layer mimics the outer fibrous layer of the periosteum, while a random coaxial electrospun PCL/GEL/aspirin (ASP) shell and PCL/silicon nanoparticles (SiNPs) core layer mimics the inner cambial layer. The bilayer controls the release of ASP, DFO, and SiNPs to precisely regulate the inflammatory, angiogenic, and osteogenic phases of bone repair. The random coaxial inner layer can effectively antioxidize, promoting cell recruitment, proliferation, differentiation, and mineralization, while the aligned outer layer can promote angiogenesis and prevent fibroblast infiltration. In particular, different stages of bone repair are modulated in a rat skull defect model to achieve faster and better bone regeneration. The proposed biomimetic periosteum is expected to be a promising candidate for bone defect healing.

Intelligent wound dressing for simultaneous in situ detection and elimination of pathogenic bacteria.

Wound infections hinder the healing process and potentially result in life-threatening complications, which urgently require rapid and timely detection and treatment pathogens during the early stages of infection. Here, an intelligent wound dressing was developed to enable in situ detection and elimination of pathogenic bacteria through a combination of point-of-care testing and antibacterial photodynamic therapy technology. The dressing is an injectable hydrogel composed of carboxymethyl chitosan and oxidized sodium alginate, with addition of 4-methylumphulone beta-D-glucoside (MUG) and up-converted nanoparticles coated with titanium dioxide (UCNPs@TiO2). The presence of bacteria can be visually detected by monitoring the blue fluorescence of 4-methylumbellione, generated through the reaction between MUG and the pathogen-associated enzyme. The UCNPs@TiO2 photosensitizers were synthesized and demonstrated high antibacterial activity through the generation of reactive oxygen species when exposed to near-infrared irradiation. Meanwhile, a smartphone-based portable detection system equipped with a self-developed Android app was constructed for in situ detection of pathogens in mere seconds, detecting as few as 103 colony-forming unit. Additionally, the dressing was tested in a rat infected wound model and showed good antibacterial activity and pro-healing ability. These results suggest that the proposed intelligent wound dressing has potential for use in the diagnosis and management of wound infections. STATEMENT OF SIGNIFICANCE: An intelligent wound dressing has been prepared for simultaneous in situ detection and elimination of pathogenic bacteria. The presence of bacteria can be visually detected by tracking the blue fluorescence of the dressing. Moreover, a smartphone-based detection system was constructed to detect and diagnose pathogenic bacteria before reaching the infection limit. Meanwhile, the dressing was able to effectively eliminate key pathogenic bacteria on demand through antibacterial photodynamic therapy under NIR irradiation. The proposed intelligent wound dressing enables timely detection and treatment of infectious pathogens at an early stage, which is beneficial for wound management.

NIR-Light-Triggered Mild-Temperature Hyperthermia to Overcome the Cascade Cisplatin Resistance for Improved Resistant Tumor Therapy.

Currently, cisplatin resistance has been recognized as a multistep cascade process for its clinical chemotherapy failure. Hitherto, it remains challenging to develop a feasible and promising strategy to overcome the cascade drug resistance (CDR) issue for achieving fundamentally improved chemotherapeutic efficacy. Herein, a novel self-assembled nanoagent is proposed, which is constructed by Pt(IV) prodrug, cyanine dye (cypate), and gadolinium ion (Gd3+), for systematically conquering the cisplatin resistance by employing near-infrared (NIR) light activated mild-temperature hyperthermia in tumor targets. The proposed nanoagents exhibit high photostability, GSH/H+-responsive dissociation, preferable photothermal conversion, and enhanced cellular uptake performance. In particular, upon 785-nm NIR light irradiation, the generated mild temperature of ≈ 43 °C overtly improves the cell membrane permeability and drug uptake, accelerates the disruption of intracellular redox balance, and apparently enhances the formation of Pt-DNA adducts, thereby effectively overcoming the CDR issue and achieves highly improved therapeutic efficacy for cisplatin-resistant tumor ablation.

Visible-Light Cross-Linkable Multifunctional Hydrogels Loaded with Exosomes Facilitate Full-Thickness Skin Defect Wound Healing through Participating in the Entire Healing Process.

The management of severe full-thickness skin defect wounds remains a challenge due to their irregular shape, uncontrollable bleeding, high risk of infection, and prolonged healing period. Herein, an all-in-one OD/GM/QCS@Exo hydrogel was prepared with catechol-modified oxidized hyaluronic acid (OD), methylacrylylated gelatin (GM), and quaternized chitosan (QCS) and loaded with adipose mesenchymal stem cell-derived exosomes (Exos). Cross-linking of the hydrogel was achieved using visible light instead of ultraviolet light irradiation, providing injectability and good biocompatibility. Notably, the incorporation of catechol groups and multicross-linked networks in the hydrogels conferred strong adhesion properties and mechanical strength against external forces such as tensile and compressive stress. Furthermore, our hydrogel exhibited antibacterial, anti-inflammatory, and antioxidant properties along with wound-healing promotion effects. Our results demonstrated that the hydrogel-mediated release of Exos significantly promotes cellular proliferation, migration, and angiogenesis, thereby accelerating skin structure reconstruction and functional recovery during the wound-healing process. Overall, the all-in-one OD/GM/QCS@Exo hydrogel provided a promising therapeutic strategy for the treatment of full-thickness skin defect wounds through actively participating in the entire process of wound healing.

Lecithin/chitosan nanoparticle drug carrier improves anti-tumor efficacy of Monascus pigment rubropunctatin.

Rubropunctatin, a metabolite isolated from the fungi of the genus Monascus, is a natural lead compound applied for the suppression of tumors with good anti-cancer activity. However, its poor aqueous solubility has limited its further clinical development and utilization. Lecithin and chitosan are excellently biocompatible and biodegradable natural materials, which have been approved by the FDA as drug carrier. Here, we report for the first time the construction of a lecithin/chitosan nanoparticle drug carrier of the Monascus pigment rubropunctatin by electrostatic self-assembly between lecithin and chitosan. The nanoparticles are near-spherical with a size 110-120 nm. They are soluble in water and possess excellent homogenization capacity and dispersibility. Our in vitro drug release assay showed a sustained release of rubropunctatin. CCK-8 assays revealed that lecithin/chitosan nanoparticles loaded with rubropunctatin (RCP-NPs) had significantly enhanced cytotoxicity against mouse mammary cancer 4T1 cells. The flow cytometry results revealed that RCP-NPs significantly boosted cellular uptake and apoptosis. The tumor-bearing mice models we developed indicated that RCP-NPs effectively inhibited tumor growth. Our present findings suggest that lecithin/chitosan nanoparticle drug carriers improve the anti-tumor effect of the Monascus pigment rubropunctatin.

Effects of Various Cell Surface Engineering Reactions on the Biological Behavior of Mammalian Cells.

Cell surface engineering technologies can regulate cell function and behavior by modifying the cell surface. Previous studies have mainly focused on investigating the effects of cell surface engineering reactions and materials on cell activity. However, they do not comprehensively analyze other cellular processes. This study exploits covalent bonding, hydrophobic interactions, and electrostatic interactions to modify the macromolecules succinimide ester-methoxy polyethylene glycol (NHS-mPEG), distearoyl phosphoethanolamine-methoxy polyethylene glycol (DSPE-mPEG), and poly-L-lysine (PLL), respectively, on the cell surface. This work systematically investigates the effects of the three surface engineering reactions on the behavior of human umbilical vein endothelial cells (HUVECs) and human skin fibroblasts, including viability, growth, proliferation, cell cycle, adhesion, and migration. The results reveals that the PLL modification method notably affects cell viability and G2/M arrest and has a short modification duration. However, the DSPE-mPEG and NHS-mPEG modification methods have little effect on cell viability and proliferation but have a prolonged modification duration. Moreover, the DSPE-mPEG modification method highly affects cell adherence. Further, the NHS-mPEG modification method can significantly improve the migration ability of HUVECs by reducing the area of focal adhesions. The findings of this study will contribute to the application of cell surface engineering technology in the biomedical field.

Multi-crosslinked hydrogels with strong wet adhesion, self-healing, antibacterial property, reactive oxygen species scavenging activity, and on-demand removability for seawater-immersed wound healing.

In general, seawater-immersed wounds are associated with tissue necrosis, infection, prolonged healing period, and high mortality because of high salinity, hyperosmosis, and the presence of various pathogenic bacteria in seawater. However, current wound dressings can hardly achieve strong and stable wet adhesion and antibacterial properties, thus limiting their application to seawater-immersed wounds. Here a multifunctional hydrogel (OD/EPL@Fe) comprising catechol-modified oxidized hyaluronic acid (OD), ε-poly-L-lysine (EPL), and Fe3+ was prepared primarily through Schiff-base reaction, metal chelation, cation-π, and electrostatic interaction. The hydrogel with high wet adhesion (about 78 kPa) was achieved by combining the mussel-inspired strategy, dehydration effect, and cohesion enhancement, which is higher than that of commercial fibrin glues and cyanoacrylate glues. Meanwhile, the hydrogel can eliminate Marine bacteria (V. vulnificus and P. aeruginosa) and inhibit their biofilm formation. In addition, the hydrogel demonstrated injectability, self-healing, reactive oxygen species scavenging activity, photothermal effect, seawater isolation, on-demand removal, and hemostatic properties. In vivo results showed that the hydrogel had good adhesion to dynamic wounds in a rat neck full-thickness skin wound model. In particular, the hydrogel exhibited antibacterial, anti-inflammatory, and antioxidant properties in a rat seawater-immersed infected wound model and accelerated the reconstruction of skin structure and functions. The results demonstrated that the OD/EPL@Fe would be a potential wound dressing for seawater-immersed wound healing. STATEMENT OF SIGNIFICANCE: A multifunctional OD/EPL@Fe hydrogel has been prepared for the treatment of seawater-immersed wounds. The hydrogel with high wet adhesion was achieved by combining the mussel-inspired strategy, dehydration effect, and cohesion enhancement. The results revealed that the wet adhesion value of hydrogel was about eight times greater than commercial fibrin glues and 1.5 times greater than commercial cyanoacrylate glues. The hydrogel can be easily removed after being sprayed with deferoxamine mesylate. Notably, the inherent antimicrobial material of the hydrogel combined with the photothermal effect can eliminate marine bacteria and inhibit their biofilm formation. Moreover, the hydrogel can accelerate the healing of seawater-immersed infected wound on mice.

Electrospun Fe3O4-chitosan/polyvinyl alcohol nanofibrous film for improved capture and elimination of foodborne pathogens.

This study developed a new "capture and killing" antibacterial approach for efficient elimination of foodborne pathogens. Fe3O4-Chitosan (CS)/polyvinyl alcohol (PVA) nanofibrous films with improved antibacterial and mechanical properties were fabricated by a simple, environmentally friendly, and cost-effective electrospinning technique. The relationship between the physical properties (viscosity, surface tension, and conductivity) and spinnability of CS/PVA as fiber forming matrix was explored. Electrospun Fe3O4-CS/PVA films (0.03-0.12 mm) with smooth and bead-free nanofibrous structures (145-169 nm) were successfully obtained. Compared with the film electrospun from neat CS/PVA, incorporating Fe3O4 nanoparticles (NPs) (1.25-5 wt%) in CS/PVA nanofibrous film promoted bacterial attachment and increased the final inactivated efficiency, showing a difference with Fe3O4 loading and bacterial strain, which had the highest value against Escherichia coli (E. coli) and Staphyloccus aureus (S. aureus) being 90 % and 66.30 %, respectively. The tensile strength and elongation at break of Fe3O4-CS/PVA films enhanced by 46-192 % and 92-141 %, respectively. Results of the cytotoxicity test indicated that the resulting films had high biocompatibility. These promising findings provide a novel strategy for effective foodborne pathogens elimination, which could apply to sterilizing and food packaging to extend the shelf life of liquid food.

Biomimetic multifunctional hybrid sponge via enzymatic cross-linking to accelerate infected burn wound healing.

Preparing sponge dressings with stable wet adhesion remains difficult in wound repair, especially in burn wounds with bleeding and large amounts of exudate. In this work, a multifunctional hybrid sponge dressing (DHGT+PHMB+TiO2NPs) with good wet adhesion was developed by combining biomimetic and enzymatic cross-linking reactions. The sponge dressing matrix (DHGT) was prepared by tyrosinase-catalyzed cross-linking of dopamine-modified hyaluronic acid (DOPA-HA) and gelatin. The multifunctional hybrid sponge dressing was obtained by loading polyhexamethylene biguanide (PHMB) and titanium dioxide nanoparticles (TiO2NPs) onto the DHGT matrix. The newly developed sponge dressing exhibited high mechanical properties, good wet adhesion, antibacterial activity, reactive oxygen species (ROS) scavenging, biocompatibility, and excellent hemostasis ability. In vivo studies showed that the multifunctional hybrid sponge dressing could significantly accelerate the healing of infected full-thickness burn wounds by inhibiting bacterial growth, accelerating skin tissue reepithelialization, collagen deposition, and angiogenesis, as well as regulating the expression of inflammatory factors and cytokines.

A multifunctional hydrogel loaded with two nanoagents improves the pathological microenvironment associated with radiation combined with skin wounds.

Persistent oxidative stress and recurring waves of inflammation with excessive reactive oxygen species (ROS) and free radical accumulation could be generated by radiation. Exposure to radiation in combination with physical injuries such as wound trauma would produce a more harmful set of medical complications, which was known as radiation combined with skin wounds (RCSWs). However, little attention has been given to RCSW research despite the unsatisfactory therapeutic outcomes. In this study, a dual-nanoagent-loaded multifunctional hydrogel was fabricated to ameliorate the pathological microenvironment associated with RCSWs. The injectable, adhesive, and self-healing hydrogel was prepared by crosslinking carbohydrazide-modified gelatin (Gel-CDH) and oxidized hyaluronic acid (OHA) through the Schiff-base reaction under mild condition. Polydopamine nanoparticles (PDA-NPs) and mesenchymal stem cell-secreted small extracellular vesicles (MSC-sEV) were loaded to relieve radiation-produced tissue inflammation and oxidation impairment and enhance cell vitality and angiogenesis individually or jointly. The proposed PDA-NPs@MSC-sEV hydrogel enhanced cell vitality, as shown by cell proliferation, migration, colony formation, and cell cycle and apoptosis assays in vitro, and promoted reepithelization by attenuating microenvironment pathology in vivo. Notably, a gene set enrichment analysis of proteomic data revealed significant enrichment with adipogenic and hypoxic pathways, which play prominent roles in wound repair. Specifically, target genes were predicted based on differential transcription factor expression. The results suggested that MSC-sEV- and PDA-NP-loaded multifunctional hydrogels may be promising nanotherapies for RCSWs. STATEMENT OF SIGNIFICANCE: The small extracellular vesicle (sEV) has distinct advantages compared with MSCs, and polydopamine nanoparticles (PDA-NPs), known as the biological materials with good cell affinity and histocompatibility which have been reported to scavenge ROS free radicals. In this study, an adhesive, injectable, self-healing, antibacterial, ROS scavenging and amelioration of the radiation related microenvironment hydrogel encapsulating nanoscale particles of MSC-sEV and PDA-NPs (PDA-NPs@MSC-sEV hydrogel) was synthesized for promoting radiation combined with skin wounds (RCSWs). GSEA analysis profiled by proteomics data revealed significant enrichments in the regulations of adipogenic and hypoxic pathways with this multi-functional hydrogel. This is the first report of combining this two promising nanoscale agents for the special skin wounds associated with radiation.