A unidirectional water-transport antibacterial bilayer nanofibrous dressing based on chitosan for accelerating wound healing.

Excessive accumulation of exudate from wounds often causes infection and hinders skin regeneration. To handle wound exudate quickly and prevent infection, we developed an antibacterial Janus nanofibrous dressing with a unidirectional water-transport function. The dressing consists of a hydrophilic chitosan aerogel (CS-A) as the outer layer and a hydrophobic laurylated chitosan (La-CS) nanofibrous membrane as the inner layer. These dressings achieved excellent liquid absorption performance (2987.8 ±â€¯123.5 %), air and moisture permeability (997.8 ±â€¯23.1 g/m2/day) and mechanical strength (5.1 ±â€¯2.6 MPa). This performance was obtained by adjusting the density of CS-A and the thickness of the La-CS membrane. Moreover, the dressing did not induce significant toxicity to cells and can prevent bacterial aggregation and infection at the wound site. Animal experiments showed that the dressing can shorten the inflammatory phase, enhance blood vessel generation, and accelerate collagen deposition, thus promoting wound healing. Overall, these results suggest that this Janus dressing is a promising material for clinical wound care.

A wet-adhesive carboxymethylated yeast ß-glucan sponge with radical scavenging, bacteriostasis and anti-inflammatory functions for rapid hemostasis.

Local hemostats still face obstacles to efficiently achieving hemostasis and promoting wound healing. Herein, a series of multifunctional well-degradable hemostatic sponges based-on carboxymethylated yeast ß-glucan (CMYG) were fabricated by lyophilization. The porous CMYG sponge not only could absorb blood quickly (44.12 g/g), but also possessed unexpected tissue adhesion (∼30 kPa), and it represented good biocompatibility in vitro on fibroblasts and red blood cells. Notably, compared with the commercial Celox™, the CMYG sponge achieved more rapid hemostasis and significantly reduced blood loss in liver injury rat models by rapid wound block. Interestingly, the developed sponge showed an outstanding effect on antioxidant, anti-infection, anti-inflammatory, and cell proliferation, which are beneficial for further wound repair. Overall, these results suggest that the CMYG sponge is a promising candidate for the clinical management of uncontrollable hemorrhage and the further development of wound dressing materials throughout skin defect repair.

Prompting immunostimulatory activity of curdlan with grafting methoxypolyethylene glycol.

The immunostimulatory activity of polysaccharides can improve human immunity, but their activity is low and prompting the activity is a great challenge. Curdlan, is a linear beta-1,3-glucan and has the potential to induce immune responses. However, owing to its tight triple helix structure and insolubility in water, its immunostimulatory activity is weakened. The keyway to promote its immunostimulatory activity is to relax its tight triple helix structure. In this work, methoxypolyethylene glycol (mPEG) was grafted onto curdlan (curdlan-g-mPEG) to unwind its triple helix structure. With its grafting mPEG, the water solubility of curdlan was enhanced. Moreover, with curdlan-g-mPEG treatment, macrophages secreted more tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 and exhibited favorable phagocytosis of bacteria (Staphylococcus aureus and Pseudomonas aeruginosa). These results reveal that curdlan-g-mPEG as an immunostimulant has potential applications in immunology and antibiotics.

Development of an in vitro insulin resistance dissociated model of hepatic steatosis by co-culture system.

The evidence shows that there is an associated relationship between hepatosteatosis and insulin resistance. While some existing genetic induction animal and patient models challenge this relationship, indicating that hepatosteatosis is dissociated from insulin resistance. However, the molecular mechanisms of this dissociation remain poorly understood due to a lack of available, reliable, and simplistic setup models. Currently, we used primary rat hepatocytes (rHPCs), co-cultured with rat hepatic stellate cells (HSC-T6) or human foreskin fibroblast cells (HFF-1) in stimulation with high insulin and glucose, to develop a model of steatosis charactered as dissociated lipid accumulation from insulin resistance. Oil-Red staining significantly showed intracellular lipid accumulated in the developed model. Gene expression of sterol regulatory element-binding protein 1c (SREBP1c) and elongase of very-long-chain fatty acids 6 (ELOVL6), key genes responsible for lipogenesis, were detected and obviously increased in this model. Inversely, the insulin resistance related genes expression included phosphoenolpyruvate carboxykinase 1 (PCK1), pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4), and glucose-6-phosphatase (G6pase) were decreased, suggesting a dissociation relationship between steatosis and insulin resistance in the developed model. As well, the drug metabolism of this developed model was investigated and showed up-regulation of cytochrome P450 3A (CYP3A) and down-regulation of cytochrome P450 2E1 (CYP2E1) and cytochrome P450 1A2 (CYP1A2). Taken together, those results demonstrate that the in vitro model of dissociated steatosis from insulin resistance was successfully created by our co-cultured cells in high insulin and glucose medium, which will be a potential model for investigating the mechanism of insulin resistance dissociated steatosis, and discovering a novel drug for its treatment.

A hydrogen-bonded antibacterial curdlan-tannic acid hydrogel with an antioxidant and hemostatic function for wound healing.

Manufacturing facile and low-cost wound dressings that simultaneously meet the needs of the entire repair process remains the major challenge of effective wound healing. Herein, a series of curdlan-tannic acid hybrid hydrogels were successfully fabricated through the annealing technique. Notedly, when the mixing weigh ratio was 1:1, the hydrogel exhibited excellent physicochemical properties, including swellability, degradability, water retention, porosity, and rheology. Additionally, the hydrogel did not display significant cytotoxicity to fibroblasts and the hemolysis rate at 12 h was 3%. Interestingly, the hybrid hydrogel showed multifunctional properties, including remarkable antioxidant, antibacterial, and rapid hemostasis effects reduce blood loss by 0.35 g, that were achieved through the temperature-dependent release of tannic acid. Moreover, a full-thickness skin defect animal model was used to verify that the multifunctional hydrogel could accelerate wound healing in vivo. These results suggest that this hybrid hydrogel is a promising candidate for the clinical treatment of full-thickness wounds.

Preparation and characterization of a dual cross-linking injectable hydrogel based on sodium alginate and chitosan quaternary ammonium salt.

The development of cheap and easily available injectable hydrogel is an urgent problem in the field of biomedical engineering. Herein, we used chitosan quaternary ammonium salt and sodium alginate to prepare a dual crosslinking hydrogel. The hydrogel formed in-situ crosslinking and can be injected continuously. Interestingly, the formed hydrogel possessed a homogeneous 3D network structure and exhibited reasonable mechanical properties. Moreover, the hydrogels had excellent injectability, and the compression strength of the hydrogel (Gel-0.5) was up to 27.65 kPa. Additionally, the hydrogel showed good biocompatibility that evaluated by cytotoxicity. Notably, the hydrogel was nontoxic toward NIH-3T3 cells. In summary, the hydrogel we produced can be used as an ideal biomaterial for further applications in the field of biomedical engineering.

Preparation of AAEK-functionalized cellulose film with antibacterial and anti-adhesion activities.

Bacterial adhesion infection caused by medical materials in clinical application has become a serious threat, and it urgently needs new strategies to deal with these clinical challenges. The purpose of this study is to explore the effectiveness of surface-decorated aryl (ß-amino) ethyl ketones (AAEK), a promising sorting enzyme A (SrtA) inhibitor of Staphylococcus aureus, to improve the anti-adhesion ability of biomaterials. AAEK was covalently grafted onto cellulose films (CF) via copper-catalyzed azide-alkyne 1, 3-dipolar cycloaddition click reaction. The data of contact angle measurements, ATR-FTIR and XPS proved the successful covalent attachment of AAEK-CF, and the antimicrobial efficacy of AAEK coating was assessed by CFUs, crystal violet staining, scanning electron microscopy and Living/Dead bacteria staining assay. The results illustrated that AAEK-CF exhibited excellent anti-adhesion ability to Staphylococcus aureus, and significantly reduced the number of bacteria adhering to the film. More importantly, AAEK-CF could hinder the formation of bacterial biofilm. Furthermore, AAEK-CF indicated no cytotoxicity to mammalian cells, and the cells could grow normally on the modified surface. Hence, our present work demonstrated that the grafting of the SrtA inhibitor-AAEK onto cellulose films enabled to combat bacterial biofilm formation in biomedical applications.

Cellulose membrane modified with LED209 as an antibacterial and anti-adhesion material.

Bacterial adhesion infection caused by medical materials in clinical application has become a serious threat, and it urgently needs new strategies to deal with these clinical challenges. In this work, LED209, a highly selective histidine sensor kinase inhibitor of Gram-negative bacteria, was covalently attached on cellulose membrane (CM) via click reaction. The data of contact angle measurements, ATR-FTIR and X-ray photoelectron spectroscopy confirmed the successful synthesis of LED-CM. In addition, the results of antibacterial activity of the membranes shown that LED-CM exhibited excellent anti-adhesion ability to Enterohemorrhagic Escherichia coli (EHEC), and significantly reduced the formation of bacterial biofilm. Importantly, LED-CM was able to repress the expression of virulence genes in EHEC. Furthermore, LED209-functionalized cellulose membrane indicated no cytotoxicity to mammalian cells. Hence, our present work demonstrated that CM modified with LED209 possessed markedly anti-adhesion activity against EHEC, which offered a potent antimicrobial material for combating bacterial infections.

A comparative study on agarose acetate and PDLLA scaffold for rabbit femur defect regeneration.

The development of degradable polymer scaffolds is a key issue in bone regeneration. Poly(D, L-lactide) (PDLLA) and its derivatives have usually been applied to the construction of degradable scaffolds, but these scaffolds had problems with acidic degradation products and quick loss of mechanic strength during the later degradation, which usually led to scaffold collapse and cavity formation because of the slower rate of bone regeneration. In the present paper, a polysaccharide derivative, agarose acetate (AGA), was synthesized and a novel porous AGA scaffold was successfully developed through a salt-leaching process. The AGA scaffold had over 90% porosity without swelling in water, and compared to collapse and acidic products of PDLLA scaffold during degradation, the AGA scaffold maintained a stable morphology and a nearly neutral pH value over 18 months' degradation in PBS. A bone mesenchymal stem cells (BMSCs) adhesion and proliferation experiment showed that more cells adhered to the AGA scaffold than to the PDLLA scaffold. A subcutaneous implant test showed that the AGA scaffold slowly degraded and did not cause an inflammatory response surrounding the implantation lesion site. AGA scaffold was implanted into femur defects in New Zealand white rabbits to test its in vivo performance. Results indicated that the AGA scaffold accelerated the process of bone regeneration compared to the PDLLA group and, with time, new bone was formed from the margin toward the center of the scaffolds, and the scaffold left in place retained its porous structure without collapsing. Meanwhile, the AGA scaffold showed a low degradation rate and kept its shape during the in vivo degradation compared to the PDLLA scaffold. This performance could have the benefit of integrated regenerative bone being formed instead of cavities due to the quickly degraded scaffold disappearing. These results demonstrate that the AGA scaffold has significant potential in bone regeneration applications.

LED 209 conjugated chitosan as a selective antimicrobial and potential anti-adhesion material.

The rapid emergence of antibiotic-resistant Gram-negative bacteria (GNB) is becoming a global healthcare concern, and it urgently needs novel strategies to match the clinical challenge. In this work, we conjugated chitosan (CS) with LED 209, a highly selective inhibitor of QseC of GNB, to create the novel selective antimicrobial agent CS/LED. The data of FT-IR, NMR and elemental analysis for CS/LED conjugates proved the successful conjugation of CS with LED 209. Interestingly, the fluorescence signal detected in MDR-E. coli of CS/LED-FITC was about 2 times than that of CS-FITC at 3 h. The results shown that compared with CS, CS/LED exhibited higher selective antimicrobial on MDR-E. coli. Moreover, CS/LED exhibited the lower selectivity and cytotoxicity to mammalian cell than CS. Additionally, an unexpected enhancement of anti-adhesion activity against MDR-E. coli was determined by cellulose membrane coating CS/LED. The results demonstrated that CS/LED could reduce the adhesion of bacteria to the cellulose membrane by about 67.8%, while CS only reduced by about 45.3%. The dressings coated with CS/LED possessed the stronger ability to prevent microbial adhesion compared to the CS-coated dressing. Our present work firstly demonstrated that CS/LED had a highly selective activity and anti-adhesion activity against MDR-E. coli, which offered a potent and selective antimicrobial for combating multidrug-resistant GNB infections.