Antimicrobial liposomes-in-nanofiber wound dressings prepared by a green and sustainable wire-electrospinning set-up

Increasing prevalence of infected and chronic wounds demands improved therapy options. In this work an electrospun nanofiber dressing with liposomes is suggested, focusing on the dressing's ability to support tissue regeneration and infection control. Chloramphenicol (CAM) was the chosen antibiotic, added to the nanofibers after first embedded in liposomes to maintain a sustained drug release. Nanofibers spun from five different polymer blends were tested, where pectin and polyethylene oxide (PEO) was identified as the most promising polymer blend, showing superior fiber formation and tensile strength. The wire-electrospinning setup (WES) was selected for its pilot-scale features, and water was applied as the only solvent for green electrospinning and to allow direct liposome incorporation. CAM-liposomes were added to Pectin-PEO nanofibers in the next step. Confocal imaging of rhodamine-labelled liposomes indicated intact liposomes in the fibers after electrospinning. This was supported by the observed in vitroCAM-release, showing that Pectin-PEO-nanofibers with CAM-liposomes had a delayed drug release compared to controls. Biological testing confirmed the antimicrobial efficacy of CAM and good biocompatibility of all CAM-nanofibers. The successful fiber formation and green production process with WES gives a promising outlook for industrial upscaling.

Development of a novel beta-glucan supplemented hydrogel spray formulation and wound healing efficacy in a db/db diabetic mouse model

To relief the severe economic and social burdens and patient suffering caused by the increasing incidence of chronic wounds, more effective treatments are urgently needed. In this study, we focused on developing a novel sprayable wound dressing with the active ingredient β-1,3/1,6-glucan (βG). Since βG is already available as the active ingredient in a commercial wound healing product provided as a hydrogel in a tube (βG-Gel), the sprayable format should bring clinical benefit by being easily sprayed onto wounds; whilst retaining βG-Gel's physical stability, biological safety and wound healing efficacy. Potentially sprayable βG hydrogels were therefore formulated, based on an experimental design setup. One spray formulation, named βG-Spray, was selected for further investigation, as it showed favorable rheological and spraying properties. The βG-Spray was furthermore found to be stable at room temperature for more than a year, retaining its rheological properties and sprayability. The cytotoxicity of βG-Spray in keratinocytes in vitro, was shown to be promising even at the highest tested concentration of 100 μg/ml. The βG-Spray also displayed favorable fluid affinity characteristics, with a capacity to both donate and absorb close to 10% fluid relative to its own weight. Finally, the βG-Spray was proven comparably effective to the commercial product, βG-Gel, and superior to both the water and the carrier controls (NoβG-Spray), in terms of its ability to promote wound healing in healing-impaired animals. Contraction was found to be the main wound closure mechanism responsible for the improvement seen in the βG-treatment groups (βG-Spray and βG-Gel). In conclusion, the novel sprayable βG formulation, confirmed its potential to expand the clinical use of βG as wound dressing.

Multifunctional Nanofibrous Dressing with Antimicrobial and Anti-Inflammatory Properties Prepared by Needle-Free Electrospinning

An active wound dressing should address the main goals in wound treatment, which are improved wound healing and reduced infection rates. We developed novel multifunctional nanofibrous wound dressings with three active ingredients: chloramphenicol (CAM), beta-glucan (βG) and chitosan (CHI), of which βG and CHI are active nanofiber-forming biopolymers isolated from the cell walls of Saccharomyces cerevisiae and from shrimp shells, respectively. To evaluate the effect of each active ingredient on the nanofibers' morphological features and bioactivity, nanofibers with both βG and CHI, only βG, only CHI and only copolymers, polyethylene oxide (PEO) and hydroxypropylmethylcellulose (HPMC) were fabricated. All four nanofiber formulations were also prepared with 1% CAM. The needle-free NanospiderTM technique allowed for the successful production of defect-free nanofibers containing all three active ingredients. The CAM-containing nanofibers had a burst CAM-release and a high absorption capacity. Nanofibers with all active ingredients (βG, CHI and CAM) showed a concentration-dependent anti-inflammatory activity, while maintaining the antimicrobial activity of CAM. The promising anti-inflammatory properties, together with the high absorption capacity and antimicrobial effect, make these multifunctional nanofibers promising as dressings in local treatment of infected and exuding wounds, such as burn wounds.

Sprayable Carbopol hydrogel with soluble beta-1,3/1,6-glucan as an active ingredient for wound healing - Development and in-vivo evaluation

Chronic wounds represent a significant health problem worldwide. There is a need for advanced- and cost-efficient wound healing products able to increase patient comfort and reduce the healing time. The aim of this study was to develop a sprayable hydrogel dressing with beta-glucan (βG) as the active ingredient, targeting future application in the treatment of both chronic and burn wounds. The βG was chosen as an active ingredient because of its promising wound healing capabilities, whereas Carbopol 971P NF (Carbopol) was chosen as the thickening agent in the formulation due to several attractive characteristics such as its low viscosity, low toxicity, high transparency and good ion tolerance. Four different hydrogel formulations were prepared with varying Carbopol concentrations. The higher Carbopol concentration, 0.5% (w/w), was used to prepare three formulations comprising the HighCP:NoβG, HighCP:LowβG and the HighCP:MediumβG formulation, respectively. Lower Carbopol concentration, 0.25% (w/w), was used to prepare the LowCP:HighβG formulation. The content of βG varied from 0.25% in the HighCP:LowβG, 0.5% in the HighCP:MediumβG and 1.0% (w/w) in the LowCP:HighβG formulation, respectively. The first part of the study focused on the rheological characterization of the hydrogels and the fluid affinity testing. All formulations were confirmed to be stable gels; the βG was shown to augment the gel strength by increasing the yield strength of the gel in a dose dependent manner. The stability of the formulations containing either Carbopol alone or in a combination with βG did not deteriorate over 26weeks, and the fluid donation and absorption study indicated a fluid donation profile, which favors healing of dry wounds. The in vivo efficacy of the formulations, evaluated in the modified diabetic male mice (db/db mice), showed that Carbopol alone was unable to induce improved healing and caused adverse reactions in some wounds. The inclusion of βG increased the epithelialization and wound contraction in the db/db mice when given at high βG:Carbopol ratio. The positive effect of βG was, however, not sufficient to counteract the adverse effect of Carbopol, thus a more suitable thickening agent should be investigated for further development of a sprayable wound care product.

Cardioprotective effect of pretreatment with β-glucan in coronary artery bypass grafting

BACKGROUND

Beta-glucan pretreatment has been shown to attenuate inflammatory response and to protect against ischemia-reperfusion injury in animal studies. The aims of the present study were to examine the safety of pretreatment with beta-1,3/1,6-glucan in patients scheduled for coronary artery bypass grafting (CABG), and to investigate whether beta-1,3/1,6-glucan pretreatment could suppress inflammatory response and protect against ischemia-reperfusion injury following CABG.

METHODS

Twenty one patients scheduled for CABG were assigned to oral beta-1,3/1,6-glucan 700 mg (Group 1) or 1 400 mg (Group 2) five consecutive days before surgery and were compared with a control group (Group 3). Blood samples were drawn preoperatively and on the first, third and fifth postoperative day for analysis of acute-phase reactants, hematology, cytokines and myocardial enzymes.

RESULTS

The study drug was well tolerated. Creatine kinase isoenzyme MB was significantly lower in Group 2 compared with controls on the first postoperative day (p = 0.028). Mean change in cardiac troponin T was lower in Group 2 compared with controls (p = 0.028).

CONCLUSIONS

Beta-1,3/1,6-glucan pretreatment is safe in patients undergoing CABG and may protect against ischemia reperfusion injury following CABG.

The effect of soluble beta-1,3-glucan and lipopolysaccharide on cytokine production and coagulation activation in whole blood

Soluble beta-1,3-glucan has been demonstrated to protect against infection and shock in rats and mice, and clinical studies suggest that administration of soluble glucans to trauma/surgical patients decreases septic complications and improves survival. However, little is known about the precise mechanisms by which glucans influence the state of activation of blood cells, which are responsible for the fulminant cytokine production and the activation of the coagulation system observed in serious gram-negative infection. We studied therefore the effect of an underivatized, soluble yeast beta-1,3-glucan and lipopolysaccharide (LPS), either alone or in combination, on tumor necrosis factor-alpha (TNFalpha), interleukin-6 (IL-6), IL-8 and IL-10 secretion and monocyte tissue factor (TF) expression in human whole blood. As expected, LPS induced the secretion of substantial amounts of all measured parameters, whereas only minor amounts of TNFalpha, IL-6, and IL-10 were induced by beta-glucan itself. However, beta-glucan itself induced the production of significant amounts of IL-8 and TF. Soluble beta-1,3-glucan had a strong synergistic effect on the LPS-induced secretion of IL-8, IL-10, and on monocyte TF activity, but not on TNFalpha and 1L-6 production. On the other hand, soluble beta-glucan strongly primed LPS stimulation of all parameters, including TNFalpha and IL-6. beta-Glucan also induced detectable neutrophil degranulation within 15 min, whereas a response to LPS was first detected after 90 min. In conclusion, soluble beta-1,3-glucan upregulated leukocyte activity, both on its own and in concert with LPS.

Enhanced lysozyme production in Atlantic salmon (Salmo salar L.) macrophages treated with yeast beta-glucan and bacterial lipopolysaccharide

Atlantic salmon head kidney macrophages grown in the presence of particulate yeast beta-glucan and bacterial lipopolysaccharide (LPS) showed increased production of lysozyme in the culture supernatants compared to non-treated controls. The increased lysozyme production started at day 3 and was five- to six-fold higher compared to controls at day 6 in culture. Beta-glucan showed an approximate linear dose-response curve between 1 and 250 microg x ml(-1) whereas LPS showed a dose-response curve with a well-defined optimum concentration (10 microg x ml(-1)). The increase in lysozyme activity was accompanied by an accumulation of lysozyme gene transcript in the stimulated cells. Recombinant human tumor necrosis factor alpha, known for its ability to stimulate lysozyme in human macrophages and to elevate respiratory burst activity of rainbow trout macrophages, failed to stimulate lysozyme production of Atlantic salmon macrophages. Macrophages isolated from fish suffering from a non-lethal Ichthyobodo necator infection displayed a highly increased ability to produce lysozyme in response to both beta-glucan and LPS. As in higher vertebrates, lysozyme production may reflect the differentiation stage of the Atlantic salmon macrophages as well as a direct activation of lysozyme gene transcription by biological response modifiers. The rather late increase in lysozyme production induced by beta-glucan and LPS may thus be explained by stimulation of differentiation of the macrophages in culture eventually combined with direct activation of transcription of the lysozyme gene.

Specificity of a beta-glucan receptor on macrophages from Atlantic salmon (Salmo salar L.)

This study was undertaken to study the specificity of a beta-glucan receptor on Atlantic salmon macrophages. Previous in vitro studies have shown that Atlantic salmon macrophages express a receptor that rapidly recognizes and mediates uptake of nonopsonized beta-glucan particles. The ingestion of particles was shown to be inhibited by preincubating the macrophages with glucans containing beta-1,3-linkages, but not by glucans containing other linkages. In the present study we have shown that small oligomers from formolyzed beta-glucan particles, and linear beta-1,3-linked oligomers with a degree of polymerization (DP) > or = 3, were efficient inhibitors of uptake of glucan particles. Oligomers from beta-1,6-linked pustulan, or small size oligomers with linkages other than beta-1,3, were not able to inhibit uptake of glucan particles. The inhibitory effect of laminarin and laminariheptaose was abolished by degrading the nonreducing terminal ends by sodium periodate treatment. The inhibitory effect of laminarin was regained by a complete Smith degradation; that is, periodate oxidation followed by reduction and hydrolysis. Modification of the reducing end of laminariheptaose had no effect on its ability to inhibit uptake. Furthermore, it was shown that periodate-oxidized glucan particles were not taken up by salmon macrophages, and that the uptake was regained when the particles were hydrolyzed to recover the nonreducing terminal end. Lastly, it was shown that endo-beta-1,6-glucanase treatment of the yeast glucan particles did not reduce uptake, confirming that beta-1,6-linkages are not involved in the recognition. These results suggest that Atlantic salmon macrophages possess a receptor that may recognize even very short beta-1,3-linked glucosyl chains extending from yeast cell walls.

Recognition of yeast cell wall glucan by Atlantic salmon (Salmo salar L.) macrophages

Phagocytosis of yeast (Saccharomyces cerevisiae) glucan particles by Atlantic salmon (Salmo salar L.) pronephric macrophages was studied. The particles contained > 95% glucose linked through beta-1,3- and beta-1,6-glycosidic linkages. The macrophages rapidly phagocytized both native and opsonized glucan particles although the latter were taken up at a higher rate. Within 30 min, 40-60% of the macrophages had taken up > 1 native glucan particle. The uptake of native glucan particles could be inhibited by preincubating the macrophages with laminarin, a soluble beta-1,3-linked glucan, and a soluble yeast glucan made by partial formolysis of glucan particles. Soluble yeast glucan, on the other hand, did not inhibit uptake of serum opsonized glucan particles or sheep red blood cells, which showed that it did not interfere with phagocytosis in general or inhibit phagocytosis through complement receptors. Polyglucoses with glycosidic linkages other than beta-1,3, like dextran, glycogen, and pustulan or the polymannose mannan, showed little or no inhibition of phagocytosis of native glucan particles. Altogether these observations indicate that Atlantic salmon macrophages may have a specific receptor for yeast glucan. Studies with chelator- and heat-treated salmon serum showed that glucan particles were opsonized primarily by activation of the alternative complement pathway. However, the data indicate that serum components other than complement may also be involved in the opsonization of glucan particles.