Electrospinning of nanofibers with chitosan and B-glucan as active wound healing ingredients: Optimization and characterization

Wound healing is a complex and highly regulated process, vital for preserving the barrier function of the skin. However, several underlying pathologies have the ability to influence the cascade of events involved in this process, resulting in the development of chronic wounds. The heterogeneous nature of chronic wounds increases the requirements of novel wound dressings. Hence, the development of advanced wound dressings capable of interacting with the wound by stimulating and facilitating regenerative processes, are in high demand. Nanofibers as a novel class of wound dressings, is a relevant example of such an innovation. The incentive of this thesis was to further develop the nanofibers previously produced in the Drug Transport and Delivery Research Group, containing the patented soluble B-glucan (SBG®) as active ingredient. By incorporating chitosan as a second active ingredient, we introduced an antimicrobial effect in addition to B-glucans immune stimulating effect. Hydroxypropyl methylcellulose and polyethylene oxide were included as co-polymers, and water, ethanol and acetic acid as solvents. The focus of this thesis was thereby the characterization and optimization of this novel nanofibrous formulation. The nanofibers were produced using the needleless Nanospider™ technology through an attempted optimized electrospinning process. To evaluate the properties of produced nanofibers, suitable methods for characterization of both spinning solutions and final nanofibers were applied. To characterize the polymer solutions, the conductivity, surface tension and rheological properties were examined, while the produced nanofibers were evaluated by determining their tensile properties, morphologies, diameters and absorption capacities. We found that optimization of electrospinning conditions was crucial to obtain homogeneous nanofibers, as relative humidity influenced the nanofiber morphology notably. The conductivity of the polymer solutions was determined to be the primary factor affecting their spinnability. Moreover, solvent volatility was found to affect the morphology of the produced nanofibers by influencing fiber diameter. The tensile properties of the fibers were proven to be limited, due to the influence of polymer composition. Lastly, the nanofibers ability to absorb simulated wound fluid was found to be high, suggesting that they would be suitable for treatment of wounds with moderate to high exudate production. Keywords: Chitosan; Beta-glucan; Nanofiber; Needleless Electrospinning; Nanospider; Wound dressing; Wound healing; Chronic wound