Evaluation of electrospun lignin/polyvinyl alcohol/cellulose nanofiber mats

Sammanfattning: Polymeric electrospun nanofiber mats have recently emerged as a promising alternative to conventional wound dressings for non-healing wounds. Its large surface area, porosity and scalability are only a few of the promising characteristics of electrospun nanofibers.  Nanocellulose, separated from biomass, have also proven a suitable reinforcement to these electrospun nanofibers, giving them stability and strength. Lignin has shown to possess antimicrobial and antioxidant activity, that could aid the healing process. In this project, kraft lignin, polyvinyl alcohol (PVA) and (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidised cellulose nanofibers (CNF) has been electrospun into nanofiber mats and their applicability as a wound dressing was investigated. The electrospinning process was evaluated at different ratios of PVA/lignin: CNF, and the obtained nanofiber mats were crosslinked to restrict water solubility. Physical crosslinking was made through a heat treatment and a freeze thawing process. Mechanical properties, swelling capacity and oxygen permeability were evaluated and analysed based on the CNF content of the electrospun solutions, as well as the crosslinking methods used. Results show that the electrospun nanofiber mats where stable in water after a heat treatment at 150 °C and 3 freeze-thawing cycles. These crosslinking methods did not affect the morphology or size of the fibers. However, tensile strength and elastic modulus was improved with it. The addition of 0.1 wt% CNF into the electrospinning solution improved oxygen permeability, mechanical properties, and swelling capacity, which can be attributed to a small fiber diameter and increased crystallinity. However, exceeding that level of CNF deteriorated the same properties because of uneven fibers with beading. This material is showing promising characteristics of a wound dressing, with high oxygen permeability and swelling capacity owing to thin nanofibers and a porous network.