Imination of chitosan nanofibers in a heterogeneous system. Synthesis optimization and impact on fiber morphology

Abstract

The paper aimed to prepare imino-chitosan fibers by the imination reaction in a heterogenous system, targeting the improvement of anti-pathogenic activity. To this end, porous neat chitosan fibers were prepared by electrospinning of the polyethylene glycol/chitosan blend, followed by polyethylene glycol removal. Imination of the neat chitosan fibers was carried out in three liquid phase systems using solvents of different polarity and, consequently, different ability to swell the solid phase chitosan fibers. The successful imination was qualitatively and quantitatively assessed by FTIR and 1H-NMR spectroscopy, and the impact of the liquid phase on the fibers’ morphology was evaluated by SEM, POM and AFM microscopy. Further, the antimicrobial activity of the imino-chitosan fibers was investigated on relevant bacterial and fungal strains. It was concluded that the prior swelling in water of the fibers improved the imination degree, while the use of a less polar solvent, such as toluene, favored the preservation of the fibrous morphology. The imination with an antimicrobial aldehyde endowed the chitosan fibers with the ability to create a physical barrier against pathogens.