Hristo Penchev

Hybrid nanofibrous yarns based on N-carboxyethylchitosan and silver nanoparticles with antibacterial activity prepared by self-bundling electrospinning.

Hybrid nanofibrous materials with antibacterial activity consisting of yarns from N-carboxyethylchitosan (CECh) and poly(ethylene oxide) (PEO) that contain 5 wt% or 10 wt% silver nanoparticles (AgNPs) were prepared. This was achieved by electrospinning using formic acid as a solvent and as a reducing agent for silver ions. AgNO₃ was used as an Ag(+)-containing salt. Its concentration was selected to be 0.02 mol/L or 0.04 mol/L in order the content of the AgNPs in the electrospun nanofibers to be 5 wt% or 10 wt%, respectively. The self-bundling of the fibers into yarns with a mean diameter of ca. 35 μm was enabled only by using a grounded needle electrode. The reduction of the silver ions to an elemental silver was evidenced by UV-vis spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The transmission electron microscopy (TEM) analyses revealed that AgNPs formed at AgNO₃ concentration of 0.02 mol/L were with a mean diameter of 4±0.5 nm and were distributed uniformly within the fiber. The increase of AgNO₃ concentration to 0.04 mol/L led to the preparation of AgNPs with a higher mean diameter and a broader diameter distribution as well as to aggregate formation. The performed studies on the antibacterial activity of CECh/PEO/AgNPs fibrous materials against Staphylococcus aureus showed that at AgNPs content of 5 wt% the mats had bacteriostatic, and at AgNPs content of 10 wt%-bactericidal activity.

Electrospun Hybrid Nanofibers Based on Chitosan or N‐Carboxyethylchitosan and Silver Nanoparticles

Hybrid nanofibers from chitosan or N-carboxyethylchitosan (CECh) and silver nanoparticles (AgNPs) were prepared by electrospinning using HCOOH as a solvent. AgNPs were synthesized in situ in the spinning solution. HCOOH slowed down the cross-linking of the polysaccharides with GA enabling the reactive electrospinning in the presence of poly(ethylene oxide) (PEO). EDX analyses showed that AgNPs are uniformly dispersed in the nanofibers. Since AgNPs hampered the cross-linking of chitosan and CECh with GA in the hybrid fibers, the imparting of water insolubility to the fibers was achieved at a second stage using GA vapors. The surface of chitosan/PEO/AgNPs nanofibers was enriched in chitosan and 15 wt.-% of the incorporated AgNPs were on the fiber surface as evidenced by XPS.