Polyelectrolyte complex nanofibers from poly(γ-glutamic acid) and fluorescent chitosan oligomer

Polyelectrolyte complex (PEC) nanofibers were fabricated via electrospinning using anionic poly(γ-glutamic acid) (γ-PGA) and cationic fluorescent chitosan oligomer (CHI-O). First, the PEC formation behavior was investigated as a function of the solution concentration, viscosity and blend ratio. The optimum blend ratio and concentration of the anionic γ-PGA and cationic CHI-O for electrospinning was 10/13 (w/w), and continuous nanofibers were obtained at that condition with an average diameter of 370 nm without beads. The resulting PEC nanofibers were chemically crosslinked using glutaraldehyde vapor to provide dimensional stability against water. Confocal microscopy revealed that the fluorescent intensity of the PEC nanofibers increased gradually as the fluorescent CHI-O increased. Also, the fluorescent CHI-O was distributed evenly in the PEC nanofibers through the formation of PEC with anionic γ-PGA. Therefore, the electrospinnability of anionic γ-PGA improved significantly with the PEC formation with cationic CHI-O. This result indicates that anionic biopolymers with a poor electrospinnability can be converted to nanofibers via PEC formation with polycations.