Electrospinning of chitosan from different acid solutions

Electrospinning is a production technique for obtaining polymer nanofibers relatively low-cost and straightforward to produce fine fibers. Chitosan (CTS) is a well-known biopolymer widely used for drug delivery, hydrogels, tissue engineering, wound healing, and mats. This work aims to study different chitosan-organic acid solutions' conductivity using electrochemical impedance spectroscopy and equivalent circuit fitting to understand this parameter's influence in the electrospinning process for fiber formation in different organic acids as solvents. The conductivity of dilute chitosan solutions decreases until reaching a minimum value as chitosan concentration increases; conductivity increases linearly as concentration increases. We measured solution resistance, polarization resistance, and relaxation time of chitosan solutions in acetic, formic, lactic, and citric acids using electrical impedance spectroscopy with equivalent circuit modeling. There is no direct correlation between the electrospinnability of the different organic acids solutions with their solution conductivity. We obtained chitosan nanofibers and particles when electrospun a chitosan concentrated solution (4 wt%) in concentrated acetic acid (90 vol%) and obtained submicron particles with a more diluted solution (1 wt%) in concentrated acetic acid (90 vol%). We also obtained chitosan particles from formic acid solutions and completely different ordered and elongated particles with citric acid solutions. Getting insight into the organic acid-chitosan interactions will help improve the electrospinning process to obtain fibers, particles, or both in a controlled fashion and may help design tailored materials.