Non-covalent crosslinkers for electrospun chitosan fibers

Electrospun chitosan fibers have numerous potential in biomedical, food, and pharmaceutical applications. However, the mats formed are often not chemically stable in a wide range of pHs unless crosslinked. Here, we report on the use of glycerol phosphate (GP), tripolyphosphate (TPP) and tannic acid (TA) as a new set of non-covalent crosslinkers for electrospun chitosan fibers. Crosslinking with or without heat or base activation were performed either prior to (one-step or activated one-step) or after (two-step or activated two-step) electrospinning with either GP or TA. TPP crosslinking was performed in two-step and activated two-step. FESEM, FTIR and UV–vis transmittance at 600 nm were used to determine fiber surface morphology, chemical interactions and solubility in 1 M AA (pH 3), water (∼pH 6) and 1 M NaOH (pH 13), respectively. Crosslinking of chitosan with GP and TA yields fibers with a mean diameter range of 145–334 nm and 143–5554 nm, respectively. TPP crosslinking produced branched fibers with mean diameters of 117–462 nm range. Two-step chitosan-TA did not dissolve in 1 M AA even after 72 h while all chitosan-TPP, activated two-step chitosan-TA and two-step heat activated chitosan-GP fibers survived in water after 72 h.