Pyridine catalyzed acylation of electrospun chitosan membranes by C6-C12 acyl chlorides: Effect of reaction time and chain length

Abstract

Chitosan nanofiber membranes manufactured via electrospinning are attractive for drug delivery applications due to their increased surface area. The as-spun fibers contain trifluoroacetate (TFA)-salts that cause swelling and loss of nanofiber structure in physiological solutions and are cytotoxic. Here, a post-electrospinning treatment has been reported using fatty acyl chlorides and pyridine to O-acylate the membranes with different acyl chain-length (C6, C8, C10, and C12). The O-acylation reactions were carried out with acyl chlorides in a basic environment for 2 hr, 3 hr, 4 hr and, 5 hr. The effects of the acyl chain length and the reaction time were assessed using various physio-chemical characterization techniques including FTIR, NMR, Contact Angle, XPS, and SEM. The acylated nanofibers displayed hydrophobic properties and allowed the removal of the cytotoxic TFA salts without compromising the nanofibrous structure. The fiber diameter increased with the increasing length of the substituted acyl chain. The degree of substitution of the acyl chains did not change significantly when reacted for a longer period indicating the completion of the reaction within 2 hr. This could allow the faster modification of the membranes for potential application in the delivery of hydrophobic drugs.