A smart methodology to fabricate electrospun chitosan nanofiber matrices for regenerative engineering applications

The electrospinning of chitosan remains challenging due to its rigid crystalline structure, insufficient viscosity, and limited solubility in common organic solvents. This work presents a “smart” chitosan modification that allows electrospinning irrespective of molecular weight or deacetylation value and without blending with synthetic polymers. A novel derivative, namely 2‐nitrobenzyl‐chitosan (NB), at various molar compositions of chitosan:2‐nitrobenzaldehyde (1:1 (NB‐1), 1:0.5 (NB‐2), 1:0.25 (NB‐3)) was synthesized by the reaction between amino groups of chitosan and aldehyde groups of 2‐nitrobenzaldehyde. In this Schiff base, 2‐nitrobenzaldehyde protects the amine functionalities of chitosan and improves its solubility in trifluoroacetic acid. 2‐nitrobenzaldehyde is a photoactivatable‐caged compound that cleaves off from iminochitosan on ultraviolet exposure yielding neat chitosan. Derivatives showed improved solubility in trifluoroacetic acid and dynamic viscosities in the range of 1.34 ± 0.7 to 12 ± 0.5 Pa·s based on the degree of substitution and concentration. Electrospinning conditions were optimized to produce bead free nanofibers in the range of 100–600 nm, and concentrations beyond 12% (wt/v) for NB‐1 and NB‐2, and 15% (wt/v) for NB‐3 were suitable. Photolysis did not alter fiber morphology; however, regenerated chitosan matrices were soluble in culture media presumably due to the presence of 2‐nitrosobenzoic acid in trace amounts. Human skin fibroblasts exhibited excellent (>90%) cytocompatibility on treatment with polymer extractions from cross‐linked regenerated chitosan matrices prepared to the ISO standard. Newly synthesized iminochitosan derivatives were very effective against microorganisms including bacteria (Gram‐positive and Gram‐negative), fungi, and yeast. These fiber matrices may serve as scaffolds for a variety of tissue healing and factor delivery applications. Copyright © 2014 John Wiley & Sons, Ltd.