Stearic Acid-Modified Starch/Chitosan Composite Sponge with Asymmetric and Gradient Wettability for Wound Dressing

In this work, we developed a facile approach for the fabrication of stearic acid-modified starch/chitosan composite sponge with asymmetric wettability and gradient wettability via mediating the amount of starch. The starch/chitosan composite sponge exhibited heterogeneous wetting properties on its two surfaces after stearic acid modification. The superhydrophobic top surface with a water contact angle of 150 degrees could prevent water, blood, and bacterial permeation without losing the breathability of the sponge, whereas the superhydrophilic bottom surface possessed optimal water and blood absorption and clotting abilities. The asymmetric wettability of starch/chitosan composite sponge was attributed to the synergistic contribution of gradient distribution of starch, rough three-dimensional skeleton structure induced capillary effect and the nonuniform surface distribution of hydrophilic/ hydrophobic groups. Furthermore, the sponge also possessed good biodegradability and noncytotoxicity to the human normal hepatocyte. The results indicated that the stearic acid-modified starch/chitosan composite sponge with ideal liquid absorption, vapor transmission rate, self-cleaning and stain-repellent ability could be used as a promising candidate for wound dressing.