A method for preparing a wound dressing including forming a first solution by mixing a zinc solution with a Tragacanth solution, immersing a substrate in the first solution, forming a second solution by adjusting pH of the first solution containing the substrate, forming a modified substrate by synthesizing a plurality of ZnO nanoparticles with a particle size between 55 nm and 70 nm on the substrate by applying ultrasound radiation to the second solution, and forming a plurality of Ammoniacum nanocapsules with a particle size between 20 nm and 80 nm on the modified substrate.