Once a uniform viscous mixture was obtained, 3 wt% glutaraldehyde was added dropwise. The mixture was then gently stirred for 4 h to prevent bubble formation before casting onto a Petri dish. The resulting hydrogel was placed in an oven at 45 °C until it became dry. After removing from the oven, the hydrogels in the form of thin films were removed from the Petri dish and rinsed with distilled water to leach out any unreacted chemicals.