3.4. Preparation of pH-Responsive Hydrogel

The pH-responsive hydrogel was prepared using a free radical polymerization approach adapted from a previous procedure [22]. The procedure was adapted to obtain a product more suitable for topical administration to infected wounds that were also more sensitive to pH changes. The typical synthesis was as follows, 1 mL of methacrylic acid (mAA), 1.67 g of acrylamide (AAm), 500 µL of tetramethylethylenediamine (TEMED), 16.35 mg of N, N’-methylenebisacrylamide (MBAm), and 5.5 mL of MilliQ water were combined in a Schott bottle. The solution was sonicated for 5 min to dissolve all the components then poured into a plastic petri dish. Then 1.18 mL of ammonium persulfate (APS) dissolved in water at 80 mg/mL was added to initiate the polymerization at room temperature (~20 °C). The petri dish was swirled to mix the two solutions. The reaction was left overnight with a hydrogel visibly forming after 1 h. The final poly(mAA-co-AAm) based hydrogel was purified by 50 L ultrapure water being flowed through the swollen hydrogel for 12 h continuously, completely removing residual monomers as confirmed by liquid chromatography. Subsequently, the purified hydrogel was cut into 1 cm³ cube size and dried in a vacuum oven at 45 °C, overnight for 18 h. The AgNPs were loaded into the hydrogel by immersing a dried piece of a hydrogel in 5 mL of the AgNPs suspension overnight at ambient temperature. Swollen AgNPs containing hydrogels were washed with 3 × 5 mL of water by fully submerging the hydrogel in water to remove any remaining surface bound AgNPs.