*2.6. Antibacterial Activity*

Bacterial strains were obtained from bacterial culture collection of the Biomedical Innovation Department, at Scientific Research and High Education Center from Ensenada. The Gram (−) strain was *E. coli*, and the Gram (+) strain was *S. aureus*. The antimicrobial activity of hydrogels was performed by modification of the agar disk di ffusion method of Collins et al. [40]. Approximately 106 colony-forming units of each bacterium were inoculated on Luria–Bertani (LB) plates. To verify the exponential growth phase of each strain, we measured OD600 values of the bacterial strains over time. The inhibition of the bacterial growth was assessed by triplicate using samples grafted by the photochemical (UV) or gamma irradiation treatments, with or without AgNPs. Silver nanoparticles and silver-free samples were used as a control, and carbencillin (500 μg/mL), a broad-spectrum antibiotic, was used as a positive control. The inhibition zone (mm) was defined as the area in which no bacterial growth was detected. The plates were incubated for 24 h at 37 ◦C.
