Novel Antibacterial Hydrogels Incorporating Quaternary Ammonium Monomethacrylate: A Pilot Study on Swelling Behavior...

Poly(acrylamide) (PAM) hydrogels offer biomedical potential, but bacterial colonization limits their long-term use. This study examines PAM hydrogels modified with quaternary ammonium monomethacrylate (QAHAMA-10) for antimicrobial properties. Five formulations with QAHAMA-10 to acrylamide (AA) molar ratios ranging from 2.5 to 30 mol.% and crosslinked with 1 mol.% N,N'-methylenebisacrylamide (bis-AA) were evaluated. QAHAMA-10 improved hydrogel stability, especially at 10 mol.%, which showed the best structural integrity and transparency. The degree of swelling (DS) decreased with increasing QAHAMA-10 content, from 394.4% (2.5 mol%) to 180.0% (30 mol%), versus 938.4% for the reference. No bacterial growth was detected in suspensions recovered from wells with experimental hydrogels. The hydrogels inhibited Staphylococcus aureus ATCC 25923, with inhibition zones ranging from 16.2 to 23.1 mm depending on the QAHAMA-10 content, while the reference showed no inhibition. In contrast, no activity was observed against Escherichia coli ATCC 25922 in the disk diffusion assay. Alamar Blue reduction in fibroblast L929 cells decreased with higher QAHAMA-10 content, ranging from 70.8% to 27.7% after 24 h and 74.4% to 26.1% after 48 h, compared to 78.1% and 94.2% for the reference. Overall, 2.5 mol.% QAHAMA-10 offered the best balance of anti-S. aureus activity and cytocompatibility, while 10 mol.% provided optimal physicochemical properties.