Potent Antimicrobial Activity of Chitosan Hydrogels: Effects of Plasma‐Activated Water and Carvacrol

ABSTRACT This study describes the preparation and analysis of chitosan hydrogels (HCS) incorporating plasma‐activated water (PAW) and carvacrol to achieve potent antimicrobial activity. Hydrogels were prepared from a 3% high molecular weight chitosan solution with 2% (v/v) PAW and 2% (v/v) carvacrol before gelation at pH 7. PAW was generated by treating tap water with an air plasma jet for 3, 30, or 60 min. Materials were characterized using FTIR/ATR, DSC, TGA, and SEM, and evaluated through swelling tests, in vitro hemolysis assays, and antimicrobial tests. Plasma activation increased water pH and conductivity. Hydrogels exhibited high thermal stability, with major degradation above 220°C, and pH‐responsive swelling, degrading at pH 2 and swelling at pH 7.4 and pH 12. All hydrogels were non‐hemolytic (< 2% hemolysis) per ASTM F756‐17, confirming excellent blood compatibility. While control HCS showed no antimicrobial effect, PAW–carvacrol hydrogels exhibited strong broad‐spectrum activity against Escherichia coli , Staphylococcus aureus , and Aspergillus niger . These results demonstrate that the synergistic incorporation of PAW and carvacrol produces a thermally stable, biocompatible hydrogel with remarkable antimicrobial properties, making it a promising material for biomedical uses such as wound healing and drug delivery.