Voltage–Frequency Tuned Argon Plasma Jets Enable Targeted H₂O₂ Delivery to Overcome Redox Resistance in Colorectal Cancer Cells

Colorectal cancer (CRC) poses a significant therapeutic challenge due to intrinsic chemoresistance and molecular heterogeneity. This study introduces a tunable voltage and frequency argon plasma jet, powered by kHz AC (1–20 kV, 18–28 kHz) as a novel platform for spatially targeted hydrogen peroxide (H₂O₂)-mediated cytotoxicity in chemoresistant HT29 CRC cells. By precisely modulating voltage and frequency, we achieved precise control over extracellular H₂O₂ concentrations (291–371 µM) in the culture medium, which correlated linearly (R² = 0.995, p  < 0.001) with dose-dependent cell death. Optimized parameters (10.5 kV, 28 kHz, 3 min) induced near-complete cytotoxicity (9.2% ± 3.6% viability), surpassing conventional plasma therapies. Morphological analysis revealed hallmark apoptotic phenotypes—rounding, membrane blebbing, and detachment—consistent with H₂O₂-driven oxidative stress overwhelming HT29’s antioxidant defenses. Notably, this tunable system bypasses resistance mechanisms observed in helium plasma-treated cells, where Nrf2/Srx upregulation neutralizes reactive species. Our findings establish spatially controlled H₂O₂ delivery as a potent strategy to overcome CRC chemoresistance, positioning argon plasma jets as a scalable, non-thermal modality for precision oncology.