H₂O₂-mediated Redox Priming by Non-thermal Microplasma Enhances Macromolecule Delivery to HL-60 Cells via Endocytosis

Efficient delivery of therapeutic macromolecules into hematopoietic suspension cells remains a bottleneck for gene- and immune-therapy workflows. Here we frame a contact-free microplasma priming approach as ReMod (Redox-guided Modulation): a reversible, cytocompatible “tune-rather-than-force” strategy that gates uptake through controlled extracellular redox inputs. A 150-kDa fluorescein isothiocyanate–dextran (FD-150) was used as a model cargo in HL-60 leukemia cells. Culture-medium RONS were tuned using N₂ + 0–10% O₂ + H₂O, Ar + 0–10% O₂ + H₂O, and Ar + 0–10% N₂ + H₂O, all at a total flow of 4 Lmin⁻¹. A brief 3-min non-thermal exposure produced a chemically tunable plasma–liquid interface and revealed a cytocompatible RONS “sweet spot” for FD-150 internalization, maximized under N₂ + 5% O₂ + H₂O. Scavenger experiments, together with exogenous H₂O₂, indicated that extracellular H₂O₂ is a principal effector of uptake. Time-integrated intracellular ROS showed a modest O₂-dependent increase, whereas NO-related fluorescence exhibited a larger fold-increase at 1–5% O₂, suggesting that NO signaling may act as a later, reinforcing component of the redox response. qRT-PCR profiling of endocytic markers was consistent with clathrin-mediated endocytosis and macropinocytosis as dominant uptake routes under ReMod priming. These findings define a practical redox-gating window for macromolecule delivery into suspension leukemia cells without electroporation and provide a basis for extending microplasma ReMod to nucleic-acid or immunotherapeutic payloads.