Cold Atmospheric Plasma Potentiates the Photodynamic Effects of Protoporphyrin IX-Loaded Mesoporous Silica-Coated Iron Oxide Nanoclusters in HaCaT Cells

Photodynamic therapy (PDT) is a reactive oxygen species (ROS)-based treatment modality whose efficacy is often limited by poor photosensitizer stability and delivery. In this study, mesoporous silica-coated iron oxide nanoclusters (MNCs) were synthesized and loaded with protoporphyrin IX (PPIX) to obtain a multifunctional PPIX@MNC nanoplatform. Physicochemical characterization was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential analysis, and Fourier-transform infrared spectroscopy (FTIR). The biological effects of MNC, free PPIX, and PPIX@MNC were evaluated in HaCaT cells—as a general epithelial model—under dark conditions, light irradiation, cold atmospheric plasma (CAP) exposure, and combined CAP-assisted photodynamic treatment. FTIR, DLS, and zeta potential analyses confirmed successful incorporation of PPIX into the nanoclusters. Cell viability assays revealed pronounced phototoxicity of free PPIX, with the IC50 value decreasing from 44.4 ± 3.5 nM under dark conditions to 14 ± 2 nM following light activation, corresponding to a phototoxicity index of 3.17. CAP further enhanced PPIX-mediated cytotoxicity, and the CAP-assisted photodynamic group exhibited the strongest response, with an IC50 value of 9.6 ± 1.1 nM. CAP further enhanced PPIX-mediated cytotoxicity. Increased ROS generation, enhanced apoptosis, and marked mitochondrial membrane potential disruption were observed particularly in CAP-Light-PPIX-treated cells. Although encapsulation of PPIX within MNCs reduced acute cytotoxicity compared with free PPIX, the nanoplatform retained responsiveness to light and CAP stimulation. These findings demonstrate that CAP potentiates PPIX-mediated photodynamic effects through enhanced oxidative stress and suggest that mesoporous silica-coated magnetic nanoclusters represent a promising platform for controlled photosensitizer delivery in CAP-assisted PDT applications.