Evaluation of Selective Efficacy of Indocyanine Green-Mediated Photodynamic Therapy ICG-PDT in MCF-7 Breast Cancer Cells Compared to Healthy Cells in a 3D Hollow Fiber Bioreactor Model

<b>Objective:</b> This study investigates the efficacy of indocyanine green-mediated photodynamic therapy (PDT) in targeting MCF-7 breast cancer cells, a representative model of luminal A subtype, compared to healthy breast epithelial cells. <b>Methods:</b> MCF-7 cells and healthy breast cells were cultured in a three-dimensional (3D) hollow fiber bioreactor to mimic the tumor microenvironment in vivo. Cells were treated with ICG at concentrations ranging from 1 to 1000 μM and then photoactivated using a diode laser. Cell viability was assessed by trypan blue staining, and the production of reactive oxygen species (ROS), including singlet oxygen (¹O₂) was measured. <b>Results:</b> Cell viability, assessed via trypan blue exclusion, decreased dose-dependently with ICG concentrations (1-1000 μM), with MCF-7 viability dropping from 94.5% ± 0.8% at 0.1 μM to 15.83% ± 0.66% at 1000 μM, compared to healthy cells retaining >50% viability up to 500 μM (55.2% ± 2.0% at 1000 μM). Student's t-tests confirmed significant differences (<i>p</i> < 0.05) between MCF-7 and control (0 μM) at all concentrations, and between MCF-7 and healthy cells, indicating selective cytotoxicity (IC₅₀: ~75 μM for MCF-7). Flow cytometry revealed MCF-7 cell concentrations were significantly lower than healthy cells' across all ICG doses and seeding densities (<i>p</i> < 0.05). Spectroscopic analyses showed ICG absorption peaks at 800-900 nm, fluorescence at 800-820 nm, and singlet oxygen phosphorescence at 1270 nm, confirming effective ROS generation. <b>Conclusions:</b> Cell concentrations confirmed selective MCF-7 cytotoxicity (<i>p</i> < 0.05). Spectroscopic data validated ROS generation, supporting ICG-PDT's potential as a selective therapy for early-stage breast cancer within a 50-500 μM therapeutic window.