Fig. 6: Wavelength-selective, pixel-resolved photocytotoxicity on Au–TiO₂ q-BIC metasurfaces.

Cells were cultured directly on patterned metasurfaces and imaged in three channels: White LED (bright field, top row), PI (propidium iodide; dead, middle row), and Merged (Calcein-AM/PI overlay; live/dead, bottom row). Columns (left to right): I–III 10 μM RB control, 125 s exposure; IV–VI 532 nm irradiation for 75 s; VII–IX 532 nm for 125 s; X–XII 562 nm for 125 s. Dashed boxes mark representative metasurface pixels used for comparison. Under 532 nm illumination (IV–IX), PI-positive cells concentrate in resonance-mapped zones corresponding to designs scaled to S = 1.104 and S = 1.106; surrounding, off-resonant regions retain Calcein fluorescence. When the excitation is shifted to 562 nm (X–XII), cell death localizes to pixels red-tuned to S = 1.112, consistent with spectral matching. Scale bars, 10 μm. Together, these data demonstrate spatially selective, resonance-matched photodynamic cytotoxicity arising from localized singlet-oxygen generation