Enhanced reactive oxygen species generation using photonic platforms containing polyethylene glycol hydrogel doped with a photosensitizer for photodynamic therapy

This work presents the design and analysis of a symmetric one-dimensional photonic crystal incorporating a polyethylene glycol hydrogel doped with porphyrin derivatives (TBPP, TMPP, TPP, TCPP, and TAPP) for enhancing reactive oxygen species generation in photodynamic therapy. The photonic structure is engineered such that the defect resonance mode overlaps the absorption Q-band of porphyrins. Simulation results show that increasing the intrinsic refractive index of porphyrin systematically red-shifts the resonance wavelength from 715.27 nm (TBPP) to 716.58 nm (TAPP). Among all derivatives, TCPP and TAPP show the best optical metrics such as the quality factor, detection limit, and figure of merit. Also, the electric field distribution analysis reveals intense light localization, up to 150-fold enhancement within the defect region. The supposed biosensor exhibit high quality factors (nearly 4700), narrow linewidths (Δλ_FWHM=0.152 nm), high sensitivity (83-88 nm·RIU⁻¹), low detection limits (1.8×10⁻³ RIU), and large figures of merit (546-580). Our study introduces a photonic platform that acts as an optical booster which concentrates light to enhance the activation efficiency of photosensitizers at the defect site.