NUMERICAL SIMULATION OF PHOTODYNAMIC ANTITUMOR DOUBLE-LAYER MICRONEEDLES

In response to the challenges of low photosensitizer delivery efficiency and insufficient light penetration depth in photodynamic therapy (PDT) for skin cancer, this study presents a double-layer microneedles system designed for enhanced photodynamic anti-tumor treatment. The double-layer microneedles consists of a dissolvable needle tip and an insoluble base. The dissolvable tip enables precise and targeted delivery of the photosensitizer to the tumor tissue, ensuring high-efficiency delivery of the photosensitizer. Upon the dissolution of the needle tip, the insoluble base remains embedded within the tissue, providing a stable optical conduit for high-energy photon transmission. This design significantly enhances light penetration, allowing photons to reach deeper tissue layers and activate the photosensitizer effectively. To optimize the double-layer microneedles' performance in both drug delivery and photon transmission, a photosensitizer diffusion model within skin tissue was established using COMSOL Multiphysics.This model quantitatively examines the relationship between the geometric parameters of the needle tip and the corresponding diffusion concentration of the drug. Furthermore, a Monte Carlo-based optical model of melanoma tissue was developed to analyze the effects of the base geometry on photon transmission within melanoma tissue, providing insights into the optimal light conduction properties. Based on the results of these analysis, the double-layer microneedles geometry with the best combination of delivery and photoconductivity performance was successfully determined. Additionally, a mechanical model was constructed using ANSYS Workbench software to validate the penetration capability of the microneedles.The findings indicate that the proposed double-layer microneedles design demonstrates exceptional mechanical properties, enabling efficient and smooth skin penetration. It ensures the precise, targeted delivery of photosensitizer directly to the tumor sites via the dissolvable tip.The insoluble base establishes a stable photon transmission pathway within the tumor tissue, significantly enhancing light propagation. This microneedles design offers a highly efficient strategy for photodynamic anti-tumor therapy, paving the way for novel, non-invasive cancer treatment approaches.