Highly Efficient Two‐Photon Photodynamic Therapy Using Light‐Sheet Excitation

Two‐photon photodynamic therapy (TP‐PDT), which utilizes near‐infrared light to excite photosensitizer via two‐photon excitation (TPE), is a promising modality in the treatment of deeply seated tumors or thick tumors. However, the TPE domain is much smaller than the tumor volume, significantly limiting the therapeutical outcomes of TP‐PDT. Here, a light‐sheet TPE system is designed and constructed using a cylindrical lens for highly efficient TP‐PDT. The light‐sheet TPE performance is characterized and optimized via theoretical analysis and experimental studies in solution, phantom, and tumor. The optimized excitation system can reach a large TPE domain of 2.6 × 2.7 × 0.09 mm in the tumor, which is not achievable using conventional TPE methods, enabling TPE and subsequently generated reactive oxygen species to cover the whole tumor under line‐scanning. Outstanding TP‐PDT therapeutic performance of 70% tumor growth inhibition rate is achieved under line‐scanned light‐sheet TPE, making the proposed light‐sheet excited TP‐PDT a potential therapeutic tool for future translational research.