Two-photon excitation nanoparticles for photodynamic therapy

) which can kill cancer cells. The long-wavelength light used to excite TPE NPs allows for deeper tissue penetration to achieve efficient PDT of deep-seated tumors. Moreover, TPE nanoparticles normally have large two-photon absorption (TPA) cross-sections, which hold great potential as efficient two-photon donors in PDT. In this review, we will summarize the recent advances made in the development of TPE nanoparticles for cancer PDT. Five different TPE nanoparticles, including quantum dots (QDs), carbon nanomaterials, silica nanoparticles, gold nanomaterials, and polymer nanoparticles, are summarized in detail, and the existing challenges as well as the future perspectives are also discussed.