In vivo photodynamic therapy (PDT)

Mice in the PDT pretreatment groups were irradiated with NIR light from a 690 ± 20 nm light-emitting diode (LED) source, 4 h after the administration of 3.3 nmol of the PSMA-targeted photosensitizer, YC-9. This dose was determined from our previous study with YC-9, where four cycles of 10 nmol of YC-9 and PDT at 48 h intervals were needed to achieve complete tumor eradication ⁵⁰. Although a single PDT treatment cycle after a YC-9 dose of 10 nmol caused a reduction in the tumor volume in that study, it did not completely eradicate the tumors ⁵⁰. Accordingly, to investigate the feasibility of using this PDT method to enhance tumor vascular permeability and nanoparticle delivery, we decided to use a lower YC-9 dose that did not cause a reduction in the tumor volume in our previous study ⁵⁰.

Briefly, 4 h after YC-9 administration, each mouse was covered with aluminum foil, except at the tumor site, to prevent non-specific activation of the photosensitizer in other parts of the body. The tumors were then irradiated at a total fluence of 200 J/cm². Mice were then imaged 18 h, 42 h, and 66 h after PDT (24 h, 48 h, and 72 h after YC-9 administration, respectively).