The process of drug discovery for PDT involves the identification, design, and synthesis of the photosensitizer (PS), its photo physical characterization, the development of a formulation for efficient delivery and its therapeutic assessment both in vitro and in vivo. In vitro assays have traditionally depended on two-dimensional (2D) cell cultures, but they fail to accurately capture tissue complexity. Therefore, three-dimensional (3D) cultures are being introduced in drug discovery to bridge the gap between 2D cultures and animal models, since they integrate multiple cues that arise from extracellular matrix and cells, closer to an in vivo scenario.
