Fig. 1.

Illustration of the procedures for 3 different tumor penetration evaluation models. (A) Cultivation of multicellular spheroids via the hanging droplet method, followed by drug incubation and observation of drug penetration into the depth of multicellular spheroids under confocal microscopy. (B) A multilayer cell penetration model by introducing drugs into the cell culture media. (C) Evaluation of drug permeability via in vivo and ex vivo imaging. (Fig. 1 was created with BioRender.com.).