The lack of charged chemical groups and the small size of benzoselenadiazoles are essential to retain recognition and uptake through cell-surface transporters. Aminobenzoselenadiazoles mimic the stereospecificity of chiral amino acids (as shown in L-Ala vs D-Ala derivatives, Figure ) and replicate the uptake of natural biomolecules, as demonstrated with the glucose analogue 15 in GLUT transporters (Figure ). Of note, GLUT-mediated transport was not observed for other glucose-based photosensitizers, such as Nile Blue or TPE. We have demonstrated that the active uptake of aminobenzoselenadiazoles is essential to: 1) minimize off-target toxicity in healthy cells, as shown in human co-cultures and in vivo (Figures and), and 2) accumulate concentrations of photosensitizer inside target cells that can generate cytotoxic levels of singlet oxygen under clinical PDT exposure (Figures 4, 5 and 6). Furthermore, given that aminobenzoselenadiazoles can be excited by single and