Selective Ablation of β‐Galactosidase‐Expressing Cells with a Rationally Designed Activatable Photosensitizer

We have developed an activatable photosensitizer capable of specifically inducing the death of β-galactosidase-expressing cells in response to photoirradiation. By using a selenium-substituted rhodol scaffold bearing β-galactoside as a targeting substituent, we designed and synthesized HMDESeR-βGal, which has a non-phototoxic spirocyclic structure owing to the presence of the galactoside moiety. However, β-galactosidase efficiently converted HMDESeR-βGal into phototoxic HMDESeR, which exists predominantly in the open xanthene form. This structural change resulted in drastic recovery of visible-wavelength absorption and the ability to generate singlet oxygen ((1)O2). When HMDESeR-βGal was applied to larval Drosophila melanogaster wing disks, which express β-galactosidase only in the posterior region, photoirradiation induced cell death in the β-galactosidase-expressing region with high specificity.