<title>Photodynamic therapy with cationic photosensitizers</title>

Abstract

We characterized sites of photodamage catalyzed by two cationic photosensitizers tetrabromo- rhodamine 123 (TBR), which is recognized by the multidrug transporter, and a monocationic porphyrin (MCP), which is not. The transporter is an outward transport system associated with examples of drug resistance. Irradiation of multidrug-resistant cells treated with TBR resulted in highly selective photodamage to the transporter site, while MCP catalyzed non- specific membrane damage to cells regardless of transporter expression.