Conjugating M13 bacteriophage targeting folate receptor alpha with multiple photosensitizers: a flexible phototheranostic platform against ovarian cancer.

Ovarian cancer remains one of the deadliest malignancies in women, largely due to late-stage diagnosis and limited efficacy of current chemotherapies. To address this challenge, we introduce an advanced phage-based phototheranostic platform that leverages genetic programmability and modular chemical functionalization for selective tumor eradication. We first generated a single-chain variable fragment derived from the anti-folate receptor α (FRα) antibody MORAb-003, then we engineered M13 bacteriophage displaying this targeting moiety, enabling high-affinity recognition of FRα-overexpressing ovarian cancer cells. Using orthogonal bioconjugation, we then conjugated multiple copies of two complementary photosensitizers, chlorin e6 (Ce6) and rose bengal (RB), onto the phage capsid, yielding a photoresponsive nanoconstruct with dual excitation/emission profiles. This multifunctional viral scaffold seamlessly integrates tumor targeting, fluorescence imaging, and light-activated cytotoxicity into a single biocompatible architecture. The resulting M13FRα-Ce6-RB conjugates exhibit potent photodynamic activity under both red and green light irradiation, highlighting the potential of refactored M13 phages as flexible nanocarriers for precision phototherapy. This work presents a customizable and translationally relevant nanoplatform for image-guided treatment of chemoresistant ovarian cancer and other FRα-positive malignancies.