Structurally Precise Cationic Polythiophene–b–Polyglutamate Diblock Copolymers with Tunable Polyplex Morphologies for Efficient PCI–Mediated Gene Delivery

Abstract

A new class of structurally defined cationic polythiophene–b–polyglutamate diblock copolymers (P3ETn–b–PBLGm(DET)s) has been developed as molecularly integrated, photoactivatable gene delivery vectors. Through Kumada catalyst–transfer polycondensation (KCTP), the conjugated P3ET block length was precisely controlled, enabling fine modulation of both photophysical properties and self–assembled morphology. The resulting copolymers efficiently condensed plasmid DNA into polyplex nanoparticles whose morphology evolved from compact spheres to elongated rod–like assemblies with increasing P3ET length. This morphological transition, coupled with extended π–conjugation, promoted more efficient intersystem crossing and enhanced singlet oxygen (1O2) generation under visible light. The synergistic effects of localized reactive oxygen species production and anisotropic membrane interaction led to significantly improved photochemical internalization (PCI), facilitating rapid endosomal escape and robust gene expression upon light activation. Cytotoxicity assays further confirmed excellent biocompatibility under optimized irradiation conditions. Overall, this work establishes a rational design framework for next–generation photoresponsive non–viral gene vectors, in which structural precision at the molecular level translates into controllable nanoparticle morphology, tunable photodynamic activity, and safe, efficient, light–triggered gene transfection.