Porphyrin-based metal coordination polymers with self-assembly pathway-dependent properties for photodynamic and photothermal therapy

Abstract

Porphyrin-based metal coordination polymers (MCPs) have attracted significant attention due to their great promise for applications in phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT). However, the detailed self-assembly process of porphyrin-based MCPs is still poorly understood. This work provides a detailed study of the self-assembly process of MCPs constructed from Mn²⁺ and TCPP (TCPP: 5,10,15,20-tetrakis(4′-carboxyphenyl)porphyrin) in aqueous solution. Unlike the traditional nucleation and growth mechanism, we discover that there is a metastable metal–organic intermediate which is kinetically favored in the self-assembly process. And the metastable metal–organic intermediate nanotape structures could convert into thermodynamically favored nanosheets through disassembling into monomers followed by a reassembling process. Moreover, the two structurally different assemblies exhibit distinct photophysical performances. The intermediate Mn–TCPP aggregates show good light-induced singlet oxygen ¹O₂ generation for PDT while the thermodynamically favored stable Mn–TCPP aggregates exhibit an excellent photothermal conversion ability as photothermal agents (PTAs). This study could facilitate the control of the self-assembly pathway to fabricate complex MCPs with desirable applications.