Effect of poly(styrene sulfonate) treatment on the structural evolution and sonodynamic performance of PCN-224 nanoparticles

Abstract

Porphyrin based nanosize metal-organic frameworks (MOFs), such as PCN-224, are promising sonosensitizers for the sonodynamic therapy (SDT) due to their high porphyrin loading capacity and excellent water dispersity. However, the limited pore size of PCN-224 and the close proximity between porphyrins may impede the generation and diffusion of reactive oxygen species (ROS). In this study, a facile ligand exchange method is developed to regulate the structure and the content of tetrakis(carboxyphenyl)-porphyrin (TCPP) in the treated PCN-224 nanoparticles (NPs). Through simple incubation of PCN-224 NPs in poly(styrene sulfonate) (PSS) solution, the ligand exchange between PSS and TCPP happens and a part of TCPP is released to the solution. The ligand exchange results in the transformation of the crystalline structure to amorphous structure of PCN-224, the formation of larger pores and the decrease of surface area. The increased pore size can enhance the generation ability of 1O2 due to the favorable diffusion of substances. This effect can compensate the decreased amount of TCPP in the NPs until the incubation time reaches 8 h in a 2 mg/mL PSS. After balancing the two factors of structure change and TCPP content in the treated PCN-224 NPs, one can achieve their optimal SDT performance. Through a ligand exchange process, this work provides a facile method to regulate the structure of MOFs-based sonosensitizers and their SDT performance.