Photosensitizing metal–organic framework nanoparticles combined with tumor-sensitization strategies can enhance the phototherapeutic effect upon medullary thyroid carcinoma

Photodynamic therapy (PDT) utilizing metal-organic frameworks (MOFs) has developed as a new and efficacious treatment for malignant tumors located on the surface of the human body. In order to achieve more effective PDT treatment outcomes, the traditional method has been to increase the intensity of the laser irradiation, but this approach can easily lead to tissue burns. In this study, we developed a new type of nanoparticle, F68-PKI@PCN224, aims to achieve effective PDT upon medullary thyroid carcinoma (MTC) which is an uncommon form of thyroid cancer that originates in the parafollicular cells of the thyroid and the therapeutic outlook for patients with MTC remains unsatisfactory. F68-PKI@PCN224 combines the antitumor features of PDT with mammalian target of rapamycin (mTOR) inhibitor PKI-587 (PKI). The tumor sensitization, slow release, and pH response features of F68-PKI@PCN224 was demonstrated by a series of in vitro and in vivo experiments / assays. F68-PKI@PCN224 achieved the long-term activation and slow releasing of PKI and TCPP in MTC tumor tissues. During the process of generating PDT effects, F68-PKI@PCN224 enhanced the tumor's sensitivity to PDT, direct laser irradiation of MTC cells or subcutaneous tumor tissues. As a result, low-dose phototherapy achieves a higher anti-tumor effect upon F68-PKI@PCN224 compared with TCPP. This study reveals the synergistic effect between tumor sensitization by mTOR inhibitor and PDT and initially unveils the mechanism of action of these nanoparticles.