Photothermally enhanced photodynamic therapy based on glutathione-responsive pheophorbide a-conjugated gold nanorod formulations for cancer theranostic applications

Nanocarriers have provided a new platform for the selective delivery of therapeutic agents into targeted cells and tissues using safe, efficient, and tractable routes. In particular, the integration of multiple therapeutic/diagnostic modalities into a single system has the great potential of enhancing theranostic efficiency against serious diseases with reduced side effects. In this study, a new light-triggered theranostic system using photosensitizer-conjugated gold nanorods (AuNR) with glutathione (GSH)-sensitive linkages was developed for cancer imaging and combinational phototherapy of photodynamic therapy (PDT) and photothermal therapy (PTT) to achieve a synergistic cancer treatment. AuNRs with various aspect ratios were prepared as photothermal agents, and then a folic acid (FA)-PEG block copolymer (FAP) and pheophorbide a (Pheo) were chemically conjugated to the surface of AuNRs for active tumor targeting and PDT, respectively. The configuration of Pheo-conjugated AuNR nanocarriers has been precisely controlled through adjusting the feed composition ratio and the relationship between aspect ratio and absorption band of AuNRs. In particular, an AuNR with an aspect ratio of 3.84 and longitudinal plasmon resonance at 873 nm (Pheo-conjugated AuNR100) exhibited superior performance in singlet oxygen generation, photothermal conversion effect, and GSH-mediated selective release of Pheo. Moreover, it also showed tumor targeting activity and a PDT-PTT synergistic effect. These results indicate that this multifunctional AuNR system with tumor targeting ability and GSH-sensitive linkages would be highly efficient for noninvasive cancer treatment by integrating cancer imaging diagnostics and synergistic therapy. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.