Development of Gold-Based Phototheranostic Nanoagents through a Bioinspired Route and Their Applications in Photodynamic Therapy

Green synthesis of nanoparticles using phytoconstituents has been widely accepted. However, further applications for delivery, diagnosis, and therapy are not yet fully established. Thus, bioinspired nanomedicinal diagnostic agents have been developed with antioxidant, diagnostic, as well as therapeutic properties. The sustainable biological synthesis of fluorescent gold nanoparticles 14 using Syzygium cumini fruit extract presents a simplified process for the production of surface-functionalized nanoparticles with good antioxidant potential. The gold-based phototheranostic nanoagents (PTNAs) were engineered by conjugating nanoparticles either with a photosensitizer (rose bengal or pyridyl porphyrin) or with an imaging agent (rhodamine B). The assembled PTNAs were revealed to possess good fluorescent properties and to generate singlet oxygen, and showed antimicrobial properties when irradiated with low-cost green LED light. All of the processes and properties (synthesis, antioxidant potential, percent conjugation, fluorescence, singlet oxygen generation, and antimicrobial photodynamic therapy) of PTNAs synthesized using S. cumini were characterized and compared with those synthesized using chitosan. The antimicrobial effect of photodynamic therapy using developed PTNAs was characterized by confocal laser scanning microscopy (CLSM). The development of bioinspired PTNAs described herein will find applications of photodynamic therapy for the treatment of cancer and microbial infection.