Fluorescence Imaging Assisted Photodynamic Therapy Using Photosensitizer-Linked Gold Quantum Clusters

Fluorescence imaging assisted photodynamic therapy (PDT) is a viable two-in-one clinical tool for cancer treatment and follow-up. While the surface plasmon effect of gold nanorods and nanoparticles has been effective for cancer therapy, their emission properties when compared to gold nanoclusters are weak for fluorescence imaging guided PDT. In order to address the above issues, we have synthesized a near-infrared-emitting gold quantum cluster capped with lipoic acid (L-AuC with (Au)18(L)14) based nanoplatform with excellent tumor reduction property by incorporating a tumor-targeting agent (folic acid) and a photosensitizer (protoporphyrin IX), for selective PDT. The synthesized quantum cluster based photosensitizer PFL-AuC showed 80% triplet quantum yield when compared to that of the photosensitizer alone (63%). PFL-AuC having 60 μg (0.136 mM) of protoporphyrin IX was sufficient to kill 50% of the tumor cell population. Effective destruction of tumor cells was evident from the histopathology and fluorescence imaging, which confirm the in vivo PDT efficacy of PFL-AuC.