Liposomal Salvianolic Acid B Enhances ALA-PDT in Oral Leucoplakia via ROS and AKT/mTOR Signalling

Salvianolic acid B (SalB), a major component of Danshen, the ancient Chinese herb Salvia miltiorrhiza Bunge, has demonstrated inhibitory effects against various solid tumours. Our previous study explored a SalB-loaded nanocarrier as a photosensitizing formulation for photodynamic therapy (PDT) in vitro in oral leucoplakia (OLK) and oral cancer cells. This study aims to explore the underlying mechanisms and in vivo effects. In this study, different concentrations of SalB and 5-aminolevulinic acid (ALA) were incorporated into liposomes to synthesize the nano-photosensitizer (nano-SalB-ALA). Reactive oxygen species (ROS) levels in Cal27 and Leuk1 cells were evaluated by DCFH-DA staining, and the intracellular distribution of fluorescently labelled liposomes was visualized by confocal laser scanning microscopy (CLSM). Western blot was used to analyse the expression of PI3K/AKT/mTOR signalling proteins. In addition, a 4NQO-induced OLK mouse model was used to evaluate in vivo effects. Based on the most obvious intracellular ROS fluorescence signals and the greatest reduction in PI3K/AKT/mTOR signalling pathway expression observed in the nano-SalB 10 -ALA 250 (10 mg SalB@250 µM ALA) group, we selected it for subsequent in vitro analyses. Both in vitro and in vivo, nano-SalB 10 -ALA 250 PDT inhibited the PI3K/AKT/mTOR signalling pathway. These results indicate that SalB, in a nano-photosensitizer formulation, modulates ROS levels and PI3K/AKT/mTOR signalling, which may contribute to the enhanced efficacy of PDT for OLK. This study may provide new strategies for improving the efficacy of PDT for OLK in clinical practice.