Construction of Natural Polysaccharide-Based pH-Responsive Gold Nanorods for Combined Photothermal Therapy and Immunotherapy

Photothermal therapy and immunotherapy are emerging strategies for treating tumors. The combination of these two therapies can effectively leverage their advantages, thereby enhancing the therapeutic efficacy. Based on this premise, the natural polysaccharide was prepared from the edible Rosa roxburghii fruit and applied to coat gold nanorods (GNRs). The antitumor nanorods, designated as RRP-MPBA-GNRs, were developed to combine photothermal therapy and immunotherapy. This system employed 4-mercaptophenylboronic acid (MPBA) as the connecting unit. The hydroxy groups of RRP formed dynamic borate ester bonds with MPBA, and this conjugated bonds exhibited pH-responsive properties. The RRP-MPBA was immobilized on the surface of GNRs through sulfur–gold bonds, enhancing the stability and preserving the photothermal effects of GNRs. In vivo experiments have demonstrated that RRP-MPBA-GNRs reduced the number of cancer cells at the transplant site and inhibited metastasis. Further investigation revealed that the photothermal effects of RRP-MPBA-GNRs can increase reactive oxygen species (ROS) levels in cancer cells and induce apoptosis. RRP released from RRP-MPBA-GNRs can induce an antitumor immune response by promoting the maturation of dendritic cells and up-regulating the expression of surface marker molecules. The results suggested that RRP-MPBA-GNRs can effectively integrate photothermal therapy and immunotherapy for tumor treatment.