Enhancement of glycated chitosan in laser cancer treatment

Abstract

Glycated chitosan (GC), a novel immunoadjuvant, has been used in combination with selective photothermal interaction in treatment of metastatic tumors. It has shown to be able to induce anti-tumor immunity and to enhance treatment efficacy. To further study the effects of glycated chitosan, photodynamic therapy (PDT) was used as the mechanism of direct tumor killing. Specifically, Photofrin-based PDT was used to treat EMT6 mammary tumors in mice and mTHPC-based PDT was used to treat Line 1 lung tumors in mice. In both cases, GC was administered immediately after the PDT treatment around the treated tumors. With EMT6 tumors, the use of GC improved the PDT-mediated tumor cure rate from 37.5% to 62.5% with 0.1 ml of 0.5% GC solution and to 75% with 0.1 ml of 1.5% GC solution. With the Line 1 tumors, the non-curative PDT treatment was converted into a 37.5% cure-rate by using a post-PDT peritumoral injection of 0.09 ml of 1.67% GC solution. In comparison, the treatments with GC alone or GC plus PDT light (no photosensitizer) produced no tumor regression and had no influence on the tumor growth rate, when compared to non-treated control tumors. GC was also used for the treatment of B16 melanoma in mice, using a combination of in situ application of GC and an irradiation of an 805-nm laser. The survival rates of the mice bearing melanoma tumors increased significantly when the laser and GC were applied, particularly when GC was applied 24 hours prior to the laser irradiation. These results strongly suggested that glycated chitosan played a significant role in the treatment of tumors.