Photoimmunotherapy using indocyanine green-loaded Codium fragile polysaccharide and chitosan nanoparticles suppresses tumor growth and metastasis.

Metastasis and recurrence are the main challenges in cancer treatment. Among various therapeutic approaches, immunotherapy holds promise for preventing metastasis and recurrence. In this study, we evaluated the efficacy of treating primary cancer and blocking metastasis and recurrence with photo-immunotherapeutic nanoparticles, which were synthesized using two types of charged polysaccharides. Codium fragile polysaccharide (CFP), which exhibits immune-stimulating properties and carries a negative charge, was combined with positively charged chitosan to synthesize nanoparticles. Additionally, indocyanine green (ICG), a photosensitizer, was loaded inside these particles and was referred to as chitosan-CFP-ICG (CC-ICG). Murine colon cancer cells (CT-26) internalized CC-ICG, and subsequent 808-nanometer laser irradiation promoted apoptotic/necrotic cell death. Moreover, intratumoral injection of CC-ICG, with 808-nanometer laser irradiation eliminated CT-26 tumors in mice. Rechallenged lung metastases of CT-26 cancer were inhibited by dendritic cell activation-mediated cytotoxic T lymphocyte stimulation in mice cured by CC-ICG. These results demonstrated that CC-ICG is a natural tumor therapeutic with the potential to treat primary tumors and suppress metastasis and recurrence.