Enhancing the effects of chemotherapy by combined macrophage-mediated photothermal therapy (PTT) and photochemical internalization (PCI)

Light-based treatment modalities such as photothermal therapy (PTT) or photochemical internalization (PCI) have been well documented both experimentally and clinically to enhance the efficacy of chemotherapy. The main purpose of this study was to examine the cytotoxic effects of silica–gold nanoshell (AuNS)-loaded macrophage-mediated (Ma^NS) PTT and bleomycin BLM-PCI on monolayers of squamous cell carcinoma cells. The two modalities were applied separately and in simultaneous combination. Two different wavelengths of light were employed simultaneously, one to activate a highly efficient PCI photosensitizer, AlPcS₂a (670 nm) and the other for the Ma^NS-mediated PTT (810 nm), to evaluate the combined effects of these modalities. The results clearly demonstrated that macrophages could ingest sufficient numbers of silica–gold nanoshells for efficient near infrared (NIR) activated PTT. A significant synergistic effect of simultaneously applied combined PTT and PCI, compared to each modality applied separately, was achieved. Light-driven therapies have the advantage of site specificity, non-invasive and non-toxic application, require inexpensive equipment and can be given as repetitive treatment protocols.