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

Abstract

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.

Keywords: Gold-silica nanoshells; Photochemical internalization; Photothermal therapy; Rat macrophages; Squamous cell carcinoma.

Fig. 1

Overview of combined PCI-PTT treatment via two wavelength irradiations. (1) PEGylated nanoshells incorporated into Macrophages (Ma) forming nanoshell laden Ma (Ma^NS). (2) Ma^NS are mixed with FaDu cells to form hybrid monolayers of FaDu-Ma^NS. Photosensitizer (AlPcS2a) is added. (3) Bleomycin (BML) at different concentrations is added. (4) Each well is irradiated with either 810 and 670 nm or a combination of the two wavelengths. (5) MTS assay is used to evaluate cell survival

Fig. 2

Confocal micrographs of internalized PEGylated AuNS nanoshells by Ma. Ma was incubated with 100 μl of PEGylated (2.8 × 1011 particles/ml) nanoshells colloid for 24 h at 37 °C. a Empty Ma; b Ma with internalized AuNS. Nanoparticles are shown as dark inclusions

Fig. 3

Effects of PTT on hybrid monolayers of FaDu-Ma^NS. Hybrids were formed with FaDu:Ma^NS ratios of either 1:1 or 2:1. NIR laser powers administered at 0, 7, 14, or 28 W/cm². Cell viability assessed by MTS assay. Error bars denote standard error

Fig. 4

Effect of BLM on hybrid monolayers of FaDu-Ma^NS. BLM administered at varying concentrations, from 0 to 1.2 μg/ml. FaDu:Ma^NS ratio of 2:1 a BLM treatment combined with MHT or PTT. External MHT was applied for 45 min at either 37 or 44 °C. PTT was performed with 14 W/cm² for 6 min. b BLM treatment combined with PCI. Cells were irradiated with λ = 670 nm at exposures of 0, 0.72, or 0.96 J/cm². Cell viability was assessed by MTS assay. Error bars denote standard error

Fig. 5

Effects of PCI-BLM combined with PTT on hybrid monolayers of FaDu-Ma^NS. BLM concentration of 0.6 μg/ml. FaDu:Ma^NS ratio of 2:1 a PCI, λ = 670 nm laser irradiance of 0–0.96 J/cm². PTT NIR laser irradiance of 14W/cm². b PTT NIR laser irradiance of 0–28 W/cm². PCI, λ = 670 nm laser radiance of 0.72 J/cm². Cell viability assessed by MTS assay. Error bars denote standard error and *represents significant differences (p < 0.05) compared to controls