The effects of low irradiance long duration photochemical internalization on glioma spheroids.

BACKGROUND: Photodynamic therapy (PDT), if given over extended time periods (i.e. hours or days) and at very low irradiance in the µW/cm2 range, has been shown to be more effective than acute PDT (aPDT) administered over minutes. This has led to the concept of metronomic PDT (mPDT), which consists of ultra-low irradiance light illumination for extended periods of time along with either continuous or repetitive delivery of photosensitizer. Since the drug activating technology photochemical internalization (PCI) is based on PDT it seemed reasonable to expect that ultra-low irradiance, if administered over an extended period of time, could nevertheless result in effective metronomic PCI (mPCI) comparable to or more effective than that obtained with relatively high and short irradiance i.e. acute PCI (aPCI). METHODS: Tumor spheroids consisting of F98 cells were used as in-vitro tumor models. The amphiphilic photosensitizer Al phthalocyanine disulfonate (AlPcS2a) was used for all PCI experiments. Light treatment was administered from a diode laser at λ=670 nm at various irradiance exposures of 2 mW/cm2 for aPCI and 0.05 - 0.2 mW/cm2 for mPCI with durations ranging from 3 to 12 min for aPCI and 120 min for mPCI. RESULTS: AlPcS2a fluorescence was seen throughout the cytosol following short or long light treatment, corresponding to aPCI and mPCI respectively. Spheroid growth was significantly inhibited or completely suppressed at a mPCI radiance of 0.05 or 0.72 J/cm2 respectively, with all bleomycin (BLM) concentrations used, compared to either BLM alone or aPCI at radiant exposure at these levels. The effects of BLM-aPCI and mPCI were comparable at radiance levels of 0.96 and 1.44 J/cm2. CONCLUSIONS: Results show that mPCI could effectively cause significant spheroid growth inhibition with the delivery of extremely low light irradiance rates delivered over an extended period of time. These findings suggest that effective implementation of mPCI can deliver adequate drug efficacy at depths necessary to reach infiltrating glioma cells in the surgical resection cavity wall.

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 (MaNS) 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 MaNS-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.

Photochemical internalization enhanced macrophage delivered chemotherapy.

BACKGROUND: Macrophage (Ma) vectorization of chemotherapeutic drugs has the advantage for cancer therapy in that it can actively target and maintain an elevated concentration of drugs at the tumor site, preventing their spread into healthy tissue. A potential drawback is the inability to deliver a sufficient number of drug-loaded Ma into the tumor, thus limiting the amount of active drug delivered. This study examined the ability of photochemical internalization (PCI) to enhance the efficacy of released drug by Ma transport. METHODS: Tumor spheroids consisting of either F98 rat glioma cells or F98 cells combined with a subpopulation of empty or doxorubicin (DOX)-loaded mouse Ma (RAW264.7) were used as in vitro tumor models. PCI was performed with the photosensitizer AlPcS2a and laser irradiation at 670 nm. RESULTS: RAW264.7 Ma pulsed with DOX released the majority of the incorporated DOX within two hours of incubation. PCI significantly increased the toxicity of DOX either as pure drug or derived from monolayers of DOX-loaded Ma. Significant growth inhibition of hybrid spheroids was also observed with PCI even at subpopulations of DOX-loaded Ma as low as 11% of the total initial hybrid spheroid cell number. CONCLUSION: Results show that RAW264.7 Ma, pulsed with DOX, could effectively incorporate and release DOX. PCI significantly increased the ability of both free and Ma-released DOX to inhibit the growth of tumor spheroids in vitro. The growth of F98 + DOX loaded Ma hybrid spheroids were synergistically reduced by PCI, compared to either photodynamic therapy or released DOX acting alone.