Investigating the effect of photodynamic therapy on nerves using tissue engineered culture models

Introduction: Photodynamic therapy (PDT) shows potential as an effective treatment for prostate cancer. Clinical observations indicate that this approach causes fewer nerve damage related side-effects than conventional treatments. The aim here is to investigate the effect of PDT on nerve tissue using engineered 3-dimensional cell culture models. Initial experiments focussed on establishing photosensitiser localisation in neurones and Schwann cells, then developing a model for simulating nerve PDT in culture

Reversal of doxorubicin resistance in breast cancer cells by photochemical internalization

Multiple drug resistance (MDR) is a problem that seriously reduces the efficacy of many chemotherapy agents. One mechanism for MDR is increased acidification of endocytic vesicles and increased cytosol pH, so weak base chemotherapeutic agents, including doxorubicin, are trapped in endocytic vesicles and exhibit a drug resistant phenotype. Treatments that selectively reverse this accumulation may therefore reverse the MDR phenotype. Photochemical internalization (PCI) is a novel technology developed for site-specific enhancement of the therapeutic efficacy of macromolecules by selective photochemical rupture of endocytic vesicles and consequent release of endocytosed macromolecules into the cytosol. This study evaluates PCI for release of doxorubicin from endocytic vesicles in MDR cells. Two breast cancer cell lines, MCF-7 and MCF-7/ADR (the latter resistant to doxorubicin), were selected. They were found equally sensitive to photochemical treatment with the photosensitiser TPPS(2a) (disulfonated meso-tetraphenylporphine) and light. On exposure to doxorubicin alone, the IC(50) (drug concentration for 50% reduction in colony formation) was 0.1 mu M for MCF-7 and 1 mu M for MCF-7/ADR. After PCI (photochemical treatment followed by doxorubicin), the IC(50) concentration was 0.1 mu M for both cell lines. Comparable changes were seen with assay of cell viability using 3-(4,5-dime- thyltiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). On fluorescence microscopy in MCF-7/ADR cells, doxorubicin localised in granules identified as lysosomes. After PCI, doxorubicin was released into the cytosol and entered cell nuclei, as was seen in MCF-7 cells without PCI. In conclusion, PCI reversed the MDR phenotype of doxorubicin resistant breast cancer cells by endo-lysosomal release of the drug. The technique is a promising new approach to tackling the problem of MDR. (c) 2006 Wiley-Liss, Inc

Photosensitisation studies of silicone polymer doped with methylene blue and nanogold for antimicrobial applications

Photosensitisation of polymers has important potential clinical applications such as the prevention of catheter-associated urinary tract infections (CAUTIs). Polymers incorporated with methylene blue (MB) and 2 nm gold nanoparticles (AuNPs) are effective in killing bacteria at the surface following low power visible illumination. Studies of medical-grade silicone polymer samples including segments from urinary catheters were carried out to investigate the generation of reactive oxygen species and the involvement of Type 1 and 2 mechanisms. Singlet oxygen was observed using direct phosphorescence detection and hydroxyl radical generation using electron paramagnetic resonance (EPR) spectroscopy; we conclude that both Type 1 and 2 mechanisms can operate with polymeric photosensitisation. Transmission electron microscopy (TEM) directly demonstrated the incorporation of AuNPs at the surface of the silicone. Using silicone doped with MB AuNPs, a ≥3 log10 reduction in the number of viable Staphylococcus epidermidis bacteria was achieved when exposed to low power laser light; prior sterilisation with ethylene oxide (EO) had no influence on efficacy