Photosensitizer delivery into tissue and cells by simultaneous application of laser-induced stress wave and heating

In order to enhance the efficacy of photodynamic therapy for skin diseases, we previously demonstrated that the simultaneous application of heating and a laser-induced stress wave (LISW) accelerated skin permeabilization of porfimer sodium (Photofim) in in-vivo experiments. In this study, to investigate the uptake of Photofrin by cells within skin, we carried out in-vitro experiments using fibroblast-like cells. Immediately after replacing culture medium with 43 °C phosphate buffered saline solution of Photofrin in a well, the cells were exposed to a LISW that was generated by irradiation of a nanosecond laser pulse onto a target attached on the back of the well. Uptake of Photofrin within the cells was observed with a confocal laser scanning microscope, while the cells were stained with DAPI (4′, 6-diamidino-2-phenylindole) to evaluate the survival rate. The largest uptake was observed for the simultaneous application (heating + LISW) with high survival rates (more than 95 %). These results suggested that Photofrin was transported into fibroblasts within skin. In this method, irradiation of low-fluence laser was effective to enhance uptake, and therefore optical fiber can be used for laser delivery.