Photodynamic therapy (PDT) utilizing hematoporphyrin derivative (HPD) and a cw argon-pumped dye laser tuned to 630 nm has been shown to be a promising treatment for a number of forms of cancer. However, because tissue penetration is maximized for wavelengths greater than 700 nm, substantial effort has been directed towards finding new dyes which absorb in the near-ir (670-900 nm). The tuning range of the recently developed Ti:sapphire laser overlaps this regions, thus providing an all-solid-state alternative to the dye laser. The Phase I effort will involve cell-level experiments using two new photosensitizers: sulfonated chloraluminum phthalocyanine (CASPc) and benzoporphryin derivative monoacid A (BPD) which absorb at 680 nm and 690 nm respectively. Although a Ti:sapphire system can be operated either pulsed or cw in this wavelength region, the initial experiments will be performed with a pulsed laser, since the cw Ti:sapphire would produce results that were very similar to the cw dye. Although the primary cause of cell necrosis under cw irradiation is the creation of singlet oxygen, the high intensity levels generated by the pulsed laser may photosensitize by non-oxygen-dependent mechanisms. The long term goal would be to develop a clinically qualified solid-state laser for PDT.
