Chromophore-enhanced
photothermal therapy involves the application of an exogenous chromophore in combination with irradiation, using an appropriate wavelength, exposure duration and sufficient irradiances. The chromophore
palladium(II) octabutoxynaphthalocyanine (
PdNc(OBu)8) accumulates at satisfactory concentrations and with good selectivity between both
tumor and muscle and
tumor and skin in
tumor-bearing mice. In an attempt to thermally damage
tumor tissue with concurrent sparing of adjacent normal tissue, the potential of
PdNc(OBu)8 for
photothermal therapy was investigated. Using a Balb/c mouse model with subcutaneously implanted EMT6
adenocarcinoma, 90-100 hours after intraperitoneal application of
PdNc(OBu)8, the
tumor and surrounding tissue were irradiated with a 826nm continuous-wave
diode laser. The thermal effects on
tumor and normal tissue were evaluated histologically. Our results indicate that after
PdNc(OBu)8 administration and
tumor irradiation using 5W/cm-for 100 seconds, pronounced selective heating of the
tumor was achieved in mice, while in control animals merely an unspecific and marginal overall increase in temperature over the entire irradiation area was observed. Histological evaluation of treated areas indicated that the PdNc(OBu)8-targeted
tumor tissue showed severe thermal damage while peripheral tissue like skin and muscle remained largely unaffected. This study shows the potential of creating localized thermal effects by using
PdNc(OBu)8 and continuous-wave light for chromophore-enhanced
photothermal therapy.