Optimal light dose and drug dosage in the photodynamic treatment using PHOTOCYANINE

SummaryBackgroundTo explore the effective dose range of PHOTOCYANINE, the intensity and duration of irradiation using a 670-nm laser, and changes of local tissues after photodynamic therapy (PDT) in mice with S180 tumors to provide evidence for the clinical application of PDT.Basic methodsKunming mice were administered the photosensitizer PHOTOCYANINE. After the administration of PHOTOCYANINE, irradiation with 670-nm laser had a remarkable inhibitory effect on the growth of the grafted tumor S180.Main resultsWithin the power densities 36–144 J/cm2, the irradiation dose showed a significant dose–response relationship; under the same drug dosage, an increase in irradiation dose could enhance the inhibitory effect on tumor growth. In the groups administered PHOTOCYANINE and irradiated with a 670-nm laser, the temperature of the local surface did not increase remarkably, an effect also seen in the negative control group. Local swelling around the tumor occurred immediately after PHOTOCYANINE administration and laser irradiation, and could last for about 3 days. Vertical resection of the tumors 72 h after irradiation showed that the depth of local-tissue necrosis after PHOTOCYANINE administration and laser irradiation was 5.7–7.5 mm.Principal conclusionsThe efficacy of PHOTOCYANINE was significantly correlated with its dose; under identical irradiation conditions, the increase in drug dose increased the tumor inhibition rate (TIR) within a certain dose range. The efficacy of PHOTOCYANINE also showed significant irradiation-dependent characteristics.