We have proposed to apply the photosensitization reaction in myocardium interstitial fluid using talaporfin sodium to realize less-heated electrical conduction block for a tachyarrhythmia treatment: PD Ablation®. The cytotoxicity of the extracellular photosensitization reaction efficiency may change by the talaporfin sodium binding with serum proteins. These binding would change with solution temperature. We investigated the binding behavior of talaporfin sodium with human serum albumin (HSA), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) changing solution temperature from 17 to 37°C. We also studied the photocytotoxicity change by solution temperature of 17 and 37°C measuring cell lethality by WST assay using fetal bovine serum. The binding ratio of talaporfin sodium with HDL and LDL decreased 6.3% and 12.8% with temperature increasing from 17 to 37°C. There was no significant difference in the case of HSA. The cell lethality was increased about 30% with temperature increasing from 17 to 37°C. The myocardium tissue temperature increase was reported that less than 5°C in the case of our PD Ablation®. We think that the photocytotoxicity change by these temperature increasing would be negligible in our PD Ablation®. We suggest that the temperature maintaining would be necessary to keep the photocytotoxicity efficiency in the case of the open surgery that would cause the tissue surface temperature decreasing.