Combination photodynamic therapy of human breast cancer using salicylic acid and methylene blue.

The objective of this study was to evaluate the effects of combination therapy with methylene blue (MB) assisted photodynamic therapy (PDT) and salicylic acid (SA) as chemo-therapy anticancer agent. The binding of salicylic acid to methylene blue was studied using spectrophotometric method. The results show the 1:2 complex formation between SA and MB. The binding constants and related Gibbs free energies o are obtained (Kb1=183.74, Kb2=38.13 and ∆Gb1°=12.92kJ·mol-1, ∆Gb2°=9.02kJ·mol-1). The spectrophotometric results show the improvement in solubilization and reduction prevention for SA and MB in the complex form. These results are in agreements with cellular experiments. The dark toxicity measurements represent the improve efficacy of chemotherapy using combination of SA and MB. The photodynamic therapy results (using red LED as light source (630nm; power density: 30mWcm-2)) show that the cancer cell killing efficiency of MB increases in the combination with SA due to reduction prevention and stabilization of monomeric form of MB.