Evaluation of photodynamic effect of Indocyanine green (ICG) on the colon and glioblastoma cancer cell lines pretreated by cold atmospheric plasma

•Investigation the effect of CAP pretreatment prior to photodynamic therapy on induction of cell death.•Using ICG as a photosensitizer for PDT and a PTT agent that also has thermal effects and evaluation of photothermal and photodynamic effect of ICG on colorectal and glioblastoma cell lines.•Election of a photosensitizer that its absorption spectrum overlaps with CAP emission spectrum. Cold Atmospheric Plasma (CAP) has been proposed as a new approach based on its anticancer potential. However, its biological effects in combination with other physical modalities may also enhance efficiency and expand the applicability of the CAP method Photodynamic Therapy (PDT) may be improved by the use of indocyanine green (ICG) photosensitizer with absorption wavelength in the near infrared region to allow for deeper treatment depth.. In this study, the effectiveness of cold atmospheric helium plasma (He-CAP) as a pretreatment on the efficiency of ICG mediated PDT was investigated. First, toxicity of different concentrations of ICG on HT-29 and U-87MG cell lines was examined for 24 h. IC10 and IC30 of ICG were determined and then cells were treated with this ICG concentrations with different plasma radiation doses and light exposures for 48 h. Finally, MTT assay was performed for all treatment groups. The experiments were repeated at least 4 times at each group for two cell lines, separately. In order to compare the results, several indicators such as treatment efficiency, synergistic ratio, and the amount of optical exposure required for 50% cell death (ED50) were also defined. Finally, SPSS 20 software is used for statistical analysis of data. Pretreatment with CAP could significantly reduce cell survival in both cell lines (P