Photodynamic action of methylene blue in osteosarcoma cells in vitro

Background: Osteosarcoma is a common malignant bone tumor which threatens the life of young people worldwide. To explore alternative strategy for combating osteosarcoma, a tight-emitting diode (LED) that activates methylene blue (MB) was used in the present study to investigate cell death of osteosarcoma-derived UMR106 cells. Materials and methods: Photocytotoxicity in UMR106 cells was investigated 24 h after photodynamic activation of MB using sulforhodamine B (SRB) assay and light microscopy. Apoptosis induction was observed 24 h after photodynamic treatment using a confocal laser scanning microscopy (CLSM) with Hoechst 33342 staining. The change in mitochondrial membrane potential (MMP) was analyzed using a flow cytometry with rhodamine 123 staining. Results: MB under red tight irradiation caused a drug-concentration (0-100 mu M) and light-dose (0-32 J/cm(2)) dependent cytotoxicity in UMR106 cells. The SRB assay and light microscopy observed a significant decrease in the number of UMR106 cells attached to the bottom of culture well after LED light-activated MB (100 mu M, 32 J/cm(2)). Nuclear shrinkage, chromatin condensation and fragmentation were found in the treated cells by nuclear staining. In addition, flow cytometry showed that the MMP in UMR106 cells was rapidly reduced by photo-activated MB (100 mu M, 32 J/cm(2)). Conclusion: Photodynamic action of MB under LED irradiation could remarkably kill osteosarcoma cells and induce cell apoptosis as well as MMP collapse. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.