Chlorin-e6 and Paclitaxel loaded on Keratin based nanoparticles synergically induce cell death of osteosarcoma cell lines in vitro

Introduction. The survival rate of osteosarcoma (OS) patients has very poorly improved during the last decades. This is either due to the high doses of toxic chemotherapeutics required for treatments that in turn damage also... [ view full abstract ]

Introduction. The survival rate of osteosarcoma (OS) patients has very poorly improved during the last decades. This is either due to the high doses of toxic chemotherapeutics required for treatments that in turn damage also key organs, and to the development of chemo-resistance. Nano-formulation of chemotherapeutics has improved both low water solubility of cancer drugs and their selective delivery to the tumor sparing healthy tissues. However, chemo-resistance has been scarcely addressed by nanotechnological formulations, so far. In this work, we tested in vitro whether the efficacy of keratin nanoparticles loaded with paclitaxel (PTX) could be improved if combined with photodynamic therapy.

Methods. Keratin (Ker) based nanoparticles loaded with PTX and with the second-generation photosensitizer Chlorin-e6 (Ce6) were obtained through desolvation (des) and drug-mediated aggregation (ag) methods (PTX-Ce6@Ker_des and PTX-Ce6@Ker_ag respectively) and with different PTX/Ce6 loading ratios. In vitro metabolic and viability assays were performed on three OS cell lines, e.g. MG63, SaOS-2 e U2-OS. Cells were exposed for 24 h to the nanoparticles and then irradiated with a LED light (λ_max = 668 ± 3 nm) for 5 min at RT (fluence 263 J/cm2) and compared to not-irradiated samples.

Results. IC₅₀ values were used to measure PTX release and OS cell cycle blockage from the two nanoparticles formulations. PTX-Ce6@Ker_ag NPs were able to release PTX and block OS cells with a kinetic similar to that of free PTX, whereas PTX-Ce6@Ker_des provided a slower release profile (Fig.1). Cells viability tests show the synergic effect arising from the cytostatic activity of the released PTX and the reactive oxygen species (ROS) produced upon Ce6 irradiation (Fig. 2).

Discussion. Our results prove that our bimodal nanoparticles are able to augment PTX cytotoxicity on different OS cell lines. The proposed multimodal approach once proved to be effective in an in vivo model, would significantly enhance the efficacy of drug based treatments, facilitate the surgical removal of the tumor and increase the life expectancy of OS affected patients.

Acknowledgments. This work is supported by Associazione Italiana Ricerca sul Cancro (AIRC MFAG 2015 id16941 to Serena Duchi).