Selective Inhibition of Osteosarcoma Cell Functions Induced By Curcumin-Loaded Self-assembled Arginine-Rich-RGD Nanospheres

Osteosarcoma is the most frequent primary bone cancer today. Chemotherapy mostly used for the treatment against osteosarcoma can induce high toxicity. Therefore, the objective of this in vitro study was to develop a treatment against osteosarcoma with higher selectivity towards osteosarcoma cells and lower cytotoxicity towards normal healthy osteoblast cells.;Curcumin (or diferuloylmethane) has been found to have anti-oxidant and anti-cancer effects by multiple cellular pathways. However, with its polyphenol groups, it has low water solubility and a high degradation rate in alkaline conditions.;Self-assembled amphiphilic peptides have various applications as novel nanoscale biomaterials including hydrophobic drug delivery. In this study, the ampiphilic peptide C18GR7RGDS was used as a curcumin carrier in aqueous solution. This peptide contains a hydrophobic aliphatic tail group leading to their self-assembly by hydrophobic interactions, as well as a hydrophilic head group composed of arginine-rich and an arginine-glycine-aspartic acid (RGD) structure, which may lead to efficient cell internalization by macopinocytosis and targeting for the overexpressed &agr;nubeta3 integrins on cancer cells. Through the characterization of transmission electron microscopy (TEM), the self-assembled structures of spherical amphiphilic nanoparticles (APNPs) with diameters of 10-20 nm in water and phosphate buffer saline (PBS) were observed, but this structure opened up when the pH value was reduced to 4. Using a method of co-dissolution with acetic acid and dialysis tubing, the solubility of curcumin was enhanced and formed a homogeneous solution with the help of the presently designed APNPs. The successful encapsulation of curcumin in APNPs was then confirmed by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) analysis. Also, the cytotoxicity and cellular uptake of the APNP/curcumin complexes on both osteosarcoma and normal osteoblast cell lines were evaluated by MTT assays and confocal fluorescence microscopy. Most importantly, the curcumin-loaded APNPs exhibited a significant selective cytotoxicity against MG-63 osteosarcoma cells (15% of viability) compared to normal osteoblasts (more than 50% of viability). In this manner, it was demonstrated for the first time that APNPs can encapsulate hydrophobic curcumin in their hydrophobic cores, and the curcumin-loaded APNPs could be an innovative drug for the selective inhibition against osteosarcoma cells than osteoblasts.