Preparation of novel self-assembled coordination nanoparticles from surfactants and gadolinium ion to stabilize curcumin derivatives in buffered solution

Abstract

Curcumin is a natural polyphenol found as a major pigment extracted from turmeric rhizomes (Curcuma longa Linn.). Effective inhibition of the growth of cancer cells by curcumin Is relatively high. However, the disadvantages of curcumin derivatives are water-insolubility and instability resulting in exceedingly poor bioavailability. In this study, we have reported novel coordination nanoparticles prepared by self-assembly of surfactants and gadolinium ion (Gd³⁺) to stabilize curcumin derivatives in buffer solution. Effects of various buffers including HEPES, MOPS, Tris and phosphate and various surfactants including SDS, CTAB and Triton X-100 towards the morphology and structural properties of the nanoparticles were investigated by FT-IR, SEM, TEM, XAS, ICP-AES and XRD techniques. It was found that formation of coordination nanoparticles from Gd³⁺ , SDS and HEPES, namely, GdSH CNPs showed excellently uniform spherical nanoparticles and a possibly suitable candidate for biological tasks. Moreover, the curcumin derivatives encapsulated in self-assembled coordination nanopariticles were prepared and than characterized by UV-visible, fluorescence and FT-IR spectroscopies. The stability of curcumin derivatives was also examined by both of UV-visible and fluorescence spectroscopies and the results showed that the decrease of the normalized fluorescence intensity of curcumin incorporated in coordination nanoparticles was less than 2-fold that of free curcumin during the 2 h period. As compared to the corresponding cytotoxicity assay studies of free curcumin in DMSO and HEPES buffer solution with IC₅₀ values of 10 µg/mL and non-toxicity, respectively, GdSH CNPs can enhance in vitro anti-cancer activity of curcumin to SW620 colon cancer cells with IC₅₀ values of 8.0 µg/mL in term of cucumin-equivalent dose. Additionally, as the results of the confocal fluorescence images, the curcumin immobilized GdSH CNPs could be immediately taken to cancer cells and enhanced the fluorescence brightness. In these approaches, our novel nanoparticles would be beneficial to further development of stability of curcumin for biological tasks.