Effect of spacer of cationic gemini surfactant on solubility and stability of curcumin

Curcumin, a potential natural product with a wide range of biological and medicinal properties, limits its application from being used as a promising drug due to its meagre aqueous solubility and stability. The surfactant molecules being amphiphilic in nature, their interaction with curcumin improves the solubility and stability. In this study, curcumin was incorporated with micelles of two gemini surfactants, trimethylene-α,ω-bis(hexadecyldimethylammonium bromide) (G3) and octamethylene-α,ω-bis(hexadecyldimethylammonium bromide) (G8). The critical micelle concentration (cmc) was determined using conductometric and tensiometric studies. The cmc of G8 was found to be higher than the G3. The average hydrodynamic diameter of G3, G8, G3-Curcumin (G3-Cur) and G8-Curcumin (G8-Cur) systems determined using the dynamic light scattering experiment displayed that the incorporation of curcumin into the gemini systems decrease the size of the micelles. The solubility and stability studies revealed that G3 is capable of solubilizing curcumin more efficiently, while the stability of curcumin was substantial in the presence of G8. Fluorescence spectroscopic studies indicated encapsulation of curcumin in the hydrophobic core of G8, whereas, in the case of G3, curcumin is distributed at the micelle-water interface and the hydrophobic core. The DNA binding studies exhibited a superior binding of G8-Cur towards CT-DNA.