Curcumin nanoemulsion as a biocompatible medium to study the metal ion imbalance in a biological system

Abstract

Metal imbalance in the human body especially iron causes neurodegenerative disorder included Parkinson's disease, multiple sclerosis and Alzheimer's disease and leads to compromised antioxidant function. The metal chelator drug molecules have the ability to reduce neurodegenerative disorders. Therefore, the aim of the present study is to measure the effectiveness of curcumin ligand for the detection of metal ions i.e. Fe2+, Fe3+, Mn2+, Co2+, Cu2+, and Gd3+ in oil in water nanoemulsion (NEm). The binding of curcumin with different metal ions at 298.15, 303.15, and 308.15 K has been analyzed using fluorescence and UV–visible absorption spectroscopy. The photoluminescence emission spectrum of curcumin shows unique behavior with different metal ions. The metal ions such as Fe2+, Fe3+ and Cu2+ quenches the fluorescence intensity of curcumin whereas the metals like Mn2+, Co2+, Hg2+ and Gd3+ enhances the fluorescence intensity of curcumin. Fe2+, Fe3+ and Cu2+ display strong binding nature compared to other metal ions and bind with curcumin in the stoichiometry ratio, 1:2 (Fe2+, Fe3+/curcumin) and 1:1 (Cu2+/curcumin), respectively. Stern–Volmer plots used for the quenching mechanism depict, Fe2+ and Fe3+ quench the photoluminescence intensity of curcumin by combining static and dynamic mechanisms, whereas with Cu2+ it was found to show dynamic quenching only. All other metal ions (Mn2+, Co2+, and Gd3+) indicated weak coordination with curcumin molecules.