Solubility and stability enhancement of curcumin in Soluplus^® polymeric micelles: a spectroscopic study

Abstract

Polymer micelles are considered to be efficient carriers for solubilizing and stabilizing various hydrophobic drugs. In order to address the problem of poor bioavailability of curcumin, a different approach known as solid dispersion technique has been utilized to develop a formulation of curcumin with a novel amphiphilic polymer – Soluplus^®. The mechanism of interaction of curcumin with Soluplus^® has been elucidated using UV–vis absorption and steady-state fluorescence spectroscopy. At a molecular level, the reduced interaction of water molecules with curcumin, in the optimized system led to an enhancement of both absorption and emission intensities of curcumin accompanied by a hypsochromic shift in the fluorescence spectra. Furthermore, stability analysis indicated a much better environment for the drug with less than 3% degradation of curcumin in 3 days. The steady state anisotropy studies confirms the presence of a rigid environment for curcumin upon encapsulation by the polymer. The extra stability of this system can be ascribed to the formation of multiple intermolecular H-bonding interactions between curcumin and Soluplus^® which is proved by IR spectroscopy. Finally, in vitro cell viability assays indicated that it is a highly safe and effective system that could be further screened for a plethora of biological applications.

Graphical Abstract

Keywords:

• Curcumin
• Soluplus
• stability
• solid dispersion
• spectroscopy

Acknowledgment

The authors thank the Department of Science and Technology, Government of India (D.S.T.-PURSE Grant Phase-II) for the funding in the project, the U.S.I.C. and the Department of Chemistry at the University of Delhi for providing the advanced characterization facilities. S.R. thanks University Grants Commission (U.G.C.), Government of India for a Junior Research Fellowship. The authors thank Dr. Abhinav Grover of J.N.U. for extending help in using the Tissue Culture Facilities at J.N.U. and Sameer Sapra of I.I.T., Delhi for helping with the fluorescence anisotropy measurements.

Disclosure statement

The authors declare that they have no conflict of interest.