Solubility enhancement of curcumin via supercritical CO2 based silk fibroin carrier

A silk fibroin-based drug delivery system was fabricated in supercritical CO2 (20 MPa pressure, 1:2 curcumin:silk fibroin ratio, 1% final concentration) to improve the solubility of curcumin. The effects of various parameters, including pressure, curcumin:silk fibroin ratio, and final concentration, on particle size, size distribution, drug loading, and encapsulation efficiency, were investigated. Scanning electron microscopy results showed that the particles had spherical shapes with controllable particle size <100 nm and a narrow size distribution. The highest drug loading and encapsulation efficiencies obtained were 12% +/- 0.62 and 36% +/- 1.9, respectively. An in vitro cumulative release study showed that the solubility of curcumin was greatly enhanced; curcumin was released over 196 h. Furthermore, the release rate could be controlled by changes in the beta-sheet content of the silk fibroin. Fourier transform infrared spectroscopy results indicated that new non-covalent chemical bonds were formed between the curcumin and silk fibroin. X-ray diffraction results revealed the amorphous state of curcumin, which was also confirmed by differential scanning calorimetry and thermogravimetric analysis. In conclusion, the study indicated that the use of supercritical CO2 could be an efficient method for enhancing the solubility of poorly water-soluble drugs. (C) 2015 Elsevier B.V. All rights reserved.