RESEARCH PAPER Fabrication of silk fibroin nanoparticles for controlled drug delivery Zheng Zhao • Aizheng Chen • Yi Li • Junyan Hu • Xuan Liu • Jiashen Li • Yu Zhang • Gang Li • Zijian Zheng Received: 17 October 2010 / Accepted: 11 January 2012 Ó Springer Science+Business Media B.V. 2012 Abstract A novel solution-enhanced dispersion by supercritical CO 2 (SEDS) was employed to prepare silk fibroin (SF) nanoparticles. The resulting SF nanoparticles exhibited a good spherical shape, a smooth surface, and a narrow particle size distribution with a mean particle diameter of about 50 nm. The results of X-ray powder diffraction, thermo gravime- try-differential scanning calorimetry, and Fourier transform infrared spectroscopy analysis of the SF nanoparticles before and after ethanol treatment indicated conformation transition of SF nanoparticles from random coil to b-sheet form and thus water insolubility. The MTS assay also suggested that the SF nanoparticles after ethanol treatment imposed no toxicity. A non-steroidal anti-inflammatory drug, indomethacin (IDMC), was chosen as the model drug and was encapsulated in SF nanoparticles by the SEDS process. The resulting IDMC–SF nanoparticles, after ethanol treatment, possessed a theoretical average drug load of 20%, an actual drug load of 2.05%, and an encapsulation efficiency of 10.23%. In vitro IDMC release from the IDMC–SF nanoparticles after ethanol treatment showed a significantly sustained release over 2 days. These studies of SF nanoparticles indi- cated the suitability of the SF nanoparticles prepared by the SEDS process as a biocompatible carrier to deliver drugs and also the feasibility of using the SEDS process to reach the goal of co-precipitation of drug and SF as composite nanoparticles for controlled drug delivery. Keywords Silk fibroin  Nanoparticles  Supercritical CO 2  Indomethacin  Drug delivery Introduction In recent years, much effort has been devoted to fabricate biocompatible polymer nanoparticles for drug delivery. Nanoparticles are particles with lengths less than 100 nm in 2D or 3D (Lewinski et al. 2008). Many investigations have emphasized the significance of their size and revealed the advantages of nanopar- ticles over larger particles of the same material (Meclean et al. 1998). In general, they have a relatively higher intracellular uptake compared to microparticles (Panyam and Labhasetwar 2002); nanoparticles drug delivery can also decrease side- effects and enhance drug bioavailability (Schafer et al. 1992; Sundar et al. 2010); and nanoparticles can be Z. Zhao  A. Chen  Y. Li (&)  J. Hu  X. Liu  J. Li  Y. Zhang  G. Li  Z. Zheng Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China e-mail: tcliyi@polyu.edu.hk A. Chen College of Chemical Engineering, Huaqiao University, Xiamen 361021, Fujian, China 123 J Nanopart Res (2012) 14:736 DOI 10.1007/s11051-012-0736-5