Silk fibroin (SF) modified poly(L-lactide)-poly(ethylene glycol)-poly(L-lactide) (SF/PLLA-PEG-PLLA) nanoparticles were successfully fabricated in a process of solution-enhanced dispersion by supercritical CO2 (SEDS). The SF/PLLA-PEG-PLLA nanoparticles exhibited a composite structure with mean particle size of 634 nm and silk fibroin wrapped with PLLA-PEG-PLLA triblock polymer. Fourier transform infrared spectroscopy (FTIR) measurement indicated that minor secondary structural changes of silk fibroin occurred after the SEDS process. X-ray powder diffraction (XRPD) analysis supported the results of FTIR measurement and also revealed that the SEDS process resulted in a notable decrease in crystallinity of the PLLA-PEG-PLLA. In vitro cytotoxicity evaluation by MTS assay indicated that SF/PLLA-PEG-PLLA nanoparticles exhibited better biocompatibility than PLLA-PEG-PLLA nanoparticles. Fluorescence microscopy observation and flow cytometric analysis suggested that SF/PLLA-PEG-PLLA nanoparticles could be internalized into fibroblasts in a time-dependent manner and also possessed faster cell adhesion and internalization ability than PLLA-PEG-PLLA nanoparticles. In conclusion, SF/PLLA-PEG-PLLA nanoparticles prepared by the SEDS process could be used as potential biomaterials in the biomedical field, especially nanoparticle drug delivery systems. (C) 2014 Elsevier B.V. All rights reserved.