Generation of silk fibroin nanoparticles via solution-enhanced dispersion by supercritical CO₂

A solution-enhanced dispersion by supercritical CO2 (SEDS) was employed to prepare silk fibroin (SF) nanoparticles. The results of 2 4 full factorial experiment indicated that SF nanoparticles with particle size (PS) from 52.5 to 102.3 nm and particle size distribution (PSD) from 0.32 to 0.66 can be fabricated successfully. Moreover, reducing precipitation pressure or increasing concentration of SF solution, flow rate of SF solution, or precipitation temperature can increase PS and PSD of SF nanoparticles. The nanoparticle formation mechanism was elucidated through the formation and growth of SF nuclei in the gaseous miscible phase evolved from initial droplets generated by liquid-liquid phase split. Mass transfer between supercritical CO2 and SF solution superimposed on supersaturation was the most important process parameter affecting nanoparticle formation. Furthermore, Fourier transform infrared spectroscopy and X-ray powder diffraction analysis revealed that SF nanoparticles exhibited predominant random coil and α-helix structure with minor β-sheet conformation.