Production of submicron silk particles by milling

•Achieved less than 300 nm silk particles by milling silk fibres•Achieved narrow particle size distribution with all particles less than 1 μm•New understanding on silk particle aggregation and control•Size reduction achieved is vital for applications such as drug delivery system.

Bead milling was used to produce nano silk particles from silk fibres. Silk fibres were first milled to volume median particle size d(0.5) of 7 μm using an attritor mill. It was followed by bead milling to prepare submicron particles. Several processing parameters including milling speed, milling time, bead load, and pH were examined to reduce the particle size in the bead mill. It was found that, at pH 10 and using optimized milling parameters, d(0.5) could be reduced from 7 μm down to about 200 nm, with a narrow particle size distribution.

Graphical abstractA method for fabrication of sub-micron silk particles by a combination of attritor and bead milling processes is discussed. Particles with a volume median particle size, d(0.5), of ~7 µm was produced by attritor milling and subsequently reduced to ~0.2 µm with narrow particle size distribution using bead milling. Particle size was controlled by adjusting the pH and milling time.Figure optionsDownload full-size imageDownload as PowerPoint slide