Biomimetic Synthesis of Lysozyme−Silica Hybrid Hollow Particles Using Sonochemical Treatment: Influence of pH and Lysozyme Concentration on Morphology

The silica precipitation activity of lysozyme and the possibility of controlling the resulting particle morphologies were investigated. Lysozyme can act as not only a silica precipitation agent but also as a component of the precipitation products, namely, forming a composite of lysozyme and silica. Stirring produced lysozyme−silica hybrid granular particles (L-SHGs), while a sonochemical treatment resulted in lysozyme−silica hybrid hollow particles (L-SHHs). The silica precipitation activity of lysozyme and the formation of L-SHHs occur only around pH 9. At the optimized pH, the lysozyme concentration was found to affect the morphologies of the L-SHHs. Compared with other basic proteins, the foaming properties of lysozyme appear to be a key factor in the formation of hollow structures. The proposed formation mechanisms of L-SHGs and L-SHHs are also discussed.