Fabrication of silica hollow particles using Escherichia coli as a template

Inorganic hollow particles have attracted great interest in recent years due to their unique physico-chemical properties, as well as their potential use in various applications. In this study, we attempted to fabricate hollow particles using a gram-negative bacterium, Escherichia coli, as a biological template. Silica was synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of ammonia following the Stöber process. Silica was smoothly coated to the surface of the bacterial cells. The bacterial template could be removed by calcining at 600 °C. Interestingly, the calcinated particles retained the morphology of the biological cells even though the template was removed. This result indicates that this bacteria template technique enables the synthesis of hollow spheres, rods, wires, and other three-dimensional structures which retain the morphology of the original bacterium.