The present invention relates to a method for preparing controllably biodegradable silica fibres. The method comprises spinning the fibres from a silica sol, the viscosity of the sol being controlled. Further, the present invention relates to controllably biodegradable silica fibres prepared according to the invention and methods for controlling the biodegradability of the fibres. The invention also relates to controllably biodegradable fibres as sustained and/or controlled release delivery devices for biologically active agents, and to pharmaceutical preparations comprising such devices.
