A new approach to the drug release kinetics of a discrete system: SiO2 system obtained by ultrasonic dry spraying

Mesoporous silica materials have already proved to be non-toxic and biocompatible, and also to have large pore volume and very high specific surface area suitable for loading of small molecules. Having this in mind and the fact that silicon dioxide (SiO2) powders can be so designed to obtain particle structures organized at multi levels, SiO2 was chosen as a potential carrier for metronidazole, an antibiotic drug. SiO2 powder was synthesized in two stages: first silica sol was prepared by hydrothermal synthesis and second the sol was converted into powder by dry spraying with simultaneous incorporation of the antibiotic into its structure. Scanning and transmission electron microscopy study revealed very complex structure and sub-structure of SiO2 particles. Cell viability tests were used for estimation of cytotoxicity of so synthesized SiO2. The drug release data showed that the system can provide drug release for a long time. Also, the device behavior is fully predictable, according to our theoretical model of multilevel structure design, and gives many opportunities for model investigations of drug release and its kinetics. The pore sizes and their distribution were observed as a limiting factor of drug release kinetics. Therefore, as the pore sizes are given as a set of discrete values, the kinetics of drug release might also be given as a set of corresponding discrete values.

► We suggested a new approach to the kinetics of drug release. ► Close relationship between sub-structure of silica particles as drug carriers and rate of drug release. ► Discrete kinetics as a special field of drug release kinetics. ► The agreement between theoretically predicted and experimentally obtained data.