Мesoporous microcapsules based on polystyrol SiO2 core/shell nanoparticles: synthesis and functional carrier's properties
A novel method for preparation of hollow silica capsules was developed. The silica capsules with tuned wall thickness were obtained and used as drug carriers for amoxicillin loading and for investigation amoxicillin in vitro release.
V. V. Terekhin1,2
1Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, bld 4, 31 Leninsky prospekt, 119071 Moscow, Russian Federation
2Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoe shosse, 115409 Moscow, Russian Federation
Inorganic hollow microspheres are used in various fields of research and technology, e.g., as containers for drugs [1–4], absorbents , and catalysts . An effective technique for obtaining such capsules is the removal of the core from organic core/inorganic shell composite particles (CPs). Polystyrene (PS) core/SiO2 shell particles are apparently the most widely used CPs. The morphology of the capsules obtained by this method is determined by the structure of the original CPs.
In this study, Stober's method was used to synthesize PS core/SiO2 shell CPs. The dependences of the SiO2 shell structural parameters, including the width, roughness, uniformity, continuity, and porosity, on the conditions of its formation (pH, tetraethyl orthosilicate (TEOS) concentration, reaction time, and the concentration and molecular weight of polyvinylpyrrolidone (PVP)) were determined. It has been demonstrated that variation of these conditions allows SiO2 shells with widths from ~4 to 17 nm and different morphologies to be formed on PS particles (Fig. 1).
The PVP molecules preliminarily absorbed onto the surface of the PS particles have been shown to be incorporated into the SiO2 shell in the course of its formation, which results in pores ~3 nm in diameter. By varying the PVP concentration in the reaction mixture, one can change the number of pores and the specific areas of the surfaces of CPs and SiO2 capsules obtained from them within a wide range.
It has been demonstrated that the resultant mesoporous SiO2 capsules can be used as containers for drugs (here, amoxicillin was used as a model drug). The kinetics of the release of amoxicillin from the loaded capsules was studied under the conditions close to physiological ones (the capsules were incubated in a medium simulating a human biological fluid). The amoxicillin release has been proved to be a diffusion-controlled process, as evidenced by the pattern of dependence of the amount of the drug released on the square root of the incubation time, which was close to linear (Fig. 2). The deviation from a strictly linear dependence is explained by variation of the diffusion coefficients at different stages of the amoxicillin release.
This study was supported by the Federal Targeted Program for Research and Development of the Ministry of Education and Science of Russian Federation (Grant 14.578.21.0054, Contract No. RFMEFI57814X0054).
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