In situ preparation and protein delivery of silicate–alginate composite microspheres with core-shell structure

Abstract

The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS -A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS -A microspheres with a core-shell structure by the in situ method. This is significantly higher than that of pure A or CS -A microspheres prepared by non-in situ method, which lack a core-shell structure. CS -A microspheres with a core-shell structure showed a significant decrease in the burst release of proteins, maintaining sustained release profile in phosphate-buffered saline (PBS) at both pH 7.4 and 4.3, compared with the controls. The protein release from CS -A microspheres is predominantly controlled by a Fickian diffusion mechanism. The CS -A microspheres with a core-shell structure were shown to have improved apatite-mineralization in simulated body fluids compared with the controls, most probably owing to the existence of bioactive CS shell on the surface of the microspheres. Our results indicate that the core-shell structure of CS -A microspheres play an important role in enhancing protein delivery and mineralization, which makes these composite materials promising candidates for application in bone tissue regeneration.

Mesoporous bioactive glasses: structure characteristics, drug/growth factor delivery and bone regeneration application

“…One possible reason is that the drugs may be chelated with calcium on the pore wall, which makes it difficult to be released [37]; the other possible reason is that MBG has superior apatitemineralization ability in biological solution compared with conventional mesoporous SiO 2 materials. The apatite formed on the surface of MBG materials could help in improving drug-loading efficiency, decreasing burst release and release rate [51,62,99]. Therefore, MBG materials show improved drug-delivery ability compared with mesoporous SiO 2 materials.…”

Core–shell designed scaffolds for drug delivery and tissue engineering

“…4d). The most popular is the alginate-based core-shell, where the core is generally evacuated to create alginate capsules by means of co-concentric nozzles or microfluidics [48] (Fig. 4e).…”

Design Strategy for the Multilayer Core–Shell Bioceramics with Controlled Chemistry

“…The co‐extrusion of inorganic/organic hybrid slurry is a simple method to produce bead or complex shape . Researchers have developed Alg beads, ceramic‐Alg hybrid spheres or foams, and spherical ceramic method beads using NaAlg as sacrificial template . Formation of ceramic beads is often assisted by the use of a free dropping system to form spherical beads.…”