Fabrication and process investigation of vancomycin loaded silica xerogel/polymer core–shell composite nanoparticles for drug delivery

Biodegradable polymer–inorganic composites particles can provide significant advantages while avoiding the shortcomings of using polymer or inorganic particles alone as drug delivery vehicles. Most of the existing fabrication methods for polymer nanoparticles and silica xerogel nanoparticles are not applicable for composite nanoparticles. To overcome these difficulties, a novel gelation–emulsion method was successfully developed through the integration of sol–gel and modified double emulsion processes, in which gelation of the silica solution was enabled in nanodroplets generated in the modified emulsion process. Spherical vancomycin loaded silica xerogel/polymer core–shell composite nanoparticles with a tunable size and good drug encapsulation efficiency were fabricated through this novel method. By changing the process variables of the modified double emulsion process in terms of the second sonication time and PVA concentration, the average diameter of the composite nanoparticles could be adjusted in the range of 192–569 nm, with a maximum encapsulation efficiency up to 82.2%. With the introduction of silica xerogel as the primary core material by the sol–gel process, the prepared composite nanoparticles exhibited a higher encapsulation efficiency, lower burst drug release and longer drug complete release time than the polymer nanoparticles by 110%, 37.5% and 230%, respectively, enabling these composite nanoparticles to be better candidates for long-term sustained drug release applications. Formation mechanisms of the composite nanoparticles with respect to the second sonication time and PVA concentration were also discussed.