Versatile Preparation of Silica Nanocapsules for Biomedical Applications

Abstract

Core–shell nanocapsules are receiving increasing interest for drug delivery applications. Silica nanocapsules have been the focus of intensive studies due to their biocompatibility, versatile silica chemistry, and tunable porosity. However, a versatile one‐step preparation of silica nanocapsules with well‐defined core–shell structure, tunable size, flexible interior loading, and tailored shell composition, permeability, and surface functionalization for site‐specific drug release and therapeutic tracking remains a challenge. Herein, an interfacially confined sol–gel process in miniemulsion for the one‐step versatile preparation of functional silica nanocapsules is developed. Uniform nanocapsules with diameters from 60 to 400 nm are obtained and a large variety of hydrophobic liquids are encapsulated in the core. When solvents with low boiling point are loaded, subsequent solvent evaporation converts the initially hydrophobic cavity into an aqueous environment. Stimuli‐responsive permeability of nanocapsules is programmed by introducing disulfide or tetrasulfide bonds in the shell. Selective and sustained release of dexamethasone in response to glutathione tripeptide for over 10 d is achieved. Fluorescence labeling of the silica shell and magnetic loading in the internal cavity enable therapeutic tracking of nanocapsules by fluorescence and electron microscopies. Thus, silica nanocapsules represent a promising theranostic nanoplatform for targeted drug delivery applications.

Ultrasmall Nanocapsules Obtained by Controlling Ostwald Ripening

“…This size range falls typically in the size range of nanoparticles obtained by the miniemulsion process. When the dispersed phase is composed of TEOS, hexadecane, and an organic solvent (oleic triglyceride, Miglyol 812N, cyclohexane, m ‐xylene, olive oil, or dichloromethane), silica nanocapsules exhibited a diameter ranging from 100 nm to 200 nm [32d] . The size of nanocapsules could be tuned by varying the ratio between the dispersed and continuous phases, or by modifying the surfactant type and concentration [32d] .…”

“…Nevertheless, the lowest nanoparticles size was found to still be relatively large, that is, ca. 45 nm, even with a low amount of dispersed phase and a high concentration of surfactant [32d] …”

Tailoring the mechanoresponsive release from silica nanocapsules

“…They are ideal candidate as a delivery system for various applications 10,21,22 because their properties can be tuned by controlling their shape, size, shell thickness, or chemical composition. [23][24][25] Here, we precisely manufactured SiNCs with a controlled structure (Fig. 1) to yield a class of tunable and controllable mechanoresponsive nanocarriers.…”

In Vitro Studies of Fe3O4‐ZIF‐8 Core–Shell Nanoparticles Designed as Potential Theragnostics

“…Therefore, various coatings have been suggested to enlarge the drug loading capacity of Fe 3 O 4 nanoparticles. These include coating with various polymers, [ 11,12 ] mesoporous silica, [ 13,14 ] or graphene oxide. [ 15 ] Especially, the attempts with the mesoporous silica coating yielded nanoparticles with high drug loading.…”

“…[ 15 ] Especially, the attempts with the mesoporous silica coating yielded nanoparticles with high drug loading. [ 13,14 ] To increase the loading capacity even more and to introduce some additional features such as stimuli‐responsivity and biodegradability, we propose to combine Fe 3 O 4 nanoparticles with metal–organic frameworks (MOFs).…”