Biomimetic Silica Nanocapsules for Tunable Sustained Release and Cargo Protection

Guang-Ze Yang, David Wibowo, Jung-Ho Yun, Lianzhou Wang, Anton P.J. Middelberg, Chun-Xia Zhao

Silica nanocapsules have attracted tremendous interest for encapsulation, protection and controlled release of various cargoes due to their unique hierarchical core-shell structure. However, it remains challenging to synthesize silica nanocapsules having high cargo-loading capacity and cargo-protection capability without compromising process simplicity and biocompatibility properties. Here, we synthesized oil-core silica-shell nanocapsules under environmentally friendly conditions by a novel emulsion and biomimetic dual-templating approach using a dual-functional protein, in lieu of petrochemical surfactants, thus avoiding the necessities for the removal of toxic components. A light- and pH-sensitive compound can be facilely encapsulated in the silica nanocapsules with the encapsulation efficiency of nearly 100%. Release of the encapsulated active from the nanocapsules was not shown an indication of undesired burst release. Instead, the release can be tuned by controlling the silica-shell thicknesses i.e., 40 and 77 nm from which the cargo released at 42.0 and 31.3% of the initial amount after 32 days, respectively. The release kinetics were fitted well to Higuchi model, enabling the possibility of the prediction of release kinetics as a function of shell thickness thus achieving design-for-purpose silica nanocapsules. Furthermore, the nanocapsules showed excellent alkaline- and sunlight-shielding protective efficacies which resulted in significantly prolonged half-life of the sensitive cargo. Our biomimetic silica nanocapsules provide a nanocarrier platform for applications that demand process scalability, sustainability and biocompatibility coupled with unique cargo-protection and controlled-release properties.