A simple transformation from silica core-shell-shell to yolk-shell nanostructures: a useful platform for effective cell imaging and drug delivery

Silica-based yolk-shell nanostructures (SYSNs) are a potential platform of bioimaging and drug delivery for cancer diagnosis and therapy. Herein, a simple, flexible, green and controlled route to SYSNs is developed, in which structurally different silica core-shell-shell nanospheres are firstly prepared via a single step, and then their more porous interlayers are selectively etched by a mild agent (Na2CO3), resulting in the transformation of these silica core-shell-shell nanospheres to SYSNs. In this process, no complicated synthetic processes, special surfactants, corrosive etching agents or high-temperature treatments are involved; moreover, the size, shell thickness, shape and void space of the SYSNs are controllable by simply tuning the synthetic parameters. For cell imaging and drug delivery, the surface of the formed SYSNs is functionalized with fluorescein isothiocyanate (FITC) and polyethylene glycol (PEG), which show excellent biocompatibility and possess sustained drug release properties. Furthermore, the drug loaded nanocomposites can induce breast cancer cell death efficiently, and exhibit a long-term cytotoxicity in vitro, indicating their promising properties as drug carriers for cell imaging and cancer chemotherapy.