Biphasic-to-monophasic successive Co-assembly approach to yolk-shell structured mesoporous organosilica nanoparticles

In this work, we report a facile biphasic-to-monophasic successive co-assembly approach to synthesize yolk-shell structured mesoporous organosilica nanoparticles (MONs). The yolk-shell structured MONs possess ethane-bridged frameworks, high surface area (1023m²g^-1), radially oriented mesochannels (3.8nm), large pore volume (0.99cm³g^-1), and tunable diameter (147-324nm) and shell thickness (23-53nm). The biphasic-to-monophasic successive co-assembly method is intrinsically simple and requires neither sacrificial templates nor multistep coating processes. The key of the method is that the interiors of the mesostructured organosilica nanospheres grown in the biphasic system have a lower condensation degree and Si-C-C-Si species content than the outer shells formed in the monophasic system. Thus, the interior layer is attracted by OH^-1 anions and dissolved in the monophasic system, forming the yolk-shell structures. In vitro cytotoxicity and haemolysis assays demonstrate that the ethane-bridged yolk-shell MONs possess excellent biocompatibility. Furthermore, the chemotherapy drug doxorubicin (DOX) is loaded into the yolk-shell MONs to kill drug-resistant MCF-7/ADR human breast cancer cells. Compared with free DOX and DOX-loaded typical MONs, the DOX-loaded yolk-shell MONs have higher chemotherapeutic efficacy against MCF-7/ADR cells, suggesting the great potential of yolk-shell MONs synthesized via the biphasic-to-monophasic successive co-assembly approach in the biomedical field.