A Facile Approach to Carbon Dots-Mesoporous Silica Nanohybrids and Their Applications for Multicolor and Two-Photon Imaging Guided Chemo-/Photothermal Synergistic Oncotherapy

Multifunctional nanocarrier-based theranostics have been proposed to overcome some key problems in cancer treatments. In this contribution, a facile approach is reported to synthesize carbon dots-mesoporous silica nanohybrids (named MSNs-CDs) via a one-pot microwave heating reaction of amino-functionalized mesoporous silica nanoparticles (MSNs-NH2) and citric acid in formamide. The MSNs-CDs nanohybrids exhibit capabilities of multicolor/two-photon imaging, high photothermal conversion under NIR laser irradiation (671 nm), and anti-cancer drug delivery, and thus could potentially be applied as a multifunctional nanocarrier-based theranostic agent for cancer. Further studies revealed that CDs were in situ formed on the surface of MSNs during the reaction, which is amenable for the observed multicolor/two-photon imaging and photothermal properties. Besides, the well-preserved MSNs characters of MSNs-CDs nanohybrids (e. g., mesoporous structure, large surface area and pore volume) enable them to be an ideal nanocarrier for delivering anti-cancer drugs, such as doxorubicin (DOX). Importantly, the MSNs-CDs@DOX exhibited pH- (lower pH being preferred) and thermo-responsive DOX release behaviors, which would effectively decrease side effects and meanwhile enhance the efficacy of chemotherapy due to the weak acidic microenvironment of tumor and photothermal effect of the CDs. Finally, in vitro experiments exhibited that the highest therapeutic efficacy was obtained by MSNs-CDs@DOX with NIR irradiation, attributing to the synergistic effect of chemotherapy and PTT. This study not only provides a facile method to prepare CDs and MSNs nanohybrids, but also demonstrates that both of the superior features and functions of CDs and MSNs could be preserved and combined, which are deemed to be beneficial for the development of multifunctional theranostic nanoplatform for cancers