Fluorescent porous carbon nanocapsules for two-photon imaging, NIR/pH dual-responsive drug carrier, and photothermal therapy

An efficient nanomedical platform that can combine two-photon cell imaging, near infrared (NIR) light and pH dual responsive drug delivery, and photothermal treatment was successfully developed based on fluorescent porous carbon-nanocapsules (FPC-NCs, size ∼100 nm) with carbon dots (CDs) embedded in the shell. The stable, excitation wavelength (λex)-tunable and upconverted fluorescence from the CDs embedded in the porous carbon shell enable the FPC-NCs to serve as an excellent confocal and two-photon imaging contrast agent under the excitation of laser with a broad range of wavelength from ultraviolet (UV) light (405 nm) to NIR light (900 nm). The FPC-NCs demonstrate a very high loading capacity (1335 mg g(-1)) toward doxorubicin drug benefited from the hollow cavity structure, porous carbon shell, as well as the supramolecular π stacking and electrostatic interactions between the doxorubicin molecules and carbon shell. In addition, a responsive release of doxorubicin from the FPC-NCs can be activated by lowering the pH to acidic (from 7.4 to 5.0) due to the presence of pH-sensitive carboxyl groups on the FPC-NCs and amino groups on doxorubicin molecules. Furthermore, the FPC-NCs can absorb and effectively convert the NIR light to heat, thus, manifest the ability of NIR-responsive drug release and combined photothermal/chemo-therapy for high therapeutic efficacy.