Fluorescence imaging of biological systems in the second near-infrared window (NIR-II) has recently drawn much attention because of its negligible background noise of autofluorescence and low tissue scattering. Here we present a new NIR-II fluorescent agent, graphene quantum dots dual-doped with both nitrogen and boron (N-B-GQDs). N-B-GQDs have an ultra-small size (~ 5 nm), are highly stable in serum, and demonstrate a peak fluorescent emission at 1000 nm and high photostability. In addition to the NIR-II imaging capability, N-B-GQDs efficiently absorb and convert NIR light into heat when irradiated by an external NIR source, demonstrating a photothermal therapeutic effect that kills cancer cells in vitro and completely suppresses tumor growth in a glioma xenograft mouse model. N-B-GQDs demonstrate a safe profile, prolonged blood half-life, and rapid excretion in mice, which are the characteristics favorable for in vivo biomedical applications.

Applications of hydrophobic drug-based nanocarriers (NCs) remain largely limited because of their low loading capacity. Here, we report development of a multifunctional hybrid NC made of a magnetic Fe3O4 nanoparticle core and a mesoporous silica shell embedded with fluorescent carbon dots (CDs) and paclitaxel (PTX), and covered by another layer of silica. The NC is prepared via a one-pot process under mild condition. The PTX loading method introduced in this study simplifies drug loading process and demonstrates a high loading capacity as a result of the mesoporous silica dual-shell structure, supramolecular π-stacking between the conjugated rings of PTX molecules and aromatic rings of the CDs in the hybrid NC. The CDs also serve as both confocal and two-photon fluorescence imaging probes, while the Fe3O4 core serves as an MRI contrast agent. Significantly, NC releases PTX in response to NIR irradiation as a result of local heating of the embedded CDs and the heating of CDs also provides an additional therapeutic effect by thermally killing cancer cells in tumor in addition to the chemotherapeutic effect of released PTX. Both in vitro and in vivo results show that NC demonstrates high therapeutic efficacy through a synergistic effect from the combined chemo-photothermal treatments.

Nanostructured materials that have low tissue toxicity, multi-modal imaging capability and high photothermal conversion efficiency have great potential to enable image-guided near infrared (NIR) photothermal therapy (PTT). Here, we report a bifunctional nanoparticle (BFNP, ~16 nm) comprised of a magnetic Fe3O4core (~9.1 nm) covered by a fluorescent carbon shell (~3.4 nm) and prepared via a one-pot solvothermal synthesis method using ferrocene as the sole source. The BFNP exhibits excitation wavelength-tunable, upconverted and near-infrared (NIR) fluorescence property due to the presence of the carbon shell, and superparamagnetic behavior resulted from the Fe3O4 core. BFNPs demonstrate dual-modal imaging capacity both in vitro and in vivo with fluorescent imaging excited under a varying wavelength from 405 nm to 820 nm and with T2-weighted magnetic resonance imaging (r2 = 264.76 mM −1 s−1). More significantly, BFNPs absorb and convert NIR light to heat enabling photothermal therapy as demonstrated mice bearing C6 glioblastoma. These BFNPs show promise as an advanced nanoplatform to provide imaging guided photothermal therapy.