N-Doped CDs-GP nanospheres as a drug delivery nanocarrier system with carbon dots and a fluorescent tracer

In this study, a carbon dots-genipin covalent conjugate (CDs-GP) was synthesized, characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and fluorescence spectroscopy (FL). These carbon dots displayed three dimensional spherical structures with uniform diameters, blue fluorescence (excitation/emission maxima at 355/455 nm), and high water dispersion with a zeta potential of +17.1 mV. Moreover, the CDs-GP conjugate showed excellent biocompatibility with HeLa and A549 cells. Furthermore, the blood compatibility of CDs-GP was evaluated by hemolysis, and hemolysis rates were less than 5%. We deem that combining the outstanding properties of GP with CDs could further promote the development of CDs in biological applications, achieving multifunctional CDs with targeting, in vivo imaging and therapeutic-delivery capabilities. Our in vitro results demonstrated the high uptake of the CDs-GP by cells. Significantly, the prepared CDs-GP exhibited strong optical absorbance under 635 nm laser irradiation, thus the present research demonstrated that the prepared CDs-GP could be employed as a near infrared (NIR)-absorbing agent as well as a non-toxic drug carrier, realizing the synergistic treatment of photothermal therapy (PTT) and drug delivery. The release of heparin (Hep) could be selectively stimulated by NIR-light and low pH, enabling intracellular drug accumulation and thereby enhancing the efficiency. Overall, all these data suggest that the CDs-GP conjugate has a potential application as a drug delivery system and PTT agent.