PEI modified orange emissive carbon dots with excitation-independent fluorescence emission for cellular imaging and siRNA delivery

Although carbon dots (CDs) as a promising fluorescent nanomaterial have been studied for nearly twenty years, excitation-independent long wavelength emission CDs are rarely reported and are highly desirable for biomedical applications. Herein, we show that the excitation-independent, bright-orange-emissive, polyethylenimine-modified CDs (PEI-CDs) can be easily obtained by using 1, 2, 4-triaminobenzene and PEI as precursors through a simple hydrothermal method. PEI-CDs prepared under our experimental conditions are low-toxic and safe, and their cellular uptake can be observed via the red fluorescence of PEI-CDs appearing inside cells. Furthermore, PEI-CDs are able to bind spontaneously small interfering RNA (siRNA) to form the nano-complexes by electrostatic attraction. The PEI-CDs-siRNA complexes can effectively deliver the specific siRNA targeting hepatoma-derived growth factor (HDGF) into human glioblastoma cells, and therefore downregulate the expression of HDGF, which is considered as a potential target for glioblastoma treatment. Thus, the excitation-independent long wavelength emission PEI-CDs may constitute a new siRNA delivery carrier with imaging-trackable ability.