Preparation of Lysosome-targeting Carbon Dots and Its Application in Cell Imaging

Abstract

The lysosome-targeting carbon dots (CDs) with excellent water solubility and strong blue emission were synthesized through a one-step functional modification for long-term lysosome imaging in living cells. Based on the carboxyl-rich CDs synthesized by oxidizing carbon black in refluxing HNO3, then N,N-dimethylethylenediamine (DMEDA) was chemically linked onto the CDs through acylation reaction to obtain DMEDA modified carbon dots (M-CDs). The infrared spectrum of M-CDs showed the characteristic peak of acylamide (O=C–NH–) at 1658 cm−1, indicating the successful modification of DMEDA. The quantum yield of M-CDs was 15.6%, which was 27 times higher than the initial carboxyl rich CDs, meeting the requirement of cell imaging. The probe entered cells through the temperature-dependent endocytosis way and the co-localization experiment with commercial dye Lyso-Tracker red showed that the probe localized in lysosomes and could be used as a universal lysosome tracker in different cell lines. Moreover, compared to commercially available Lyso-Tracker blue, M-CDs were more photostable under UV light. The fluorescence of M-CDs was still brightness after time-lapsed imaging by confocal microscopy for 120 min with an interval of 5 min in living cells, implying that the M-CDs could be used for long-term imaging of lysosomes.