One-step hydrothermal synthesis of photoluminescent carbon nanodots with selective antibacterial activity against Porphyromonas gingivalis

Abstract

Carbon dots (CDs) with high quantum yield (QY), low toxicity and good biocompatibility are the major quests of biomedical research. In this paper, we develop a green, simple hydrothermal approach to synthesize water-soluble, nontoxic, highly photoluminescent carbon nanodots (CNDs) from Metronidazole, which possess selective antibacterial activity against obligate anaerobes for the first time. Metronidazole was used as a sole precursor to prepare CNDs at 250 °C (CNDs-250) for 8 h. After the CNDs-250 with an average size of 2.9 nm, consisting of a highly carbon crystalline core and various surface groups were obtained, the formation and fluorescence mechanisms of CNDs were further explored by adjusting the reaction time and reaction temperatures, respectively. Biological experimental data proved that CNDs-250 can only inhibit the growth of obligate anaerobes, such as Porphyromonas gingivalis (P. gingivalis) directly, instead of further functionalization. Besides, CNDs-250 with a QY around 28.1% exhibit an obvious excitation-dependent emission, which will be conducive to multicolor bioimaging. And it may not only develop a new approach for researchers to prepare multifunctional CDs, but also provide a valuable strategy for the theranostics of some diseases as well as other fields.

One‐Step Hydrothermal Synthesis of Nitrogen‐Doped Conjugated Carbonized Polymer Dots with 31% Efficient Red Emission for In Vivo Imaging

“…The peaks at 1568 and 1390 cm −1 are associated with the stretching vibrations of CN and CNC, respectively, which suggest the presence of imine and phenazine structures in CPDs‐50 . Furthermore, NO 2 is observed in CPDs‐50, because HNO 3 could be easily reacted with o PD through the electrophilic reaction under hydrothermal condition. In the 1 H nuclear magnetic resonance ( 1 H NMR) spectrum (Figure S3a, Supporting Information), the obvious aromatic H signals are detected in the range of 7.0–9.0 ppm, and active H signals from NH groups in 6.9 ppm are also observed .…”

“…The high resolution C 1s spectrum (Figure b) reveals four different types of C:CC/CC (284.3 eV), CN (285.0 eV), CO (286.0 eV), and CN (286.9 eV). Moreover, the N 1s spectrum (Figure c) shows four peaks at 398.9, 400.0, 401.7, and 406.5 eV, which could be assigned to Pyridinic N, Pyrrolic N, Graphitic N, and NO 2 bonds, respectively . Then the Fourier transform infrared (FTIR) spectra (Figure d) are used to determine the surface functional groups on the surface of CPDs‐50.…”

“…Synthesis of CPDs from o‐Phenylenediamine : The CPDs were synthesized by hydrothermal method according to the previous work . As for CPDs‐50: 0.5 mmol o PD was dissolved in 10 mL of deionized water (DI water), and added 50 µL (0.725 mmol) HNO 3 , stirred well.…”

“…Cellular Toxicity Test : The cellular toxicity was tested according to the previous work . Mouse osteoblastic cell line MC3T3‐E1 (10 4 cells/150 µL) were cultured in 96‐well plates first for 24 h in an incubator (37 °C, 5% CO 2 ), and for another 24 h after the culture medium was replaced by 100 µL of fresh medium, containing the CPDs‐50 with different concentrations (0, 100, 200, 300, 400, 500, 600 µg mL −1 ).…”

“…Interest in carbon dots (CDs) has increased in recent years due to their simple manufacturing process and unique properties, such as high quantum yield (QY), low toxicity, excellent water solubility, small size, high photostability, and so on . Therefore, they have wide potential applications in many fields, including fluorescent ink, bioimaging, antibacterial activity, optoelectronic devices, and more . However, most of the known CDs show blue light to green light emission under the excitation of ultraviolet (UV) light or blue light, which restrict their further applications in biomedicine and in optoelectronic devices.…”