DNA binding and luminescent response of carbon dots Clara Zehe, Dorottya Kriszan, Susan J. Quinn University College Dublin, Ireland
Carbon dots (CDs) have emerged as an exciting group of materials since their discovery in 2004 1 due to their interesting luminescent properties, low toxicity, environmental compatibility, small size and potential for cost- efficient formation. 2 Chemical composition of the CD core and surface functional groups is tuneable through variation of precursor materials or reaction conditions. Chemical composition along with CD size and heteroatom doping directs the photophysical properties of CDs, however the exact mechanism underlying their luminescence is still subject to debate. 3 The optical response of several CDs has been applied for chemical sensing including the detection of metal cations, anions or small molecules and biological cell and bacteria sensing by luminescence switching, energy transfer or aggregation-induced effects. 2,4 Luminescent switching is especially pronounced in nitrogen rich CDs, which are of particular interest for this study. Interactions of CDs with DNA are becoming an emerging field with only few reports to date. This work highlights the physical and photophysical properties of green and red luminescent N-doped CDs and demonstrates the sensitivity of their luminescence to the presence of DNA. Green luminescent CDs with sizes of 5.8 ± 2.2 nm as determined by atomic force microscopy (AFM) were prepared via a solvothermal method from o-phenylenediamine (oPD). 5 These CDs displayed bright green-yellow luminescence with a maximum at 570 nm and a PLQY of 13.6%. In presence of DNA, they demonstrated luminescent quenching and spectroscopic shifts of absorbance and emission maxima. A particularly strong optical response was observed in the presence of guanine-rich DNA systems including the proto-oncogene cMYC with great selectivity towards the guanine content and G-quadruplex topology. Red luminescent CDs with sizes of 2.8 ± 1.3 nm were prepared via a solvothermal method from the precursors oPD and dopamine (DA). 6 They displayed bright red luminescence with a maximum at 600nm. Their luminescence was strongly quenched in the presence of guanine and adenine rich DNA systems, which indicates a great sensitivity of the luminescence to presence of DNA in solution. The extent of luminescent quenching and optical shifts when CDs interact with DNA with regard to the observed selectivity could be promising tools for environmental sensing and targeted therapy in biomedical samples or cellular environments.
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© The Author(s), 2021
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