Design Synthesis Of Long Wavelength Fluorescent Carbon Dots And Their Applications In Lysosome Imaging

Carbon dots(CDs)is a new type of carbon nanomaterial with excellent properties such as low toxicity,light stability and adjustable photoluminescence,which is considered to be one of the most suitable fluorescent probes for biological imaging.However,most of the reported CDs show strong emission in the blue-green region,which not only has strong autofluorescence fluorescence,but also causes radiation damage to tissues and cells.It is an urgent problem to construct long wavelength fluorescent CDs in the application of bioimaging.Lysosome is the digestion room of cells.Monitoring lysosomal microenvironment and active molecules is of great significance for understanding the biological function of lysosome and the diagnosis and treatment of related diseases.O-phenylenediamine is easy to polymerize by itself and is one of the most commonly used carbon precursors for the synthesis of CDs.In combination with the above problems,the aim of this study is to construct long wavelength lysosome targeted CDs,and o-phenylenediamine derivatives are designed as carbon precursors to prepare three kinds of fluorescent CDs with different emission wavelengths by enhancing the electron donor ability of carbon precursors.Lysosome targeting and cell imaging of CDs are studied in detail,which provides important reference and design basis for the synthesis of long wavelength lysosomal targeted CDs and clinical monitoring of lysosome.The contents are as follows:1.Yellow fluorescent CDs prepared by N-methyl-1,2-phenylenedimaine and the study of ultrafast and wash-free lysosome imaging.Based on the design strategy of enhancing the electron donor ability of N atom of ophenylenediamine,the Me-CDs with red shift 15 nm was prepared using N-methyl-1,2-phenylenediamine hydrochloride.Me-CDs is rich in amino group and has excellent anti-photobleaching,cell permeability and biocompatibility.Me-CDs was mainly enriched in lysosome(within 20 s)through clathrin-mediated endocytosis and had the solvation effect of fluorescence quenching in polar solvent,thus can be used for wash-free imaging in weak polar cell environment.Me-CDs has been successfully used to monitor cell apoptosis and zebrafish imaging due to the excellent properties.2.Orange fluorescent CDs prepared by N-phenyl-1,2-phenylenediamine and their applications in lysosome polarity.In order to further verify that the red shift of wavelength can be achieved by enhancing the electron donor ability of the carbon source,the orange fluorescent CDs(Ph-CDs)with 595 nm emission wavelength were successfully prepared using Nphenyl-o-phenylenediamine with stronger electron donor ability.The structure and composition,spectral properties,cell imaging and endocytosis of Ph-CDs were studied through various analytical methods.The results showed that the Ph-CDs also had excellent anti-photobleaching,cell permeability and ultrafast wash-free lysosome imaging.Ph-CDs showed sensitivity to polarity and was successfully used for the monitoring of cell polarity and zebrafish imaging.3.Red fluorescent CDs prepared by N-phenyl-p-phenylenediamine and precise recognition of lysosome polarity.In order to further prove the applicability of the design strategy and prepare longer wavelength CDs,the red fluorescent CDs(PPh-CDs)with red shift 25 nm(compared with CDs prepared by p-phenylenediamine)was prepared using N-phenyl-pphenylenediamine.The emission of PPh-CDs is 620 nm and the Stokes shift is 100 nm.In addition to the same performance as the above CDs,PPh-CDs also can accurately identify polarity.The fluorescence intensity and polarity of PPh-CDs are linear in the range of 0.230-0.300((35)f),which has been successfully used for accurate detection of polarity in cells.