Preparation Of Self-functional Carbon-based Dots And Their Application In Biomedical Analysis

Due to the environmently friendly feature and abundance of species,carbon materias(CMs)have attracted great attention in recent years.Compared to macroscopical CMs,such as diamond and graphite,nano-sized CMs usually have proper band gap,so them can emit bright fluorescence(FL)with different colors via tuning their size and surface structure.Carbon-based dots(i.e.carbon dots,CDs)are a new type of fluorescent CMs found by Xu et al.in 2004,and they were widely used in the different fields,such as sensing,FL imaging,photocatalysis,and light-emitting devices.Notably,surface engineering is essential for endowing CDs with useful properties.So far,although a variety of reported works have introduced the covalent and non-covalent modification of extra materials with CDs to obtain functional CDs complexes,there still remain a few reports about the self-functional CDs prepared by one-pot method.Moreover,many CDs have been prepared for imaging of subcellular structures,but little attention has been devoted to investigating the poarlity in the microenvironment of certain organelle.Furthermore,a majority of CDs are designed to target mitochondria or nucleus,but examples of CDs for other organelles with “low-concern”,such as Golgi apparatus and endoplasmic reticulum,are much fewer.Herein,we focused our investigation on the surface functionalization of CDs.And specially,we further introduced three aspects in this paper.1.Preparing self-functional CDs by facile active structure preservation(ASP)method.Since the formation of CDs involves typical condensation,polymerization,and carbonization processes,some other molecules can be retained on the surface of the carbon core to form the CDs,thus it can make the CDs preserve the properties of its origins to some degree,which can be refered as “memory effect”.As a proof of concept for the facile ASP method proposed in this study,we prepared a new type of self-functional CDs through a hydrothermal synthesis route by taking ciprofloxacin hydrochloride as an example.Significantly,the reaction temperature was intentionally controlled below the decomposition temperature of ciprofloxacin hydrochloride to retain the functional antibacterial structure,pH-sensitive sites,and other groups.As identified by MS,FTIR,XPS analysis,we can confirm the existence of ciprofloxacin-like structures on the surface of CDs,thus the CDs not only exhibit effective antibacterial activity towards the bacteria Staphylococcus aureus(Gram-positive)and Escherichia coli(Gram-negative),but also can optically sense pH in the range from 5.02 to 9.91.Besides,FL intensity of the CDs can be enhanced in the presence of Al(III).These results indicate that ASP method is promising to engineer CDs with various functions.2.CDs with self-targeting ability and solvatochromism were used for the FL imaging of Golgi apparatus.Based on the efficient ASP method,we then selected p-phenylenediamine and ethylenediamine as starting materials to prepare the CDs through solvothermal carbonization.The obtained CDs not only show good biocompatibility,but also can selectively target Golgi apparatus in living cells.Besides,due to the high photostability,the CDs are very desirable for observing the morphological dynamics of Golgi apparatus in cell mitosis and apoptosis.Furthermore,the CDs also had a sensitive respond to environmental polarity,so it has the potential superiority in making the monitoring of the polarity-switch of Golgi apparatus successful at the process of cell apoptosis.Additionally,the as-obtained CDs-folate conjugate provides a convenient way for tracing the Golgi apparatus of folate-receptor overexpressed cancer cells.Above study is beneficial for the early diagnosis of the diseases related with Golgi apparatus and can provide the theoretical basis for further research about the Golgi in living cells.3.CDs with green FL were used for the quantitative analysis of solvent polarity and imaging of Golgi apparatus.Although previous study have reported the CDs that have polarity-sensitive emission,it is still a challenge to establish a quantitative analytic method for solvent polarity based on stokes shift of CDs.Herein,we have further prepared a new type of CDs with green emission via one direct facile hydrothermal route by using 4-amino-azobenzene and ethylenediamine as starting materials.Notably,FL intensity of obtained CDs exhibit a sensitive respond to solvent polarity,and their emission remain green colour at a broad polarity range,so a linear plot exists between FL intensity and polarity at the range from 0.265 to 0.306,which indicate that the CDs can be applied to sense other solution polarity.Furthermore,owing to the perfect biocompatibility and photostability of the CDs,they can be used for dynamic observation of the Golgi apparatus in the process of cell-cell fusion.In addition,there was a sharp decrease in emission intensity of the cell treated with ultraviolet(UV)irradiation,which could reflect the dynamic increase of the micropolarity in the Golgi apparatus during apoptosis.In summary,we focused our investigation on the surface functionalization of CDs,in which we used facile ASP method for the preparation.In this study,we discussed the applition of self-functional CDs in antibiosis,Golgi-targeted FL imaging,and detection of pH,Al(III)and environmental polarity.There are two aspects about the novely of our researches.One is the design of ASP method for facilely preparing self-functional CDs.The other one is the development of Golgi-targeted CDs that can observe the morphological dynamics of Golgi apparatus and monitor the variation of micro-polarity in the Golgi during cell apoptosis.