Preparation Of Bioinspired Functionalized Carbon Dots And Their Applications In The Modulation Of Cell Behaviors And Imaging

The physiological behaviors of cells and their interactions with the surrounding environment constitute the basic activities of organic organisms.Therefore,the research of designing nanomaterials based on their physiological environment and composition to achieve the modulation of cell behaviors is helpful to understand the role and influence of materials on organism fundamentally.However,in the process of regulating cell behavior,how to realize the imaging and tracing of cells at the same time to accurately locate their distribution is a new challenge for nanomaterials.In order to solve the above problems of existing materials,carbon dots（CDs）,as quasi-zero-dimensional carbon-based materials were chosen as the research object due to their tunable functions and photoluminescence.Apart from the above problems,there still exist some challenges in the field of CDs.In terms of material selection and synthesis optimization,there is a lack of the idea of using biomimetic inspiration to select other types of precursors to prepare CDs with specific functions.For the properties and applications,it lacks the in situ synthesis method that can build an element,functional groups and spatial structure delivery strategy for achieving the goal of integrating multifunction or targeted imaging;Moreover,it faces challenges in the cost if complex biomacromolecules or organisms are directly selected.Hence,in this paper,we select the sulfonated glycosaminoglycan（GAG）existing in the extracellular matrix,deferoxamine（DFO）which can play a role in both extracellular and intracellular part,and ribosome which only function in the cytoplasm as three kinds of substances.Through the analysis on their structures and functions,we employ some cheap precursors with similar composition and structure to prepare three functional CDs,and then explore their applications in the modulation of cell behaviors and imaging.That is“take”it from cells and use it for cells.This dissertation mainly contains the following three parts:GAG-inspired N,S-co-doped functional CDs are firstly prepared via the in situ method using glucosamine hydrochloride and sodium p-phenylene sulfonate as precursors.The size of CDs with blue emission(λ_em=455 nm)is 3～4 nm,and the absolute quantum yield（QY）is 6.38%,which is due to luminescence of the carbon core state.After entering mesenchymal stem cells（MSCs）via endocytosis,CDs can emit blue fluorescence under 365 nm irradiation and then cell imaging is achieved.Besides,CDs as chemical stimuli can disturb the physiological activities of cells especially in osteogenic/chondrogenic induction medium（CIM）,and then up-modulating the level of reactive oxygen species.Therefore,the expression of alkaline phosphatase（ALP）/type I collagen（Col-I）and GAG/type II collagen（Col-II）related to osteogenic/chondrogenic differentiation are raised,proving that CDs can promote the differentiation of MSCs.This work initially achieved the goal of preparing multi-functional CDs based on the biomimetic inspiration.Considering that the modulation of GAG-inspired CDs towards cells is in the aid of induction medium,2,5-diaminobenzenesulfonic acid and L-aspartic acid（L-Asp）are then employed to prepare DFO-inspired N,S-co-doped functional CDs to explore the modulation effects of CDs on cell behaviors under basic culture conditions or even in the presence of adverse factors.Compared with GAG-inspired CDs,the green emission(λ_em=520 nm)of CDs（5～7 nm）and increased QY（8.62%）are due to the size effect and the increase of conjugation effect in the carbon skeleton,respectively.This DFO-inspired CDs can realize the fluorescence determination of Fe³⁺in the linear range of 10-250μM and the detection limit is 1.51μM.Moreover,this CDs can also achieve the colorimetric detection of Fe³⁺due to the static quenching and fluorescence resonance energy transfer process.After entering cells via endocytosis,CDs mainly stay in the cytoplasm,thus achieving the cytoplasmic imaging.Besides,this CDs can promote the proliferation of three kinds of mammalian cells（MSCs,MC3T3 and L929）based on the role of L-Asp in biosynthesis and the"memory effect"of CDs towards L-Asp.In addition,results show that this DFO-inspired CDs can alleviate the side effect of Fe³⁺overload on cell proliferation（MC3T3）and differentiation（MC3T3 and MSCs）.That is,this CDs can modulate the cell behavior even in the presence of the adverse factors Fe³⁺,thus achieving the goal of"integration of diagnosis and treatment".This work has laid a foundation for the optimization of CDs and expanded the exploration of new applications based on the biomimetic inspiration and the functional groups/structure delivery strategy.Considering that the previous two works can only be used for simple cell imaging,ribosome-inspired CDs are prepared in this work using m-phenylenediamine and diethylenetriamine pentaacetic acid as precursors,to achieve the targeted imaging of subcellular organelles and obtain CDs with higher QY as well.The increased absolute QY（14.73%）of CDs with green emission(λ_em=525 nm)may be due to the synergistic effect the relatively uniform morphology and size of CD and the existence of molecular luminescence mechanism.Imaging results show that the CDs can be internalized in 1min and bind to the nucleic acids through the interaction such as conjugated stacking effect or conformational matching.This work expanded the synthesis strategy of functional CDs for targeted imaging based on the idea of biomimetic inspiration.To sum up,the synthesis and property of functional CDs can be optimized based on the biomimetic inspiration,which not only enriches its functions and applications,but also provides ideas for the design and development of CDs and the exploration of multi-field applications.Meanwhile,it also lays a foundation for the further design of biomimetic nanomaterials which can not only achieve regulation but also dynamically monitor cell behavior to achieve the further clinic applications.