Research On Controllable Preparation And Drug-carrying Of Nitrogen-doped Hollow Mesoporous Carbon Nanospheres

Mesoporous carbon nanomaterials with unique characteristics,such as high specific surface area,regular pore structure,low density,perfect thermal and mechanical stability,have become a hot topic in the field of new functional materials.Integrating with the structural advantages of adjustable mesoporous shell and internal cavity,hollow mesoporous carbon nanospheres demonstrated outstanding application value and development potential in the fields of adsorption separation,energy storage and transformation,drug delivery as well as electrochemistry.However,on account of the fact that the construction of hollow mesoporous carbon is mostly based on the hard template method,which is so redundant and time-consuming that it impedes its extensive application.In addition,with the deepening of the research on nanomaterials and the expansion of practical applications,it is necessary for hollow mesoporous carbon materials to behaved adjustable morphology,shell thickness and cavity size.Therefore,exploring a reasonable strategy to realize the controllable preparation of hollow mesoporous carbon still remins great challenges.In this study,mesoporous carbon nanoparticles with hollow structures were prepared by innovatively coupling the double template strategy and emulsion polymerization system.At the same time,by simply adjusting the preparation parameters,the synthesis mechanism of hollow mesoporous materials was deeply explored,and the “Self-generating dual-templates synergistic assembly” strategy was proposed for the first time which opened up new ideas for the design and construction of hollow mesoporous materials.The main research contents of this paper are as follows:(1)Hollow nitrogen-doped mesoporous carbon nanospheres(NMCNs)with tunable internal cavity size were synthesized in a nanoemulsion system by a self-generating dual-template synergistic assembly strategy.Oleic acid and triethanolamine could generate an amphiphilic surfactant(TOA)based on the action of new soap,and subsequently formed a stable oleic acid nanoemulsion droplets,which providing a "flexible" hollow template for hollow mesoporous carbon nanospheres.By adjusting the reaction parameters,the factors affecting the size of the internal cavity and the polymerization mode of the emulsion system were further investigated.The results showed that the size of the inner cavity of the mesoporous carbon nanospheres changed with the addition of oleic acid.By changing the amount of TEA,the dual-template assembly mode can be controlled,so that the internal cavity can be transformed from nothing to something.Adjusting the ethanol/water volume ratio of the system can affect the polymerization mode,so that the surface roughness of the hollow mesoporous carbon nanospheres can be adjusted.In addition,melamine is used as a carbon precursor to realize in-situ doping of nitrogen elements and improve the hydrophobicity of the surface of mesoporous carbon nanospheres.Integrating with large internal cavity,rough surface and high nitrogen content,this kind of mesoporous carbon nanospheres is an ideal candidate for drug delivery.(2)Curcumin(CUR)was used as a model drug to explore the potential of hollow nitrogen-doped mesoporous carbon nanospheres as drug carriers.The formulation and process of the CUR-loaded mesoporous carbon nano-delivery system were optimized through the Box-Behnken response,and the optimal drug loading conditions were determined to maximize drug loading.The drug loading state was investigated by scanning electron microscopy,nitrogen adsorption and desorption isotherms,X-ray diffraction and differential scanning calorimetry.Further,the drug release of the drug-loaded material was investigated at different p H.The results showed that,based on π-π interaction and steric hindrance of mesopores,hollow NMCNs had higher loading capacity for CUR and could significantly improve the release performance of CUR in vitro.The kinetic equation fitting results showed that the in vitro release of CUR/NMCNs fit the Korsmeyer-Peppas model.That is to say,the release mode is mainly based on diffusion and supplemented by swelling,which provides a reference for exploring the diffusion law of poorly soluble drug molecules in mesoporous materials.(3)In vitro biological activities of the prepared mesoporous carbon nanosystem loaded with curcumin were investigated.The biocompatibility of hollow mesoporous carbon nanospheres was evaluated by hemolysis assay and MTT assay,and the uptake capacity of cells to the nanocarriers was analyzed by fluorescence microscopy and flow cytometry.Furthermore,the antioxidant and antitumor activities of curcumin before and after loading were studied by DPPH free radical scavenging assay and MTT assay.The experimental results showed that the hollow mesoporous carbon nanospheres prepared by this method had good biocompatibility,and could significantly improve the amount of drug uptake by cells.Curcumin was loaded by the nanocellular carrier,and its scavenging effect on DPPH and inhibiting effect on liver cancer cells were significantly improved.