Studies On Construction And Functionalization Of Ultrathin Polymer Nanocapsules

Polymer nanocapsules are nanometer-sized hollow polymer spheres,which are important for a wide range of applications including delivery,encapsulation,imaging,and catalysis.Several methods to synthesize such polymer nanocapsules have been reported,which include template synthesis,self-assembly,emulsion polymerization,and core removal of dendrimers.However,most of these methods require either templates or preorganized structures to form a core-shell structure first and subsequent removal of templates or cores to produce a hollow sphere.The above processes are complex and tedious.In this context,a novel and simple method to construct polymer nanocapsules would be a highly desirable alternative.In recent years,researchers have reported a new method for the preparation of ultrathin polymer nanocapsules.This method requires two kinds of monomers.One is a rigid building block with a flat core and multiple polymerizable groups.The other is a flexible linear lingker.Polymer nanocapsules with a highly stable structure and relatively narrow size distribution can form without any preorganization,templates,or emulsifiers.So far,the research on the preparation of the ultrathin polymer nanocapsules is still in the preliminary stage.Whether the method for the construction of ultrathin nanocapsules is universal?Whether chemical bonds have an effect on the construction of polymer nanocapsules?Whether other covalent bonding methods can be used to construct polymer nanocapsules?In addition to covalent bond,can other bonding methods be used to construct polymer nanocapsules?How to functionalize novel polymer nanocapsules?Based on the above considerations,we use supramolecular interaction,dynamic covalent bond,and covalent interaction to connect two kinds of monomers to construct functional ultrathin polymer nanocapsules.The details are as follows:1.Preparation of ultrathin polymer nanocapsules with antioxidant properties based on supramolecular interactionsSupramolecular interactions include a variety of non-covalent interactions,such as multiple hydrogen bond interactions,metal coordination interactions,host-guest interactions,and?-?stacking interactions.The interconnected energies of supramolecular interaction are much lower than the bond energies of traditional covalent bond.Moreover,supramolecular interaction has a dynamic reversible property.In this work,cucurbit[8]uril?CB[8]?is supramolecular host molecular and azobenzene?Azo?and methylviologen?MV?are supramolecular guest moleculars.CB[8]can form a ternary host-guest complex with Azo and MV,which seems to be an ideal platform to conjugate multiple enzymes of cascades in close proximity.This model system has its own merits,including?1?CB[8]can combine two different molecules to introduce the catalytic centers of superoxide dismutase?SOD?and glutathione peroxidase?GPx?.?2?The structural homogeneity of CB[8]-based supramolecular assembly can minimize the coupling deviation between enzyme parameters and structures.?3?The supramolecular assembly has good stability in the cell environment,which facilitate the study of antioxidant at the cell level.2.Preparation of ultrathin polymer nanocapsules with light-harvesting properties based on dynamic covalent bondsThe bond energies of dynamic covalent bonds are between strong conventional covalent bonds and weak supramolecular interactions.Compared with covalent bonds,dynamic covalent bonds can be generated and broken under mild conditions.Compared with supramolecular interaction,dynamic covalent bond is more stable.In this work,schiff base,a dynamic covalent bond,is used to construct artificial light-harvest systems based on ultrathin polymer nanocapsules.In natural light-harvest systems,such as plant cells and photosynthetic bacteria,highly ordered light-harvesting chromophores play an important role in photosynthesis.Solar energy can be collected by light-harvesting chromophores,and turns to electronic excitation energy to reaction centers.In the energy transfer process,the spatial arrangement of the light-harvesting chromophores is related to the energy transfer efficiency.If the distance of light-harvesting chromophores is too close,the light can be quenched.If the distance is too far,the energy transfer efficiency is very low.The polymer nanocapsules are prepared by the reaction of aldehyde group and amino group,in which tetraphenylene?TPE?molecules with aggregation induced luminescence?AIE?properties are rigid molecules and ethylenediamine are flexible linkers.Furthermore,the well-aligned TPE molecules are also developed as donor chromophores in light-harvesting processes.In addition,light energy would not be quenched when the distance of donor chromophores was near enough due to the AIE effect.After subsequent surface modification by porphyrin molecules as acceptor chromophores,an efficient light-harvesting system has been integrally constructed.3.Preparation of ultrathin polymer nanocapsules with anti-tumor properties based on covalent interactionCovalent bonds are chemical bonds formed by sharing electrons between atoms and have strong bond energies.In this work,ultrathin polymer nanocapsules are constructed by covalent cross-linking of tyrosine dimerization catalyzed by horseradish peroxidase?HRP?.We chose photosensitizer porphyrins as the building blocks of ultrathin polymer nanocapsules,so that the nanocapsules can generate singlet oxygen?¹O₂?under near-infrared light for photodynamic treatment?PDT?.The nanocapsules can encapsulate glucose oxidase?GOx?and catalase?CAT?in situ to form GOx/CAT-NCs,because the polymer nanocapsules are formed in water.The GOx/CAT-NCs can be used for the multimodal synergistic cancer therapy,in which GOx can catalyze the decomposition nutriment glucose to produce H₂O₂,and CAT can further reduce H₂O₂ to generate O₂.The original and generated O₂ can be sensitized to¹O₂ by photosensitizer porphyrins when exposed to light.The GOx/CAT-NCs have the effect of hunger and photodynamic theraty for tumor.