Study On Silica Colloidosome Structure Control And Transmembrane Catalysis

A cell is the most fundamental living unit,which has unique dynamic biological membrane structures.Biological membranes of a cell not only act as the barrier to the internal environment,but also divide the organism into regions as functionalized compartments,which allows countless biochemical reactions can be carried out without interference with each other.More complex biological functions are carried by the embedded proteins and lipid molecules in the membrane.Biological membranes constructed by imitating nature has become a hot spot in the field of biology,chemistry,and materials science.In scientific research and industry,various structures that mimic the compartmentalization of biological membrane,such as liposomes,polymer vesicles,and colloidosomes,have been used in biomimetic encapsulation,drug delivery,catalysis,and biosensing.The colloidosome composed of colloidal particles has attracted people’s interest because of its good stability and robustness.A colloidosome is composed of a shell structure formed by the compact assembly of nanoparticles at the oil-water interface.This microstructure imitates biological membrane in function,but it is more similar to micelles formed by surfactant selfassembly at oil-water interfaces in assembly principle and structure.Because the easy formation,adjustable shell thickness and permeability,and advantages in mechanical strength and biocompatibility,colloidosome has attracted extensive attention.In this paper,biomimetic colloidosome was prepared by imitating the structure and function of biological membrane,and its influencing factors were explored in detail.（1）Inspired by the strategies of micelle self-assembly,a series of studies were carried out on the self-assembly behavior of colloidosome using amphiphilic silica nanoparticles（Si O2 NPs）as the structural unit and stabilizer.The regulation mechanism of colloidosomes properties was explored by adjusting four factors: the length of alkyl chains on the surfaces of Si O2 NPs,the polarity of oil solvents,the size of Si O2 NPs,and the mass ratio of Si O2 NPs to water.And a series of water-in-oil colloidosomes with controllable size in the range of 2 μm-11 μm were prepared.On this basis,a colloidosome microreactor encapsulated with glucose oxidase was constructed.The effects of reactor type and performance on enzyme catalytic efficiency in transmembrane reaction were studied by changing colloidosomes with different surface modification and sizes.It was found that the surface tension required to stabilize the emulsion is a key factor in controlling the size of the colloidosomes.When Pickering emulsions are formed,the size of the colloidosomes decreases as the interfacial tension provided by the surfactant decreases.Using glucose catalyzed by glucose oxidase as a model reaction,the concentration of hydrogen peroxide produced increases with the decrease of colloidosome size.This work demonstrates that the amphiphilic structure of Si O2 NPs can greatly regulate the permeability of biomimetic cell membranes.（2）On the basis of the above work,we also prepared hybrid colloidosomes by mixing two different sizes of Si O2 NPs（7 nm,22 nm）.The total mass of Si O2 NPs of two sizes remains the same.They are prepared by mixing according to the mass ratio of 6:1,4:1,2:1,1:2,1:4 and 1:6 to explore whether they can be assembled together to form stable colloidosome structures and the influence of the proportion on the colloidosome size.The hybrid colloidosome was prepared as a microreactor with 22 nm to 7 nm particles in the proportion of 4:0,3:1,2:2,1:3 and 0:4.The properties of the colloidosome and the encapsulation effect on the enzyme were evaluated.The results show that when the second structural unit is introduced as a stabilizer,the stable surface tension of droplets and the spatial arrangement of particles are the main reasons for adjusting the size of colloidosomes.The experience of micelle system can be used as a reference for the study of colloidosomes.