Phospholipid Self-Assemblies For The Construction Of Biomembranes And Hybrid Materials

The biological cells are the basic structural and functional unit s of all known living organizations.They represent the smallest unit of life and consist of cytoplasm and organelles enclosed within a lipid membrane.In synthetic biology,artificial cells are engineered systems that mimic one or many functions of the biological cell.The construction of full functional artificial cells is still unrealizable due to the complexity of the biological cell.However,certain functions or structures of biological cells can be replaced,supplemented or mimicked with a synthetic entity.One of the most important components of biological cells is the biomembrane,which determines the shape of the cell,the mass transport,as well as singal transfer in and out the cells.The main problem of this research field is the existing artificial models are too simple to mimic the structure and the function of biological cells.This simplicity is caused by the lack of methods of preparation of biomembrane with complex morphologies.To solve this problem,we carried out the following studies.1)The electroformation of Giant Unilamellar Vesicles(GUVs)with controlled size was performed using face to face electrodes.2)The direction of the electric field used in electroformation was investigated to form lipid tubes as high curved membrane models.3)The combination of two different types of electric waves was used to prepare double vesicles as a complex model for eukaryotic cells.4)Incorporation of carbon nanotubes and phospholipids to form biocompatible helical structures as future microrobots for advanced drug delivery.Giant unilamellar vesicles(GUVs)electroformation using plasma-treated Indium Tin Oxide(ITO)electrode surface was investigated at different electric voltages,frequencies,and temperatures using surface response methodology.GUVs from phospholipids with neutral,positive and negative charges were formulated.GUVs can be formed at a wide range of electric potential,frequency,and temperature.However,the size of these GUVs was affected by these parameters,i.e.the GUVs diameter increases with an increase of the electric potential from 1 to 5 V and decreases from 5 to 10 V;GUVs size decrease with increasing the frequency and increase with increasing the temperature.The average diameter of GUVs was determined for each formulation.The acquired data of these GUVs were successfully fitted with quadratic regression models.These models were applied to obtain the parameters for ideal GUVs with wanted diameters by the obtained phase diagrams.Lipid tubes are hollow cylindrical lipid membranes.The construction of such supramolecular hollow tubes has an important role in intracellular transport of protein and ions,which has been observed in a diverse range of cells.The lipid tubes were obtained using a modified electroformation method.The application of an elect ric field paralleling to the lipid film could maximize the electroosmotic flow near the lipid membrane interface.The maximization of the electroosmotic flow near the lipid membrane interface is the responsible force for the formation of lipid tubes.The double vesicles are a promising model to mimic eukaryotic cells,which consists of big GUV encapsulating small one.The preparation of such kinds of vesicles was performed using a successive combination of two electric waves: sinusoidal and amplitude modulated electric field.The lipid domes formed in a sinusoidal electric field.The domes grew into short tubes during the subsequent application of an AM field.These tubes deformed into double vesicles to minimize their free energy following the area-difference-elasticity model.Two forces are involved to explain the mechanism behind tube formation.The pulling force(F)is responsible to drag the domes into tubular vesicles but has to overcome a critical force(Fc).Three important parameters influence the yield of double vesicles: the application time of the sinusoidal signal,the percentage of modulation and the frequencies.The optimization of these parameters allows reaching a maximum yield for double vesicles of 63 %.These vesicles were stable for at least one week.Biomolecular self-assembly plays key role in life system.Herein the double helical DNA-like phospholipid modified carbon nanotubes(phospholi pid@CNTs)structures,first order and secondary helical phospholipid@CNTs hybrids were constructed using self-assembly of phospholipids on carbon nanotubes.The anchored phospholipid molecules on carbon nanotubes created a compressive loading(FL).Once FL is larger than a critical value,known as Euler critical loading(Fc),the phospholid@CNTs hybrids deformed into helical structures.These two forces varied against the carbon nanotube length(L).The phospholid@CNTs deforms when the CNT length is larger than the critical length(Lc).Lc values were calculated to be 2.47 ?m with the CNT wall thickness of 10 nm for the first order deformation,and 16.55 ?m with the CNT diameter of 100 nm for the secondary helical deformation.The micrometer size spring structures from phospholipid modified carbon nanotubes may find potential on biocompatible microrobots or micro swimmers for advanced drug delivery systems.