| Gene therapy introduces functional foreign DNA fragments into target cells in a certain way to help repair or compensate for defective genes,and is expected to play an important role in the treatment of major malignant diseases such as cancer,cardiovascular and cerebrovascular diseases,and hereditary diseases.Under physiological conditions,DNA is large in size and has an electrostatic repulsion with cell membrane,which makes it impossible to pass through the cell membrane alone.Therefore,a key issue in gene therapy is to find a vector to help DNA enter cells and release DNA in cells.Cationic surfactants are capable of self-assembly to form highly positively charged cationic aggregates,neutralize the negative charges of DNA and form smaller complexes with DNA to facilitate smoothly passage through cell membranes.Sugar-based surfactants are safe,non-toxic and environmentally friendly.Gemini surfactants have higher surface activity and lower critical micelle concentration.Therefore,combining their advantages,two kinds of cationic gemini surfactants were synthesized from lactose and glucose.The effects of hydrophobic chains and spacer on surface activity and aggregation properties of surfactants were investigated respectively.The interaction between DNA and surfactants was studied by spectroscopic analysis and dynamic light scattering.The paper is divided into two parts:?.Synthesis of Lactose-based Gemini Surfactants:Synthesis,Surface Activity and Interaction with DNALactose was first reacted with chloroacetyl chloride to form lactose chloroacetate,then quaternized with dodecyl dimethyl tertiary amine,tetradecyl dimethyl tertiary amine and hexadecyl dimethyl tertiary amine to form cationic gemini surfactants 5a,5b and 5c.The surface tension of the three surfactants was measured by platinum plate method.The cmc of these three surfactants were 6.31×10-4,1.78×10-4,5.62×10-5 mol/L,and the?cmc were 27.58,26.01 and 27.34 mN/m,respectively.The increase of hydrophobic chain length can significantly reduce the cmc of gemini surfactants,and for every two additional carbon atoms,the cmc decreases by about 70%.However,the length of hydrophobic chain has no significant effect on?cmc 5a,5b and 5c can form cationic aggregates by self-assembly in water.The sizes of cationic aggregates are 158.8,195.3 and 213.5 nm.Zeta potentials are+5.22,+8.63 and+23.6 mV,respectively.The UV-Vis and fluorescence spectrum analysis showed that the interaction between5a,5b and DNA was very weak.The binding constants Ka were 6.98×104 and1.32×105 L·mol-1,respectively.The interaction between 5c and DNA was strong.Ka was 1.19×107 L·mol-1.Increasing the length of hydrophobic chain was beneficial to enhancing the binding ability between surfactant and DNA.Circular dichroism spectroscopy analysis showed that with the increase of 5c concentration,DNA maintains B conformation,and 5c/DNA complexes self-assemble to form a more compacted?phase.In this process,DNA can be compacted effectively and the hydration diameter of DNA complexes can reach 143 nm.?.Glucose-based Gemini Surfactants:Synthesis,Surface Activity and Interaction with DNAGlucose was first reacted with chloroacetyl chloride to form glucose chloroacetate,then quaternized with cetyl dimethyl tertiary amine,then reacted with 1,4-butanediol,1,6-hexanediol and 1,8-octanediol to form cationic gemini surfactants 10a,10b and10c,respectively.The surface tension of these three surfactants was measured by platinum plate method.The cmc was 4.89×10-5,2.57×10-5,1.32×10-5 mol/L,and the ?cmc was 25.47,27.23 and 29.14 mN/m,respectively.The length of the carbon chain of the spacer has a significant effect on both cmc and?cmc.For the addition of two carbon atoms,the cmc decreases by about 50%and the?cmc increases by about 2 mN/m.They can self-assemble in water to form cationic aggregates with size of 142.7,156.4,187nm,Zeta potential of+12.4,+14.5,+33.6 mV,respectively.It shows that the increase of carbon chain of the spacer not only helps to improve the surface properties of surfactants,but also conduces to form aggregates with a higher multivalent positive charges.The UV-Vis and fluorescence spectrum showed that these three surfactants can interact strongly with DNA.Their binding constants Ka are 7.78×105,2.06×106 and3.25×108 L·mol-1,respectively.Among them,10c with the longest carbon chain has the strongest interaction with DNA,10a and 10b have the weakest interaction with DNA,and the Ka of 10a and 10b is less than 5c,indicating that the gemini surfactants with shorter?less than 4 carbon atoms?or longer?more than 8 carbon atoms?carbon chains have stronger binding ability to DNA,while those with medium length have weaker binding ability to DNA.The circular dichroism spectroscopy showed that DNA maintained B conformation when 10a,10b,10c interacted with DNA,and the minimum hydration diameters of the complexes were 140,133 and 106 nm,respectively.These results showed that surfactants 10a-10c have high compressibility to DNA. |
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