【作者】 张弛；

【导师】 白光月；

【作者基本信息】 河南师范大学 ， 化学， 2019， 硕士

【摘要】 具有短链间隔基团的双子型表面活性剂能够形成蠕虫状胶束,在适合的胶束长度和排列条件下,宏观上表现为凝胶形态,对生命科学、药物输送和材料科学等领域具有潜在的应用价值。本论文利用间隔基团为两个亚甲基的14-2-14阳离子gemini表面活性剂分别制备了pH为酸性和中性的两种温度响应的小分子凝胶体系,对凝胶形成的浓度、温度及凝胶的粘弹性质进行了研究。由于所制备的凝胶具有良好的剪切变稀行为,因此研究了α-糜蛋白酶的凝胶化包封。对凝胶化的酶的活性及凝胶的粘弹性质进行了表征。酶对于生物体来说是维持生命活动不可或缺的重要物质,稳定和提高酶活性在生物及医学领域有重要的应用价值,本工作是小分子凝胶在生物活性制剂方面应用研究的基础。主要研究内容如下:1.表面活性剂酸性凝胶的制备和性质季铵盐型阳离子gemini表面活性剂的聚集形态几乎不受溶剂的pH值影响,能够用于制备酸性体系的凝胶,从而可以在生物体内某些极限酸性环境下应用。为了增强凝胶的稳定性和生物相容性,以尿苷-5’-单磷酸（UMP）作为酸性添加剂,与阳离子gemini表面活性剂14-2-14以14-2-14/UMP摩尔比1:1混合制备水凝胶。14-2-14/UMP凝胶有三个温度响应的相区,在温度低于T_m-gel-gel=27℃时为白色的亚稳态凝胶,高于T_gel-sol时为粘滞性流体,在T_m-gel-gel和T_gel-sol温度之间为稳态凝胶。用差示扫描量热法（DSC）研究得到了亚稳态向稳态凝胶相转变的温度T_m-gel-gel、转变焓?H_m-gel-gel及稳态凝胶向溶胶转变的起点温度T_gel-sol。DSC实验结果显示,T_m-gel-gel和T_gel-sol均随着体系浓度增大而逐渐增大。流变学测量结果表明14-2-14/UMP凝胶体系具备典型的蠕虫状胶束流变特征,体系的结构随浓度增大逐渐增强。扫描电镜（SEM）结果显示了凝胶体系表面具有蜂窝状结构,表明了三维网络结构的存在。2.14-2-14/UMP凝胶体系与α-糜蛋白酶（α-CT）的相互作用研究用DSC技术研究了α-CT在纯水和低浓度的14-2-14/UMP中的热变性行为。实验结果表明14-2-14/UMP的加入降低了酶的变性温度T_m和转变焓?H,说明表面活性剂中影响了酶构象的稳定性,使其更容易展开。对于高浓度14-2-14/UMP的凝胶体系,流变实验结果表明,体系仍旧表现特征性的蠕虫状胶束行为,但是胶束长度变短,纠缠密度降低。体系的零剪切粘度η₀随α-CT浓度的增大逐渐降低。用紫外可见光谱法研究了14-2-14/UMP凝胶体系对α-CT活性的影响,分别用溶胶-凝胶法、两相凝胶化方法和凝胶-凝胶化方法将酶包封在凝胶中,结果表明,在酸性环境下,凝胶对酶活性具有较好的保护作用。3.14-2-14缓冲溶液体系与α-糜蛋白酶相互作用研究选用中性14-2-14/PBS凝胶体系来装载α-CT。实验结果表明,14-2-14/PBS凝胶体系对α-CT具有一定的装载和保护性,且保护能力受凝胶结构的稳定性影响。凝胶在该培养温度下越稳定,则装载效果越好,凝胶体系浓度越大,α-CT保护效应越强。流变学测量表明14-2-14/PBS凝胶体系在粘弹性质上表现出了蠕虫状胶束的特征变化。由实验结果可推测随体系浓度增大,体系中胶束的纠缠密度逐渐升高。随着添加的α-CT浓度增加凝胶的η₀逐渐降低、牛顿平台逐渐变长、相转变温度T_gel-sol逐渐降低。由于酶和表面活性剂胶束之间存在弱相互作用,改变了胶束的长度和纠缠方式。更多还原

【Abstract】 Gemini surfactants with short chain spacer groups can form wormlike micelles.Under the suitable micelle length and arrangement conditions,the gel morphology can be obtained.This has potential application in life science,drug delivery and material science.In this thesis,two kinds of small molecular gel systems at acidic and neutral pH were prepared by 14-2-14 cationic gemini surfactants with two methylene spacer groups,respectively.The concentration and temperature of gel formation and the viscoelastic properties of gel were studied.According to the obvious shear thinning behavior of the prepared gel,α-chymotrypsin was encapsulated in the surfactant gel.Then the activity of encapsulated enzyme and the viscoelastic properties of the gel in the presence of enzyme were characterized.Enzyme is an indispensable substance for organisms to maintain their lives,and it is of great application value to stabilize and improve enzyme activity in the field of biology and medicine.This work is the basic research on the application of small molecular gel with bioactivity.The main research contents are as follows:1.Preparation and properties of surfactant acidic gelThe aggregation morphology of quaternary ammonium cationic gemini surfactants doesn’t change in the solvent with different pH value and is useful for preparing the gel of acidic system.Thus,it can be used in some extreme acidic environments in organisms.In order to enhance the stability and biocompatibility of the gel,uridine-5 monophosphate（UMP）was used as acid additive.The hydrogel was prepared by mixing cationic gemini surfactants 14-2-14 and UMP at a molar ratio of 1:1.The gel exhibits three phase regions corresponding to ambient temperature,a white metastable gel below T_m-gel-gel=27°C,a viscous sol above T_gel-sol,and a stable state gel between T_m-gel-gel and T_gel-sol.The temperature T_m-gel-gel,enthalpy change?H_m-gel-gel for the phase transition from the white metastable gel to the steady-state gel and the starting temperature T_gel-sol for the transition from the steady-state gel to the sol were studied by Differential Scanning Calorimeter（DSC）.The results showed that both T_m-gel-gel and T_gel-sol increase with the increase of system concentration.The results of rheological measurement show that the 14-2-14/UMP gel system has typical wormlike micellar characteristics,and the structure of the system increases with the increase of the concentration of 14-2-14/UMP.The results of scanning electron microscope（SEM）showed that the surface of the gel system had honeycomb-like structure,which indicated the existence of three-dimensional network structure.2.Study on the interaction between 14-2-14/UMP gel system andα-chymotrypsin（α-CT）The thermal denaturation ofα-CT in pure water and in dilute 14-2-14/UMP solution was studied by DSC.The experimental results show that the addition of 14-2-14/UMP reduces the denaturation temperature T_m and enthalpy change?H of the enzyme,which indicates that the stability of the enzyme conformation is affected by the additive of 14-2-14/UMP.Its 2^nd and/or 3^rd structures are unfolded esasily.For the 14-2-14/UMP gel syetem,the results of rheological experiments show that the system still presents characteristic wormlike micelle behavior,but it seems that the micelle length becomes shorter and the entanglement density decreases.The zero shear viscosity of the system decreases asα-CT concentration increases.The effect of 14-2-14/UMP gel system onα-CT activity was studied by UV-vis spectroscopy.The enzyme was encapsulated in the gel by the sol-gel method,two-phase gelation method and gel-gel method,respectively.The results showed that the gel had a good protective effect on enzyme activity in acidic environment.3.Study on the interaction between 14-2-14 andα-chymotrypsin in PBSBuffered 14-2-14 gel at neutral pH was used to encapsulateα-CT.The experimental results show that the 14-2-14/PBS gel can load a highα-CT capacity and retain its activity.The residual activity is limitted by the stability of the gel structure.The more stable the gel is at the culture temperature,the higher the loading effect is.The higher the concentration of 14-2-14 is,the larger the residual activity ofα-CT is.The rheological measurement shows the viscoelastic properties of wormlike micelle for 14-2-14/PBS gel.It can be supposed on the experimental results that the entanglement density of micelle in the system increases gradually with the increase of 14-2-14 concentration.Asα-CT concentration increases,theη₀ of the gel decreases,the Newton platform extends to larger shear rate and the phase transition temperature T_gel-solel-sol decreases gradually.It could be considered that the length and entanglement mode of micelle are changed owing to the weak interaction between enzyme and surfactants micellet.更多还原