应用糖基化碳量子点研究甘露糖与致病菌之间的相互作用

Study on Interaction between Mannose and Bacteria Using Glycosylated Carbon Quantum Dots

以柠檬酸为碳源,通过水热法制备得到荧光碳量子点(CQDs),基于其表面的—COOH,将4-氨基苯基-α-D-吡喃甘露糖苷以共价键的方式固定在CQDs表面,得到甘露糖基化碳量子点(Man-CQDs),并通过荧光竞争法,结合Scatchard方程计算了Man-CQDs与大肠杆菌JM109、大肠杆菌DH5a和沙门氏菌S.123443的结合常数Ka。实验得到CQDs的粒径为26 nm,最大发射波长为445 nm,荧光产率相较于54%硫酸奎宁为76%,Man-CQDs荧光强度与CQDs相比基本保持不变,通过苯酚-硫酸法计算得到Man-CQDs浓度为2.832 mmol/L,Man-CQDs纳米颗粒中甘露糖含量约为40%。根据Man-CQDs、D-Mannose与致病菌竞争结合实验,结合Scatchard模型方程,计算得到Man-CQDs与大肠杆菌JM109的结合常数Ka=2.39×103L/mol,Man-CQDs与沙门氏菌S.123443的结合常数Ka=1.17×105L/mol,Man-CQDs与大肠杆菌DH5a无有效结合。研究结果显示,该方法可用于甘露糖与致病菌非共价结合的结合常数测定,为研究糖与致病菌相互作用提供了参考。

In this paper, citric acid was used as carbon source for preparing fluorescent carbon quantum dots（CQDs）. Due to the obtained CQDs had carboxyl groups on their surfaces,Man-CQDs were synthesized by immobilizing 4-aminopheny-l-α-D-mannopyanoside on the surfaces of CQDs via covalent bond.Furthermore,the binding constants of Man-CQDs and Escherichia coli JM109/Escherichia DH5a/Salmonella typhimurium S.123443 were obtained by fluorescent competition experiments.The results showed that the sizes of CQDs were approximately 26nm,the maximum excitation wavelength for CQDs was 445nm and the fluorescence yield was 76% in contrast to 54% quinine sulfate. Compared with the fluorescence intensity of CQDs,the prepared Man-CQDs remained unchanged in principle. By the Phenol-sulfate method, the concentration of Man-CQDs was calculated to be 2.832mmol/L,and the content of mannose in Man-CQDs nanoparticles was approximately 40%.Based on competition binding experiments of Man-CQDs and D-mannose with bacteria, the binding constant of Man-CQDs and bacteria was calculated by Scatchard equation, namely the binding constants of Man-CQDs with Escherichia coli JM109 and Salmonella typhimurium S.123443 were 2.39×103L/mol and 1.17×105L/mol,respectively. However, the reaction of Man-CQDs and Escherichia coli DH5a was nonspecific binding. The results suggested that the proposed method was applicable for the determination of noncovalent binding constant between mannose and bacteria. Besides, it offered a valuable reference information for the research of interaction between carbohydrate and bacteria.