Using Photo-electrochemical Biosensor For Detection Of Carbohydrateand The Interaction Between Carbohydrate With Protein

Electrochemical biosensors and photoelectrochemical biosensors are commonlyused in biological analysis field. The two detection methods have some advantages,such as high detection sensitivity, selectivity, and good stability. The instruments usedin the test process also has the characteristics of low cost, and the equipment is simple.The major contents of the thesis are as follows:(1) Amino mannose-concanavalin A (Con A) were selected as a model, andelectrochemical biosensor was utilized to investigate the interactions of carbohydrateand lectin. Firstly, electrochemical polymerization was conducted to prepare poly(indole-5-carboxylic acid) on the surface of glassy carbon electrode. The resultingmodifed electrodes were tested as sensors for lectin through the recognition ofmonosaccharide, which was covalently bound to the electrode. The quantitativebehavior of the electrochemical biosensor was assessed by measuring the dependenceof the changed current intensity (I) before and after incubated with differentconcentration of lectin. In best experimental conditions, the linear range was from2.0×10-8mol L-1to8.0×10-7mol L-1with the equation of I (μA)=0.172CConA+4.503(10-8mol L-1) and the detection limit was1.03×10-8mol L-1(3σ). This method hashigh sensitivity and selectivity, it is satisfactory for detection of lectin, and thisconvenient method can provide a theoretical basis for subsequent detection of antibodyagainst tumor-associated carbohydrate antigen.(2) In this system, a new photoelectrochemical biosensor was developed usinglow-toxic Ag2S quantum dots (QDs) as photoelectric active material. The biosensoruse Ag2S QDs as photoelectric active material to instead of highly toxic material, suchas PbS, CdSe, CdS. The preparation condition of Ag2S QDs was optimized and its structure characterization was measured. Then the developed photoelectric activeinterface was used to detect glucose and showed the good sensitivity and specificity.Under optimal condition, the linear range was from0.1mmol L-1to12.2mmol L-1with the equation of I (nA)=29.305Cglucose+5.006(10-3mol L-1), and detectionlimit of3.24×10-5mol L-1(3σ) for glucose was achieved.(3) To verified the utilization of this low toxicity Ag2S QDs in the field ofbioassay, breast cancer cell MCF-7is selected as a model cell. MCF-7cellsoverexpress sialic acid on their membrane. Monitoring of sialic acid expression on cellsurface therefore provides rational indexes of the dynamic changes in tumormalignancy, metastasis and diagnostics. The linear range for MCF-7cells was300cells·mL-1~2000cells·mL-1with a detection limit of98cells·mL-1. The toxicity ofCdSe QDs and Ag2S QDs was compared. The observations suggested that Ag2S QDsalmost did not interfere with the cell viability, which was ideal for their use in in vitroand in vivo labeling.