| The researches on carbohydrate, lectin and cells are the frontiers in life sciences. Electrochemical analysis, as one of the classical detecting means, has been generally penetrated in various traditional subjects and plays an important role in analytical chemistry and biochemistry. Piezoelectric crystal quartz sensor has been successfully employed in chemical/biological field due to its satisfactory performances, e.g., high sensitivity, facile operation and dynamic monitoring. Investigations by electrochemical methods and piezoelectric sensing technique in the thesis are given as follows for several polysaccharides, lectins and cells as well as their interactions:1. Cyclic voltammetric investigation on the electrochemical behavior of methylene blue (MB) in the absence and presence of heparin (hep) at a gold electrode was performed. The combination of MB with heparin formed a nonelectroactive complex MB-hep, which resulted in the peak current decrease of MB. The anodic peak current difference of MB was found to be proportional to the concentration of heparin in the range of 0.666 to 64.5μg mL-1 with a detection limit of 270 ng mL-1 and a satisfactory result was obtained for the determination of heparin in injection samples. The association constant Ka and the binding number m for MB-hep complex were calculated to be 7.32×105 M-2 and 1.85, respectively. The dynamic process of competition of Ba2+ with methylene blue for binding heparin was monitored using quartz crystal microbalance (QCM) measurement. The reaction rate constant between Ba2+ and MB-hep was estimated to be 0.0022 s-1.2. Two schemes were adopted for investigating the concanavalin A (Con A)-glycogen interaction on gold electrode surfaces, respectively. Based on electrochemical piezoelectric quartz crystal impedance (EPQCI) measurement during Con A reaction with glycogen adsorbed on Au electrode, the piezoelectric quartz crystal (PQC) parameters, resonant frequency shiftΔf0 and the motional resistance changeΔR1, and the electrochemical impedance (EI) parameters, electrolyte resistance changeΔRs and the double layer capacitance changeΔCs, were obtained simultaneously. The association constant Ka and the amount of the binding sites s were calculated to be 1.48×106 M-1 and 4.09, respectively. Based on single PQC measurement of glycogen reaction with Con A assembled on Au electrode, Ka was estimated to be 1.26×106 M-1. In addition, a novel method for glycogen detection was proposed by using the latter scheme.3. The processes of adhesion, spreading and proliferation of human mammary cancer cells MCF-7 on two Au electrodes with different surface roughness (Rf, and Rf=3.2 or 1.1) were monitored and clearly identified with the QCM technique. Analyses of the QCM responses on the resonant frequency shiftsΔf0 versus the motional resistance changesΔR1 revealed a significant surface-stress effect in the involved courses, in addition to a viscodensity effect and a relatively small mass effect (especially at the smooth electrode). Experiments of fluorescence microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were conducted to investigate the cell population on the electrode versus the electrode-surface roughness. Simplified equations were deduced to quantitatively evaluate the surface stress, and a novel QCM method for dynamically measuring the surface stress on an electrode in cell-culture course was thus described. It was found that the smoother surface (Rf=1.1) gave a higher surface stress during cell attachment and less cell population on it than the rougher surface (Rf=3.2). In addition, real-time QCM monitoring showed on the same electrode the surface stress induced by hepatic normal cells being notably higher than that caused by hepatic cancer cells at cell-attachment stage, suggesting that the surface-stress measurement can exhibit the difference of adhesion-performance between the healthy and ill-behaved cells.4. The real time monitoring of the agglutination process of human hepatic normal cells L-02 at the QCM Au electrode was performed. Two lectins, Con A and wheat germ agglutinin (WGA), induced the cell agglutination, resulting in the differentΔf0 andΔR1 responses from those caused by the normal cell-attachment and growth. The cell-ConA-cell aggregates had higher affinity for the Au substrate due to the excellent adsorption-ability of Con A, which was revealed by the increasedΔf0 andΔR1 shifts and the obvious mass effect of QCM. In contrast, the lower adsorption-ability of cell-WGA-cell aggregates was related to the same characteristic of WGA, presenting the decreasedΔf0 andΔR1 responses and the time-extended adhesion phase. The parallel microscopic-observation experiments were also carried out and exhibited the comparable results. TheΔf0 responses during the processes of cell-growth and cell-agglutination were analyzed using the two equations, respectively. Furthermore, the present work proved that the QCM-measurement technique based on the cell agglutination was useful for discriminating hepatic normal cells L-02 and hepatic cancer cells Bel7402.5. Selenium nanoparticles (Se NPs) were prepared based on the reduction of selenious acid, by employing sodium alginate as a template. The real-time monitoring of the drug-induced apoptosis process of human hepatic cancer cells Bel7402 was performed with the QCM measurement. The antitumor effect of adriamycin (ADM) used in combination with Se NPs was investigated. It is found that both drugs were able to inhibit cell proliferation in a dose-dependent way and the combined treatment with ADM and Se NPs was more effective in inhibiting cell growth than each of the two drugs alone. The cytotoxic effects of drug combination were evaluated with the modified Bürgi formula (Jin equation) based on theΔf0 responses. The effect-grades gradually changed from apparent synergism to simple addition with the drug-treatment time increase but the drug combination at lower concentrations still exhibited synergism after 24 hours, suggesting its potential applicability in cancer therapy.
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