The Detection Of Tumor Cells And Tumor Markers Based On The Quantum Dots

Tumor is one of the most threatening diseases of the human being．It plays an essential role in the modem medicine．Recently,many assay methods and sensors as the currently popular techniques are being developed for tumor—related biomarkers detection．And great efforts have been made worldwidely to develop and improve assays for the biomarkers detection with the target of making portable and afrordable devices．Even many advances in this field．it'S still a challenge to exploit new approaches which Can improve the simplicity,selectivity,and sensitivity of clinical assay,in order to meet the requirements of modem medical diagnostics and biomedical research aDplicatiOns．This thesis studied a novel electrochemical biosensor based of CdS and PbS quantum dots and its application in assay of MCF一7 cells and its tumor makers．The magnetic beads or polystyrene microballons as well as the ampter DNA were als0 used in this biosensor．Besides,microchip capillary electrophoresis is a new—style of microchiD system·The advantages are better separation efficiency,quicker analytical speed,less reagent consumption and SO on．Electrochemical detection is widely applied due to its low limit of detection,broad linear range,good selectivity,simple equipment and low price．This thesis mainly consists ofthe following parts:We synthesized the CdS and Pb S nanocrystals by using linker DNA as stabilizer,the mercapto group on one terminal of which participated in the synthesis progress and the amino group on the other terminal,as well as the amino group on the aptamer,reacted with the carboxyl group on the surface of the magnetic beads or polystyrene microballons．By controlling the ratio of the two DNA,a great deal of linker DNA and a small锄ount of aptamer were assembled onto the surface of the carboxyl coated magnetic beads or polystyrene microballons to obtain the magnetic MUC 1 nanoprobes and the nonmagnetic HER一3 nanoprobes,respectively．As shown in Scheme 1．in the presence of the target cells,the aptamer on the magnetic MUC 1 nanoprobe dehybridized with the capture DNA 1mmobilized on the Au electrode．and combined with the MUC 1 on the surface of the cells．After magnetic separation,the target cells were transferred to another vessel containing nonmagnetic HER·-3 nanoprobes to ensure that the HER-．3 on the surface ofthe cells could be integrated with the correlative nanoprobes through the high affinity ofthe aptamers and the proteins．Then HN03 solution was added to dissolve the CdS andPbS nanocrystals for further detection of the Cd。'and Pb。'by anodic strippingvoltammetry(ASV)．Then the number of the target cells,and the amount of MUC 1 andHER一3 on one target cells could be determined by the electrochemical signals of Cd。'andPb．Because one magnetic beads or polystyrene microballons could loaded withthousands of CdS or PbS nanocrstals,the signals were amplified significantly．The approach uses Au nanoparticle(Au NPs)as a tag in conjunction with enzymeamplified electrochemical detection during microchip electrophoresis．Target DNA wassandwiched between thiol—functionalized DNA self-assembled on Au NPs and signalDNA with marker—loaded horseradish peroxidase(HRP)．Subsequent,the separationswere performed at a separation voltage of+1．6 kV and were completed in less than 1 00 S．The HRP was used as catalytiC labels to achieve sensitive electrochemical DNA detectioncatalyzing via fast catalytic reactions．With this protocol,2 1一mer DNA fragments weresuccessfully detected within 1 00 S．The proposed method is critical tO achieve improvedlow—molecular—mass of DNA separations．...