| Accurate, sensitive methods for leukemia diagnosis facilitate the selection of effective therapeutic pathways by clinicians. Current methods are time-consuming, expensive, and require advanced instrumentation. Some more cost-effective methods requiring simple or no instrumentation yet still providing great sensitivity and accuracy would be ideal for point of care diagnosis. Aptamers, single-stranded DNA/RNA probes, are poised to become a chemist's antibody and have the potential to serve as molecular probes for a variety of biomedical applications. In this thesis, a series of studies were carried out based on aptamer for the detection of cancer cells. On the other hand, the construction of nanocomposites is of great significance for promoting the development of bone tissue engineering. The main work of this thesis is summarized as follows:1. An electrochemical biosensor was developed for CCRF-CEM acute leukemia cells based on the thiol-terminated aptamer (sgc8c) self-assembled onto gold electrode surface as recognition probe. The biosensor provided a simple, convenient, low-cost and label-free method for early leukemia diagnosis. The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The surface density of aptamers was determined by chronocoulometric method. Upon incubation of the aptamer-modified electrode with CCRF-CEM cells, the electron-transfer resistance (Ret) increased substantially. The selectivity of the sensor was excellent. A linear relationship between Ret and logarithmic value of CCRF-CEM cells concentration was found in the range of 1×10~4 to 1×10~7 cells/mL, with a detection limit of 6×10~3 cells/mL.2. A direct visualization method for cancer cell detection was developed by using unmodified gold nanoparticle (AuNPs) as indicator. The assay is essentially based on that ss-DNA can uncoil sufficiently to expose its bases, then absorb onto the AuNPs surface, and can make AuNPs stabilization at high salt concentration. The incubation of target CCRF-CEM cells with oligonucleotide strand aptamer sgc8c made the aptamer concentration in centrifugal supernatant significantly decrease. AuNPs lost the stabilization and aggregated under high salt concentration, while RAJI control cells and random sequence DNA did not elicit change in color. The assay showed excellent sensitivity with both the naked eye and based on absorbance measurements.3. In this study, biopolymer chitosan-gelatin/multiwalled carbon nanotubes nanocomposites (CG/CNTs) have been successfully prepared by a simple solution-evaporation method. The carbon nanotubes enhanced the mechanical properties of the CG films for the application in bone engineering. The morphology, hydrophilicity and mechanical properties of the CG/CNTs nanocomposites have been characterized with field emission scanning electron microscopy (SEM), contact angle and tensile tests. The CNTs were homogeneously dispersed throughout the chitosan-gelatin matrix. When compared with chitosan-gelatin film, the tensile modulus of the nanocomposites was greatly improved by about 180% with incorporation of only 0.4 wt % of CNTs into the chitosan-gelatin matrix. The growth behaviors of MG-63 osteoblastsic cells on CG and CG/CNTs films were investigated with morphology observation, acridine orange (AO) staining, and MTT assay. It was found that the CG/0.4% CNTs can not significantly influence the attachment, spreading and proliferation of the MG-63 cells. |
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