Study On The Electrochemical Behavior Of Living Cells And DNA Biosensors

The design of chemo/biosensors is an important and interesting subject in analytical chemistry and biochemistry and has been extensively studied. Cells as the basic units of the life, are very necessary for the developmental and physiological process of the organism. Under the electrical stimulation, electrical signal will be generated in the living cells. DNA and RNA encoded genetic message are important for keeping the stability of the species. It is well-known that for eucaryotic cells, DNA is located in the karyon and can not penetrate to the cytochylema and the tissue fluid because the cell membrane can act as barriers for DNA transportation. Therefore, the appearance of DNA in cell matrix and the serum can indicate that some diseases have taken place. A main reason for cancer occurrence is the mutation of DNA. It may cause the change of the sequence and expression of cancer suppressor genes. The ultimate result is that the proliferation of cancer cells is out of control. However, the probability of DNA mutation under natural process is very little, whereas this course can be accelerated in the presence of many chemical agents or under oxidation pressure. On the other hand, the separation, purification of DNA and seeking for DNA carries also call for the investigation of interaction between DNA and other substances. Electrochemical technique is very simple, rapid and cheap. Therefore, it can be easily used to study the cell viability, drug effect on living cells, DNA concentration and the interaction between chemicals and DNA. The main work of this thesis, which was based on the analysis mentioned above, is summarized as follows: 1. The electrochemical behavior of breast cancer cells was studied on a graphite electrode by cyclic voltammetry (CV) and potentiometric stripping analysis (PSA). The peak area in PSA was used to characterize the growth of the cells and the effect of diosgenin on MCF-7 cells. The results were also verified by trypan blue dyeing and morphological observation. 2. A biosensor based on chitosan doped with carbon nanotube was fabricated to detect salmon sperm DNA. Methylene blue (MB) was employed as DNA indicator. Carbon nanotubes can enhance the electroactive surface area three times and accelerate the rate of electron transfer between the redox active MB and the electrode. The interference of human serum albumin and the stability of the chitosan-CNT membrane were also investigated. 3. The interaction of DNA with five diverse surfactants was studied by cyclic voltammetry and electrical impedance. DNA modified gold electrodes were prepared and methylene blue and ferricyanide were used as the redox probes, respectively. The UV detection was also employed to prove the occurrence of interaction between DNA and the surfactants.