| Nanoscale materials exhibit many new features for its application. Nanomaterials applications, there are many gaps need to fill by scientific research. Layered double hydroxides(LDHs) are divalent metal hydroxide and tri-metal hydroxide combine inorganic nanomaterials, with good biocompatibility, low toxicity, and easy storage. LDH could be prepared in the laboratory. Different divalent, trivalent metal ions variations and combinations of ratios, can be synthesized various LDHs which show different properties. Mg/Al-LDH has been approved by FDA for the treatment of hyperacidity. By studying the adsorption mechanism, various biological macromolecules or their surface chemical groups on LDHs that can guide the applicationsas a gene carrier, drug delivery, biosensors, etc. Aluminum demand in terms of tolerance is much smaller compare to iron. There are many reportson research Mg/Al LDH, but Mg/Fe LDH is rare. The application of Mg/Fe LDH has entered clinical trials. The reports that researched on the adsorption of DNA and drug did not carry out the mechanism of adsorption. What is the interactionleaded the adsorption? Which groups in DNA or drugs involved in the adsorption? LDH bimetallic whether play the same role, and so on. Mechanism of adsorption is important for the release of DNA or drugs. In this thesis, the synthesis of Mg/Fe LDH, DNA and drug adsorption mechanism and its application in biology were studied.Thesynthesis and characterization of Mg/Fe LDH were researched. The quick synthesis method of LDH was effective. The ratio of the two metals is higher than they were in LDH. Magnesium is easy escaped from the brick structure. There is a linear relationship between the ratio in the solution and in the LDH. Toobtain the desired iron-magnesium ratio of LDH, the ratio of magnesium iron could be controlled in the synthesis solution. The color and sizes are quite different according to the ratio of two metals. The LDH crystalline form made by our method is same as the typical LDH. The less time required for the synthesis. When the ratio of magnesium with iron changed from 2: 1, 2.5: 1, 3: 1 to 4: 1, the product gradually changed color from brown to pale yellow and finally to the colorless and transparent. LDH particle size also showed an upward trend too. Their size was 25 ± 12 nm, 38 ± 21 nm, 68 ± 24 nm and 64 ± 28 nm respectively. The particle size is distribution. All the LDHs with different ratios had high ξ-potential. All of them are 60 m V, so the LDH colloidal was very stable. XRD data showed different crystallization time has no effect on crystalline form.Structure and size of Mg/Fe LDH is stable andsuitable when the ratio is 3: 1. We chose it to study the mechanism of DNA adsorption on LDH. After the FAM-labeled DNA adsorbed on LDH, the fluorescence is quenched. The ξ-potential of LDH was affected in different buffers, and LDH is very stable in slightly alkaline water. Through the competition experiments, bases, ribose and peptide nucleic acid(PNA)could not affect the adsorption of DNA; however, the single nucleotide and phosphate buffer have a greater impact on the adsorption. The facts indicated that the phosphate backbone of DNA interacted with LDH. 1m M phosphate buffer can blockthe adsorption of DNA, and 40 m M phosphate buffer could desorb the DNA that had adsorbed on the LDH previously. So, the phosphate group of DNA played a primary role in the DNA adsorption. FTIR also verified the iron and phosphate groups had coordinated action.Magnesium interacted with phosphate through hydration. Sodium chloride could not affect the DNA adsorption. XRD of conjugationof LDH and bases or single nucleotide demonstrated that DNA only adsorbed on the surface of LDH and did not intercalate the interlayer. LDH absorbed double strand DNA strongly compare to single strand DNA if they were same base pair.DNA conjugated with LDH for gene delivery was studied. Two tumor cell lines were chosen, one was breast cancer cells MDA-MB-231, and another one was lung cancer cells A549. FAM-24 mer which was alternative for Si RNA was chosen to perform the experiment of gene delivery and cytotoxicity. DNA concentration was in the range of 20 n M to 1000 n M. Compare to the pure DNA, LDH could greatly improve the efficiency of gene delivery. DNA concentration, processing time had a great influence on its delivery.The delivery efficiency was highest when the DNA concentration was 100 n M. With the increase of processing time, the gene delivery was increasedin MDA-MB-231 cell line.However, for the A549 cell line, incubated three hourswas the best for the gene delivery. Then the efficiency on A549 went down when the incubated hours was more. Fluorescence signal detection showed that the effect on A549 cells gene delivery was better than the MDA-MB-231 cells. The cytotoxicity of LDH was different in the towtumor cell lines. A549 cells could tolerate higher different concentration of DNA and LDH. In the72-hour experiment, there was not any harmful effect. In contrast, the cytotoxicity of LDH was higher for the MDA-MB-231 cell. In the 72-hour experimental results, more than 60% cells were dead. Cytotoxicity was related withthe concentration of LDH and incubated time. So the cytotoxicity could reduce by lower concentration and shorter time. Confocal photo showed LDH significantly increased the cell gene delivery, and it looked cells rarely uptake pure DNA. Meanwhile, a large area of fluorescence was showed that indicated LDH could not quench the fluorescence any more. It suggested DNA had been released from the surface of LDH. which is conducive to play a role in gene transfer. LDH played as a vesselto delivery gene, and the efficiency of gene delivery had been improved significantly. LDHholds promiseto play an integral role for the future of gene therapy.Doxorubicin is an anthracycline antitumor antibiotic, and can effectively against a variety of cancers. It is an important drug for cancer chemotherapy and has been used frequently. LDH as doxorubicin drug carrier were studied for the mechanism of adsorption. The fluorescence can be quenched by LDH, and the capacity of doxorubicin adsorption is quite high. The analogs of doxorubicin, anthracene, 7-deoxy-doxorubicin and doxorubicin-M, could be absorbed by LDH. The anthracene showed much weaker comparably. The high concentration of glucose and urea were not affected the adsorption of doxorubicin in the competed absorbed experiments. Anthracycline and ketone of the doxorubicin exhibits negative charge, and LDH has positive charges on its surface. So, electrostatic adsorption is the main force to drive the adsorption between the doxorubicin and LDH. Ethanol could reduce the adsorption to indicate that hydrophobic forces also played a certain role for the adsorption. The sugar ring and amino of doxorubicin was not contributed in the adsorption. Iron and magnesium could quench the fluorescence of doxorubicin, so both of them could interact with doxorubicin. Sodium chloride(Na Cl) could destruct hydration layer of LDH, doxorubicin adsorption was down because of aggregation of LDH. However, there was effect when the concentration of Na Cl was less than 60 m M. The impact of Na Cl was not increased after added more than 60 m M Na Cl. Fourier transform infrared spectroscopy also showed the anthracycline and ketone group interacted with LDH. XRD showed doxorubicin intercalated the layers of LDH. According to the layer space, we speculated two overlapping doxorubicin between layers of LDH. Therefore, the anthracycline was outward(anthracene has ring π electron polarization and keto showed acid), and the amino was inside(positive display). That is, doxorubicin was adsorbed by electrostatic and hydrophobic forces, and it intercalated to the sheets of LDH.The most important things for the cancer treatment are improving the efficacy of drugs and targeting drugs delivery. We studied LDH as doxorubicin carrier to effect cancer cells, and, the conjugated drug and LDH were covered by liposome, also, liposome was linked with aptamer to identify the target cells. LDH could help doxorubicin sustained release in PBS buffer. Liposome could reduce the release in the same condition. In acidity condition, doxorubicin released increased, so it is advantage for doxorubicin released in organelles of cells. LDH could adsorb a great mount of doxorubicin and be an ideal carrier. Ultrasonic method was used to cover liposome, no aggregation or flocculation was found and the particle size was still suitable for intravenous injection. LDH was cytotoxicity for MDA-MB-231 cells, but it was not for A549 cells. LDH could promote cell uptaking doxorubicin greatly. Liposome could be fused with the cell membrane, so, cells uptook more. Consequently, the two tumor cells were killed increased. Liposome showed differences in cytotoxicity. It had more toxicity on A549 han on MDA-MB-231. SYL3 C is aptamer which targets epithelial cell adhesion molecule(Ep CAM) that is produced by several tumor cells. However, the results did not show effect of target binding. There are still lots of experiments in front of us to figure out the reason.Citric acid is an important food additive, and plays a marvelous role in foodstuff, cosmetics and other industries. Our research found that low concentration of citric acid could affect DNA adsorption. LDH could highly select citrate in a variety of anions in; even the concentration anions were 10 times more than citrate. Test results showed a good linear relationship between concentration of citrate and the fluorescence of FAM-DNA. The limit of detection was 10.66 n M, and it could be applied to detect low concentration of citrate. FTIR demonstrated LDH adsorbed citrate through the carbonyl group. XRD results showed the layer distance of LDH was widely, and the citrate intercalated to the layers. The adsorption of citrate and LDH was electrostatic binding. It was not specific, so there was interference in a complex system. Particularly, phosphate was affinity with LDH too. However, it could be used to analyze citrate in relatively simple solution because of its low limit of detection. This method is simple and quick. |
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