Diazotization Of Graphene And Research Of Structures And Properties Of Multiple DNA Architectures

Graphene materials as delivery vehicles have attracted great interest in recent years due to their unique and remarkable physical and chemical properties. To the best of our knowledge, drug (or DNA or protein) delivery systems based on graphene have been completely designed from graphene oxide (GO), and the adsorption of water-insoluble drugs onto the graphene oxide plane depends mainly on the hydrophobic and π-π stacking interactions. However, according to our experimental results, the degree of conjugation of planar GO is negligible.We therefore suspect that drug-delivery materials based on GO by means of π-π stacking interactions are not scientifically possible, that the π-π stacking interaction of planar GO with water-insoluble drugs is negligible, and that the adsorption of water-insoluble drugs on planar GO depends mainly on weak hydrophobic interactions, thereby resulting in a lower drug-loading ratio. A great challenge for using reduced graphene oxide (rGO) as a drug-delivery material is that rGO has a tendency to agglomerate irreversibly due to its strong hydrophobicity, or even to restack into graphite through van der Waals interactions in the absence of stabilizer, thus making further processing difficult. Although the diazotization of rGO using the wet-chemical method has been reported, we found that the diazotization of rGO by means of a wet-chemical method in alkaline or neutral solution conflicts with textbook knowledge that the diazotization should take place in an acidic solution; otherwise side reactions would occur and byproducts would appear, and sometimes the stabilizer might also affect the diazotization reaction.We demonstrate a novel, simple, and practical wet-chemical method to covalently functionalize rGO with p-aminobenzoic acid for the preparation of rGO-C6H4-COOH in which the degree of conjugation of planar rGO is higher than that of GO. The adsorption of water-insoluble drugs by rGO-C6H4-COOH through π-π stacking interactions should be higher than that of GO. The reaction of aryl diazonium with rGO was processed under acidic conditions that were rigorously controlled. Surfactants or stabilizers were not applied, which was different from previous method. We carried two system works based on rGO-C6H4-COOH for the application as drug delivery carrier.Self-assembly from molecules to multilevel architectures has flourished in recent years; the self-assembly of nucleic acid molecules has shown unique properties for organizing and constructing versatile materials with complex architectures. Among the rich diversity of self-assembled structures, some of the most exquisite architectures were constructed using DNA origami methods; however, the DNA origami approach is restricted to discrete domains of complementary strands to link adjacent helices. A simple method to assemble double-stranded DNA (ds-DNA) via the participation of various metal ions into multidimensional architectures with the aid of anions was developed, the final architecture mainly dependent on the spatial configuration of DNA. We also found that this method can be applied to most metal ions and most water-soluble biomolecules having suitable donor atoms. We carried two system works based on this method for the preparation of multiple nanostructure.Chapter Ⅰ is a brief introduction of the basic knowledge, the research background and recent improvement related to the research of the thesis. The theoretic support and scientific significance of this thesis are also discussed at the end of this chapter and research content.In chapter Ⅱ, we developed a simple, novel and practical method to prepare rGO-C6H4-COOH, and rGO-C6H4-COOH was modified by introducing highly water-soluble polyethyleneimine (PEI) to further enhance its water solubility, and the introduction of the target molecular folic acid (FA) enhanced its targeting, and thus the drug delivery system rGO-PEI-FA was prepared. Some indexes related to drug delivery system, such as drug loading ratio, stability, cytotoxicity and cell cycle, were studied, and the results showed that the stability of drug delivery system prepared was excellent and the conjugation of drug (Doxorubicin) could induce the cancer apoptosis effectively.In chapter Ⅲ, we improved the drug delivery system, and solved the question that the cytotoxicity was large. The rGO-C6H4-COOH colloidal solution was firstly prepared according to our previous method and then the excellently water soluble PEI was engrafted to enhance the higher water-solubility of rGO-C6H4-COOH, and simultaneously Biotin was conjugated with PEI to enhance the targeting.(3-CD was also introduced into the drug delivery material to reduce the cytotoxicity of PEI and rGO-C6H4-COOH, which forms a hydrophilic layer around the rGO-C6H4-COOH sheet. The materials increased the dispersity in water and improved the biocompatibility and performance, and greatly enhanced the half-life by delaying opsonization. On the other hand, the hydrophobic interior of b-CD can form a host-guest complex with water-insoluble drugs, which is a very important consideration as part of the drug delivery material of rGO-C6H4-COOH-NH-PEI-CD-Biotin. At the same time, some indexes related to drug delivery system, such as drug loading ratio, stability, cytotoxicity and cell cycle, were studied, and the results showed that the cytotoxicity of drug delivery system prepared almost was no cytotoxicity, and the performance of other indexes was very well.In chapter Ⅳ, we demonstrated a simple method to assemble linear double-stranded DNA (ds-DNA) via the participation of various metal ions into multidimensional architectures with the aid of anions was developed, and the self-assemble process was clarified elaborately, and explained the self-assemble mechanism. At the same time, the general applicability of this unsophisticated method was further demonstrated, and we anticipate that our strategy for self-assembling various custom architectures is applicable to most biomolecules possessing donor atoms that can form coordination complexes with metal ions.In chapter Ⅴ, we demonstrated that DNA molecules which have different structure shape (X-DNA, T-DNA and linear Ds-DNA) and different base pair length (such as15,80and so on) could self-assemble into exquisite multi-dimensional nanostructures also, and we have preliminarily explained the forming reaction mechanism of multi-dimensional nanostructure. We anticipate that our strategy for self-assembling various architectures based on metal ions and biomolecules will provide a novel and general route to the engineering and assembly of advanced materials.