| Biominerals are organized from the nanoscale to the macroscopic scale with complex morphology and structure. They often far exceed the human-made counterparts in performance. Mimicking of biominerals has inspired various new materials which show great potential applications in areas as diverse as photonics, catalysis and biotechnology including drug delivery. The graceful right-handed double helix of DNA draws much attention since the structure was resolved, and numerous forms of counterion-induced DNA liquid crystal have been studied extensively. The packing behavior of DNA in vivo is not yet fully understood, and the structure mimicking silica mineralization in vitro remains unresolved. Study of DNA-induce silica biomineralization opens new horizons for the study of functional metamaterials as well as physical theory of DNA assembly and biological macromolecular interaction.However, in general DNA is not capable of directing surface deposition of silica. This is due to the well-known difficulty that the negatively charged silica species could not interact with the DNA polyanion under pH 4.3-11.9, the range that is needed to maintain the double-helix configuration of DNA. Therefore, a co-interacting species between DNA and silicate is needed in the study of DNA-induce silica biomineralization.Che et al first introduced the concept of co-structure directing agent (CSDA) into the synthesis system of mesoporous materials, and synthesized mesoporous silicas with diverse structures (AMS-n) using anionic surfactants as the templates. The work in this paper is based on CSDA route. We synthesized different DNA induced silica mineralized materials and investigated the structure control and formation mechanism. Positively charged head groups of CSDA interact with negatively charged phosphate groups in the DNA backbone. The alkoxysilane sites of TMAPS are co-condensed with tetraalkoxysilane and subsequently assembled into the silica framework. Structure of the mineralization products could be controlled by tuning the interaction between CSDA and DNA. The deposition of silica is fast considering the ambient solution conditions of neutral pH and room temperature.In chapter 2, DNA and DNA superstructure was transcribed into pore-structure-tunable mesoporous silica fibers based on CSDA route. By varying of the pH of solution from 5.5 to 6.9 and 11.5, the different degrees of ionization of the DNA backbone led to different aggregation state of DNA, and transcription products such as DNA arrays, DNA toroids, single and intertwined DNA with chirality were synthesized. After removal of template by exhaustive solid-liquid extraction, the functional groups were remained on the surface of the pore. A weak induced circular dichroism (ICD) signal indicated a possible imprinting of helical arranged groups.In chapter 3, by exploiting the cooperative effects of a quaternary ammonium silane, which acts both as a DNA condensation agent and CSDA in the DNA-induce silica mineralization, p4mm and p6mm DNA-silica complex were synthesized at different DNA concentrations. According to simulation results based on Kornyshev-Leikin theory and previous reports on cation crystallized DNA, the small interaxial separation of ~25 ? formed upon quaternary ammonium–phosphate electrostatic"zipping"along the DNA–DNA contacts and the silica wall formed between the DNAs in the diagonal position were considered to be optimal for the formation of the p4mm structure. The large distance formed at lower DNA concentrations and the formation of silica surrounding their surface would make the DNA column a uniform cylinder, as well as result in hexagonal close packing. The p4mm DNA-silica complex was inconsistent with the hexagonal platelet morphology and was not a single crystal but contains several domains arranged by 60o. Time course study indicated a transition from p6mm to p4mm structure.Chapter 4 sums up the work and proposes the outlook.
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