| DNA biosensor is the leading subject in biosensor research at present. It is of great scientific significance and application value to enhance the research and application of DNA biosensors. Studies on DNA biosensor have been carried out in China for over a decade, and now have entered the substantial stage. Among all DNA biosensors, studies on optical DNA biosensor have drawn wide attention. However, most application studies still stay at the experimental stage. Multi-disciplinary fields shall be explored to realize practical application of DNA biosensors.Gold nanoparticle is a nano-scale metal particle, which has excellent and unique surface plasmon resonance effect and good surface chemical properties. The properties of gold nanoparticles have been utilized to successfully develop numerous DNA biosensors with excellent performance, e.g. colorimetric sensors, SERS sensors and fluorescent sensors, etc. However, in the most gold nanoparticle-based optical DNA biosensors, gold nanoparticles will change from dispersed state to aggregated state, which will reduce the stability of gold nanoparticles in the solution and bring some interference with reproducibility of the results. In order to solve the above problem, this paper has proposed a colorimetric and SERS sensor based on non-aggregated nanoparticles.Moreover, DNA computing has become a hot spot of academic research in recent years. In most cases, the computing results are obtained by means of fluorescence in pure DNA system. It has become an important research field for the application of DNA biosensors to combine DNA-functionalized gold nanoparticles with modern information technology and realize the value of DNA nanosensor in the field of DNA computing. At present, a small number of studies have introduced DNA-functionalized gold nanoparticles into DNA computing system. Due to the good dispersibility and biocompatibility of gold nanoparticles, together with its suitability for colorimetric and SERS detection that can avoid the inherent deficiencies of fluorescent molecules (such as photobleaching, spectral overlap, etc), it has become one of the most important studies to introduce gold nanoparticle-based optical readout system into DNA computing. Based on the above considerations, this paper will introduce DNA-functionalized gold nanoparticles into DNA logic computing, to promote the development in this field.Based on the above studies, this paper has designed and prepared gold nanoparticle-based DNA colorimetric sensors and SERS sensors, and constructed unary and binary-input DNA logic gates. The main contents include:Chapter2. The impact of surfactants and Raman signal molecules on the preparation of gold nanoparticle probes has been studied, and lower concentration of thiolated DNA has been used to prepare gold nanoparticle probes. The results show that competitive reaction between signal molecules and surfactants will occur on the surface of gold nanoparticles. With the presence of surfactant, it is almost impossible for dye molecules to combine with gold nanoparticles through adsorption. Reducing the concentration of DNA is conducive to preparing stable DNA-functionalized gold nanoparticle probes, which is more cost-efficient as well.Chapter3. DNA modification has been conducted on gold nanoparticles and magnetic particles, and colorimetric DNA sensor based on non-aggregated gold nanoparticles has been constructed. UV-Vis spectra has been used to study the changes of characteristic absorption peak after adding target DNA, and realize the visual detection and quantitative detection of target DNA.Chapter4. Dual multiplexing colorimetric DNA biosensor has been constructed using DNA-modified gold nanoparticles,gold&silver core-shell nanoparticles and magnetic particles as probes. The difference between gold nanoparticles and gold&silver core-shell nanoparticles in visible spectrum has been used to realize the quantification of two kinds of target DNA. After combined with non-negative matrix factorization technique, simultaneous quantitative detection of two kinds of target DNA has been achieved in the dual multiplexing mode.Chapter5. DNA-functionalized gold nanoparticle probes labeled by two kinds of Raman active molecules have been prepared and combined with magnetic DNA probes to construct SERS sensors that can simultaneously detect two-component DNA. The carboxyl group of Raman active molecule enables aminated DNA modification on the surface of gold nanoparticles through cross-linking reaction. The difference between homemade and commercial magnetic particles in surface non-specific adsorption properties has been discussed. The difference between characteristic peaks of SERS probes has been used to realize the simultaneous detection of two types of DNA.Chapter6. Gold&silver core-shell nanoparticles have been used as SERS substrates to construct SERS DNA molecular switch and NOT logic gates. Systematic study has been conducted on the impact of silver content on SERS enhancement capability of nanoparticles. This "turn off-based molecular switch is also unary-input NOT logic gates.Chapter7. DNA-functionalized gold nanoparticles have been introduced into dual-input DNA logic computing field, and a series of DNA logic gates have been studied, e.g. NAND gate, NOR gate, XOR gate and NOT gate. In addition, a half-subtracter logic circuit has been constructed. The relationship between two groups of gold nanoparticles in the system is similar to host-guest chemistry. The composite structure of DNA logic gates is built on the surface of host gold nanoparticles, while the guest gold nanoparticles only have single-stranded DNA. In case of DNA output, both gold nanoparticles will form aggregates for UV-Vis and SERS detection. The flexible structure can realize logic functions and computing at a variety of molecular levels along with the changes of protection strand in logic gate structure. The advantage of SERS spectral peak in width can be used to realize one-time reading of half-subtracting computing result. |
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