Adsorption Behavior Of Biomolecules On Metal Ions Modified Au Nanoparticles

New separation methods in bio-separation technology have come forthcontinuously due to the expensive cost in the extraction process. Nanomaterials haveattracted widely attentions in the field of biotechnology as the rapid development ofthe controlled synthesis, assembly and modification technologies. It has greatpotential especially in the biological separation. Compared to other nanomaterials, Aunanoparticles have many advantages, such as large specific surface area, goodbiocompatibility, easy to be functionalized and well established surface chemicalmechanism. Therefore it can be used as effective extractant for the extraction andenrichment of bio-analyte from mixture.DNA adsorbed on Au nanoparticles has been widely used in biological analysisand biomedical. Previous works usually used electrostatic interaction to achieve theadsorption of DNA. It was found that metal ions will cause the crimp of DNA chainby coordinated with the phosphate group of DNA. Since coordination interactions aremuch stronger than electrostatic interactions, we can use coordination interaction toenhance the DNA adsorption efficiency. Also the coordination interactions are notsensitive to salt concentration and show good selectivity to reduce nonspecificadsorption. We hope to design some materials which have high efficiency andspecificity adsorption to DNA in any salt concentration.The adsorption of protein on the surface of nanoparticles was used in many bio-technology fields. In recent years, magnetic nanoparticles are extensively studied forseparation purposes due to their several interesting properties, such as chemicalstability and biocompatibility. Immobilized metal ion affinity chromatography (IMAC) is one of the most effective methods for the adsorption of proteins. IMAC introducesan interesting approach for selectivity of materials on the basis of their affinities forchelated metal ions. The separation is based on the interaction of a Lewis acid(electron pair donor) with an electron acceptor group on the surface of the protein.Proteins are assumed to interact mainly through the imidazole group of histidine and,to a lesser extent, the indoyl group of tryptophan and the thiol group cysteine. Thesemethods have many shortages, for example time consuming, large wastage, operationtrival and pollution of the environment.We hope to design a fast, easy and efficiencyway to improve it.In chapter2, Au nanoparticles were modified by glutathione (γ-Glu-Cys-Gly)through Au-S bond. The aggregation of Au nanoparticles induced by different metalions was investigated. At pH lower than9.0, the Au nanoparticles were sensitive tothe metal ions with strong affinity to carboxyl group, such as Cu2+ions and Fe3+ions.Other metal ions such as Ca2+ions, Ni2+ions and Zn2+ions were less effective toinduce the aggregation of the Au nanoparticles due to their weak affinity to thecarboxyl groups. At pH9.8, the metal ions with strong affinity to the deprotonatedamine group, such as Ni2+ions, Cu2+ions and Zn2+ions, were more effective toinduce the aggregation of the Au nanoparticles than those with weak affinity to theamine group, for example Fe3+ions. At pH12.0, all the metal ions became lesseffective to induce the cross-linking of the Au nanoparticles due to the competitioneffect of the hydroxyl groups. In particular, GSH has two free-COOH groups and aNH2group to provide a hydrophilic interface and a handle for further reactivity withother functional molecules.In chapter3, the adsorption of DNA on Fe3+immobilized gold nanoparticles wasinvestigated. At lower pH, DNA could be adsorbed efficiently on the particles surfacedriven by the coordination interactions between the Fe3+ions and phosphate groups ofDNA, which provided higher efficient adsorption than driven by the salt bridges, andwas almost not affected by the salt concentration in the solutions.In Chapter4, we investigated the adsorption of BHb and BSA on Ni2+immobilized gold nanoparticles. We found that the Ni2+immobilized particles have higher extraction efficiency on BHb that has more histidine groups. The mechanism issimilar to IMAC. We also discussed the optimal condition for protein adsorption.In chapter5，The adsorption behavior of BHb, BSA and DNA on Ni2+or Fe3+modified Au nanoparticles was systematically investigated in protein and DNAmixture. We found that Ni2+modified Au nanoparticles have higher adsorptionefficiency to BHb. So, BHb should be extracted from the mixture of BHb and DNA orBHb and BSA by Ni2+modified Au nanoparticles. Fe3+modified nanoparticles showhigher adsorption ability to DNA, and then it can be used to extract DNA from BHband DNA mixture. However, it also shows high affinity to BSA. At pH7.0, Fe3+modified nanoparticles can be used to purify BHb from protein and DNA mixture.