Nanocomposites And Assemblies Between Amino Copolymers And Inorganic Nanoparticles

During the last decade,there have been more and more research interests focus on inorganic nanoparticles,originating from semiconductors or metals.Due to their interesting properties,such as the unique properties of semiconductor,gold and super paramagnetic nanoparticles,they have illustrated large potential in biological, diagnostic and medical applications.In order to meet the requirement of biological application,the biocompatibility,immune recognition and in vivo circulation time of nanoparticles should be considered.In practice,however,complicated biological environments result in the inherent nonspecific adsorption and aggregation of inorganic nanoparticles and toxicity associated with the nanoparticles pose serious risks to biological systems.In addition,some of the inorganic nanoparticles could only be dispersed in non-aqueous system.As such,surface modification of such nanopartMes has been developed to solve this problem and extend their applications.Among the approaches to surface modifications of inorganic nanoparticles, polymer and nanoparticles composite opens a door to applications for biological environment.To the best of our knowledge,many methods have been developed to form polymer-nanoparticle composite colloids less than 100nm,either by utilizing polymers as ligands or through the self-assemblies between polymers and nanoparticles.Considering the formation of complexation between the amino copolymer and non-aqueous nanoparticles,and the electrostatic interaction between the protionized amino copolymer and aqueous nanoparticles,the amino copolymer possessed the ability to modify not only the non-aqueous but also the aqueous nanoparticles.This paper focused on the nanocomposition and assembly between amino copolymer(PEG-b-PDMAEMA and h-PAMAM-g-PEG) and inorganic nanoparticles, through which regular composite assemblies were obtained and the modification of nanoparticles were achieved.The main work of this paper was divided into 3 chapters:1.In Chapter 2,we synthesized Poly(ethylene glycol)-b-poly (N,N-dimethylamino ethylmethacrylate)(PEG-b-PDMAEMA) block copolymer,and prepared nanocomposite assemblies through the electrostatic interaction between the block copolymer and thiolglycolic acid(TGA) stabilized CdTe luminescent semiconductor nanoparticles.Core-shell nanocomposite assemblies were obtained, which interior core was made via interaction between positively charged PDMAEMA segments and negatively charged CdTe nanoparticles and shell was composed of PEG segments.The more CdTe used in the assemble process,the smaller nanocomposite assemblies were obtained.Because of the core-shell structure of the assemblies,the interior CdTe was isolated from the acidic condition and radicals and its fluorescence was maintained.Since the existence of biocompatible PEG which also providing steric stabilization,and low toxic PDMAEMA,the nanocomposite assemblies illustrated superior stabilization and cytotoxicity.2.In Chapter 3,we synthesized PEG grafted hyperbranched poly(amido amine)(h-PAMAM-g-PEG).The h-PAMAM possessed similar properties to that of dendrimer PAMAM.Based on our former results,we extended our research to nanocomposite assemblies between the h-PAMAM-g-PEG and three various aqueous nanoparticles(CdSe,Au and Fe₃O₄).Due to the electrostatic interaction between h-PAMAM-g-PEG and nanoparticles,core-shell nanocomposite assemblies were obtained.The core was composed of h-PAMAM and nanoparticles and the shell was composed of PEG segments.In addition,the increasing number of grafted PEG showed negative effect on the formation nanocomposite assemblies.Besides,the assemblies consisting of h-PAMAM-g-PEG could be further cross-linked due to the primary and secondary amino groups in h-PAMAM segment,which made the assemblies robust in various conditions.The nanocomposite assemblies illustrated low cytotoxicity.Furthermore,the nanocomposite assemblies consisting of CdTe nanoparticles could be directly applied to bioimaging.3.In Chapter 4,in order to enhance the dispersion ability of non-aqueous nanoparticles in water while maintaining the unique properties of the nanoparticles, we utilized the h-PAMAM-g-PEG used in electrostatic nanocomposite assembly to modify the non-aqueous nanoparticles and extend its application in biology. Considering the large amounts of amino groups in h-PAMAM segments,strong complexation interaction between h-PAMAM-g-PEG and nanoparticles was achieved and ligands exchange between copolymers and small molecules occurred.In addition, the increasing number of grafted PEG showed negative effect on the ligands exchange process.Since the existence of biocompatible h-PAMAM-g-PEG ligands,the nanocomposite particles illustrated superior stabilization and cytotoxicity,and could be directly applied in bioimaging.