Bioconjugation And Co-assembly Of Amphiphilic Hyperbranched Multiarm Copolymers And DNA

With the development of structural DNA nanotechnology, DNA nano-assembly and DNA hybrid materials have received considerable attention in both academic and industrial fields. As the genetic code carrier of the naturally evolved systems, DNA with its remarkable molecular recognition properties and structural features has proved to be a powerful building block for precisely organizing any deliberately designed nano-structures and functional nano-devices. In parallel, as a newly emerging interdisciplinary subject, supramolecular chemistry has exhibited extremly important theoretical significance and an extensive prospect in a wide range of fields including material science, nanoscience, information science, and life science. Recently, a new research area termed ‘supramolecular DNA assembly’, which blend together the programmability of DNA with the structural and functional diversity achieved by supramolecular chemistry, has emerged. This field combines DNA building blocks together with synthetic organic, inorganic and polymeric materials, which not only enriches the structural motifs and functionality of DNA nanotechnology, but also enable the programmable assembly of supramolecular chemistry. Therefore, how to design and develop supramolecular systems with controlled structure and tunable function by using the biological properties and programmable nature of DNA, has become present research focues in the field of supramolecular DNA assembly. In this dissertation, a series of supramolecular assembling systems containing DNA with distinct structures and functions have been successfully fabricated by using different synthetic and self-assmbly strategies, and further study on their potential biomedical applications including bioimaging, drug and gene delivery. This dissertation can be divided into four major sections, and the main research contents and conclusions are shown as follows:1. Targeted cancer imaging of hyperbranched multiarm copolymers functionalized with aptamerAmphiphilic hyperbranched multiarm copolymer HBPO-star-PEO was first synthesized through the cationic ring-opening and oxyanionic ring-opening polymerization methods. Then the functional species with targeted ability and fluorescence performance were synthesized respectively through the end group modification. By a simple co-assembly method, two functional species can self-assemble into bifunctional polymeric micelles, which show a well-defined spherical core-shell nano-structure investigated using DLS and TEM. Meanwhile, the optical property of assemblies was studied using UV-Vis spectroscopy and fluorescence spectroscopy. The cytotoxicity and cellular uptake of micelles in vitro were also evaluated by MTT assay, flow cytometry, and confocal laser scanning microscopy. The results have shown that this polymeric micelles exhibit low cytotoxicity, enhanced cell uptake, and smart targeting capability, which have great potential to be promising carriers for bioimaging and cancer specific delivery.2. Synthesis and self-assembly of dumbbell-shaped p H-responsive supramolecular polymers based on DNA for drug deliveryTwo kinds of DNA-hyperbranched block copolymers bioconjugates HBPO-b-ss DNA and HPG-b-ss DNA were successfully synthesized through cationic ring-opening polymerization and oxyanionic ring-opening polymerization, respectively. Then, dumbbell-shaped p H-responsive supramolecular block copolymer HBPO-ds DNA-HPG was obtained by co-solvent assembly and the base-pairing rule of DNA. DLS, TEM and fluorescence spectroscopy were used to directly study the assembly behavior of polymer. The results indicated that the supramolecular polymer can self-assemble into nanoscale vesicle, and disassembled under acid environment. In vitro release studies demonstrated that vesicles have exhibited excellent the capability of controlled release of drugs. The anticancer proliferation behavior and celluar uptake of vesicles loaded with modular drug in vitro were evaluated using MTT assay, flow cytometry, and confocal laser scanning microscopy. The result shows that these supramolecular block copolymers vesicles based on p H-responsive DNA are very promising carriers for drug delivery.3. Construction of amphiphilic multiarm copolymers based on PDMAEMA for gene deliveryTo investigate structure-transfection property relationships, a series of amphiphilic hyperbranched multiarm copolymers PEHO-g-PDMAEMAs with different topological structures was synthesized by the atom transfer radical polymerization(ATRP). By evaluating the gene transfection behavior of polymers, including the buffering ability, DNA compaction, self-assembly, cytotoxicity and gene transfection efficiency in vitro, the effect of the degrees of branching and the lengths of PDMAEMA arms on the cytotoxicity and gene transfection efficiency was systematic analysized. The results indicated that the incorporation of hydrophobic groups and high degree of branching can effectively reduce the cytotoxicity of PDMAEMA and improve the gene transfection efficiency in vitro, further extend their applications as non-viral gene vectors.4. DNA-induced self-assembly of hyperbranched polymersDNA-functional hyperbranched multiarm copolymer was first synthesized through the end group modification. Then, the structure was confirmed by NMR, UV-Vis, and GPC. The amphiphilic hyperbranched multiarm copolymers can self-assemble into nanoscale vesicles according to TEM and AFM. Meanwhile, the morphology transition of assemblies induced by the complementary DNA strands was also investigated. TEM and AFM results indicated that polymeric vesicles can transform to helix nanofibers through the process of the aggregation and fusion of vesicles by utilizing the sequence-selective recognition properties of DNA.