Synthesis And Biological Application Of Linear And Branched Block Copolymer Nano-contrast Agents

Cancer is the most threatening disease to human safety and health.Since the appearance of tumor imaging examination technology,especially magnetic resonance imaging,humans have developed rapidly in the field of tumor diagnosis.High-resolution magnetic resonance imaging requires the aid of contrast agents.The small molecular contrast agents currently in clinical use can no longer meet the needs of high-precision imaging.The nano-contrast agent synthesized with amphiphilic polymer modified inorganic magnetic materials can greatly improve the relaxation performance of the contrast agent due to its special nano-structure,and has broad application prospects.In this paper,two kinds of amphiphilic block copolymers were designed and synthesized by reversible addition-fragmentation chain transfer polymerization method,and they were used as ligands to synthesize gadolinium-based nano-contrast agents,which can be used for magnetic resonance imaging.details as follows.1.An amphiphilic linear block copolymer P（AA-b-OEGMA）was synthesized,and NaGdF₄ nanoparticles were hydrophilically modified with different polymerization degrees of P（AA-b-OEGMA）to obtain nano-contrast agent with different aggregation forms.Modification of NaGdF₄ by a copolymer with a high degree of polymerization results in an aggregated nano-contrast agent with a relaxation performance higher than that of a mono-dispersed nano-contrast agent synthesized from a copolymer with a low degree of polymerization.The nano-contrast agent synthesized with the polymer as a ligand has good stability and safety,the relaxation rate is higher than that of clinical commercial contrast agents,and the synthesis method is simple,easy to use and store,and has the potential to transform into clinical magnetic resonance contrast agents.2.This chapter synthesizes an amphiphilic branched block copolymer nanometer,with hydrophobic P（EGDMA-n-BMA）cross-linked copolymer as the "core" and POEGMA as the hydrophilic "outer arm" in aqueous solution.No self-assembly is required to form polymer nanostructures.Using this polymer nanoparticle as the ligand,the gadolinium ion is chelated on the POEGMA segment,and the tumor targeting molecule octreotide is introduced to form a new type of targeted magnetic resonance nano-contrast agent.The experimental results show that this new nano-contrast agent has good stability and biological safety,a high relaxation rate and a significant targeting effect on tumor tissue,and can be applied to clinical tumor-specific imaging.