Abstract
Synchrotron X-ray is an intense and coherent radiation, which can efficiently induce radiation-chemical reactions. In this thesis, we evaluated the use of synchrotron X-ray for synthesizing polymers and nanoparticles and applying the resulting products to biomedical studies. Synchrotron X-ray is a promising radiation to polymerize alkane compounds. Polymerization of alkane does not commonly be observed in conventional polymerizations with radiations or chemical reagents. Linear-like polyethylenimine (LPEI) and linear-like polyethylenimine-co-polyethylene glycol (LPEI-co-PEG) were produced by irradiating the monomers of ethylenediamine and ethanolamine, respectively. The LPEI-based polymers were used to carry siRNAs for arresting cell cycle, silencing expression of green fluorescent protein (GFP) and suppressing tumor growth. Besides, ethylene glycol, another alkane monomer, was also polymerized to generate non-linear polyethylene glycol (NLPEG). The NLPEG was further modified onto a wafer and formed a compact layer for protein resistance that can be probably used on biomedical devices to increase durability and performance. For synthesis of metal nanoparticles, synchrotron X-ray can induce water radiolysis and generate reducing species, such as solvated electron and hydrogen radical, which can reduce metal ions to nanoparticles with a suitable ligand or template in aqueous solution. First, gum arabic (GA) was used as a template to assist synthesizing a nanocomposite of GA-protected gold nanoparticles (AuNPs@GA). Because gum arabic is a branched polysaccharide with porous structure, the growth of gold nanoparticles is limited by reducing insufficient gold ions in the structure. The nanocomposite of AuNPs@GA was subsequently activated by neutron flux and formed radioactive 198AuNPs@GA for tumor suppression. The tumor growth was significantly suppressed via intravenous injection or intratumoral injection of 198AuNPs@GA. After the treatment, AuNPs were gradually excreted from the body that prevents potential toxicity of long-term nanoparticle accumulation. In the other study, silica nanoparitcle was used as a stabilizing template to synthesize bare AuNPs on the surface without any other chemical ligands. The bare AuNPs synthesized on silica nanoparitcle were easy for HS-PEG modification and subsequently released from template surface to solution. The Pegylated AuNPs from silica template were further proved a higher PEG coverage on the AuNP surface, comparing the AuNPs from citrate reduction and stabilization. This synthetic approach is potential to produce superior AuNP with the high ligand density. Synchrotron X-ray is powerful radiation for synthesis of polymers and nanoparticles with good functionality in a few minutes, and is possible to carry out reactions and products that are still not discovered. Synchrotron X-ray assisted synthesis of nanoscale materials is worth further study.