Synthesis of bismuth oxyhalide-based nanocomposites with enzyme-like activity for sensing and antibacterial applications

• Main Authors: Chia-Lun Hsu, 許家綸
• Other Authors: Huan-Tsung Chang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/76s9es

博士 === 國立臺灣大學 === 化學研究所 === 105 === This disssertation focus on the preparation of switchable enzyme-like activity of bismuth oxyhalides (BiOX, X = Cl, Br, I) nanocomposites that exhibit peroxidase-like (POX) or oxidase-like (OX) activity. The BiOX nanomaterials facilitate catalytic conversion of Amplex Red (AR) to fluorescent resorufin in the presence or absence of H2O2. Enzymimic nanomaterials are further applied for the detection of proteins, and heavy metal ions. The nanomaterials also acts as antimicrobial agent. Chapter 1, the detailed background of bismuth oxyhalide nanomaterials including their catalytic properties and applications is reviewed. Chapter 2, the self-assembled gold/bismuth oxychloride nanocomposites are prepared from an aqueous mixture of aptamer-modified gold nanoparticles (AptAu NPs), bismuth ions and chloride ions. AptAu NPs are immobilized on bismuth oxychloride (BiOCl) nanosheets in situ to form AptAu NPs/BiOCl nanocomposites. The synergistic effects of AptAu NPs/BiOCl nanocomposites leads to at least 90-fold higher POX-like activity than AptAu NPs or BiOCl nanosheets. Catalytic activity of AptAu NPs/BiOCl nanocomposites is suppressed by vascular endothelial growth factor-A165 (VEGF-A165) molecules that specifically interact with the aptamer units (Del-5-1 and v7t-1) on the nanocomposites surface. AR/H2O2AptAu NPs/BiOCl nanocomposites probe shows high selectivity (>1000-fold over other proteins) and sensitivity (detection limit ~0.5 nM) for the detection of VEGF-A165. Chapter 3, we demonstrate enzyme-like activity of BiOI nanonetworks that can be regulated through homogeneous deposition of metal atoms/ions or nanoparticles. BiOI nanonetworks exhibited much stronger (425-fold) POX-like activity than BiOCl or BiOBr nanosheets. In situ formation and deposition of Au NPs onto BiOI nanonetworks enhanced the OX-like activity of the nanocomposites. The deposition of metals such as Ni, Zn or Mn on the BiOI nanonetworks boosted their POX activity by at least 3-fold. Au NPs/BiOI nanocomposites and NiO NPs/BiOI nanocomposites were used for the detection of heavy metal ions such as Hg2+ and Pb2+, respectively. These BiOI nanocomposite-based probes allow selective detection of Hg2+ and Pb2+ down to nanomolar quantities. The practicality of the probes is validated in environmental water samples. Chapter 4, we developed a simple one step route to prepare Au/BiOI nanocomposites from an aqueous mixture of gold ions, bismuth ions and iodide ions. Au NPs were in situ formed and doped into BiOI nanonetworks that exhibited ca. 4-fold higher OX-like activity than BiOI nanosheets. OX-like Au/BiOI nanocomposites were prepared by doping of gold and generation of oxygen vacancies in BiOI nanostructures. Au/BiOI nanocomposites show wide spectrum antimicrobial activity against nonmultidrug-resistant E. coli, K. pneumoniae, S. enteritidis, S. aureus, and B. subtilis bacteria and multidrug-resistant bacteria, as well as methicillin-resistant S. aureus (MRSA). Minimal inhibitory concentration value of Au/BiOI nanocomposite is much lower (>4000-fold) than BiOI nanosheets. Au/BiOI exhibits synergistic effect through strong interaction between nanocomposites and bacterial membrane that cause the disruption and generation of reactive oxygen species (ROS). In vitro and in vivo cytotoxicity, rabbit corneal keratocytes and hemolysis assays evaluation by using the rabbit eye model revealed superior biocompatibility of Au/BiOI nanocomposites, suggesting that it can effectively alleviate S. aureus induced bacterial keratitis in rabbits.