Synthesis And Anti-Helicobacter Pylori Properties Of Bismuth Subcarbonate Nanomaterials

With the development of nanoscience and nanotechnology, nanostructured materials have been widely applied in electronics, energy and biomedicine, because of their unique physical, chemical and biological properties. Various nanomaterials have been achieved great progress in the development of antibacterial agents, drug carrier systems and new drugs. Up to now, different nanostructures such as nanoparticles, nanowires, nanocages, nanotubes have been applied in various drug-delivery applications. It was also found that the nanomaterials with different morphologies and sizes exhibited different properties. Helicobacter pylori (H. pylori) is a Gram-negative bacteria, which plays a key role in the nosogenesis of gastritis and peptic ulcers. An effective therapy for H. pylori infection is very important to the human healthy. Recently, bismuth compounds have been widely used in gastroenterology, especially for the treatment of H. pylori infection. The commonly used agents include colloidal bismuth subcitrate (CBS), bismuth subsalicylate (BSS) and ranitidine bismuth citrate (RBC). Bismuth subcarbonate ((BiO)2CO3) was also found to exhibit antibacterial properties against H. Pylori. Hence, in this thesis, studies are focused on the synthesis, characterization and anti-H. pylori properties of (BiO)2CO3nanomaterials. It provides the potential applications in the development of nanomedicine and bismuth multiple therapy for H. pylori infection. The main work can be summarized as follows:1. Using bismuth citrate and urea are as the precursors, well-crystallized bismuth subcarbonate ((BiO)2CO3) nanoparticles with average size of9nm were successfully synthesized by water-in-oil (w/o) microemulsion-assisted hydrothermal method. The products were characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray microanalysis (EDX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). In the reaction, the thermal decomposition of citrate ions leads to the formation of major carbonate anion. The reaction, nucleation and growth process of (BiO)2CO3nanoparticles are confined inside the water droplets, which leads the formation of nearly uniform and well-crystallized spherical nanoparticles. By a standard antibacterial properties measurement, the MIC50value of these nanoparticles was evaluated to be10μg/mL, indicated that it exhibited comparable anti-H. pylori activities compared with colloidal bismuth subcitrate (CBS) and exhibited slightly enhanced and comparable inhibitory properties compared with the bulky (BiO)2CO3.2. Different (BiO)2CO3nanostructures such as cube-like, polyhedral-like nanoparticles and nanobars, were synthesized from bismuth nitrate via solvethermal method.(BiO)2CO3nanoplates were fabricated using bismuth citrate as precursor by refluxing method. All products were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy-dispersive X-ray microanalysis (EDX). In the solvothermal synthesis, both mannitol concentration and reagent have a significant influence on the morphologies and dispersity of the (BiO)2CO3nanostructures. It was also found that the mannitol molecule plays an important role in the formation of (BiO)2CO3cube-like nanoparticles. Under the refluxing, bismuth citrate plays an important role in the formation of nanoplate. By a standard antibacterial properties measurement, the MIC50of (BiO)2CO3cube-like nanoparticles nanoplates value was evaluated to be15and10μg/mL, which showed enhanced antibacterial activities compared with clinically used antiulcer drug, colloidal bismuth subcitrate (CBS).3. Well-separated bismuth micro-and nanospheres were successfully prepared from bismuth citrate and urea by a simple refluxing reaction at198℃in ethylene glycol in the presence of poly (vinyl pyrrolidone)(PVP). The sizes of the micro/nanospheres varied from400nm to800nm. In the synthesis, bismuth subcarbonate ((BiO)2CO3) particles were formed with the assistant of PVP at the first stage. Then bismuth micro-and nanospheres were fabricated through the process of reduction by ethylene glycol. It was also found that the amount of PVP has an influence on the morphologies of bismuth nanostructure.