Study on physicochemical properties and methodologies of nanosized mineral nutrients : 나노 무기영양소의 이화학적 특성 및 분석법 연구

다국어 초록 (Multilingual Abstract)

Nanotechnology has been received a lot of attention in recent years in various fields because of its limitless potential. Physicochemical properties of nanoparticles are different from their macroparticle counterparts. For this reason nanosized materials could interact with biological system in different manner. Therefore, establishment of safety and toxicity of nanomaterials is very important due to the many experimental challenges and issues encountered when assessing the toxicity of nanomaterials. However, conventional analytical methods may or may not be proper to determine physicochemical properties of nanomaterials. Thus, evaluating the physicochemical properties of nanoparticles and its behavior in the human body is necessary especially for food applications before in vitro and in vivo test. The objectives of this study are to determine physicochemical properties of nanosized mineral particles and their behavior under in vitro digestion model. For this study, calcium carbonate and iron oxide nanoparticles were used because they are two of the most necessary minerals in the human body. Particle size and size distribution were measured using electron microscopy and dynamic light scattering (DLS) methods. But, mineral particles are insoluble in water. Therefore, some attempts to increase dispersibility are required. For this study, solvent replacement method for calcium carbonate nanoparticles and surface charge modification method was used for iron oxide nanoparticles. The specific surface area was determined using three different methods which were nitrogen adsorption, dynamic vapor sorption (DVS) system and calculation methods. Zeta potential was measured to determine the disperse stability in aqueous media by electrophoretic light scattering (ELS) method. In the electron micrograph results, particle size of calcium carbonate nanoparticles (CaCO3 NP) was around 100 nm uniformly. On the other hand calcium carbonate microparticles (CaCO3 MP) showed wide range of particle size distribution. The particle sizes of CaCO3 NP and MP in dimethyl surfoxide were 292.1 and 500.8 nm, respectively, which were determined by DLS method. Zeta potential of CaCO3 NP was higher than CaCO3 MP. But they are all unstable due to low zeta potential (less than -10 mV). The specific surface area of CaCO3 NP was higher than CaCO3 MP. The particle sizes of iron oxide nanoparticle and microparticle (Fe2O3 NPAE, MPAE and MPAA) were 166.10, 196.8 and 358.87 nm, respectively, which were analyzed by DLS method. This results showed similar results compared with that determined by electron micrographs. Zeta potentials were similar to each other. Surface modified Fe2O3 particles were more stable at neutral pH. The size of Fe2O3 particles under in vitro digestion conditions was larger than that of raw materials. Furthermore, zeta potential was slightly lower in raw materials especially at pH 6-7. This means that iron oxide particles became unstable in the aqueous media with ions despite surface modification to provide hydrophilicity. In conclusion, methods for determining physicochemical properties and behavior of mineral nanoparticles are expected to characterize nanomaterials to assess their functionality and toxicity using the methods reported in this study.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• Chapter 2. Physicochemical properties of iron oxide nanoparticles and their behavior under in vitro digestion conditions 7
• 1.Introduction 7
• 2.Materials and Methods 9
• 2.1.Materials 9
• 2.2.Physicochemical properties measurement 9
• 2.2.1.Electron Microscopy 9
• 2.2.2.Particle size distribution measurement 10
• 2.2.3.Zeta potential measurement 10
• 2.2.4.Surface modification of iron oxide particles 11
• 2.2.5.Specific surface area 11
• 2.3.In vitro digestion test 12
• 2.3.1.In vitro digestion model 12
• 2.3.2.Physicochemical properties measurement under in vitro digestion condition 14
• 3.Results and Discussion 15
• 3.1.Physicochemical properties of iron oxide nanoparticles 15
• 3.1.1.Electron microscopy 15
• 3.1.2.Particle size distribution 18
• 3.1.3.Zeta potential 22
• 3.1.4.Specific surface area 25
• 3.2.In vitro digestion conditions 27
• 3.2.1.Electron microscopy 27
• 3.2.2.Particle size distribution 30
• 3.2.3.Zeta potential 33
• 4.Conclusions 37
• Chapter 3. Physicochemical properties of calcium carbonate nanoparticles and their behavior under in vitro digestion model 38
• 1.Introduction 38
• 2.Materials and Methods 40
• 2.1.Materials 40
• 2.2.Physicochemical properties measurement 40
• 2.2.1.Electron Microscopy 40
• 2.2.2.Particle size distribution measurement 41
• 2.2.3.Zeta potential measurement 41
• 2.2.4.Specific surface area 42
• 2.3.In vitro digestion test 43
• 2.3.1.Labeling of fura-2 fluorescent dye with CaCO3 43
• 2.3.2.In vitro digestion model 45
• 3.Results and Discussion 47
• 3.1.Physicochemical properties of CaCO3 nanoparticles 47
• 3.1.1.Electron microscopy 47
• 3.1.2.Particle size distribution 50
• 3.1.3.Zeta potential 52
• 3.1.4.Specific surface area 54
• 3.2.In vitro digestion test 56
• 3.2.1.Stability of fura-2 dye at storage temperature 56
• 3.2.2.Intensity of fura-2 under in vitro digestion conditions 58
• 4.Conclusions 60
• Summary 62
• References 64