CONVECTIVE ASSEMBLY OF ROD-SHAPED MELANOSOME IN DILUTE POLYMER SOLUTION A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements of the Degree Master of Science Jiuzhou Zhao May, 2016 CONVECTIVE ASSEMBLY OF ROD-SHAPED MELANOSOME IN DILUTE POLYMER SOLUTION Jiuzhou Zhao Thesis Approved: Accepted: _______________________________ _______________________________ Advisor Dean of the College Dr. Ali Dhinojwala Dr. Eric J. Amis _______________________________ _______________________________ Co-Advisor Dean of the Graduate School Dr. Matthew Shawkey Dr. Chand Midha _______________________________ _______________________________ Department Chair Date Dr. Coleen Pugh ii ABSTRACT Bird feathers have developed most diverse structural colorations. Many of them are produced by orderly packing melanosomes (submicron melanin-filled organelles) structures. These melanosomes come in different morphologies such as spherical, rod-like, and disk-like shapes and they may be solid or hollow. But it is still unclear how such ordered structures of anisotropic melanosomes are formed and it is also challenging to mimic those structures using in-vitro assembly technique. In this work, we extracted rod-shaped melanosomes from crow feathers and investigated their assembly behavior in the evaporating sessile droplets containing polyvinyl pyrrolidone (PVP) or polyethylene oxide (PEO). We used zeta potential to monitor the interaction between polymer and melanosomes, high-speed video to track melanosome movement during evaporation, and optical/electron microscopy to study the packing behavior of melanosomes. We have found melanosomes packed densely at the deposition edge, forming a “coffee ring” pattern after drying PEO-melanosome droplet. While at the same position of PVP-melanosome solution the coffee ring effect was suppressed and melanosome did not form densely packing structure. This is mostly due to the adsorption of PVP on melanosome surface that can bring the particle to the air-water interface instead of arriving at contact line. This work helps iii our better understanding of anisotropic particles assembly in polymer solution and also makes it possible towards mimicry of the structures of bird feathers. iv ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Ali Dhinojwala, and my committee member, Dr. Matthew Shawkey, for their encouragement and guidance on my work. I really enjoy the process of scientific research. Also, I want to express my gratitude to my mentor, Ming Xiao for teaching me a lot of basic knowledge and the operation method of many machines. I cannot learn so many things without his help at the beginning of my experiment. I appreciate the help from all the group members in Dr. Dhinojwala’s lab and Dr. Shawkey’s lab. We had a great time working together in the past two years. I am deeply grateful to my parents for their support. They give me everything without preconditions so that I can finish this work with all my efforts. v TABLE OF CONTENTS Page LIST OF FIGURES…………………………………………………………………viii CHAPTER I. INTRODUCTION………………………………………………………………..1 1.1 Structure Color……………………………………………………………………1 1.1.1 Melanosome and Melanin…………………………………………………1 1.1.2 Structure Color on Avian Plumage ……………………………………..3 1.2 Coffee Ring Effect………………………………………………………………..6 1.2.1 Capillary Flow……………………………………………………………...7 1.2.2 Marangoni Flow……………………………………………………………8 1.3 Description of This Work ……………………………………………………….10 II. EXPERIMENT……………………………………………………………………12 2.1 Material…………………………………………………………………………..12 2.1.1 Extraction of Natural Melanosome……………………………………….12 2.1.2 Clean Silicon Wafer………………………………………………………14 2.1.3 Water-Soluble Polymer…………………………………………………...14 2.2 Experiments………………………………………………………………………15 2.2.1 Characterization Method………………………………………………….15 2.2.2 Experimental Detail……………………………………………………….15 2.2.3 Detection on Experiment Solution………………………………………..16 2.2.4 High-Speed Video and Scanning Electron Microscopy…………………..17 III. RESULTS AND DISCUSSION…………………………………………………18 3.1 Morphology and Size of Melanosomes…………………………………………..18 3.2 Assembled Patterns after Drop Casting………………………………………….19 3.3 High Speed Video………………………………………………………………..24 vi 3.4 Influence Factors Analysis ……………………………………………………….28 3.4.1 Effect of Particle Charge………………………………………………….28 3.4.2 Effect of Viscosity………………………………………………………...30 3.4.3 Effect of Surface Tension…………………………………………………31 IV. CONCLUSION………………………………………………………………......32 V. FUTURE WORK…………………………………………………………………34 REFERENCES……………………………………………………………………….35 vii LIST OF FIGURES Figure Page 1.1-1. Biosynthetic way of eumelanin and pheomelanin……………………………..2 1.1-2. Generation process of melanosomes……………………………………………3 1.1-3. The breast feathers of male bird change color from (A) yellow-orange to (B) blue-green by changing the observe angle of barbules. (C) Transverse section gives the angle of the bent is nearly 120 degree. The span of right hand slope of 15 layers is 8 micrometers. (D) Cross section model of Parotia Lawesii barbules…………………………………………………………………………4 1.1-4. SEM images of cortex cross section in barbules for green (a) and brown (b)….5 1.1-5. (a) Pica Pica with a long tail; (b) Cross section of a barbule; (c) Structure model……………………………………………………………………………6 1.2-1. Coffee Ring Effect………………………………………………………….......7 1.2-2. Cross Section of Capillary Flow Regime……………………………………….7 1.2-3. Tears of wine……………………………………………………………………9 1.3-1. Radially arrangement due to the phase separation…………………………….10 1.3-2. Slow evaporation for high aspect ratio silica rods…………………………….11 2.2-1. Drop Casting Method………………………………………………………….16 3.1-1. SEM image of extracted melanin particles……………………………………18 3.2-1. Optical and SEM images for melanosome solution …………………………..19 3.2-2. Optical & SEM image for PEO-Melanosome solution. Form top to bottom the PEO concentration is 0.002 mg/mL, 0.004 mg/mL, 0.02 mg/mL. The evaporation condition is 21°C, 15% relative humidity………………………..20 viii 3.2-3. Optical & SEM image for PVP-Melanosome solution. Form top to bottom the PVP concentration is 0.002 mg/mL, 0.004mg/mL, 0.02 mg/mL. The evaporation condition is 21°C, 15% relative humidity………………………..21 3.2-4. Order parameter for PEO-melanosome solution under 15% RH, 21℃……….23 3.2-5. Particle-packing density under 15% RH, 21℃………………………………..24 3.3-1. Particle speed under 15% RH, 21°C condition………………………………..25 3.3-2. Snapshot of melanosome solution at start……………………………………..26 3.3-3. Meniscus thickness of different solutions……………………………………..27 3.4-1. Zeta potential for different solutions…………………………………………..29 3.4-2. Surface tension measure for different solutions……………………………….31 ix CHAPTER I INTRODUCTION 1.1 Structure Color Structural coloration is the production of color by microscopically structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments. In bird feathers, the colors have close relationship with melanin. 1.1.1 Melanosome and melanin Melanin is a general term for a series of pigments that widely existed in organisms. The mainly two types of melanin are eumelanin and pheomelanin.1 They are generated by different precursors in biosynthetic pathway. Figure 1.1-1 shows the current understanding of the very beginning step of melanin biosynthetic pathways.1 Because of the chemical structure of eumelanin and pheomelanin are different, their synthesis way also different. 1 Figure 1.1-1 Biosynthetic way of eumelanin and pheomelanin1 Melanosomes are organelles found in living body tissues throughout the kingdom of animals. And melanosomes also have different shapes: diameter until 1µm sphere particles, and ellipsoid particles with scale up to nearly 2 µm, but varies in aspect ratios.1 Melanosomes also have many different functions. It has strong adsorption of UV-visible light, low quantum yield of radioactive, good property of anti-oxidize, and 2 Figure 1.1-2 Generation process of Melanosomes2 it can get rid of the free radicals.3 Melanosomes contain varieties of biomolecules such as lipids and proteins. But the main constituent is melanin. The functions that melanosomes have mainly attribute to the chemical properties that melanin have. Recent research found melanosomes generate from vesicles.2 The whole process is shown in Figure 1.1-2. This kind of vesicles created by the trans-Golgi network. High degrees of dendritic melanocytes under through a series of morphology change stages due to the network contain tyrosinase. The whole procession begins with pigment precursors and ends with the membrane-enclosed bladder of melanin. 1.1.2 Structure color on avian plumage In avian feather barbules, the nanostructure of air, keratin, and melanosomes are well organized, which generates iridescent colors.4 Here is the picture of breastplate feathers of male bird of paradise (Parotia lawesii). The feathers display color changes from yellow-orange to blue-green when viewed from different angle of barbules on 3 feather tips.4 And the color showing on this kind of birds is really beautiful so that it’s attractive people to explore why it can generates this color. Figure 1.1-3 The breast feathers of male bird change color from (A) yellow-orange to (B) blue-green by changing the observe angle of barbules. (C) Transverse section gives the angle of the bent is nearly 120 degree. The span of right hand slope of 15 layers is 8 micrometers. (D) Cross section model of Parotia Lawesii barbules.5 These kinds of feathers have unique thin-film and multi-film interference combination in single feather barbules. Melanin