The Iterative Design of Aptamer-Functionalized Membranes to Enable Detection, Sequestration, and Recovery of Small-Molecule Compounds Öffentlichkeit

Abstract

Decontaminating our increasingly scarce sources of fresh water has become of paramount importance. Of the available treatment purifications methods, membrane filtration is advantageous due to its simplistic design, affordability, and applicability. However, one of the biggest drawbacks is its inability to retain small molecules of interest (< 1 μm). This matter becomes more pressing because contaminants arise from multiple industries, human pollution, and natural bacteria. This thesis is focused on exploring the preparation of a filtration system capable of removing small molecules from water by leveraging the use of aptamers. Aptamers are single-stranded DNA that have strong affinity and specificity to small molecules. When we couple aptamers to current filtration systems, we can pave the way to remove small-molecule and macromolecular contaminants, toxins, and microorganisms from water in a user-friendly manner. In Chapter 1, I provide a literature review to introduce the concepts of water scarcity, current technologies and methods for water decontamination, the use of membranes in decontamination, and utilization of aptamers in environmental applications. In Chapter 2, I create the first aptamer- functionalized membrane and demonstrate its ability to remove bisphenol A. In Chapter 3, I explore this system further by optimizing each component of the preparation process and therefore the increase of aptamer attachment. We also demonstrate the depletion of more than one small molecule synergistically. In Chapter 4, I talk about applications of the membrane system developed that go further than removal of small-molecule contaminants from water sources. I evaluate the creation of a membrane that can self-regenerate by not only removing but also degrading a small-molecule contaminant with the aid of an enzyme. In Chapter 5, I reflect about my time in graduate school, where apart from research, I got intensive training on teaching, science communication, and outreach. Finally, in Chapter 6, I discuss the practical applications and consider future directions of the system developed. Together, this research sheds a light in the development efficient methods that can sequester and remove micro- and macro- molecules from our water supplies, which due to the imminence of fresh-water scarcity, it has become critical to study. 

Table of Contents

Table of Contents

Abstract............................................................................................................................ iv

Dedications.. .................................................................................................................... vi

Acknowledgements ........................................................................................................... vii

List of Tables and Figures .............................................................................................. xii

Chapter 1: Combatting Small-Molecule Environmental Toxins: Detection and Sequestration using Functional Nucleic Acids

1.1 Abstract...................................................................................................................... 2

1.2 Introduction................................................................................................................ 3

1.3 Earth's Freshwater Crisis........................................................................................... 5

1.4 Technologies and Method used in Water Decontamination ...................................... 7

1.4.1 Sedimentation......................................................................................................... 9

1.4.2 Boiling/Distillation.................................................................................................. 10

1.4.3 Chemical Treatment ............................................................................................. 11

1.4.4 Disinfection ........................................................................................................... 17

1.4.5 Filtration................................................................................................................ 19

1.5 Use of Membranes for Water Decontamination....................................................... 20

1.5.1 Effect of Pore Size and its Limitations to Filtration .............................................. 26

1.5.2 Cost and Availability of Water Decontamination Technologies ............................ 28

1.6 Aptamers and DNAzymes for Detection and Sequestration.................................... 29

1.6.1 Selection............................................................................................................... 31

1.6.2 Detection of Small-Molecule Toxins ..................................................................... 33

1.6.3 Sequestration and Removal of Small-Molecule Toxins ........................................ 36

1.7 Motivation for Study ................................................................................................. 38

1.8 Summary and Objective of this Dissertation............................................................ 38

1.9 References .............................................................................................................. 41

Chapter 2: Sequestration of Bisphenol A by the Aptamer- Functionalized Membrane

2.1 Abstract.................................................................................................................... 54

2.2 Introduction.............................................................................................................. 55

2.3 Membrane Formation and Grafting.......................................................................... 57

2.4 Membrane Functionalization with DNA Aptamers ................................................... 67

2.5 Depletion of BPA from Water................................................................................... 73

2.6 Regeneration of the Aptamer-Functionalized Membrane........................................ 79

2.7 Conclusions ............................................................................................................. 81

2.8 Appendix.................................................................................................................. 82

2.9 References .............................................................................................................. 85

Chapter 3: Sequestration and Removal of Multiple Small Molecule Contaminants using an Optimized Aptamer-Based Ultrafiltration System

3.1 Abstract.................................................................................................................... 89

3.2 Introduction.............................................................................................................. 90

3.3 Results and Discussion ........................................................................................... 92

3.3.1 Membrane Formation ........................................................................................... 93

3.3.2 Membrane Grafting............................................................................................... 95

3.3.3 Membrane Functionalization................................................................................. 98

3.3.4 Multi-Analyte Removal.......................................................................................... 99

3.3.5 Application in Environmental samples................................................................ 103

3.4 Experimental Section............................................................................................. 105

3.5 References ............................................................................................................ 112

Chapter 4: Applications of Aptamer-Functionalized Membranes: Sequestration and Degradation of Small Molecules

4.1 Abstract.................................................................................................................. 118

4.2 Introduction............................................................................................................ 119

4.3 Self-Regeneration of Membranes Using Membranes............................................ 120

4.4 Conclusions ........................................................................................................... 131

4.5 References ............................................................................................................ 133

Chapter 5: Graduate School is More Than Research: A Path of Professional Development

5.1 Abstract.................................................................................................................. 138

5.2 Introduction............................................................................................................ 139

5.3 Science Communication........................................................................................ 141

5.4 Teaching................................................................................................................ 143

5.5 Outreach................................................................................................................ 146

5.6 Conclusion............................................................................................................. 149

Chapter 6: Conclusions and Future Directions

6.1 Conclusions ........................................................................................................... 152

6.2 Future Directions ................................................................................................... 139

6.2.1 Use of a Single-Layer Nanoparticle System....................................................... 141

6.2.2 Recovery of Small-Molecules using Aptamer-Functionalized Membranes ........ 143

6.3 References ............................................................................................................ 158 

About this Dissertation

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School	Laney Graduate School
Department	Chemistry
Degree	Ph.D.
Submission	Dissertation
Language	English
Research Field	Chemistry, Organic Chemistry, Polymer Chemistry, Biochemistry
Stichwort	Aptamer Contaminants Toxins Teaching Outreach Membrane Science Communication Water Purification Small Molecules Decontamination
Committee Chair / Thesis Advisor	Dr. Jen Heemstra, Emory University
Committee Members	Dr. Nathan Jui, Emory University Dr. Simon Blakey, Emory University

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