DEVELOPMENT AND ANALYSIS OF ENZYME-POWERED DEVICES
Open Access
- Author:
- Valdez, Lyanne
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 08, 2018
- Committee Members:
- Ayusman Sen, Dissertation Advisor/Co-Advisor
Ayusman Sen, Committee Chair/Co-Chair
Christine Dolan Keating, Committee Member
Thomas E Mallouk, Committee Member
Peter J Butler, Outside Member - Keywords:
- Enzymes
Micropumps
Nanomotors
Fluid Motion - Abstract:
- Surface-immobilized enzyme systems can be used as micropumps in the presence of enzyme-specific substrates. In other words, the enzymes transduce chemical energy from the reaction into fluid motion. This discovery enables the design of non-mechanical, self-powered nano/microscale pumps that precisely control flow rate and turn on and off in response to specific analytes. In order to obtain spatio-temporal control over enzyme micropumps with different architectures, it is essential to understand in detail how solutal and thermal buoyancy affect the speed and pumping directionality. Presented are the results of separately probing the effects of solutal and thermal buoyancy on the behavior of phosphatase-based micropumps through experiments and modeling. One of the key outcomes of this study is that even though the reactions catalyzed by phosphatases are fairly exothermic, the primary driver behind pumping is the difference between the densities of the products versus the reactants. To further investigate the mechanisms driving enzyme micropumps, both glutamate dehydrogenase (GLDH) and alcohol dehydrogenase (ADH), enzymes that catalyze reversible reactions with the assistance of cofactors, were studied. These types of reactions are important to consider as a part of the fundamental understanding of pumps because many of the enzymes found in nature catalyze reversible reactions, including enzymes that are involved in metabolism, by which cells can harvest energy to perform important functions. GLDH and ADH pumps have been studied with the substrates only (in the absence of the respective cofactors) to understand the pumping behavior when these enzymes are not catalyzing any reaction. The resulting dehydrogenase pumping behavior in the presence of only substrates implies that the interaction between substrates and enzyme is sufficient to power the enzyme microfluidic pumping. Supplementary experiments were done to confirm that the interaction of enzyme and substrate can produce sufficient mechanical work. Fluorescence correlation spectroscopy (FCS) was done to show that the diffusion of free enzymes increases in the presence of only substrates. In addition, isothermal titration calorimetry (ITC) was done to determine the thermodynamic parameters of GLDH and its substrates. Another goal of this work was the development of an alternative enzyme pump architecture, particle-based enzyme pumps, which can potentially be used in directed fluid transport. Different enzyme particle pumps were studied in the presence of their substrates and proved more versatile in comparison to the 2D surface-patterned pumps previously studied. In one study, enzymes were anchored onto microparticles resulting in enhanced and directed fluid pumping. In a final study, enzymes were encapsulated inside virus-like particles and demonstrated their ability to move and power the motion of other particles, similar to a mobile pump. These two systems could aid in the development of enzyme pump networks, which can be explored for its application in fluidic delivery.