DESIGN OF ENZYME CASCADE AND CRISPR-CAS9 NETWORKS FOR ENABLING BIOELECTRONIC COMMUNICATION

Abstract

There is an increasing emphasis on building closed loop systems in human health where real time monitoring and analysis is connected to feedback and treatment. Building such systems requires bridging the information loop across the different signal modalities of biology and electronics. In this work, I have created two different networks at biology-electronic interface to enable the communication from biology to electronics and vice versa. The first network is a multi-step enzyme cascade assembled on a microchip to enable conversion of biologic information into electro-chemical information. I first devised a modular construction approach using microbial transglutaminase (mTG) based conjugation chemistry where multiple enzyme components are assembled on an abiotic surface in a ‘plug and play’ fashion. Integration of bio-components with electronics requires a scaffold material for functionalization of the bio-electronic interface. To address this challenge, I engineered a self-assembling Tobacco Mosaic Virus-Virus Like Particle into a 3D scaffold displaying desired functional groups at the interface. Using the 3D scaffolds and mTG mediated conjugation chemistry, I assembled a synthetic 3-enzyme cascade on a microchip for conversion of methyl cycle intermediates into homocysteine, an electrochemically readable molecule. The modular construction approach and the scaffold materials that I developed can enable facile assembly of multi-subunit bio-components and diversify the range of metabolites that can be detected on a microchip for use in biosensing applications. Next, I focused on mediating communication from electronics to specific genes in the genome of biological systems. An electrogenetic promoter that is responsive to the electrical stimuli was reported in E. coli. In this work, I integrated the precise gene targeting capabilities of the CRISPR-Cas9 system with the electrogenetic promoter to target specific host transcriptional processes. I displayed temporal silencing of several host defense mechanisms against the electrical signals resulting in an overall positive feedback for electrogenicity in E. coli. A more sophisticated control of host transcriptional processes by the CRISPR-Cas9 system is a valuable addition to the existing electrogenetic toolbox, one that could enhance the interoperability of electrogenetic systems and mediate bio-electronic communication between strains and species.